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Developmental changes in the mouthparts of juvenile Caribbean spiny lobster, Panulirus argus: Implications for aquaculture
Aquaculture 283 (2008) 168–174
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Aquaculture j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / a q u a - o n l i n e
Developmental changes in the mouthparts of juvenile Caribbean spiny lobster, Panulirus argus: Implications for aquaculture Serena L. Cox a,b,⁎, Andrew G. Jeffs c, Megan Davis a a b c
Aquaculture Division, Harbor Branch Oceanographic Institute at Florida Atlantic University, 5600 US 1 North, Fort Pierce, Florida 34946, USA National Institute of Water and Atmospheric Research, Private Bag 14901, Kilbirnie, Wellington 6241, New Zealand Leigh Marine Laboratory, University of Auckland, P.O. Box 349, Warkworth 0941, New Zealand
a r t i c l e
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Article history: Received 5 May 2008 Received in revised form 14 July 2008 Accepted 14 July 2008 Keywords: Mouthparts Spiny lobster Panulirus argus Feeding Puerulus Juvenile
a b s t r a c t Light microscopy and video analysis were used to examine the mouthpart morphology and feeding behaviour of the Caribbean spiny lobster from puerulus (megalopal stage) (5–8 mm carapace length, CL) to adult (85 mm CL). Upon settlement the pueruli did not possess fully functional mouthparts, however, efficient feeding appendages appeared in the first instar juvenile (after the first moult from puerulus). From this stage the density, robustness and complexity of setation on the mouthparts, together with the size and calcification of the mouthparts increased progressively with the size of the lobster. The changes correlated well with previously observed ontogenetic changes in natural prey, from small and soft prey in early juveniles to large and well-armoured molluscs, crustaceans and echinoderms in late juveniles and adults. The efficiency of shredding and tearing food items, mostly with the second maxillipeds, increased concomitantly with lobster size, as did the ability of the mandibles to grind and process food. Based on morphological and behavioural observations it is recommended that formulated feeds for first instar juvenile lobsters should be small (1–2 mm in diameter), soft and pulpy in texture to maximise feed intake. For large juvenile lobsters (45–80 mm CL), food items should increase to 5–10 mm in diameter and be of firmer consistency. Differences in feeding behaviour between spiny lobster species suggest that formulated diets developed to be efficient in one species may not be directly transferable to other species. © 2008 Elsevier B.V. All rights reserved.
1. Introduction The Caribbean spiny lobster, Panulirus argus, is an excellent candidate for commercial aquaculture because of rapid growth and straightforward husbandry (Lellis, 1991; Booth and Kittaka, 2000; Jeffs and Davis, 2003). However, the development of a formulated feed for this spiny lobster species remains a significant impediment to its commercial aquaculture despite some initial research (Jeffs and Davis, 2003; Williams, 2007). There is an underlying lack of knowledge of the feeding capabilities and behaviour of spiny lobsters, including for the Caribbean lobster. Recent reviews of the nutrition of spiny lobsters in culture concluded that understanding the feeding capabilities and the corresponding format of formulated feeds are critical for advancing the development of formulated feeds for spiny lobster aquaculture, by maximising intake and reducing feed wastage (Nelson et al., 2006; Williams, 2007). For example, up to 50% of formulated feed pellets fed to juveniles of the spiny lobster, Jasus edwardsii, were wasted through
⁎ Corresponding author. National Institute of Water and Atmospheric Research, Private Bag 14901, Kilbirnie, Wellington 6241, New Zealand. Tel.: +64 4 386 0300; fax: +64 4 386 2153. E-mail address: [email protected] (S.L. Cox). 0044-8486/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2008.07.019
inefficient handling by lobsters, and simple changes in pellet dimensions were found to reduce waste by as much as 19% (Sheppard et al., 2002). Investigations of species-specific feeding behaviour and functional morphology, as well as digestive capabilities, over a range of lifehistory stages is an effective means of identifying ontogenetic changes in dietary capabilities (Cox and Johnston, 2004). This approach has been used successfully in a wide range of crustaceans and in many instances leading to advances in the design and method of delivery of formulated feeds for aquaculture. This approach has already been used with considerable success for larval spiny lobsters (Cox and Johnston, 2003), as well as slipper lobsters (Suthers and Anderson, 1981; Johnston and Alexander, 1999), blue crabs (McConaugha, 2002), and shrimp (Alexander and Hindley, 1985). While the feeding morphology and behaviour of adult spiny lobsters has been described (Mikami and Takashima, 1994), it is not well known in the puerulus (megalopal stage which is often incorrectly called the “postlarva” — Williamson, 1982) and the subsequent juvenile, which frequently undergo marked ontogenetic changes in habitat and diet (Butler et al., 2006). For example, the puerulus of the Caribbean lobster settles and remains within dense inshore macroalgal beds. Once it has molted to the first instar juvenile it begins to feed, mostly on small resident crustaceans and molluscs, before emerging at N15 mm carapace length (CL) to seek
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shelter in nearby crevices and begin feeding locally on larger prey (Andrée, 1981; Marx and Herrnkind, 1985; Lalana et al., 1987). Larger juveniles then move offshore, particularly around reefs, and are more mobile, ranging across an array of habitats in search of a much wider variety of prey (Cox et al., 1997; Briones-Fourzán et al., 2003). Therefore, the aim of this research was to describe the morphology and functioning of the mouthparts in the Caribbean spiny lobster from puerulus to young adult to determine the changes in feeding capabilities that could lead to improvements in the design of formulated feeds for aquaculture. 2. Methods and materials 2.1. Animal collection and husbandry Approximately 100 newly settled P. argus pueruli were collected from 10 Witham collectors (Witham et al., 1968) moored in surface waters in the Florida Keys, following the new moon in March and April 2005. Newly settled pueruli were sorted from more advanced developmental stages on the basis of well-established staging criteria (Lewis et al., 1952). The pueruli were transported in seawater to the Harbor Branch Oceanographic Institute at Florida Atlantic University in Fort Pierce, Florida, and placed into holding tanks which included a selection of natural macroalgal (Caulerpa sp.) and artificial refuges. The lobsters were fed frozen brine shrimp, Artemia salina and wild food items (i.e., worms, amphipods, and other various small crustaceans, as well as frozen natural seafood items). Lobsters were held at 14:10 light–dark cycle, at 28 ± 1 °C and salinity maintained at 30 ± 2‰. Ten transparent pueruli (b5 days after settling) were used for mouthpart analysis immediately upon arrival at the laboratory, and remaining individuals were on-grown in the tanks until they subsequently reached the required developmental stage of early juveniles (10–15 mm CL), juvenile (15–44 mm CL), late juvenile–adult (45–80 mm CL) for video analysis of feeding behaviour and mouthpart morphology. 2.2. Mouthpart morphology and video analysis For each size range of lobsters, five individuals were tethered with cyanoacrylic adhesive to fine wire (0.25 mm diameter), at the midsection of the dorsal surface of the cephalothorax and then placed into a glass evaporating dish containing fresh seawater. Experimental temperature was maintained at 28 ± 1 °C and light levels were kept constant at 2 lx. Feeding responses and mouthpart movements were induced by placing frozen A. salina or fresh clam tissue (Mercenaria mercinaria) within the oral field of the tethered lobster. The mouthpart movements and function during food capture, manipulation and mastication were observed using an inverted Meiji EM28TR compound microscope (Martin Microscope Company, USA) with fibre optic illumination and Sony Digital Handycam, which recorded directly onto DVD for later analysis. After recording was completed, the five individual lobsters were euthanized by rapid cooling in an ice slurry and the mouthparts dissected out, photographed and then drawn. In the following descriptions, the terminology of Paterson (1968) and Nishida et al. (1990) is used for the mouthparts and that of Factor (1978) is used to describe the setae. 3. Results 3.1. Puerulus (b9 mm CL) The mandibles, maxillae and maxillipeds of the puerulus were small in size, lacked calcification, and had only a limited number of setae. Microscopic examination of the mouthparts and the gut confirmed that the puerulus stage is non-feeding by the inadequacy of the mouthparts and the absence of any food in the gut.
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The oesophagus was not fully formed and the opening into the oesophagus appeared to be covered by a fleshy membrane. The overlying mandibles and maxillae were fleshy, soft structures which did not move, even when physically stimulated. The mandibles were asymmetrical and simplified, with an unsegmented, laterally attached mandibular palp which was partially covered posteriorly by the paragnaths (Fig. 1A). The left mandible incisor process consisted of an undeveloped single, blunt tooth. The first maxillae were flattened, with a spinose exopod and epipod, and a rudimentary endopod, together forming three flat lobes (Fig. 1B). The second maxilla gave rise to an elongated scaphognathite-like epipod, divided into proximal and distal endites, and a smaller lobe-like endopod (Fig. 1C). A fringe of setae was present along the distal edges of the exopod and a small tuft of simple spinose setae on the proximal endite. The distal and proximal endites are much reduced in the first maxilliped, with the endopod fused to the elongated exopod (Fig. 1D). A distal flagellum was present on the anterior tip of the exopod. The epipod resembled a flattened and membranous plate. Setae were present along the distal margins of both the exopod and endopod. The second and third maxillipeds were more elongated compared with the maxilla or first maxilliped (Fig. 1E and F). The endopods consisted of five segments each. The exopod on the second maxilliped was elongated with four segments, whereas the exopod on the third maxilliped was much reduced and only had two segments. Setae were present along the inner margin of the endopod dactyl and carpus of the third maxilliped. Among the five individuals examined for feeding behaviour, there was consistency in their mouthpart morphology and movement, including the absence of any feeding behaviour. Close observations of untethered pueruli in the tanks indicated that the lack of feeding behaviour was not a response to the experimental tethering treatment. 3.2. Early juvenile (10–15 mm CL) The relative position of the six pairs of mouthparts (mandibles, maxillae I and II, and maxillipeds I, II and III) as well as the labrum, paired paragnaths, and the posterioventral fleshy lobe (membranous lobe), remained constant between the puerulus and all subsequent juvenile stages, including early juveniles. The main changes between the puerulus and first instar juveniles were the development of additional setae and spines, increased mouthpart robustness (i.e., calcification), an immediate transition to fully functional mouthparts, and almost doubling in the overall dimensions of the mouthparts. In the first instar juvenile, the mandibular palps had developed simple setae on the proximal tips and had become segmented. The incisor process had also become more defined, bearing a more prominent groove in the molar process. The epipod, endopod and exopod of the first maxilla all bear setae and spines (Fig. 2A). The distal and proximal endites of the epipod of the second maxilla both bear setae. The exopod and the endopod have a fringe of setae along the lateral edges. The first maxilliped is similar in structure to the puerulus, however, the distal flagellum is elongated and the interior edge of the endopod is flatter and broader. The major difference between the second and third maxilliped in the early juveniles is the development of setation along the inner margin of the dactyl, propodus, merus and basis (Fig. 2B and C). Segmentation develops between the basis and coxa of the third maxilliped (Fig. 2C). The exopod is elongated and the distal segment also bears setae. Among the five individuals examined, there was consistency in their mouthpart morphology with mouthparts increasing in proportion to changes in body size. The mouth aperture was approximately 300 μm diameter, however, soft, fleshy food particles ranging from 1–2 mm and whole juvenile A. salina (up to 2 mm total length) were observed being pushed between the mandibles by the maxillae. Early juvenile lobsters were capable of efficiently shredding fleshy clam tissue and adult A. salina into small (1–3 mm) pieces.
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Fig. 1. Mouthparts of P. argus puerulus. (A) Mandibles. Scale 500 μm. (B) First maxilla. Scale 500 μm. (C) Second maxilla. Scale 1 mm (D) First maxilliped. Scale 500 μm. (E) Second maxilliped. Scale 500 μm. (F) Third maxilliped. Scale 1 mm. b, basis; c, carpus; co, coxa; d, dactyl; de, distal endite; en, endite; ep, epipod; ex, exopod; i, ishium; ip, incisor process; m, merus; mdp, mandibular palp; mp, molar process; p, propodus; pa, paragnaths; pe, proximal endite; pr, protopod; sc, scaphognathite.
3.3. Juvenile (15–44 mm CL) The mandibles and paragnaths showed little developmental change compared with the early juvenile stage, however, the anterior surfaces of the mandibles and the palps had developed pigmentation. The incisor process has become more pointed and the molar process had low tubercles located along the internal edge. The first and second maxilla were almost identical to those observed in early juveniles, although there was increased setation around the anterior margins of the exopods and epipods, including both the distal and proximal endites. The first maxilliped of juveniles was also similar to the early juveniles, however, there was increased setation on the interior
margin of the endopod, and on the distal tip of the exopod. The only major differences between the second and third maxilliped in the early juveniles and the subsequent juveniles were the development of pigmentation and slightly increased setation along the margins of the five segments of the endopod. Among the five juveniles examined there was a proportional increase in mouthpart size in relation to body size, and general increase in setation and robustness of mouthparts. Juvenile lobsters were capable of shredding fleshy prey items into small pieces (approximately 2–3 mm) prior to ingestion. Whole adult A. salina (up to approximately 5 mm) were observed being ingested, indicating the maxillae and mandibles are able to shred and process the tough external carapace of these crustacean prey.
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Fig. 2. P. argus early juvenile mouthparts. (A) First maxilla. (B) Second maxilliped (C) Third maxilliped. All scale bars 1 mm. am, attachment muscle; b, basis; c, carpus; co, coxa; d, dactyl; en, endite; ep, epipod; ex, exopod; i, ishium; m, merus; p, propodus; pr, protopod.
3.4. Late juvenile–adult (45–80 mm CL) The asymmetrical mandibles in the late juveniles were more calcified, with tubercles along the interior edge of the molar process and a notably more defined incisor process on the opposing left mandible (Fig. 3A). A deep notch separated this incisor process from the molar process. The mandibles were capable of easily crushing the tough chitinous exoskeletons of large adult A. salina and various similar-sized crustaceans (5–9 mm), once the maxillae and maxillipeds had shredded them into smaller pieces. The mandibular palp had developed from two into three segments, with coarse setae covering the distal segment. Although larger, the first maxilla is similar in structure and degree of setation to the same structures in the earlier developmental stages. The scaphognathite of the second maxillae was larger in the late juveniles, but essentially the same shape. The endopod was enlarged and setose along the anterior and lateral edges (Fig. 3B). The distal and proximal endites had coarser setae along the entire length. The first maxilliped of the late juvenile is larger than in the juvenile, but the general shape and structure remains similar. The exopods in both the second and third maxillipeds were elongated and both had simple and plumose setae (Factor, 1978) (Fig. 3C and D). The five segments of the endopods were considerably
larger, more robust and pigmented, compared with earlier developmental stages. The five individuals examined were capable of efficiently shredding and tearing large pieces of clam tissue (up to 10 mm), whole adult A. salina (up to 6–7 mm), and various other prey items (i.e., worms, crustaceans) into smaller pieces (3–5 mm) prior to ingestion. 3.5. Feeding behaviour Detailed examination of the video recordings revealed that all juvenile lobster stages, except the puerulus, exhibited similar feeding behaviour and consistently utilised the paired mouthparts in a similar manner for manipulating food. Food items were speared in a grabbing motion using the terminal dactyls of pereiopods 1 and 2, and passed toward maxilliped 3. The third maxillipeds typically grasped food items and manipulated the food inwards, towards the anterior second maxillipeds. When not holding food items, the third maxillipeds swept back and forth across the surface of the mouth region, over an arc of approximately 90°, articulating at the segment between the basis and coxa. Pereiopods 1, 2 and 3 were also observed sweeping in this arc, in synchrony with the third maxillipeds. The exopod either moved dependently with the endopod, or it was observed beating
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Fig. 3. P. argus late juvenile mouthparts. (A) Mandibles (B) Second maxilla (C) Second maxilliped (D) Third maxilliped. All scale bars 1 mm. b, basis; c, carpus; co, coxa; d, dactyl; de, distal endite; i, ishium; ip, incisor process; m, merus; mdp, mandibular palp; p, propodus; pa, paragnaths; pe, proximal endite; pr, protopod; sc, scaphognathite.
sporadically with inconsistent frequency when the lobster was feeding. The third maxillipeds also played an important grooming role, removing debris from the oral region by sweeping the surface of the mandibles, maxillae, and first and second maxillipeds. The exopods of the second maxillipeds were very active during feeding, beating continuously which appeared to facilitate the movement of food particles toward the mouth. The endopod of the second maxillipeds received food items from the pereiopods or maxilliped 3, and when food items were within close proximity to the mouth these endopods were observed moving frequently, sweeping back and forth across the surface of the mandibles and first maxillipeds. The endopods were also observed being held together in a medial position, preventing food items from being lost anterioventrally whilst the food was being manipulated by the first maxillipeds. The second maxillipeds also adjusted the location of the food between the mandibles, assisting in the shredding and maceration of larger food items. In addition, the endopods of the second maxillipeds were in close contact with the mandibular palps. The first maxillipeds played a similar role to the second and third by assisting in guiding food items between the mandibles with lateromedial movements. The first maxillipeds also prevented food particles being lost anterioventrally. The second and first maxillae were not visible on the video as they were obscured by the maxillipeds. The second maxillae were restricted to movements in the lateromedial plane between the first maxillae and first maxillipeds, but allowing the scaphognathite to move dorsoventrally and possibly associated with flushing the gill
chamber with seawater. The dense setae which line the edge of the second maxillae would, together with the two endites pointing into the mouth, appear to help guide food between the mandibles. However, the setose nature of these mouthparts makes them well suited for filtration or helping to handle small food items such as crumbly invertebrate gonadal tissue. The first maxillae were ventral to the mandibles, but obscured by the second maxillae and the maxillipeds. However, the second maxillae bear setae as well as prominent, robust spines along the medial edge of the exopods, endopods and epipods. These spines appeared to assist in probing for food, holding the food items between the mandibles during each bite, and were also possibly used for pushing unwanted food particles anteriorly where they could be expelled. The mandibles operated along a lateral plane, using the pointed incisor process of the left mandible to shear against the calcified, tubercled surface of the right mandible. The cutting and crushing action of the mandibles effectively processed pieces of food into smaller, masticated pieces that were soft enough to be pushed into the mouth by the maxillae. The mandibular palps were located distally on each mandible, and were only observed making small movements, independent of the mandibles. The setae on the distal segment of the palps made contact with the food during feeding, however, they did not appear to manipulate the food items. It is possible they function as a barrier, preventing food from escaping anteriorly. In addition, the setae on the palps may also have a chemosensory role, assessing food palatability prior to ingestion. The paragnaths or labrum were not observed to move during feeding. It
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appears food particles were pushed into the oesophagus by the maxillae, after shredding, softening and crushing by the mandibles. It is possible peristaltic foregut contractions assist in movement of food into the oesophagus and through into the gut. Late juvenile lobsters were capable of handling and ingesting larger prey items than the juvenile or early juvenile lobsters. The mouthparts efficiently shredded prey into 5 mm diameter (on average) pieces in late juveniles, whereas juvenile lobsters tended to tear and shred food into smaller (average 3 mm diameter) pieces, and smaller again in early juvenile lobsters (1–2 mm pieces). The ability to handle and ingest larger prey items was reflected in the processing ability of the mouthparts, due to increasing setation, robustness and calcification, as well as the increasing dimensions of the mouthparts observed over the sequential stages of juvenile lobster development. All stages of juvenile lobsters examined were untidy eaters, with a significant portion of shredded food material being lost laterally, especially where the food material was crumbly, such as with ripe gondal material from clams. Larger prey items also tended to tangle in the pereiopods and third maxillipeds, particularly in the late juvenile– adult stage. 4. Discussion The puerulus stage of all spiny lobster species is widely considered to be a non-feeding, transitional stage between pelagic and benthic lifestyles (Nishida et al., 1990; Phillips et al., 2006). The incomplete development of the mouthparts, a fleshy obstruction at the entrance to the oesophagus, the absence of food in the gut, and the absence of any feeding behaviour confirms earlier speculation that the puerulus of P. argus is also non-feeding (Wolfe and Felgenhauer, 1991). In the subsequent first instar juvenile, the feeding appendages show significant development, almost doubling in size and setation from the puerulus. The mouth was only 300 μm in diameter, but larger soft, fleshy food particles of up to 2 mm in diameter were handled and consumed. This is entirely consistent with the size and texture of the majority of the prey items found in the stomachs of juvenile lobsters in the wild (Marx and Herrnkind, 1985) and in agreement with observations of the mouthparts from other juvenile Palinurids (Nishida et al., 1990). Beds of the macroalgae, Laurencia spp., into which the lobster pueruli settle and subsequently dwell as early juveniles, contain very large numbers of small invertebrates (mostly less than 5 mm long) such as isopods, amphipods, polychaetes, gastropods, copepods, ostracods and ophiuroids (Marx and Herrnkind, 1985). These small crustaceans, worms, molluscs and echinoderms can be readily consumed by early juvenile lobsters because this small prey can be easily handled and the relatively unprotected soft bodies pulled apart in the lobster mouthparts in the same manner as A. salina were in our experimental observations. In contrast, juvenile lobsters (15–44 mm CL) no longer remain within the macroalgal beds, but occupy crevice shelters in shallow water habitats and forage in the immediate vicinity. The diet of these juvenile lobsters mostly consists of gastropods, bivalves, chitons, arthropods and echinoderms (Andrée, 1981; Herrera et al., 1991; Cox et al., 1997; Briones-Fourzán et al., 2003; Nizinski, 2007). These prey items are mostly well protected with hardened calcareous exoskeletons. The ability of juvenile lobsters to overcome the exterior defences of these prey is facilitated by a marked increase in the size, strength, complexity and hardening of the mouthparts. The increasing ability of progressively larger juvenile lobsters to feed effectively on well-armoured molluscan, arthropod and echinoderm prey has been observed in other species of spiny lobsters (Griffiths and Seiderer, 1980; James and Tong, 1998). The overall trend in the development of the mouthparts is continued with late juvenile to adult lobsters (45–80 mm CL) which forage across a wide range of habitats in more exposed waters closer to the outer reef margins. The mouthparts of these lobsters, as well as larger adults
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(Garm, 2004), are well suited to the handling and opening of large prey with strong shells, such as top-shells (Trochidae) and moon snails (Polinices spp.) which can make up a significant proportion of the natural diet of these larger lobsters (Cox et al., 1997; Briones-Fourzán et al., 2003; Garm, 2004). Considerable effort is currently being directed toward the development of appropriate formulated feeds for spiny lobster aquaculture. However, early key requirements for designing an effective formulated feed are ensuring the format of the diet maximises food intake, and minimises wastage through leaching and fragmentation. Formulated diet format includes parameters such as size, shape, texture and hardness, which may also need to be altered to better meet developmental changes in a target aquaculture organism. Relatively little research to date has addressed this concern specifically in spiny lobsters. Sheppard et al. (2002) found that the intake of pellets of a formulated diet by juveniles of the lobster J. edwardsii could be increased as much as 19% with small changes in the size of pellets to match the feeding abilities of the lobsters. Furthermore, early juveniles (25–30 mm CL) had difficulty handling and feeding on experimental pellets which resulted in high levels of wastage (up to 50%) due to fragmentation of the formulated diet. Our observations of the feeding of P. argus from puerulus to adult indicated marked morphological and behavioural changes in the food handling and processing ability of the mouthparts. These changes must be considered in the development of a formulated diet because size, shape, texture and consistency of the diet need to reflect the physical characteristics and capabilities of different juvenile stages. This study indicates that food does not need to be provided to the non-feeding puerulus stage of P. argus. However, the feeding behaviour and mouthpart structure of early juveniles (10–15 mm CL) suggests that small (1–2 mm) and elongated food items that are soft and pulpy would be ideal. For the subsequent juveniles, late juveniles and adults, food items that are increasingly larger in size, while being firmer, and fleshier will assist in improving artificial diet intake. The co-ordinated development of teeth on the mandibles and spines/setae on the maxillipeds indicates that P. argus lobsters are able to deal successfully with more substantial food in the benthic environment (Factor, 1989). Juveniles and late juveniles (N15 mm CL) were observed to be capable of processing a wide variety of prey, indicating that the size of a formulated feed item may not be important. However, if small fragments were generated when larger food items were shredded by the mouthparts, these fragments were most frequently not captured and ingested by the lobster. For a formulated diet to be effective it will need to avoid this potential wastage by ensuring an appropriate combination of diet shape and consistency to reduce fragmentation. Observations of the behaviour of juveniles of a range of sizes in the lobster J. edwardsii feeding on prepared pellets indicated differences in the handling and processing of food items by the mouthparts when compared to our results from P. argus (Sheppard et al., 2002). These differences are likely to be due to dissimilarities in the ecology and diet of juveniles of these two species (Booth, 2006). This being the case, formulated diets developed to be effective in one species of spiny lobster may not be directly transferable to other species. Acknowledgements The authors wish to thank the staff at the Florida Fish and Wildlife Conservation Commission and the Keys Marine Laboratory, as well as Jerry Corsaut, Harbor Branch Oceanographic Institute at Florida Atlantic University (HBOI) for the collection of lobsters. Jackie Aronson (HBOI volunteer) and Erika McKay (NIWA) kindly prepared illustrations of the lobster mouthparts. The draft manuscript benefited from helpful comments from an anonymous referee. This work was funded by a HBOI Postdoctoral Fellowship. This is HBOI Contribution number 1705.
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References Alexander, C.G., Hindley, J.P.R., 1985. The mechanism of food ingestion by the banana prawn, Penaeus merguiensis. Mar. Behav. Physiol. 12, 33–46. Andrée, W.S., 1981. Locomotory activity patterns and food items of benthic postlarval spiny lobsters Panulirus argus. MSc thesis, Florida State University, Miami. Booth, J.D., 2006. Jasus species. In: Phillips, B. (Ed.), Lobsters; Biology, Management, Aquaculture and Fisheries. Blackwell Publishing, Oxford, pp. 340–358. Booth, J.D., Kittaka, J., 2000. Spiny lobster growout. In: Phillips, B.F., Kittaka, J. (Eds.), Spiny Lobsters: Fisheries and Culture. Fishing News Books, Oxford, pp. 556–585. Briones-Fourzán, P., Castañeda-Fernández de Lara, V., Lozano-Álvarez, E., Estrada-Olivo, J., 2003. Feeding ecology of the three juvenile phases of the spiny lobster Panulirus argus in a tropical reef lagoon. Mar. Biol. 142, 855–865. Butler, M.J., Steneck, R.S., Herrnkind, W.F., 2006. Juvenile and adult ecology. In: Phillips, B. (Ed.), Lobsters; Biology, Management, Aquaculture and Fisheries. Blackwell Publishing, Oxford, pp. 263–309. Cox, S.L., Johnston, D.J., 2003. Feeding biology of spiny lobster larvae and implications for culture. Rev. Fish. Sci. 11, 89–106. Cox, S.L., Johnston, D.J., 2004. Developmental changes in foregut functioning of packhorse lobster, Jasus (Sagmariasus) verreauxi (Decapoda: Palinuridae), phyllosoma larvae. Mar. Freshw. Res. 55, 145–153. Cox, C., Hunt, J.H., Lyons, W.G., Davis, G.E., 1997. Nocturnal foraging of the Caribbean spiny lobster (Panulirus argus) on offshore reefs of Florida, USA. Mar. Freshw. Res. 48, 671–679. Factor, J.R., 1978. Morphology of the mouthparts of larval lobster, Homarus americanus (Decapoda: Nephropidae), with special emphasis on their setae. Biol. Bull. 154, 383–408. Factor, J.R., 1989. Development of the feeding apparatus in decapod crustaceans. In: Felgenhauer, B.E., Watling, L. (Eds.), Functional Morphology of Feeding and Grooming of Selected Crustacea. AA Balkema, Rotterdam, pp. 185–203. Garm, A., 2004. Mechanical functions of setae from the mouth apparatus of seven species of decapod crustaceans. J. Morphol. 260, 85–100. Griffiths, C.L., Seiderer, J.L., 1980. Rock lobsters and mussels — limitations and preferences in a predator–prey interaction. J. Exp. Mar. Biol. Ecol. 44, 95–109. Herrera, A., Ibarzábal, D., Foyo, J., Expinosa, J., 1991. Alimentación natural de la langosta Panulirus argus en la region de Los Indios (plataforma SW de Cuba) y su relación con el bentos. Rev. Investig. Mar. 12, 172–182. James, P.J., Tong, L.J., 1998. Feeding technique, critical size and size preference of Jasus edwardsii fed cultured and wild mussels. Mar. Freshw. Res. 49, 151–156. Jeffs, A., Davis, M., 2003. An assessment of the aquaculture potential of the Caribbean spiny lobster, Panulirus argus. Proc. Gulf Caribb. Fish. Inst. 45, 413–426. Johnston, D.J., Alexander, C.G., 1999. Functional morphology of the mouthparts and alimentary tract of the slipper lobster Thenus orientalis (Decapoda: Scyllaridae). Mar. Freshw. Res. 50, 213–223. Lalana, R.R., Díaz, E., Brito, R., Kodjo, D., Cruz, R., 1987. Ecología de la langosta (Panulirus argus) al SE de la Isla de la Juventud. III. Estudio cualitativo y cuantitativo del bentos. Rev. Investig. Mar. 8, 31–43.
Lellis, W.A., 1991. Spiny lobster: a mariculture candidate for the Caribbean? World Aquac. 22, 60–63. Lewis, J.B., Moore, H.B., Babis, W., 1952. The post-larval stages of the spiny lobster Panulirus argus. Bull. Mar. Sci. 2, 324–337. Marx, J.M., Herrnkind, W.F., 1985. Macroalgae (Rhodophyta: Laurencia spp.) as habitat for young juvenile spiny lobsters, Panulirus argus. Bull. Mar. Sci. 36, 423–431. McConaugha, J., 2002. Alternative feeding mechanisms in megalopae of the blue crab Callinectes sapidus. Mar. Biol. 140, 1227–1233. Mikami, S., Takashima, F.,1994. Functional morphology of the digestive system. In: Phillips, B., Cobb, J.S., Kittaka, J. (Eds.), Spiny Lobster Management. Fishing News Books, Oxford, pp. 473–482. Nelson, M.M., Bruce, M.P., Nichols, P.D., Jeffs, A.G., Phleger, C.F., 2006. Nutrition of wild and cultured lobsters. In: Phillips, B. (Ed.), Lobsters; Biology, Management, Aquaculture and Fisheries. Blackwell Publishing, Oxford, pp. 205–230. Nishida, S., Quigley, B.D., Booth, J.D., Nemoto, T., Kittaka, J., 1990. Comparative morphology of the mouthparts and foregut of the final-stage phyllosoma, puerulus, and postpuerulus of the rock lobster Jasus edwardsii (Decapoda: Palinuridae). J. Crustac. Biol. 10, 293–305. Nizinski, M.S., 2007. Predation in subtropical soft-bottom systems: spiny lobster and molluscs in Florida Bay. Mar. Ecol., Prog. Ser. 345, 185–197. Paterson, N.F., 1968. The anatomy of the Cape rock lobster, Jasus lalandii (H. Milne Edwards). Ann. Sth. Afr. Mus. 51, 1–232. Phillips, B.F., Booth, J.D., Cobb, S.J., Jeffs, A.G., Mc William, P., 2006. Larval and postlarval ecology. In: Phillips, B. (Ed.), Lobsters; Biology, Management, Aquaculture and Fisheries. Blackwell Publishing, Oxford, pp. 231–262. Sheppard, J.K., Bruce, M.P., Jeffs, A.G., 2002. Optimal feed pellet size for culturing juvenile spiny lobster Jasus edwardsii (Hutton, 1875) in New Zealand. Aquac. Res. 33, 913–916. Suthers, I.M., Anderson, D.T., 1981. Functional morphology of mouthparts and gastric mill of Ibacus peronii (Leach) (Palinura: Scyllaridae). Aust. J. Mar. Freshw. Res. 32, 931–944. Williams, K.C., 2007. Nutritional requirements and feeds development for post-larval spiny lobster: a review. Aquaculture 263, 1–14. Williamson, D.I., 1982. Larval morphology and diversity. In: Abele, L.G. (Ed.), The Biology of Crustacea: Vol 2: Embryology, Morphology, and Genetics. Academic Press, New York, pp. 43–110. Witham, R., Ingle, R.M., Joyce, E.A., 1968. Physiological and ecological studies of Panulirus argus from the St. Lucie Estuary. Florida State Board of Conservation Technical Series No. 53. Florida State Board of Conservation, St Petersberg, Florida. Wolfe, S.H., Felgenhauer, B.E., 1991. Mouthpart and foregut ontogeny in larval, postlarval and juvenile spiny lobster, Panulirus argus Latrielle (Decapoda: Palinuridae). Zool. Scr. 20, 57–75.
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Aquaculture j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / a q u a - o n l i n e
Developmental changes in the mouthparts of juvenile Caribbean spiny lobster, Panulirus argus: Implications for aquaculture Serena L. Cox a,b,⁎, Andrew G. Jeffs c, Megan Davis a a b c
Aquaculture Division, Harbor Branch Oceanographic Institute at Florida Atlantic University, 5600 US 1 North, Fort Pierce, Florida 34946, USA National Institute of Water and Atmospheric Research, Private Bag 14901, Kilbirnie, Wellington 6241, New Zealand Leigh Marine Laboratory, University of Auckland, P.O. Box 349, Warkworth 0941, New Zealand
a r t i c l e
i n f o
Article history: Received 5 May 2008 Received in revised form 14 July 2008 Accepted 14 July 2008 Keywords: Mouthparts Spiny lobster Panulirus argus Feeding Puerulus Juvenile
a b s t r a c t Light microscopy and video analysis were used to examine the mouthpart morphology and feeding behaviour of the Caribbean spiny lobster from puerulus (megalopal stage) (5–8 mm carapace length, CL) to adult (85 mm CL). Upon settlement the pueruli did not possess fully functional mouthparts, however, efficient feeding appendages appeared in the first instar juvenile (after the first moult from puerulus). From this stage the density, robustness and complexity of setation on the mouthparts, together with the size and calcification of the mouthparts increased progressively with the size of the lobster. The changes correlated well with previously observed ontogenetic changes in natural prey, from small and soft prey in early juveniles to large and well-armoured molluscs, crustaceans and echinoderms in late juveniles and adults. The efficiency of shredding and tearing food items, mostly with the second maxillipeds, increased concomitantly with lobster size, as did the ability of the mandibles to grind and process food. Based on morphological and behavioural observations it is recommended that formulated feeds for first instar juvenile lobsters should be small (1–2 mm in diameter), soft and pulpy in texture to maximise feed intake. For large juvenile lobsters (45–80 mm CL), food items should increase to 5–10 mm in diameter and be of firmer consistency. Differences in feeding behaviour between spiny lobster species suggest that formulated diets developed to be efficient in one species may not be directly transferable to other species. © 2008 Elsevier B.V. All rights reserved.
1. Introduction The Caribbean spiny lobster, Panulirus argus, is an excellent candidate for commercial aquaculture because of rapid growth and straightforward husbandry (Lellis, 1991; Booth and Kittaka, 2000; Jeffs and Davis, 2003). However, the development of a formulated feed for this spiny lobster species remains a significant impediment to its commercial aquaculture despite some initial research (Jeffs and Davis, 2003; Williams, 2007). There is an underlying lack of knowledge of the feeding capabilities and behaviour of spiny lobsters, including for the Caribbean lobster. Recent reviews of the nutrition of spiny lobsters in culture concluded that understanding the feeding capabilities and the corresponding format of formulated feeds are critical for advancing the development of formulated feeds for spiny lobster aquaculture, by maximising intake and reducing feed wastage (Nelson et al., 2006; Williams, 2007). For example, up to 50% of formulated feed pellets fed to juveniles of the spiny lobster, Jasus edwardsii, were wasted through
⁎ Corresponding author. National Institute of Water and Atmospheric Research, Private Bag 14901, Kilbirnie, Wellington 6241, New Zealand. Tel.: +64 4 386 0300; fax: +64 4 386 2153. E-mail address: [email protected] (S.L. Cox). 0044-8486/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2008.07.019
inefficient handling by lobsters, and simple changes in pellet dimensions were found to reduce waste by as much as 19% (Sheppard et al., 2002). Investigations of species-specific feeding behaviour and functional morphology, as well as digestive capabilities, over a range of lifehistory stages is an effective means of identifying ontogenetic changes in dietary capabilities (Cox and Johnston, 2004). This approach has been used successfully in a wide range of crustaceans and in many instances leading to advances in the design and method of delivery of formulated feeds for aquaculture. This approach has already been used with considerable success for larval spiny lobsters (Cox and Johnston, 2003), as well as slipper lobsters (Suthers and Anderson, 1981; Johnston and Alexander, 1999), blue crabs (McConaugha, 2002), and shrimp (Alexander and Hindley, 1985). While the feeding morphology and behaviour of adult spiny lobsters has been described (Mikami and Takashima, 1994), it is not well known in the puerulus (megalopal stage which is often incorrectly called the “postlarva” — Williamson, 1982) and the subsequent juvenile, which frequently undergo marked ontogenetic changes in habitat and diet (Butler et al., 2006). For example, the puerulus of the Caribbean lobster settles and remains within dense inshore macroalgal beds. Once it has molted to the first instar juvenile it begins to feed, mostly on small resident crustaceans and molluscs, before emerging at N15 mm carapace length (CL) to seek
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shelter in nearby crevices and begin feeding locally on larger prey (Andrée, 1981; Marx and Herrnkind, 1985; Lalana et al., 1987). Larger juveniles then move offshore, particularly around reefs, and are more mobile, ranging across an array of habitats in search of a much wider variety of prey (Cox et al., 1997; Briones-Fourzán et al., 2003). Therefore, the aim of this research was to describe the morphology and functioning of the mouthparts in the Caribbean spiny lobster from puerulus to young adult to determine the changes in feeding capabilities that could lead to improvements in the design of formulated feeds for aquaculture. 2. Methods and materials 2.1. Animal collection and husbandry Approximately 100 newly settled P. argus pueruli were collected from 10 Witham collectors (Witham et al., 1968) moored in surface waters in the Florida Keys, following the new moon in March and April 2005. Newly settled pueruli were sorted from more advanced developmental stages on the basis of well-established staging criteria (Lewis et al., 1952). The pueruli were transported in seawater to the Harbor Branch Oceanographic Institute at Florida Atlantic University in Fort Pierce, Florida, and placed into holding tanks which included a selection of natural macroalgal (Caulerpa sp.) and artificial refuges. The lobsters were fed frozen brine shrimp, Artemia salina and wild food items (i.e., worms, amphipods, and other various small crustaceans, as well as frozen natural seafood items). Lobsters were held at 14:10 light–dark cycle, at 28 ± 1 °C and salinity maintained at 30 ± 2‰. Ten transparent pueruli (b5 days after settling) were used for mouthpart analysis immediately upon arrival at the laboratory, and remaining individuals were on-grown in the tanks until they subsequently reached the required developmental stage of early juveniles (10–15 mm CL), juvenile (15–44 mm CL), late juvenile–adult (45–80 mm CL) for video analysis of feeding behaviour and mouthpart morphology. 2.2. Mouthpart morphology and video analysis For each size range of lobsters, five individuals were tethered with cyanoacrylic adhesive to fine wire (0.25 mm diameter), at the midsection of the dorsal surface of the cephalothorax and then placed into a glass evaporating dish containing fresh seawater. Experimental temperature was maintained at 28 ± 1 °C and light levels were kept constant at 2 lx. Feeding responses and mouthpart movements were induced by placing frozen A. salina or fresh clam tissue (Mercenaria mercinaria) within the oral field of the tethered lobster. The mouthpart movements and function during food capture, manipulation and mastication were observed using an inverted Meiji EM28TR compound microscope (Martin Microscope Company, USA) with fibre optic illumination and Sony Digital Handycam, which recorded directly onto DVD for later analysis. After recording was completed, the five individual lobsters were euthanized by rapid cooling in an ice slurry and the mouthparts dissected out, photographed and then drawn. In the following descriptions, the terminology of Paterson (1968) and Nishida et al. (1990) is used for the mouthparts and that of Factor (1978) is used to describe the setae. 3. Results 3.1. Puerulus (b9 mm CL) The mandibles, maxillae and maxillipeds of the puerulus were small in size, lacked calcification, and had only a limited number of setae. Microscopic examination of the mouthparts and the gut confirmed that the puerulus stage is non-feeding by the inadequacy of the mouthparts and the absence of any food in the gut.
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The oesophagus was not fully formed and the opening into the oesophagus appeared to be covered by a fleshy membrane. The overlying mandibles and maxillae were fleshy, soft structures which did not move, even when physically stimulated. The mandibles were asymmetrical and simplified, with an unsegmented, laterally attached mandibular palp which was partially covered posteriorly by the paragnaths (Fig. 1A). The left mandible incisor process consisted of an undeveloped single, blunt tooth. The first maxillae were flattened, with a spinose exopod and epipod, and a rudimentary endopod, together forming three flat lobes (Fig. 1B). The second maxilla gave rise to an elongated scaphognathite-like epipod, divided into proximal and distal endites, and a smaller lobe-like endopod (Fig. 1C). A fringe of setae was present along the distal edges of the exopod and a small tuft of simple spinose setae on the proximal endite. The distal and proximal endites are much reduced in the first maxilliped, with the endopod fused to the elongated exopod (Fig. 1D). A distal flagellum was present on the anterior tip of the exopod. The epipod resembled a flattened and membranous plate. Setae were present along the distal margins of both the exopod and endopod. The second and third maxillipeds were more elongated compared with the maxilla or first maxilliped (Fig. 1E and F). The endopods consisted of five segments each. The exopod on the second maxilliped was elongated with four segments, whereas the exopod on the third maxilliped was much reduced and only had two segments. Setae were present along the inner margin of the endopod dactyl and carpus of the third maxilliped. Among the five individuals examined for feeding behaviour, there was consistency in their mouthpart morphology and movement, including the absence of any feeding behaviour. Close observations of untethered pueruli in the tanks indicated that the lack of feeding behaviour was not a response to the experimental tethering treatment. 3.2. Early juvenile (10–15 mm CL) The relative position of the six pairs of mouthparts (mandibles, maxillae I and II, and maxillipeds I, II and III) as well as the labrum, paired paragnaths, and the posterioventral fleshy lobe (membranous lobe), remained constant between the puerulus and all subsequent juvenile stages, including early juveniles. The main changes between the puerulus and first instar juveniles were the development of additional setae and spines, increased mouthpart robustness (i.e., calcification), an immediate transition to fully functional mouthparts, and almost doubling in the overall dimensions of the mouthparts. In the first instar juvenile, the mandibular palps had developed simple setae on the proximal tips and had become segmented. The incisor process had also become more defined, bearing a more prominent groove in the molar process. The epipod, endopod and exopod of the first maxilla all bear setae and spines (Fig. 2A). The distal and proximal endites of the epipod of the second maxilla both bear setae. The exopod and the endopod have a fringe of setae along the lateral edges. The first maxilliped is similar in structure to the puerulus, however, the distal flagellum is elongated and the interior edge of the endopod is flatter and broader. The major difference between the second and third maxilliped in the early juveniles is the development of setation along the inner margin of the dactyl, propodus, merus and basis (Fig. 2B and C). Segmentation develops between the basis and coxa of the third maxilliped (Fig. 2C). The exopod is elongated and the distal segment also bears setae. Among the five individuals examined, there was consistency in their mouthpart morphology with mouthparts increasing in proportion to changes in body size. The mouth aperture was approximately 300 μm diameter, however, soft, fleshy food particles ranging from 1–2 mm and whole juvenile A. salina (up to 2 mm total length) were observed being pushed between the mandibles by the maxillae. Early juvenile lobsters were capable of efficiently shredding fleshy clam tissue and adult A. salina into small (1–3 mm) pieces.
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Fig. 1. Mouthparts of P. argus puerulus. (A) Mandibles. Scale 500 μm. (B) First maxilla. Scale 500 μm. (C) Second maxilla. Scale 1 mm (D) First maxilliped. Scale 500 μm. (E) Second maxilliped. Scale 500 μm. (F) Third maxilliped. Scale 1 mm. b, basis; c, carpus; co, coxa; d, dactyl; de, distal endite; en, endite; ep, epipod; ex, exopod; i, ishium; ip, incisor process; m, merus; mdp, mandibular palp; mp, molar process; p, propodus; pa, paragnaths; pe, proximal endite; pr, protopod; sc, scaphognathite.
3.3. Juvenile (15–44 mm CL) The mandibles and paragnaths showed little developmental change compared with the early juvenile stage, however, the anterior surfaces of the mandibles and the palps had developed pigmentation. The incisor process has become more pointed and the molar process had low tubercles located along the internal edge. The first and second maxilla were almost identical to those observed in early juveniles, although there was increased setation around the anterior margins of the exopods and epipods, including both the distal and proximal endites. The first maxilliped of juveniles was also similar to the early juveniles, however, there was increased setation on the interior
margin of the endopod, and on the distal tip of the exopod. The only major differences between the second and third maxilliped in the early juveniles and the subsequent juveniles were the development of pigmentation and slightly increased setation along the margins of the five segments of the endopod. Among the five juveniles examined there was a proportional increase in mouthpart size in relation to body size, and general increase in setation and robustness of mouthparts. Juvenile lobsters were capable of shredding fleshy prey items into small pieces (approximately 2–3 mm) prior to ingestion. Whole adult A. salina (up to approximately 5 mm) were observed being ingested, indicating the maxillae and mandibles are able to shred and process the tough external carapace of these crustacean prey.
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Fig. 2. P. argus early juvenile mouthparts. (A) First maxilla. (B) Second maxilliped (C) Third maxilliped. All scale bars 1 mm. am, attachment muscle; b, basis; c, carpus; co, coxa; d, dactyl; en, endite; ep, epipod; ex, exopod; i, ishium; m, merus; p, propodus; pr, protopod.
3.4. Late juvenile–adult (45–80 mm CL) The asymmetrical mandibles in the late juveniles were more calcified, with tubercles along the interior edge of the molar process and a notably more defined incisor process on the opposing left mandible (Fig. 3A). A deep notch separated this incisor process from the molar process. The mandibles were capable of easily crushing the tough chitinous exoskeletons of large adult A. salina and various similar-sized crustaceans (5–9 mm), once the maxillae and maxillipeds had shredded them into smaller pieces. The mandibular palp had developed from two into three segments, with coarse setae covering the distal segment. Although larger, the first maxilla is similar in structure and degree of setation to the same structures in the earlier developmental stages. The scaphognathite of the second maxillae was larger in the late juveniles, but essentially the same shape. The endopod was enlarged and setose along the anterior and lateral edges (Fig. 3B). The distal and proximal endites had coarser setae along the entire length. The first maxilliped of the late juvenile is larger than in the juvenile, but the general shape and structure remains similar. The exopods in both the second and third maxillipeds were elongated and both had simple and plumose setae (Factor, 1978) (Fig. 3C and D). The five segments of the endopods were considerably
larger, more robust and pigmented, compared with earlier developmental stages. The five individuals examined were capable of efficiently shredding and tearing large pieces of clam tissue (up to 10 mm), whole adult A. salina (up to 6–7 mm), and various other prey items (i.e., worms, crustaceans) into smaller pieces (3–5 mm) prior to ingestion. 3.5. Feeding behaviour Detailed examination of the video recordings revealed that all juvenile lobster stages, except the puerulus, exhibited similar feeding behaviour and consistently utilised the paired mouthparts in a similar manner for manipulating food. Food items were speared in a grabbing motion using the terminal dactyls of pereiopods 1 and 2, and passed toward maxilliped 3. The third maxillipeds typically grasped food items and manipulated the food inwards, towards the anterior second maxillipeds. When not holding food items, the third maxillipeds swept back and forth across the surface of the mouth region, over an arc of approximately 90°, articulating at the segment between the basis and coxa. Pereiopods 1, 2 and 3 were also observed sweeping in this arc, in synchrony with the third maxillipeds. The exopod either moved dependently with the endopod, or it was observed beating
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Fig. 3. P. argus late juvenile mouthparts. (A) Mandibles (B) Second maxilla (C) Second maxilliped (D) Third maxilliped. All scale bars 1 mm. b, basis; c, carpus; co, coxa; d, dactyl; de, distal endite; i, ishium; ip, incisor process; m, merus; mdp, mandibular palp; p, propodus; pa, paragnaths; pe, proximal endite; pr, protopod; sc, scaphognathite.
sporadically with inconsistent frequency when the lobster was feeding. The third maxillipeds also played an important grooming role, removing debris from the oral region by sweeping the surface of the mandibles, maxillae, and first and second maxillipeds. The exopods of the second maxillipeds were very active during feeding, beating continuously which appeared to facilitate the movement of food particles toward the mouth. The endopod of the second maxillipeds received food items from the pereiopods or maxilliped 3, and when food items were within close proximity to the mouth these endopods were observed moving frequently, sweeping back and forth across the surface of the mandibles and first maxillipeds. The endopods were also observed being held together in a medial position, preventing food items from being lost anterioventrally whilst the food was being manipulated by the first maxillipeds. The second maxillipeds also adjusted the location of the food between the mandibles, assisting in the shredding and maceration of larger food items. In addition, the endopods of the second maxillipeds were in close contact with the mandibular palps. The first maxillipeds played a similar role to the second and third by assisting in guiding food items between the mandibles with lateromedial movements. The first maxillipeds also prevented food particles being lost anterioventrally. The second and first maxillae were not visible on the video as they were obscured by the maxillipeds. The second maxillae were restricted to movements in the lateromedial plane between the first maxillae and first maxillipeds, but allowing the scaphognathite to move dorsoventrally and possibly associated with flushing the gill
chamber with seawater. The dense setae which line the edge of the second maxillae would, together with the two endites pointing into the mouth, appear to help guide food between the mandibles. However, the setose nature of these mouthparts makes them well suited for filtration or helping to handle small food items such as crumbly invertebrate gonadal tissue. The first maxillae were ventral to the mandibles, but obscured by the second maxillae and the maxillipeds. However, the second maxillae bear setae as well as prominent, robust spines along the medial edge of the exopods, endopods and epipods. These spines appeared to assist in probing for food, holding the food items between the mandibles during each bite, and were also possibly used for pushing unwanted food particles anteriorly where they could be expelled. The mandibles operated along a lateral plane, using the pointed incisor process of the left mandible to shear against the calcified, tubercled surface of the right mandible. The cutting and crushing action of the mandibles effectively processed pieces of food into smaller, masticated pieces that were soft enough to be pushed into the mouth by the maxillae. The mandibular palps were located distally on each mandible, and were only observed making small movements, independent of the mandibles. The setae on the distal segment of the palps made contact with the food during feeding, however, they did not appear to manipulate the food items. It is possible they function as a barrier, preventing food from escaping anteriorly. In addition, the setae on the palps may also have a chemosensory role, assessing food palatability prior to ingestion. The paragnaths or labrum were not observed to move during feeding. It
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appears food particles were pushed into the oesophagus by the maxillae, after shredding, softening and crushing by the mandibles. It is possible peristaltic foregut contractions assist in movement of food into the oesophagus and through into the gut. Late juvenile lobsters were capable of handling and ingesting larger prey items than the juvenile or early juvenile lobsters. The mouthparts efficiently shredded prey into 5 mm diameter (on average) pieces in late juveniles, whereas juvenile lobsters tended to tear and shred food into smaller (average 3 mm diameter) pieces, and smaller again in early juvenile lobsters (1–2 mm pieces). The ability to handle and ingest larger prey items was reflected in the processing ability of the mouthparts, due to increasing setation, robustness and calcification, as well as the increasing dimensions of the mouthparts observed over the sequential stages of juvenile lobster development. All stages of juvenile lobsters examined were untidy eaters, with a significant portion of shredded food material being lost laterally, especially where the food material was crumbly, such as with ripe gondal material from clams. Larger prey items also tended to tangle in the pereiopods and third maxillipeds, particularly in the late juvenile– adult stage. 4. Discussion The puerulus stage of all spiny lobster species is widely considered to be a non-feeding, transitional stage between pelagic and benthic lifestyles (Nishida et al., 1990; Phillips et al., 2006). The incomplete development of the mouthparts, a fleshy obstruction at the entrance to the oesophagus, the absence of food in the gut, and the absence of any feeding behaviour confirms earlier speculation that the puerulus of P. argus is also non-feeding (Wolfe and Felgenhauer, 1991). In the subsequent first instar juvenile, the feeding appendages show significant development, almost doubling in size and setation from the puerulus. The mouth was only 300 μm in diameter, but larger soft, fleshy food particles of up to 2 mm in diameter were handled and consumed. This is entirely consistent with the size and texture of the majority of the prey items found in the stomachs of juvenile lobsters in the wild (Marx and Herrnkind, 1985) and in agreement with observations of the mouthparts from other juvenile Palinurids (Nishida et al., 1990). Beds of the macroalgae, Laurencia spp., into which the lobster pueruli settle and subsequently dwell as early juveniles, contain very large numbers of small invertebrates (mostly less than 5 mm long) such as isopods, amphipods, polychaetes, gastropods, copepods, ostracods and ophiuroids (Marx and Herrnkind, 1985). These small crustaceans, worms, molluscs and echinoderms can be readily consumed by early juvenile lobsters because this small prey can be easily handled and the relatively unprotected soft bodies pulled apart in the lobster mouthparts in the same manner as A. salina were in our experimental observations. In contrast, juvenile lobsters (15–44 mm CL) no longer remain within the macroalgal beds, but occupy crevice shelters in shallow water habitats and forage in the immediate vicinity. The diet of these juvenile lobsters mostly consists of gastropods, bivalves, chitons, arthropods and echinoderms (Andrée, 1981; Herrera et al., 1991; Cox et al., 1997; Briones-Fourzán et al., 2003; Nizinski, 2007). These prey items are mostly well protected with hardened calcareous exoskeletons. The ability of juvenile lobsters to overcome the exterior defences of these prey is facilitated by a marked increase in the size, strength, complexity and hardening of the mouthparts. The increasing ability of progressively larger juvenile lobsters to feed effectively on well-armoured molluscan, arthropod and echinoderm prey has been observed in other species of spiny lobsters (Griffiths and Seiderer, 1980; James and Tong, 1998). The overall trend in the development of the mouthparts is continued with late juvenile to adult lobsters (45–80 mm CL) which forage across a wide range of habitats in more exposed waters closer to the outer reef margins. The mouthparts of these lobsters, as well as larger adults
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(Garm, 2004), are well suited to the handling and opening of large prey with strong shells, such as top-shells (Trochidae) and moon snails (Polinices spp.) which can make up a significant proportion of the natural diet of these larger lobsters (Cox et al., 1997; Briones-Fourzán et al., 2003; Garm, 2004). Considerable effort is currently being directed toward the development of appropriate formulated feeds for spiny lobster aquaculture. However, early key requirements for designing an effective formulated feed are ensuring the format of the diet maximises food intake, and minimises wastage through leaching and fragmentation. Formulated diet format includes parameters such as size, shape, texture and hardness, which may also need to be altered to better meet developmental changes in a target aquaculture organism. Relatively little research to date has addressed this concern specifically in spiny lobsters. Sheppard et al. (2002) found that the intake of pellets of a formulated diet by juveniles of the lobster J. edwardsii could be increased as much as 19% with small changes in the size of pellets to match the feeding abilities of the lobsters. Furthermore, early juveniles (25–30 mm CL) had difficulty handling and feeding on experimental pellets which resulted in high levels of wastage (up to 50%) due to fragmentation of the formulated diet. Our observations of the feeding of P. argus from puerulus to adult indicated marked morphological and behavioural changes in the food handling and processing ability of the mouthparts. These changes must be considered in the development of a formulated diet because size, shape, texture and consistency of the diet need to reflect the physical characteristics and capabilities of different juvenile stages. This study indicates that food does not need to be provided to the non-feeding puerulus stage of P. argus. However, the feeding behaviour and mouthpart structure of early juveniles (10–15 mm CL) suggests that small (1–2 mm) and elongated food items that are soft and pulpy would be ideal. For the subsequent juveniles, late juveniles and adults, food items that are increasingly larger in size, while being firmer, and fleshier will assist in improving artificial diet intake. The co-ordinated development of teeth on the mandibles and spines/setae on the maxillipeds indicates that P. argus lobsters are able to deal successfully with more substantial food in the benthic environment (Factor, 1989). Juveniles and late juveniles (N15 mm CL) were observed to be capable of processing a wide variety of prey, indicating that the size of a formulated feed item may not be important. However, if small fragments were generated when larger food items were shredded by the mouthparts, these fragments were most frequently not captured and ingested by the lobster. For a formulated diet to be effective it will need to avoid this potential wastage by ensuring an appropriate combination of diet shape and consistency to reduce fragmentation. Observations of the behaviour of juveniles of a range of sizes in the lobster J. edwardsii feeding on prepared pellets indicated differences in the handling and processing of food items by the mouthparts when compared to our results from P. argus (Sheppard et al., 2002). These differences are likely to be due to dissimilarities in the ecology and diet of juveniles of these two species (Booth, 2006). This being the case, formulated diets developed to be effective in one species of spiny lobster may not be directly transferable to other species. Acknowledgements The authors wish to thank the staff at the Florida Fish and Wildlife Conservation Commission and the Keys Marine Laboratory, as well as Jerry Corsaut, Harbor Branch Oceanographic Institute at Florida Atlantic University (HBOI) for the collection of lobsters. Jackie Aronson (HBOI volunteer) and Erika McKay (NIWA) kindly prepared illustrations of the lobster mouthparts. The draft manuscript benefited from helpful comments from an anonymous referee. This work was funded by a HBOI Postdoctoral Fellowship. This is HBOI Contribution number 1705.
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References Alexander, C.G., Hindley, J.P.R., 1985. The mechanism of food ingestion by the banana prawn, Penaeus merguiensis. Mar. Behav. Physiol. 12, 33–46. Andrée, W.S., 1981. Locomotory activity patterns and food items of benthic postlarval spiny lobsters Panulirus argus. MSc thesis, Florida State University, Miami. Booth, J.D., 2006. Jasus species. In: Phillips, B. (Ed.), Lobsters; Biology, Management, Aquaculture and Fisheries. Blackwell Publishing, Oxford, pp. 340–358. Booth, J.D., Kittaka, J., 2000. Spiny lobster growout. In: Phillips, B.F., Kittaka, J. (Eds.), Spiny Lobsters: Fisheries and Culture. Fishing News Books, Oxford, pp. 556–585. Briones-Fourzán, P., Castañeda-Fernández de Lara, V., Lozano-Álvarez, E., Estrada-Olivo, J., 2003. Feeding ecology of the three juvenile phases of the spiny lobster Panulirus argus in a tropical reef lagoon. Mar. Biol. 142, 855–865. Butler, M.J., Steneck, R.S., Herrnkind, W.F., 2006. Juvenile and adult ecology. In: Phillips, B. (Ed.), Lobsters; Biology, Management, Aquaculture and Fisheries. Blackwell Publishing, Oxford, pp. 263–309. Cox, S.L., Johnston, D.J., 2003. Feeding biology of spiny lobster larvae and implications for culture. Rev. Fish. Sci. 11, 89–106. Cox, S.L., Johnston, D.J., 2004. Developmental changes in foregut functioning of packhorse lobster, Jasus (Sagmariasus) verreauxi (Decapoda: Palinuridae), phyllosoma larvae. Mar. Freshw. Res. 55, 145–153. Cox, C., Hunt, J.H., Lyons, W.G., Davis, G.E., 1997. Nocturnal foraging of the Caribbean spiny lobster (Panulirus argus) on offshore reefs of Florida, USA. Mar. Freshw. Res. 48, 671–679. Factor, J.R., 1978. Morphology of the mouthparts of larval lobster, Homarus americanus (Decapoda: Nephropidae), with special emphasis on their setae. Biol. Bull. 154, 383–408. Factor, J.R., 1989. Development of the feeding apparatus in decapod crustaceans. In: Felgenhauer, B.E., Watling, L. (Eds.), Functional Morphology of Feeding and Grooming of Selected Crustacea. AA Balkema, Rotterdam, pp. 185–203. Garm, A., 2004. Mechanical functions of setae from the mouth apparatus of seven species of decapod crustaceans. J. Morphol. 260, 85–100. Griffiths, C.L., Seiderer, J.L., 1980. Rock lobsters and mussels — limitations and preferences in a predator–prey interaction. J. Exp. Mar. Biol. Ecol. 44, 95–109. Herrera, A., Ibarzábal, D., Foyo, J., Expinosa, J., 1991. Alimentación natural de la langosta Panulirus argus en la region de Los Indios (plataforma SW de Cuba) y su relación con el bentos. Rev. Investig. Mar. 12, 172–182. James, P.J., Tong, L.J., 1998. Feeding technique, critical size and size preference of Jasus edwardsii fed cultured and wild mussels. Mar. Freshw. Res. 49, 151–156. Jeffs, A., Davis, M., 2003. An assessment of the aquaculture potential of the Caribbean spiny lobster, Panulirus argus. Proc. Gulf Caribb. Fish. Inst. 45, 413–426. Johnston, D.J., Alexander, C.G., 1999. Functional morphology of the mouthparts and alimentary tract of the slipper lobster Thenus orientalis (Decapoda: Scyllaridae). Mar. Freshw. Res. 50, 213–223. Lalana, R.R., Díaz, E., Brito, R., Kodjo, D., Cruz, R., 1987. Ecología de la langosta (Panulirus argus) al SE de la Isla de la Juventud. III. Estudio cualitativo y cuantitativo del bentos. Rev. Investig. Mar. 8, 31–43.
Lellis, W.A., 1991. Spiny lobster: a mariculture candidate for the Caribbean? World Aquac. 22, 60–63. Lewis, J.B., Moore, H.B., Babis, W., 1952. The post-larval stages of the spiny lobster Panulirus argus. Bull. Mar. Sci. 2, 324–337. Marx, J.M., Herrnkind, W.F., 1985. Macroalgae (Rhodophyta: Laurencia spp.) as habitat for young juvenile spiny lobsters, Panulirus argus. Bull. Mar. Sci. 36, 423–431. McConaugha, J., 2002. Alternative feeding mechanisms in megalopae of the blue crab Callinectes sapidus. Mar. Biol. 140, 1227–1233. Mikami, S., Takashima, F.,1994. Functional morphology of the digestive system. In: Phillips, B., Cobb, J.S., Kittaka, J. (Eds.), Spiny Lobster Management. Fishing News Books, Oxford, pp. 473–482. Nelson, M.M., Bruce, M.P., Nichols, P.D., Jeffs, A.G., Phleger, C.F., 2006. Nutrition of wild and cultured lobsters. In: Phillips, B. (Ed.), Lobsters; Biology, Management, Aquaculture and Fisheries. Blackwell Publishing, Oxford, pp. 205–230. Nishida, S., Quigley, B.D., Booth, J.D., Nemoto, T., Kittaka, J., 1990. Comparative morphology of the mouthparts and foregut of the final-stage phyllosoma, puerulus, and postpuerulus of the rock lobster Jasus edwardsii (Decapoda: Palinuridae). J. Crustac. Biol. 10, 293–305. Nizinski, M.S., 2007. Predation in subtropical soft-bottom systems: spiny lobster and molluscs in Florida Bay. Mar. Ecol., Prog. Ser. 345, 185–197. Paterson, N.F., 1968. The anatomy of the Cape rock lobster, Jasus lalandii (H. Milne Edwards). Ann. Sth. Afr. Mus. 51, 1–232. Phillips, B.F., Booth, J.D., Cobb, S.J., Jeffs, A.G., Mc William, P., 2006. Larval and postlarval ecology. In: Phillips, B. (Ed.), Lobsters; Biology, Management, Aquaculture and Fisheries. Blackwell Publishing, Oxford, pp. 231–262. Sheppard, J.K., Bruce, M.P., Jeffs, A.G., 2002. Optimal feed pellet size for culturing juvenile spiny lobster Jasus edwardsii (Hutton, 1875) in New Zealand. Aquac. Res. 33, 913–916. Suthers, I.M., Anderson, D.T., 1981. Functional morphology of mouthparts and gastric mill of Ibacus peronii (Leach) (Palinura: Scyllaridae). Aust. J. Mar. Freshw. Res. 32, 931–944. Williams, K.C., 2007. Nutritional requirements and feeds development for post-larval spiny lobster: a review. Aquaculture 263, 1–14. Williamson, D.I., 1982. Larval morphology and diversity. In: Abele, L.G. (Ed.), The Biology of Crustacea: Vol 2: Embryology, Morphology, and Genetics. Academic Press, New York, pp. 43–110. Witham, R., Ingle, R.M., Joyce, E.A., 1968. Physiological and ecological studies of Panulirus argus from the St. Lucie Estuary. Florida State Board of Conservation Technical Series No. 53. Florida State Board of Conservation, St Petersberg, Florida. Wolfe, S.H., Felgenhauer, B.E., 1991. Mouthpart and foregut ontogeny in larval, postlarval and juvenile spiny lobster, Panulirus argus Latrielle (Decapoda: Palinuridae). Zool. Scr. 20, 57–75.