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Temperature effects on growth-ration relationships of juvenile sea cucumber Apostichopus japonicus (Selenka)
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Aquaculture 272 (2007) 644 – 648 www.elsevier.com/locate/aqua-online
Temperature effects on growth-ration relationships of juvenile sea cucumber Apostichopus japonicus (Selenka) Zhenhua An, Yunwei Dong ⁎, Shuanglin Dong The Key Laboratory of Mariculture, Ministry of Education, Fisheries College, Ocean University of China, Qingdao 266003, People's Republic of China Received 13 March 2007; received in revised form 18 August 2007; accepted 20 August 2007
Abstract We studied the effects of temperature (16, 18, 20 and 22 °C) and ration (0%, 0.3%, 0.6% and 1.4% body weight day− 1) on the growth of juvenile sea cucumber Apostichopus japonicus (mean body weight 5.4 ± 0.1 g) over 35days. For any given ration, food intake (FI), specific growth rate (SGR) and food conversion efficiency (FCE) decreased with increasing temperature. The relationship among SGRw (in terms of weight), SGRe (in terms of energy), temperature (T), and ration (% body weight) could be described by the regression equations: SGRw = 0.132 − 0.024 T + 0.284 R (r2 = 0.724, n = 64), and SGRe = −0.014 − 0.030 T + 0.312 R (r2 = 0.654, n = 64). These equations show that the minimum and maximum amount of energy required for maintenance occurred at 16 °C and at 22 °C, respectively. Furthermore, the energy requirements for maintenance at high temperatures exceeded the energy intake. The patterns of energy allocation revealed that energy required for respiration increased with increasing temperature. The aestivation of sea cucumbers in summer might be in response to a shortfall in energy intake with respect to an increase of energy consumed in respiration at high temperature. © 2007 Elsevier B.V. All rights reserved. Keywords: Temperature; Ration; Apostichopus japonicus; Growth; Energy budget
1. Introduction The sea cucumber Apostichopus japonicus Selenka, a holothurian believed to have aphrodisiac and medical properties, is becoming an important aquaculture species in China and Japan (Chen, 2004). Temperature has a major influence on growth and physiology (Li et al., 2002; Yang et al., 2006; Dong and Dong, 2006; Dong et al., 2006); and the optimum temperature for the growth of juvenile A. japonicus is about 15.5 °C (Dong et al., 2005). A. japonicus cease feeding and aestivate at temperatures
of 24 °C and above (Liu et al., 1996; Yu and Song, 1999; Yang et al., 2005, 2006). Oxygen consumption of mature A. japonicus decreased when temperature exceeded the aestivation threshold, which depends on location, body size and age (Yang et al., 2005; Wang and Liao, 2001). The present study examined the effect of super-optimal temperature (16–22 °C) on the growth-food availability (ration) relations of juvenile A. japonicus to provide a preview for the large-scale sea cucumber aquaculture. 2. Materials and methods 2.1. Source of animals
⁎ Corresponding author. Tel.: +86 532 82032435; fax: +86 532 82894024. E-mail address: [email protected] (Y. Dong). 0044-8486/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2007.08.038
The experiment was conducted from May 1 to July 5 2005 at the Mariculture Research Laboratory, Ocean University of
Z. An et al. / Aquaculture 272 (2007) 644–648
China, Qingdao, P R China. The sea cucumbers were grown in and supplied by the ZhuoYue Aquaculture Corporation, Qingdao, P. R. China. 2.2. Acclimation and rearing conditions Juvenile A. japonicus underwent a 10-day acclimation at 16 °C in continuously aerated seawater in several fiberglass tanks. At the end of this period, 192 animals of similar size (5.39 ± 0.16 g) were selected and transferred into 64 glass aquaria (450 mm × 250 mm × 350 mm) containing 30L seawater at different temperatures (16, 18, 20 and 22 °C) for a 7-day acclimation. Seawater used in the experiment was filtered using a sand filter. During the course of the experiment, water salinity was 28 ppt to 30 ppt. Water pH was around 7.8 and ammonia was less than 0.24 mg L− 1. Water salinity, pH and ammonia were determined with salinity refractometer (AIAGO, Japan), pH meter (PH3150i, WTW, Germany), and Hypobromite methods, respectively. A simulated natural photoperiod (14-h light/10-h dark) was used. Each tank had a 1500W electric heater controlled via a thermostat. Aeration was provided continuously and one-third of the water volume was exchanged everyday with the water from a spare aquarium at the same temperature in order to maintain the same temperature. Aeration was provided continuously and the dissolved oxygen was maintained above 4.0 mg L− 1. During the acclimation period, the animals were fed ad libitum twice a day (0800 h and 1800 h) with sifted pieces of semi-dried Sargassum thunbergii (11.70% crude protein, 0.67% crude lipid, 12.89% ash, moisture b 1.00%; energy 8.55 kJ g− 1 dry mass) and the pieces (radius around 0.8 mm, weight around 2.5 mg) were insoluble in the sea water.
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−20 °C for the analysis of energy and nitrogen content. At the end of the experiment, the animals were starved for 24 h then weighed and dried at 65 °C for 48 h, and then ground to powders with a small grinder for measurement of energy and nitrogen content. 2.4. Energy determination and estimation of energy budget The energy contents of the food, sea cucumber bodies, feces were measured with a Parr 1281 Oxygen Bomb Calorimeter (Parr, USA). The energy budget was calculated by the following equation (Carfoot, 1987): C ¼GþF þU þR Where C is the energy consumed in food; G is the energy deposited as growth; F is the energy lost in feces; U is the energy lost in excretion and R is the energy used for respiration. The value of C and F can be calculated by the weight of the samples of food intake, feces weight and their energy content per gram. G can be calculated by the following equation: G ¼ ðFw Ef Þ ðIw Ei Þ Where Fw and Iw are final body weight and initial body weight of the sea cucumbers, respectively; Ef and Ei are the energy content per gram of final body and initial body of the sea cucumbers, respectively. The nitrogen contents of the sea cucumber bodies, food and feces were measured with a VarioEL III elemental analyzer (Elementar, Germany). The estimation of U was based on the nitrogen budget equation (Levine and Sulkin, 1979): U ¼ ðCN GN FN Þ 24; 830
2.3. Experimental design and procedure The acclimation was followed by starvation for 24 h. The initial individual wet weight measurements were taken with 1min of removal from seawater and external water was removed from the specimens by drying them on sterile gauzes, then 64 individuals of similar weight (5.36 ± 0.03 g) from each acclimation temperature were selected and dried in an oven at 65 °C to constant weight, homogenized and stored at −20 °C for subsequent measurement of body composition and energy content. The remaining 128 test individuals, with initial body weight 5.4 ± 0.1 g, were allocated to 64 aquaria (2 individuals / aquarium). There were 16 tanks (450 mm × 250 mm × 350 mm) at each of four temperatures (16, 18, 20 and 22 °C) with four tanks for each of the four levels of food supply (ration) (0%, 0.3%, 0.6% and 1.4% body weight day− 1). There was no significant difference in the initial body weight among the different treatments. The rearing conditions and feed were similar to those used during the acclimation period. During the 35-day course of the experiment, the weight of each ration was recorded. Uneaten food and feces were removed by siphon and separated immediately to avoid decomposition, and then they were dried at 65 °C, ground, weighed and kept at
Where, CN is the nitrogen consumed from food; FN is the nitrogen lost in feces; GN is the nitrogen deposited in the body; 24,830 is the energy content (J g− 1) of excreted nitrogen. The value of R was calculated by the energy budget equation: R¼CGF U 2.5. Calculation and data analysis Specific growth rate in terms of weight (SGRw) and energy (SGRe), food intake (FI), food conversion efficiency (FCE) and ration level (RL) were calculated as: SGRw kday1 ¼ 100 ðlnW2 lnW1 Þ=D SGRe kday1 ¼ 100 ðlnE2 lnE1 Þ=D FI kbody weight day1 ¼ 100 I=½D ðW2 þ W1 Þ=2 FCEðkÞ ¼ 100 ðW2 W1 Þ=I RLw ¼ 100 Cw =W1 RLe ¼ 100 Ce =E1
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Z. An et al. / Aquaculture 272 (2007) 644–648
where, W2 and W1 are the final and initial body weight of the sea cucumbers, respectively; E2 and E1 are the final and initial energy content of the sea cucumbers, respectively; D is the duration of the experiment; Cw and Ce are the total weight of food and energy consumed, respectively; I is the total food intake during the whole experiment. RLw and RLe are ration level in terms of weight and energy. The data were analyzed by the SPSS for Windows (Version 10.0) statistical package. Two-way analysis of variance (ANOVA) was used to test for the effect of the interaction between temperature and ration on growth, FI and FCE. The effects of temperature and ration on SGR were tested using stepwise multiple regression analysis. Differences were considered statistically significant if P b 0.05. 3. Results 3.1. Growth The maximum and minimum of SGR (SGRw and SGRe) occurred at treatment (16 °C, 1.4% ration) and treatment (22 °C, starvation), respectively. Stepwise multiple regression analysis showed that SGRw and SGRe decreased with increasing temperature, and increased with increasing ration at any given temperature (Fig. 1). The relationship among SGRw and SGRe, temperature (T) and ration (Ra) can be described by the regression equations: SGRw ¼ 0:132 0:024T þ 0:284Ra r2 ¼ 0:724;n ¼ 64
ð1Þ
SGRe ¼ 0:014 0:030T þ 0:312Ra r2 ¼ 0:654;n ¼ 64
ð2Þ
The results of the two-way ANOVA analysis showed no significant interaction between the temperature and the ration on SGR of A. japonicus (P N 0.05). According to the equation, growth decreased with increasing temperature beyond the optimum, and increased with increasing ration. According to the Eq. (1), the maintenance ration levels in terms of weight (RLw) at 16 °C, 18 °C, 20 °C and 22 °C were 0.91%, 1.08%, 1.25% and 1.43% of body weight, respectively. According to the Eq. (2) the maintenance ration levels in terms of energy at 16 °C, 18 °C, 20 °C and 22 °C were 1.59%, 1.78%, 1.98% and 2.17% of body energy, respectively. The minimum and maximum maintenance rations occurred at 16 °C and 22 °C, respectively. The maintenance ration levels increased with increasing temperature. 3.2. Food intake (FI), food conversion efficiency (FCE) FCE decreased with increasing temperature (P b 0.05). There was no significant difference in FI between different temperatures (P N 0.05) (Table 1). FCE and FI were both affected significantly by ration (P b 0.05). The highest FCE occurred at treatment (16 °C, 1.4% ration). FCE and FI were
Fig. 1. Effect of different temperatures and rations on the specific growth rate (% day− 1) in terms of weight (SGRw) (a) and energy (SGRe) (b) in sea cucumber Apostichopus japonicus.
not significantly affected by the interaction of temperature and ration (P N 0.05). 3.3. Energy allocation The patterns of energy allocation in the test animals revealed significant differences among treatments (Table 2). In the temperature range of this experiment, the energy deposited as growth decreased with rising temperature (P b 0.05). The consumption of energy for respiration increased with increasing temperature (P b 0.05). Temperature had no significant influence on fecal or excretion energy (P N 0.05).
4. Discussion Although temperature is an important factor that affects the growth and metabolism of A. japonicus, there is still limited information available, especially about growth at temperatures below the threshold for aestivation (Dong
Z. An et al. / Aquaculture 272 (2007) 644–648 Table 1 Effect of temperature and ration on the feed intake (FI) and food conversion efficiency (FCE) in sea cucumber A. japonicus1 Temperature (°C) Ration (%)
FCE (% day− 1)2
FI (% day− 1)3
16
− 121.41 ± 15.75 5.57 ± 0.84e 9.22 ± 2.16e − 102.31 ± 10.26b 4.35 ± 3.04e 7.25 ± 2.57e − 114.43 ± 5.03b − 1.32 ± 0.76d 1.49 ± 0.52e − 133.61 ± 8.67a − 31.53 ± 9.39c − 9.49 ± 2.11d
0.26 ± 0.01a 0.50 ± 0.02b 1.13 ± 0.05c 0.26 ± 0.08a 0.52 ± 0.01b 1.08 ± 0.04c 0.25 ± 0.01a 0.46 ± 0.03b 1.14 ± 0.10c 0.25 ± 0.01a 0.51 ± 0.02b 1.11 ± 0.04c
18
20
22
0.3 0.6 1.4 0.3 0.6 1.4 0.3 0.6 1.4 0.3 0.6 1.4
ab
(Satiation)
(Satiation)
(Satiation)
(Satiation)
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22 °C, suggesting that the decrease of SGR might be attributed to the lower FCE at high temperature. This result was similar to those of previous studies on other aquatic animals, such as fish (Micropterus salmoides, Beamish, 1972; Salmo trutta, Elliott, 1976; Scophthalmus maximus, Koskela et al., 1997; S. maximus, Van Ham et al., 2003) and shrimp (Fenneropenaeus chinensis, Tian et al., 2006). In this experiment, the energy budget of juvenile A. japonicus at 16 °C and maximum ration was: 100 C = 27.66 F + 2.94 U + 22.36 G + 47.04 R. This result indicated that the energy required for metabolism by juvenile A. japonicus was greater than fecal energy. This conclusion is different from that reached for a previous study of mature (32.5 ± 0.1 g) A. japonicus fed diets containing dried bivalve feces and/or powdered algae (Yuan et al., 2006). The differences of food types and body sizes of the test sea cucumbers in the two studies might be the basis for the differences (González et al., 1993; Dong et al., 2005; Yang et al., 2006). In general, at the satiation condition, oxygen consumption increased with increasing temperature (Hopcroft et al., 1985) and at the temperatures of 16 °C, 18 °C, 20 °C and 22 °C, the ratios of energy required for respiration /energy consumed in food (R/C) were 47.04%, 64.06%, 67.67%, and 83.36%, respectively (Table 2). Temperature had no significant effect on the energy lost in the feces or excretion, indicating that the increase of energy used for metabolism at high temperature or poor absorption of food was the major factor in the decrease of growth. In conclusion, the decrease of growth in juvenile A. japonicus at high temperature is attributed to the
1
Values (mean ± S.E. of four replications) in the same column not sharing a common superscript letter are significantly different (P b 0.05). 2 FI (%) = 100 × F/[D × (W2 + W1)/2]. 3 FCE (%) = 100 × (W2 − W1)/F. W2 and W1 are the final and initial wet body weight of the sea cucumbers, respectively; D is the duration of the experiment; F is the total food taken by sea cucumbers during the whole experiment.
et al., 2005, 2006; Yang et al., 2005; Dong and Dong, 2006). Sea cucumber A. japonicus can survive in a temperature range of 0–30 °C, but growth occurs only between 12 °C and 21 °C, and the optimum temperature for growth is 15–18 °C (Yu and Song, 1999; Asha and Muthiah, 2005). The threshold temperature for aestivation of A. japonicus is nearly 23–24.5 °C (Liu et al., 1996; Yang et al., 2006). In this study, SGRw, SGRe and FCE decreased significantly with increasing temperature from 16 °C to Table 2 Energy budgets in A. japonicus at different temperatures and rations 1 Temperature (°C)
Ration (% body weight day− 1)
16 °C
0.00 0.30 0.60 1.4 (Satiation) 0.00 0.30 0.60 1.4 (Satiation) 0.00 0.30 0.60 1.4 (Satiation) 0.00 0.30 0.60 1.4 (Satiation)
18 °C
20 °C
22 °C
1
Food consumption (J.g0 1.d− 1) 116.86 ± 7.85a 242.58 ± 13.65b 540.07 ± 24.82c 117.56 ± 1.39a 243.08 ± 12.06b 505.69 ± 49.98c 115.13 ± 7.52a 218.53 ± 20.89b 543.65 ± 51.58c 108.54 ± 4.46a 237.74 ± 14.82b 504.52 ± 24.78c
Growth (J.g− 1.d− 1) − 223.98 ± 26.63 d − 141.53 ± 12.66c 6.07 ± 4.64b 120.77 ± 26.37a − 223.98 ± 26.62ab − 194.68 ± 25.17a − 119.04 ± 6.83b 14.07 ± 25.24c − 248.56 ± 17.95a − 207.81 ± 29.77ab − 199.88 ± 8.42b − 22.37 ± 57.11c − 284.27 ± 47.43a − 244.77 ± 9.91b − 170.09 ± 32.70c − 64.45 ± 25.00d
Common letter denotes no significant difference between means (P b 0.05).
Faecal (J.g− 1.d− 1) 52.73 ± 4.15a 79.20 ± 3.46b 149.36 ± 7.73c 47.59 ± 3.75a 71.48 ± 3.13b 134.80 ± 6.98c 44.76 ± 3.52a 64.51 ± 2.82b 139.99 ± 15.75c 39.58 ± 3.11a 59.45 ± 2.60b 112.12 ± 5.80c
Excretion (J.g− 1.d− 1)
Metabolism (J.g− 1.d− 1)
37.33 ± 1.43b 36.65 ± 1.77b 16.79 ± 1.05a 15.89 ± 1.68a 46.05 ± 3.48b 48.47 ± 2.99b 32.93 ± 1.03a 32.83 ± 6.10a 38.90 ± 2.69a 39.53 ± 2.49a 40.51 ± 2.70a 56.47 ± 3.59b 53.85 ± 4.48b 40.87 ± 1.45a 34.21 ± 4.38a 36.28 ± 4.02a
152.62 ± 6.26a 169.02 ± 11.21a 181.74 ± 19.05a 254.04 ± 14.54b 177.93 ± 23.45a 195.21 ± 24.77a 257.71 ± 17.03b 323.93 ± 70.37c 209.66 ± 15.84a 239.95 ± 26.65a 313.39 ± 15.62b 367.87 ± 9.19b 230.41 ± 43.08a 272.86 ± 11.05ab 314.17 ± 21.97b 420.56 ± 46.96c
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decrease of FCE and the increase of energy consumed by respiration. Due to the low energy content of its food (mainly contains alga pieces, mud and organic debris) and its low eating efficiency, sea cucumber A. japonicus can not obtain plentiful energy everyday. At the temperature beyond 22 °C (near the temperature threshold for aestivation), energy requirement exceeded energy intake. Therefore, sea cucumber A. japonicus has to decrease its energy requirement and metabolic rate by aestivation when ambient temperature exceeds the threshold point. Acknowledgements We are grateful to the anonymous referees and Dr. David Cushley for their helpful comments. We thank Dr. Xiangli Tian and Dr. Fang Wang for their technical support and helpful suggestions. The Chinese National Natural Science Foundation (grant No.30400333) and National Key Technologies R&D Program of China (grant No. 2006BAD09A01, 2006BAD09A06) supported this study. References Asha, P.S., Muthiah, P., 2005. Effects of temperature, salinity and pH on larval growth, survival and development of the sea cucumber Holothuria spinifera Theel. Aquaculture 250, 823–829. Beamish, F.W.H., 1972. Ration size and digestion in largemouth bass, Micropterus salmoides Lacepede. Can. J. Zool. 50, 153–164. Carfoot, T.H., 1987. Animal Energetics. Academic Press, New York, pp. 407–515. Chen, J.X., 2004. Present status and prospects of sea cucumber industry in China. In: Lovatelli, A., Conand, C., Purcell, S., Uthicke, S., Hamel, J.F., Mercier, A. (Eds.), Advances in sea cucumber aquaculture and management, 463. FAO, Rome, pp. 25–38. Dong, Y.W., Dong, S.L., 2006. Growth and oxygen consumption of the juvenile sea cucumber Apostichopus japonicus (Selenka) at constant and fluctuating water temperatures. Aquac. Res. 37, 1327–1333. Dong, Y.W., Dong, S.L., Tian, X.L., Wang, F., 2005. Effects of water temperature on growth, respiration and body composition of young sea cucumber Apostichopus japonicus. Fish. Sci. China. 1, 33–37 (In Chinese with English abstract). Dong, Y.W., Dong, S.L., Tian, X.L., Wang, F., Zhang, M.Z., 2006. Effects of diel temperature fluctuations on growth, oxygen
consumption and proximate body composition in the sea cucumber Apostichopus japonicus Selenka. Aquaculture 255, 514–521.
Elliott, J.M., 1976. Energy losses in the waste products of brown trout (Salmo trutta L.). J. Anim. Ecol. 45, 561–580. González, M.L., Pérez, M.C., López, D.A., Pino, C.A., 1993. Effects of algal diet on the energy available for growth of juvenile sea urchins Loxechinus albus (Molina, 1782). Aquaculture 115, 87–95. Hopcroft, R.R., Ward, D.B., Roff, J.C., 1985. The relative significance of body surface and cloacal respiration in Psolus fabricii (Holothuroidea: Dendrochirotida). Can. J. Zool. 63, 2878–2881. Koskela, J., Pirhonen, J., Jobling, M., 1997. Feed intake, growth rate and body composition of juvenile Baltic salmon exposed to different constant temperatures. Aquac. Int. 5, 351–360. Levine, D.M., Sulkin, S.D., 1979. Partitioning and utilization of energy during the larval development of the xanthid crab, Rithropanopeus harrisii (Gould). J. Exp. Mar. Biol. Ecol. 40, 247–257. Li, B.Q., Yang, H.S., Zhang, T., Zhou, Y., Zhang, C.X., 2002. Effect of temperature on respiration and excretion of sea cucumber, Apostichopus japonicus. Limnol. ET Oceanogr. Sin. 33, 182–187 (In Chinese with English abstract). Liu, Y., Li, F., Song, B., Sun, H., Zhang, X., Gu, B., 1996. Study on aestivating habit of sea cucumber Apostichopus japonicus (Selenka). J. Fish. Sci. China 3, 17–57 (In Chinese with English abstract). Tian, X., Dong, S., Wang, F., Wu, L., 2006. The growth of juvenile Chinese shrimp, Fenneropenaeus chinensis Osbeck, at constant and diel fluctuating temperatures. J. Shellfish. Res. 25, 1007–1011. Van Ham, E.H., Berntssen, M.H.G., Imsland, A.K., Parpoura, A.C., Wendelaar Bonga, S.E., Stefansson, S.O., 2003. The influence of temperature and ration on growth, feed conversion, body composition and nutrient retention of juvenile turbot (Scophthalmus maximus). Aquaculture 217, 547–558. Wang, R.C., Liao, C.Y., 2001. Aquaculture technique book. Shanghai Publishing House, Shanghai, China, pp. 98–223. Yang, H.S., Yuan, X.T., Zhou, Y., Mao, Y.Z., Zhang, T., Liu, Y., 2005. Effects of body size and water temperature on food consumption and growth in the sea cucumber Apostichopus japonicus (Selenka) with special reference to aestivation. Aquac. Res. 36, 1085–1092. Yang, H.S., Zhou, Y., Zhang, T., Yuan, X.T., Li, X.X., Liu, Y., Zhang, F.S., 2006. Metabolic characteristics of sea cucumber Apostichopus japonicus (Selenka) during aestivation. J. Exp. Mar. Biol. Ecol. 330, 505–510. Yu, D.X., Song, B.X., 1999. Survival rate and growth characteristics of juvenile sea cucumbers in breeding ponds. Fish. Sci. China 6, 109–110 (In Chinese with English abstract). Yuan, X.T., Yang, H.S., Zhou, Y., Mao, Y.Z., Zhang, T., Liu, Y., 2006. The influence of diets containing dried bivalve feces and/or powdered algae on growth and energy distribution in sea cucumber Apostichopus japonicus (Selenka) (Echinodermata: Holothuroidea). Aquaculture 256, 457–467.
Aquaculture 272 (2007) 644 – 648 www.elsevier.com/locate/aqua-online
Temperature effects on growth-ration relationships of juvenile sea cucumber Apostichopus japonicus (Selenka) Zhenhua An, Yunwei Dong ⁎, Shuanglin Dong The Key Laboratory of Mariculture, Ministry of Education, Fisheries College, Ocean University of China, Qingdao 266003, People's Republic of China Received 13 March 2007; received in revised form 18 August 2007; accepted 20 August 2007
Abstract We studied the effects of temperature (16, 18, 20 and 22 °C) and ration (0%, 0.3%, 0.6% and 1.4% body weight day− 1) on the growth of juvenile sea cucumber Apostichopus japonicus (mean body weight 5.4 ± 0.1 g) over 35days. For any given ration, food intake (FI), specific growth rate (SGR) and food conversion efficiency (FCE) decreased with increasing temperature. The relationship among SGRw (in terms of weight), SGRe (in terms of energy), temperature (T), and ration (% body weight) could be described by the regression equations: SGRw = 0.132 − 0.024 T + 0.284 R (r2 = 0.724, n = 64), and SGRe = −0.014 − 0.030 T + 0.312 R (r2 = 0.654, n = 64). These equations show that the minimum and maximum amount of energy required for maintenance occurred at 16 °C and at 22 °C, respectively. Furthermore, the energy requirements for maintenance at high temperatures exceeded the energy intake. The patterns of energy allocation revealed that energy required for respiration increased with increasing temperature. The aestivation of sea cucumbers in summer might be in response to a shortfall in energy intake with respect to an increase of energy consumed in respiration at high temperature. © 2007 Elsevier B.V. All rights reserved. Keywords: Temperature; Ration; Apostichopus japonicus; Growth; Energy budget
1. Introduction The sea cucumber Apostichopus japonicus Selenka, a holothurian believed to have aphrodisiac and medical properties, is becoming an important aquaculture species in China and Japan (Chen, 2004). Temperature has a major influence on growth and physiology (Li et al., 2002; Yang et al., 2006; Dong and Dong, 2006; Dong et al., 2006); and the optimum temperature for the growth of juvenile A. japonicus is about 15.5 °C (Dong et al., 2005). A. japonicus cease feeding and aestivate at temperatures
of 24 °C and above (Liu et al., 1996; Yu and Song, 1999; Yang et al., 2005, 2006). Oxygen consumption of mature A. japonicus decreased when temperature exceeded the aestivation threshold, which depends on location, body size and age (Yang et al., 2005; Wang and Liao, 2001). The present study examined the effect of super-optimal temperature (16–22 °C) on the growth-food availability (ration) relations of juvenile A. japonicus to provide a preview for the large-scale sea cucumber aquaculture. 2. Materials and methods 2.1. Source of animals
⁎ Corresponding author. Tel.: +86 532 82032435; fax: +86 532 82894024. E-mail address: [email protected] (Y. Dong). 0044-8486/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2007.08.038
The experiment was conducted from May 1 to July 5 2005 at the Mariculture Research Laboratory, Ocean University of
Z. An et al. / Aquaculture 272 (2007) 644–648
China, Qingdao, P R China. The sea cucumbers were grown in and supplied by the ZhuoYue Aquaculture Corporation, Qingdao, P. R. China. 2.2. Acclimation and rearing conditions Juvenile A. japonicus underwent a 10-day acclimation at 16 °C in continuously aerated seawater in several fiberglass tanks. At the end of this period, 192 animals of similar size (5.39 ± 0.16 g) were selected and transferred into 64 glass aquaria (450 mm × 250 mm × 350 mm) containing 30L seawater at different temperatures (16, 18, 20 and 22 °C) for a 7-day acclimation. Seawater used in the experiment was filtered using a sand filter. During the course of the experiment, water salinity was 28 ppt to 30 ppt. Water pH was around 7.8 and ammonia was less than 0.24 mg L− 1. Water salinity, pH and ammonia were determined with salinity refractometer (AIAGO, Japan), pH meter (PH3150i, WTW, Germany), and Hypobromite methods, respectively. A simulated natural photoperiod (14-h light/10-h dark) was used. Each tank had a 1500W electric heater controlled via a thermostat. Aeration was provided continuously and one-third of the water volume was exchanged everyday with the water from a spare aquarium at the same temperature in order to maintain the same temperature. Aeration was provided continuously and the dissolved oxygen was maintained above 4.0 mg L− 1. During the acclimation period, the animals were fed ad libitum twice a day (0800 h and 1800 h) with sifted pieces of semi-dried Sargassum thunbergii (11.70% crude protein, 0.67% crude lipid, 12.89% ash, moisture b 1.00%; energy 8.55 kJ g− 1 dry mass) and the pieces (radius around 0.8 mm, weight around 2.5 mg) were insoluble in the sea water.
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−20 °C for the analysis of energy and nitrogen content. At the end of the experiment, the animals were starved for 24 h then weighed and dried at 65 °C for 48 h, and then ground to powders with a small grinder for measurement of energy and nitrogen content. 2.4. Energy determination and estimation of energy budget The energy contents of the food, sea cucumber bodies, feces were measured with a Parr 1281 Oxygen Bomb Calorimeter (Parr, USA). The energy budget was calculated by the following equation (Carfoot, 1987): C ¼GþF þU þR Where C is the energy consumed in food; G is the energy deposited as growth; F is the energy lost in feces; U is the energy lost in excretion and R is the energy used for respiration. The value of C and F can be calculated by the weight of the samples of food intake, feces weight and their energy content per gram. G can be calculated by the following equation: G ¼ ðFw Ef Þ ðIw Ei Þ Where Fw and Iw are final body weight and initial body weight of the sea cucumbers, respectively; Ef and Ei are the energy content per gram of final body and initial body of the sea cucumbers, respectively. The nitrogen contents of the sea cucumber bodies, food and feces were measured with a VarioEL III elemental analyzer (Elementar, Germany). The estimation of U was based on the nitrogen budget equation (Levine and Sulkin, 1979): U ¼ ðCN GN FN Þ 24; 830
2.3. Experimental design and procedure The acclimation was followed by starvation for 24 h. The initial individual wet weight measurements were taken with 1min of removal from seawater and external water was removed from the specimens by drying them on sterile gauzes, then 64 individuals of similar weight (5.36 ± 0.03 g) from each acclimation temperature were selected and dried in an oven at 65 °C to constant weight, homogenized and stored at −20 °C for subsequent measurement of body composition and energy content. The remaining 128 test individuals, with initial body weight 5.4 ± 0.1 g, were allocated to 64 aquaria (2 individuals / aquarium). There were 16 tanks (450 mm × 250 mm × 350 mm) at each of four temperatures (16, 18, 20 and 22 °C) with four tanks for each of the four levels of food supply (ration) (0%, 0.3%, 0.6% and 1.4% body weight day− 1). There was no significant difference in the initial body weight among the different treatments. The rearing conditions and feed were similar to those used during the acclimation period. During the 35-day course of the experiment, the weight of each ration was recorded. Uneaten food and feces were removed by siphon and separated immediately to avoid decomposition, and then they were dried at 65 °C, ground, weighed and kept at
Where, CN is the nitrogen consumed from food; FN is the nitrogen lost in feces; GN is the nitrogen deposited in the body; 24,830 is the energy content (J g− 1) of excreted nitrogen. The value of R was calculated by the energy budget equation: R¼CGF U 2.5. Calculation and data analysis Specific growth rate in terms of weight (SGRw) and energy (SGRe), food intake (FI), food conversion efficiency (FCE) and ration level (RL) were calculated as: SGRw kday1 ¼ 100 ðlnW2 lnW1 Þ=D SGRe kday1 ¼ 100 ðlnE2 lnE1 Þ=D FI kbody weight day1 ¼ 100 I=½D ðW2 þ W1 Þ=2 FCEðkÞ ¼ 100 ðW2 W1 Þ=I RLw ¼ 100 Cw =W1 RLe ¼ 100 Ce =E1
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where, W2 and W1 are the final and initial body weight of the sea cucumbers, respectively; E2 and E1 are the final and initial energy content of the sea cucumbers, respectively; D is the duration of the experiment; Cw and Ce are the total weight of food and energy consumed, respectively; I is the total food intake during the whole experiment. RLw and RLe are ration level in terms of weight and energy. The data were analyzed by the SPSS for Windows (Version 10.0) statistical package. Two-way analysis of variance (ANOVA) was used to test for the effect of the interaction between temperature and ration on growth, FI and FCE. The effects of temperature and ration on SGR were tested using stepwise multiple regression analysis. Differences were considered statistically significant if P b 0.05. 3. Results 3.1. Growth The maximum and minimum of SGR (SGRw and SGRe) occurred at treatment (16 °C, 1.4% ration) and treatment (22 °C, starvation), respectively. Stepwise multiple regression analysis showed that SGRw and SGRe decreased with increasing temperature, and increased with increasing ration at any given temperature (Fig. 1). The relationship among SGRw and SGRe, temperature (T) and ration (Ra) can be described by the regression equations: SGRw ¼ 0:132 0:024T þ 0:284Ra r2 ¼ 0:724;n ¼ 64
ð1Þ
SGRe ¼ 0:014 0:030T þ 0:312Ra r2 ¼ 0:654;n ¼ 64
ð2Þ
The results of the two-way ANOVA analysis showed no significant interaction between the temperature and the ration on SGR of A. japonicus (P N 0.05). According to the equation, growth decreased with increasing temperature beyond the optimum, and increased with increasing ration. According to the Eq. (1), the maintenance ration levels in terms of weight (RLw) at 16 °C, 18 °C, 20 °C and 22 °C were 0.91%, 1.08%, 1.25% and 1.43% of body weight, respectively. According to the Eq. (2) the maintenance ration levels in terms of energy at 16 °C, 18 °C, 20 °C and 22 °C were 1.59%, 1.78%, 1.98% and 2.17% of body energy, respectively. The minimum and maximum maintenance rations occurred at 16 °C and 22 °C, respectively. The maintenance ration levels increased with increasing temperature. 3.2. Food intake (FI), food conversion efficiency (FCE) FCE decreased with increasing temperature (P b 0.05). There was no significant difference in FI between different temperatures (P N 0.05) (Table 1). FCE and FI were both affected significantly by ration (P b 0.05). The highest FCE occurred at treatment (16 °C, 1.4% ration). FCE and FI were
Fig. 1. Effect of different temperatures and rations on the specific growth rate (% day− 1) in terms of weight (SGRw) (a) and energy (SGRe) (b) in sea cucumber Apostichopus japonicus.
not significantly affected by the interaction of temperature and ration (P N 0.05). 3.3. Energy allocation The patterns of energy allocation in the test animals revealed significant differences among treatments (Table 2). In the temperature range of this experiment, the energy deposited as growth decreased with rising temperature (P b 0.05). The consumption of energy for respiration increased with increasing temperature (P b 0.05). Temperature had no significant influence on fecal or excretion energy (P N 0.05).
4. Discussion Although temperature is an important factor that affects the growth and metabolism of A. japonicus, there is still limited information available, especially about growth at temperatures below the threshold for aestivation (Dong
Z. An et al. / Aquaculture 272 (2007) 644–648 Table 1 Effect of temperature and ration on the feed intake (FI) and food conversion efficiency (FCE) in sea cucumber A. japonicus1 Temperature (°C) Ration (%)
FCE (% day− 1)2
FI (% day− 1)3
16
− 121.41 ± 15.75 5.57 ± 0.84e 9.22 ± 2.16e − 102.31 ± 10.26b 4.35 ± 3.04e 7.25 ± 2.57e − 114.43 ± 5.03b − 1.32 ± 0.76d 1.49 ± 0.52e − 133.61 ± 8.67a − 31.53 ± 9.39c − 9.49 ± 2.11d
0.26 ± 0.01a 0.50 ± 0.02b 1.13 ± 0.05c 0.26 ± 0.08a 0.52 ± 0.01b 1.08 ± 0.04c 0.25 ± 0.01a 0.46 ± 0.03b 1.14 ± 0.10c 0.25 ± 0.01a 0.51 ± 0.02b 1.11 ± 0.04c
18
20
22
0.3 0.6 1.4 0.3 0.6 1.4 0.3 0.6 1.4 0.3 0.6 1.4
ab
(Satiation)
(Satiation)
(Satiation)
(Satiation)
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22 °C, suggesting that the decrease of SGR might be attributed to the lower FCE at high temperature. This result was similar to those of previous studies on other aquatic animals, such as fish (Micropterus salmoides, Beamish, 1972; Salmo trutta, Elliott, 1976; Scophthalmus maximus, Koskela et al., 1997; S. maximus, Van Ham et al., 2003) and shrimp (Fenneropenaeus chinensis, Tian et al., 2006). In this experiment, the energy budget of juvenile A. japonicus at 16 °C and maximum ration was: 100 C = 27.66 F + 2.94 U + 22.36 G + 47.04 R. This result indicated that the energy required for metabolism by juvenile A. japonicus was greater than fecal energy. This conclusion is different from that reached for a previous study of mature (32.5 ± 0.1 g) A. japonicus fed diets containing dried bivalve feces and/or powdered algae (Yuan et al., 2006). The differences of food types and body sizes of the test sea cucumbers in the two studies might be the basis for the differences (González et al., 1993; Dong et al., 2005; Yang et al., 2006). In general, at the satiation condition, oxygen consumption increased with increasing temperature (Hopcroft et al., 1985) and at the temperatures of 16 °C, 18 °C, 20 °C and 22 °C, the ratios of energy required for respiration /energy consumed in food (R/C) were 47.04%, 64.06%, 67.67%, and 83.36%, respectively (Table 2). Temperature had no significant effect on the energy lost in the feces or excretion, indicating that the increase of energy used for metabolism at high temperature or poor absorption of food was the major factor in the decrease of growth. In conclusion, the decrease of growth in juvenile A. japonicus at high temperature is attributed to the
1
Values (mean ± S.E. of four replications) in the same column not sharing a common superscript letter are significantly different (P b 0.05). 2 FI (%) = 100 × F/[D × (W2 + W1)/2]. 3 FCE (%) = 100 × (W2 − W1)/F. W2 and W1 are the final and initial wet body weight of the sea cucumbers, respectively; D is the duration of the experiment; F is the total food taken by sea cucumbers during the whole experiment.
et al., 2005, 2006; Yang et al., 2005; Dong and Dong, 2006). Sea cucumber A. japonicus can survive in a temperature range of 0–30 °C, but growth occurs only between 12 °C and 21 °C, and the optimum temperature for growth is 15–18 °C (Yu and Song, 1999; Asha and Muthiah, 2005). The threshold temperature for aestivation of A. japonicus is nearly 23–24.5 °C (Liu et al., 1996; Yang et al., 2006). In this study, SGRw, SGRe and FCE decreased significantly with increasing temperature from 16 °C to Table 2 Energy budgets in A. japonicus at different temperatures and rations 1 Temperature (°C)
Ration (% body weight day− 1)
16 °C
0.00 0.30 0.60 1.4 (Satiation) 0.00 0.30 0.60 1.4 (Satiation) 0.00 0.30 0.60 1.4 (Satiation) 0.00 0.30 0.60 1.4 (Satiation)
18 °C
20 °C
22 °C
1
Food consumption (J.g0 1.d− 1) 116.86 ± 7.85a 242.58 ± 13.65b 540.07 ± 24.82c 117.56 ± 1.39a 243.08 ± 12.06b 505.69 ± 49.98c 115.13 ± 7.52a 218.53 ± 20.89b 543.65 ± 51.58c 108.54 ± 4.46a 237.74 ± 14.82b 504.52 ± 24.78c
Growth (J.g− 1.d− 1) − 223.98 ± 26.63 d − 141.53 ± 12.66c 6.07 ± 4.64b 120.77 ± 26.37a − 223.98 ± 26.62ab − 194.68 ± 25.17a − 119.04 ± 6.83b 14.07 ± 25.24c − 248.56 ± 17.95a − 207.81 ± 29.77ab − 199.88 ± 8.42b − 22.37 ± 57.11c − 284.27 ± 47.43a − 244.77 ± 9.91b − 170.09 ± 32.70c − 64.45 ± 25.00d
Common letter denotes no significant difference between means (P b 0.05).
Faecal (J.g− 1.d− 1) 52.73 ± 4.15a 79.20 ± 3.46b 149.36 ± 7.73c 47.59 ± 3.75a 71.48 ± 3.13b 134.80 ± 6.98c 44.76 ± 3.52a 64.51 ± 2.82b 139.99 ± 15.75c 39.58 ± 3.11a 59.45 ± 2.60b 112.12 ± 5.80c
Excretion (J.g− 1.d− 1)
Metabolism (J.g− 1.d− 1)
37.33 ± 1.43b 36.65 ± 1.77b 16.79 ± 1.05a 15.89 ± 1.68a 46.05 ± 3.48b 48.47 ± 2.99b 32.93 ± 1.03a 32.83 ± 6.10a 38.90 ± 2.69a 39.53 ± 2.49a 40.51 ± 2.70a 56.47 ± 3.59b 53.85 ± 4.48b 40.87 ± 1.45a 34.21 ± 4.38a 36.28 ± 4.02a
152.62 ± 6.26a 169.02 ± 11.21a 181.74 ± 19.05a 254.04 ± 14.54b 177.93 ± 23.45a 195.21 ± 24.77a 257.71 ± 17.03b 323.93 ± 70.37c 209.66 ± 15.84a 239.95 ± 26.65a 313.39 ± 15.62b 367.87 ± 9.19b 230.41 ± 43.08a 272.86 ± 11.05ab 314.17 ± 21.97b 420.56 ± 46.96c
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decrease of FCE and the increase of energy consumed by respiration. Due to the low energy content of its food (mainly contains alga pieces, mud and organic debris) and its low eating efficiency, sea cucumber A. japonicus can not obtain plentiful energy everyday. At the temperature beyond 22 °C (near the temperature threshold for aestivation), energy requirement exceeded energy intake. Therefore, sea cucumber A. japonicus has to decrease its energy requirement and metabolic rate by aestivation when ambient temperature exceeds the threshold point. Acknowledgements We are grateful to the anonymous referees and Dr. David Cushley for their helpful comments. We thank Dr. Xiangli Tian and Dr. Fang Wang for their technical support and helpful suggestions. The Chinese National Natural Science Foundation (grant No.30400333) and National Key Technologies R&D Program of China (grant No. 2006BAD09A01, 2006BAD09A06) supported this study. References Asha, P.S., Muthiah, P., 2005. Effects of temperature, salinity and pH on larval growth, survival and development of the sea cucumber Holothuria spinifera Theel. Aquaculture 250, 823–829. Beamish, F.W.H., 1972. Ration size and digestion in largemouth bass, Micropterus salmoides Lacepede. Can. J. Zool. 50, 153–164. Carfoot, T.H., 1987. Animal Energetics. Academic Press, New York, pp. 407–515. Chen, J.X., 2004. Present status and prospects of sea cucumber industry in China. In: Lovatelli, A., Conand, C., Purcell, S., Uthicke, S., Hamel, J.F., Mercier, A. (Eds.), Advances in sea cucumber aquaculture and management, 463. FAO, Rome, pp. 25–38. Dong, Y.W., Dong, S.L., 2006. Growth and oxygen consumption of the juvenile sea cucumber Apostichopus japonicus (Selenka) at constant and fluctuating water temperatures. Aquac. Res. 37, 1327–1333. Dong, Y.W., Dong, S.L., Tian, X.L., Wang, F., 2005. Effects of water temperature on growth, respiration and body composition of young sea cucumber Apostichopus japonicus. Fish. Sci. China. 1, 33–37 (In Chinese with English abstract). Dong, Y.W., Dong, S.L., Tian, X.L., Wang, F., Zhang, M.Z., 2006. Effects of diel temperature fluctuations on growth, oxygen
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