Subaerial hunting behaviour in Natica Gualteriana (naticid gastropod)

Palaeogeography, Palaeoclimatology, Palaeoecology, 74 (1989): 355-364

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Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

SUBAERIAL HUNTING BEHAVIOUR IN NATICA GUALTERIANA (NATICID GASTROPOD) E N R I C O S A V A Z Z I a n d R I C H A R D A. R E Y M E N T Paleontologiska Institutionen, Box 558, S-75122 Uppsala (Sweden)

(Received November, 14 1988; revised and accepted June 7, 1989)

Abstract Savazzi, E. and Reyment, R. A., 1989. Subaerial hunting behaviour in Natica gualteriana (naticid gastropod). Palaeogeogr., Palaeoclimatol., Palaeoecol., 74:355 364. Natica gualteriana, as observed on intertidal sand bars in Bantayan Island, Philippines, emerges from the sand at low tide when the bottom is exposed to the air, and hunts epifaunally for the trochacean gastropod Umbonium vestiarium. N. gualteriana captures U. vestiarium with a quick extension of the foot, triggered by direct contact with the prey. The shell aperture of the prey is subsequently plugged with a small amount of mucus, that forces U. vestiarium to remain retracted inside its shell (chemically benumbed?), but neither kills nor permanently affects it. Drilling of the prey takes place infaunally, after burrowing. This seems to be the first record of subaerial hunting in naticid gastropods.

Introduction D r i l l i n g g a s t r o p o d s h a v e c o n s i d e r a b l e int e r e s t for t h e p a l a e o e c o l o g i s t , n o t t h e l e a s t b e c a u s e of t h e i r v a l u e for r e c o n s t r u c t i n g p a s t e n v i r o n m e n t s . T h e first r e a l l y f u n d a m e n t a l studies on t h e b e h a v i o u r of drills a r e t h o s e of F i s c h e r - P i e t t e (1935) a n d C a r r i k e r (1955) for m u r i c i d s a n d Z i e g e l m e i e r (1954) for naticids. All t h r e e m o n o g r a p h s h a v e in c o m m o n t h a t t h e y a r e t h e p r o d u c t s of careful, well docum e n t e d studies in t h e field a n d l a b o r a t o r y . In g e n e r a l , one m a y j u s t l y c l a i m t h a t t h e m a i n facts of t h e b e h a v i o u r of drilling g a s t r o p o d s w e r e e s t a b l i s h e d in t h e s e works, n o t w i t h s t a n d ing l a t e r i m p o r t a n t c o n t r i b u t i o n s by A n s e l l (1960), C a r r i k e r (1961, 1981) a n d K i t c h e l l et al. (1981), for e x a m p l e . Briefly, m u r i c i d s a r e u s u a l l y a c c e p t e d to p r e y e p i f a u n a l l y on a n i m a l s living on t h e s u r f a c e of t h e sediment; t h e y will also feed on c a r r i o n . N a t i c i d s a r e g e n e r a l l y t a k e n to a t t a c k 0031-0182/89/$03.50

e n d o f a u n a l a n d e p i f a u n a l i n h a b i t a n t s , b u t to a l w a y s drill w i t h i n t h e s e d i m e n t (Ziegelmeier, 1954; C a r r i k e r , 1981). G i v e n t h a t m u r i c i d s f o r a g e on the s u r f a c e of the sediment, a n d a r e p o t e n t p r e d a t o r s of m u s s e l s a n d b a r n a c l e s , it is n o t s u r p r i s i n g t h a t t h e y c a n be f o u n d feeding i n t e r t i d a l l y , alt h o u g h t h e p r e f e r r e d e n v i r o n m e n t is d o u b t l e s s s u b a q u e o u s . Naticids, on t h e o t h e r h a n d , h a v e a l w a y s b e e n r e p o r t e d to f u n c t i o n in m o d e r a t e l y s h a l l o w to m o d e r a t e l y deep w a t e r (with occasional finds of drilled shells in a b y s s a l waters). I f t h e d e p t h r e q u i r e m e n t s of m u r i c i d s seem to be a d e q u a t e l y u n d e r s t o o d , t h o s e for n a t i c i d s are not. I t a p p e a r s t h a t t h e d e p t h - f a c t o r for t h a t g r o u p is b o u n d to t h e species involved. Z i e g e l m e i e r (1954) w a s c o n c e r n e d w i t h L u n a t i a n i t i d a in t h e N o r t h Sea, w h e r e a m i n i m u m d e p t h of 36 m s e e m s to apply. H e had, h o w e v e r , no difficulty in g e t t i n g n a t i c i d s to f o r a g e a n d drill i n f a u n a l l y in a simple a q u a r i u m . G u e r r e r o a n d R e y m e n t (1988) f o u n d T e c t o n a t i c a filosa

© 1989 Elsevier Science Publishers B.V.

356 (Philippi) at depths of only 5 10 m at Fuengirola, Spain. It was also found that this species displays a programme of attack and drilling that is at variance with the paradigm, in its being extrasedimentary (though still underwater). It came, therefore, not entirely as a shock to learn t h a t another naticid, to wit, Natica gualteriana, deviates from the generally accepted behavioural norm in t h a t it forages subaerially. The present note presents the observations pertaining to the discovery, and places the new information in the general context of the palaeoecology of drills and their prey. Material and m e t h o d s Shells of naticids collected in the field (see below), were identified by F. J. Springsteen (University of Melbourne, Australia) and F. E. Wells (Western Australian Museum, Perth, Australia) as belonging to two morphs of Natica (Natica) gualteriana Recluz, 1844. The two morphs differ principally in the colour of

the outer and inner shell surfaces (Fig.lA and Fig.lB, C, respectively). The size and shape of the umbilicus is variable within both morphs, but the lighter morph (Fig. 1B) tends to have a wider umbilicus. A few individuals intermediate between the two morphs have also been observed. According to F. J. Springsteen (pers. comm.), several intergrading morphs of N. gualteriana have been described, and have been found living side-by-side. It is therefore possible that we have a case of discrete polymorphism confounded with ecophenotypy. Observations were carried out by the first author in Baigad, Sillon and Pook in B a n t a y a n Island, NW of Cebu, Philippines, in midFebruary 1988. The shore at these localities consists of clean, fine- to medium-grained white sand, containing frequent bioclasts of variable size and nature. Sandbars are exposed at low tide at a distance of 10-30 m from the high-tide strand-line. The environment at low tide is characterized by the presence of several invertebrates: seaward portions of the sandbars are densely inhabited by U. vestiarium,

Fig.1. A-C. Naticagualteriana, x 2.5 (A: dark-colouredmorph, B-C: lighter morph). D F: Umbonium vestiariumwith naticid boreholes, x 4. The specimen in F was recovered while being consumedby N. gualteriana.

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N. gualteriana, Polinices sp. and unidentified, submillimeter-sized crustaceans. Arachnoidid echinoderms (cf. Arachnoides sp.) were seen to emerge from the sand and to move towards the retreating waterline. Several species of Nassarius abound along the shore, and on the portions of the sandbanks facing the shore. Some portions of the sandbanks are covered with a thin algal mat, which is inhabited by Neritina sp. and hermit crabs. In other places, small polychaete worms wander in large numbers in the water trapped between ripple marks, and are preyed upon by Conus magus, C. ebraeus, C. fulmen, C. aristophanes and Cypraea carneola. Dense colonies of crabs (cf. Dotilla sp.) emerge from the sand at low tide to feed on sand pellets. All organisms metioned above, with the exception of hermit crabs, remain buried during high tide. Some of them (e.g., U. vestiarium) filter-feed while buried. Epifaunal and semi-infaunal predators (durophagous fishes, portunid, calappid and leucosiid crabs) patrol the submerged areas in large numbers up to the waterline, and often become trapped in depressions of the bottom by the receding tide. The behaviour of N. gualteriana and U. vestiarium was observed and photographed in the field at low tide. Predation of N. gualteriana on U. vestiarium was observed (1) without interfering with the molluscs, and (2) by handcollecting specimens of U. vestiarium and placing them at short distances in the paths of advancing naticids. Traces left by these gastropods were photographed, and the buried N. gualteriana at the end of the tracks were collected, together with their prey. Manipulation caused N. gualteriana to release the prey immediately and to retreat into its shell, so that the boring process could not be observed. The position of buried Polinices sp. was detected from the presence of a characteristic mound of sand above the shell. This species was never observed to emerge spontaneously from the sand. Specimens of N. gualteriana, U. vestiarium and Polinices sp. were collected and placed in an aquarium. Since electricity for running an

air pump was not available, observations could only be made over a few hours. The specimens illustrated in Fig.1 are in the possession of the first author. Observations

Behaviour of Umbonium vestiarium During low tide, undisturbed U. vestiarium (Linnaeus) remain shallowly buried and iramobile, totally invisible form the surface of the sediment. Upon detecting a disturbance, however, they react by suddenly extending the foot, emerging from the sand, and initiating a series of escape jumps. The foot of U. vestiarium is cylindrical, highly muscular and extensible, and comparable in morphology and function with the foot of sand-burrowing bivalves (e.g., Donax). Jumping is effected by bending the foot laterally, placing its tip against the sediment, and quickly straightening it. Successive jumps take place by alternately bending the foot in opposite directions, so that the general direction of locomotion remains approximately straight. After a few jumps, the mollusc begins to move by means of a normal creeping locomotion, and burrows shortly thereafter. The creeping locomotion of U. vestiarium produces shallow furrows, narrower than those made by N. gualteriana (Fig.2). In the field, the vibrations and compressive forces generated in the sand by the nearby passage of human observers often cause buried U. vestiarium to emerge and initiate the escape sequence. In the field, as well as in the aquarium, contact of the soft parts of U. vestiarium with those of naticids releases the escape reaction, while contact with other U. vestiarium usually does not. Therefore, the escape reaction of U. vestiarium appears to be triggered by mechanical, as well as chemical stimuli.

Hunting behaviour of Natica gualteriana N. gualteriana remains buried during high tide. As the sea withdraws at low tide, it

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Fig.2. Foraging tracks produced by Natica gualteriana, approximately x 0.15. The smaller tracks are produced by escaping Umbonium vestiarium. A N. gualteriana and several escaping U. vestiarium are visible at the end of their tracks in D.

emerges from the sand when the bottom is no longer swashed. Some water may still be present, trapped in the depressions among ripple marks, but it drains away rapidly. The naticids immediately begin to move about at the surface of the sand, ploughing a shallow furrow as they progress. The depth of their traces depends on the consistency of the sediment. Because of the uneven level and drainage of the bottom, portions of the same t r a c k may have uneven depths (Fig.2A, C, D). Little or no mucus is left in t h e trail. H u n t i n g N. gualteriana follow an irregular spiralling or undulating path (Fig.2). The path does not

normally r e t r a c e or cross itself. The speed of a foraging adult of N. gualteriana is 3-5 mm/s. The shells of hunting N. gualteriana are covered by a r a t h e r large quantity of wet sand, that tends to conceal them and thus makes pictures difficult to analyze. The amount of adhering sand shown in Fig.3 is less than usual. This specimen was used for the illustrations, since its shell was largely visible. The sand adheres to the shells when the molluscs emerge from the sediment; apparently they make no effort to remove it. The wet sand adhering to the shell possibly hinders surface locomotion, but it may have a positive effect,

359 such as hiding the mollusc from visually h u n t i n g predators (e.g., birds), and retarding the desiccation and increase in t e m p e r a t u r e deriving from direct exposure to sunlight. It is possible t h a t adherence of the sediment to the shell is enhanced by mucus secreted by the naticid. It is also possible t hat the polymorphism in colour displayed by these naticids is a consequence in this connection. Upon coming into contact with prey, N. gualteriana rapidly lifts the ant er i or region of the foot from the sediment, and extends it forward like a hood to grasp the shell of U. vestiarium (Fig.3A). Up to one second may lapse between the c o n tact with an Umbonium and the reaction by N. gualteriana. S i n c e the escape reaction of U. vestiarium is practically instantaneous, most attempts made by N. gualteriana to capture U. vestiarium fail, and the tracks left by h u n t i n g N. gualteriana are flanked by several smaller tracks produced by escaping U. vestiarium (Fig.2). Even after N. gualteriana has grasped an individual, the prey occasionally succeeds in breaking free by performing a series of vigorous movements with the foot. In spite of the efficiency of the escape mechanism of the prey, U. vestiarium occurs in such a high density t h a t most N. gualteriana make a capture after foraging for 50cm to l m . At the observed speed noted above, this implies t hat successful h u n tin g takes no longer t han about 5 min, which compares favourably with the results achieved by naticids hunt i ng in the ~'conventional" manner. All specimens of N. gualteriana found buried at the end of their foraging tracks had captured an individual of

U. vestiarium. Size-selection of the prey by N. gualteriana may take place: a 5 mm long N. gualteriana was offered several specimens of U. vestiarium 2 4 mm wide, which it captured, but they were rejected after a brief handling. These specimens of U. vestiarium had partially or totally re t ra c ted into their shells after being handcollected, and their escape r eact i on was not fast enough to be successful. The same specimen of N. gualteriana was subsequently offered and succeeded in overpowering a 6 mm wide

U. vestiarium. However, there does not seem to be any selection on the upper size of the prey (other t han t hat resulting from failure to capture prey too large to be immobilized): a 6 mm long N. gualteriana was seen to capture a 10mm wide U. vestiarium (without intervention by the observer). In most cases, however, the prey was observed to be smaller t han the predator. We find this observation to be interesting in the light of recent discussion on the concept of a "size-refuge", with particular reference to predation by drills (cf. Kitchell et al., 1981; Reyment et al., 1987). The situation observed for adult naticids is t hat they normally attack animals much larger t han themselves. According to the observations of the first author, the capture-reaction of N. gualteriana is triggered by direct cont act of the naticid with the soft parts of the prey, or occasionally, by cont act with the shell of a moving U. vestiarium. Contact with the shell of a living but immobile prey was never observed to release the capture sequence, which suggests that chemotaxis is not involved (cf. Carriker, 1981). In fact, it is usually the escape reaction of buried U. vestiarium t h a t brings them within the reach of N. gualteriana. No detectable difference was observed in the hunting behavi our of the two morphs of N. gualteriana. Post-capture behaviour of Natica and Umbonium After capturing an individual of U. vestiarium, N. gualteriana completely envelops the prey within its mantle, by moving directly on top of it (Fig.3B). After a few seconds, N. gualteriana resumes surface locomotion, dragging with it the captured U. vestiarium by holding on to its shell with the posterior region of the foot (Fig.3C, D) At this point, U. vestiarium could, conceivably, easily escape from the grasp of the predator by using the same movements of the foot as employed in its escape sequence. However, all captured specimens were observed to remain ret reat ed within their shells.

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B

Fig.3. Capture (A), handling (B) and post-capture (C-F) behaviour ofNatica gualteriana, approximately x 1.8. The drawings along the right side show the position of N. gualteriana and of the captured U. vestiarium, which in the photographs are partly obscured by adhering sand.

Umbonium vestiarium taken from N. gualteriana at this stage were observed to have the apertural region of the shell loosely plugged with a mucous deposit, covered with adhering sand grains. This mucus is easily removed by handling, and care had to be taken in order not to loosen it accidentally. Therefore, the mucus probably has little mechanical effect in forcing U. vestiarium to remain retracted, since the mollusc could easily push it aside by extending its foot from the aperture of the shell. In order to test whether the mucus has any permanent debilitating influence on the prey, specimens of U. vestiarium were taken from N. gualteriana t h a t had just captured them. A first group of individuals had the mucus

immediately displaced by rubbing the shells with sand. A second group was left with the apertures plugged by mucus. For control purposes, specimens t h a t had not been in contact with naticids were also collected. The specimens were kept separated by putting them in plastic boxes half-filled with sand, placed on the bottom of an aquarium. All specimens without mucus began moving after a few minutes, while the specimens with plugged apertures remained retracted and immobile. Removal of the mucus after approximately two hours resulted in U. vestiarium resuming normal activity within the following half-hour. Two specimens t h a t had been left plugged overnight were observed the following morn-

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\ E

F Fig.3. Continued. ing to be filter-feeding in the normal infaunal position. The control specimens burrowed immediately, whereupon they engaged in filterfeeding. It can therefore be concluded t h a t the mucus exerts a chemical action in preventing U. vestiarium from extending its foot, and t h a t this action wears off after a few hours, or when the mucus is removed. This supports the suggestion put forward by Carriker (1981) concerning the anaesthetizing properties of muricid mucus. The mucus plugging the shell aperture has no observable permanent effect on U. vestiarium, but only keeps it immobile for the time necessary for N. gualteriana to consume its prey. N. gualteriana drags the captured prey for a short distance, presumably while searching for a suitable place to reburrow (Fig.3F). Burrow-

ing takes place in a way similar to that described by T r u e m a n (1968) in other naticids. Since the sediment is exposed to the air, the burrow often remains partially open behind the naticid (Fig.2B). Drilling of the prey could not be observed directly, since digging near a buried N. gualteriana always caused it to abandon its activities, and r e t r a c t into its shell. Specimens of U. vestiarium t h a t had been captured up to 15 min earlier showed no trace of drilling. However, a specimen retrieved from a N. gualteriana, buried at the end of a hunting t r a c k in the upper part of a sand bar, had already been drilled; the tissues of the prey were visible t h r o u g h the borehole (Fig.iF). This region of the sand bar had been emergent for no longer t h a n three hours, and hence, this must be the maximum time taken by N. gual-

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teriana to drill through the shell of its prey, a remarkably short interval (cf. Kitchell et al., 1981; Guerrero and Reyment, 1988). Shells of U. vestiarium displaying naticid boreholes and inhabited by hermit crabs were recovered closer to the shore (Fig.lD, E). It is likely, although not certain, t h a t they were drilled by either of the morphs of N. gualteriana (or possibly, also by Polinices sp.). All but one were drilled below the periphery of the last whorl, roughly opposite the aperture, in the same position as the specimen found while being consumed by a N. gualteriana (Fig.lD, E, Fig.4). Multiple naticid borings on the same shell were never observed. Behaviour of Polinices sp. This naticid appears to be an exclusively infaunal species. When extracted from the sand, it soon starts to reburrow without moving about at the surface. When the bottom is still covered by water, Polinices sp. moves slowly, always infaunally, 2-3 cm below the surface of the sand, but apparently stops moving shortly after the bottom emerges. The occurrence of buried Polinices sp. can be detected by the presence of a small mound of

I -"----

sand directly above the mollusc. Several specimens were collected in this way, but they were never found in close proximity to other mollusc shells. Therefore, it was not possible to ascertain the diet of this naticid.

Behaviour of Natica and Umbonium in the aquarium Most N. gualteriana burrowed as soon as placed in the aquarium, while a few individuals engaged in surface locomotion. Buried individuals stopped moving shortly after burrowing, and occasionally emerged from the sand, to reburrow shortly thereafter. Apparently, buried N. gualteriana do not engage in subsurface locomotion. Attempts by N. gualteriana to capture U. vestiarium were never observed in the aquarium, in spite of naticids frequently coming into contact with U. vestiarium. On these occasions, N. gualteriana always reacted by stopping briefly, and then resuming locomotion in a different direction. Most of the specimens of N. gualteriana placed in the aquarium were collected in the field while h u n t i n g epifaunally, and therefore, were presumably ready to feed. Observations on aquarium-kept individuals could be carried out for only a few hours, and they are therefore not conclusive. However, it appears that the foraging behavour in N. gualteriana is triggered by the exposure of the bottom to the air at low tide. On the other hand, U. vestiarium placed in the aquarium readily burrowed and started to filter feed. Whenever they accidentally came into contact with N. gualteriana, they reacted with the same escape behaviour as observed in the field. Discussion

.......

/ '.)-l'.',,,ctJJ Fig.4. Pope diagram of the naticid holes observed on empty shells of Umbonium vest,iarium. The hole at the bottom right is the only one on the aboral surface of the shell (see also Fig.1 D).

Subaerial h u n t i n g has not previously been described in naticid gastropods. However, with the exception of the environment in which hunting takes place, and possibly of the lunging movement used to grasp the prey, the hunting behavour of N. gualteriana is not substantially different from that of other

363 naticids (Ziegelmeier, 1954). The low successrate in capturing prey, compared with the frequency of total attempts, makes this hunting s t r a t e g y only feasible where prey is abundant, and possibly points to the r ecent evolution of this behavioural pattern. From an ev o lu tio n a r y perspective, the hunting b e h av io u r of N. gualteriana can be seen as the result of contrasting environmental pressures. Umbonium vestiarium, like many other suspension-feeding invertebrates, lives in dense colonies, and therefore constitutes a potentially ab u n d an t source of food. In fact, this species is also preyed upon by ot her naticids, albeit not subaerially (see Berry, 1982). The escape reaction of U. vestiarium renders attempts at infaunal predation unlikely to succeed (in fact, this escape reaction seems especially tailored to t h w a r t infaunal predators). On the other hand, epifaunal hunting in a subaqueous environment would make N. gualteriana vulnerable to the numerous epifaunal predators observed in the n a t u r a l environment. The chances of falling victim to one of these predators can be reduced, if the initiation of epifaunal h u n t i n g is timed to immediately precede exposure of the bottom at low tide, since most predators would be forced to r e t r e a t into deeper water. Possibly, this has been the stepping-stone to the evolution of subaerial h u n tin g in N. gualteriana. However, even at this time, predation would remain a relevant source of selective pressure on epifaunally h u n tin g naticids, since crabs and durophagous fishes may v e n t u r e up to the edge of the water. This is actually seen in the n a t u ral environment, where conspicuous numbers of durophagous fishes (probably tetrodontids) remain trapped on the sandbars at each low tide. These fishes are r e m ar ka bl y resistant to desiccation, and can recover after lying exposed to the air and to the sun for a few hours. Some of them are capable of excavating a small depression in the sand, in order to collect drainage water and r e t a r d desiccation. Therefore, the next evol ut i onar y step for N. gualteriana would have been to start foraging after the bottom was exposed at low tide.

Since the prey animal is abundant (sometimes in excess of 1000 individuals of U. vestiarium per m2), and the speed of N. gualteriana hunt i ng epifaunally is one to two orders of magnitude higher t han t hat of infaunal naticids, even a low rate of success guarantees an adequate intake of food. F u r t h e r behavioural adaptations to the subaerial environment in N. gualteriana include the use of moist sand to cover the shell, and the parsimonious use of mucus in surface locomotion and in capturing of prey. The time available for hunt i ng is limited: 15 30 min after the bottom emerges at low tide, the sediment becomes too compact to allow reburrowing. This statement is supported by observations made on N. gualteriana, Polinices sp., U. vestiarium and several species of Nassarius t h a t had been hand-collected and moved to the upper portions of the sandbars. Sea-birds were rarely seen on the sandbars inhabited by N. gualteriana, and none of the other organisms observed in this environment seems to pose a t h r e a t to subaerially hunt i ng naticids. Conclusions The palaeoecological implications attaching to the find presented in this note are immediately obvious. Firstly, the presence of undoubted naticid holes in a fossil shell can no longer be t aken as unequivocal evidence of a subtidal paleohabitat of the victim. Secondly, it also seems reasonable to postulate t hat the mucus secreted by Natica gualteriana possesses some kind of anesthetizing property, thus immobilizing the prey during the critical initial phase of the attack. This provides a measure of support, albeit indirect, for Carriker's (1981) hypothesis to t hat effect. We make no claims for a wide occurrence of the behavioural pat t ern reported here. It is quite obvious t hat it can only be successful where the animal being preyed upon occurs in super-abundance, bearing also in mind t hat Umbonium vestiarium possesses a highly efficient escape-mechanism. From the evolutionary aspect, the present account would appear

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to point to perhaps unexpected behavioural plasticity in naticids, thus casting doubt upon the oft-made assertion that their predatory behaviour is a stereotyped replica of a pattern established more than 100 million years ago.

Acknowledgements F. J. Springsteen (University of Melbourne, Australia) and F. E. Wells (Western Australian Museum, Perth, Australia) helped by identifying naticid specimens. The present paper is a partial result of field work in the Philippines financed by the Swedish Natural Science Research Council.

References Ansell, A. D., 1960. Observations on predation of Venus striatula (Da Costa) by Natica alderi (Forbes). Proc. Malacol. Soc. Lond. 34: 157-164. Berry, A. J., 1982. Predation by Natica maculosa Lamarck (Naticidae: Gastropoda) upon the trochacean gastropod Umbonium vestiarium (L.) on a malaysian shore. J. Exp. Mar. Biol. Ecol., 64: 71-89.

Carriker, M. R., 1955. Critical review of biology and control of oyster drills Urosalpinx and Eupleura. U.S. Dep. Int. Fish Wildl. Serv. Spec. Rep. 148:1-150 Carriker, M. R., 1961. Comparative functional morphology of boring mechanisms in gastropods. Am. Zool., 1: 263-266. Carriker, M. R., 1981. Shell penetration and feeding by naticacean and muricacean predatory gastropods: a synthesis. Malacologia, 20: 403-422. Fischer-Piette, E., 1935. Historie d'une mouli~re. Observations sur une phase d~s~quilibre faunique. Bull. Biol. Fr. Belg. 69:153 177. Guerrero, S. and Reyment, R. A., 1988. Predation and feeding in the naticid gastropod Naticarius intricatoides (Hidalgo). Palaeogeogr., Palaeoclimatol., Palaeoecol., 68: 49-52. Kitchell, J. A., Boggs, C. H., Kitchell, J. F. and Rice, J. A. 1981. Prey selection by naticid gastropods: experimental tests and application to the fossil record. Paleobiology, 7: 533-552. Reyment, R. A., Reyment, E. R. and Honigstein, A., 1987. Predation by boring gastropods on Late Cretaceous and Early Palaeocene ostracods. Cretaceous Res., 8: 189-209. Trueman, E. R., 1968. The mechanism of burrowing of some naticid gastropods in comparison with that of other mollusks. J. Exp. Biol., 48: 663-678. Ziegelmeier, E., 1954. Beobachtungen fiber den Nahrungserwerb bei der Naticide Lunatia nitida Donovan (Gastropoda Prosobranchia). Helgoland. Wiss. Meeresunters., 5: 1-33.