刺参生活在潮间带，需要耐受水温的昼夜和季节变动。体色多样是刺参的生理特征之一，最近威海乳山海域发现了两种新的色型刺参——白刺参和紫刺参，并成功培育出其子代。将青刺参、白刺参和紫刺参（1.5 ± 0.1 g）分别在水温10 °C、14 °C、18 °C、22 °C和26 °C条件下饲养60天，并测定温度对刺参生长、能量收支及生理酶活的影响。结果显示，温度对刺参的生长、能量收支及生理酶活影响显著（P<0.05）。三种色型刺参的特定生长率、食物转化效率以及生长能比例均在18 °C时达到峰值，而摄食率和摄入能量在22 °C最高。耗氧率和溶菌酶活性随着温度的升高而升高。三种色型刺参的超氧化物歧化酶、过氧化氢酶以及胰蛋白酶活性均在18 °C时达到最大值。水温18 °C和22 °C时，紫刺参的生长率、食物转化效率以及生长能比例显著高于青刺参和白刺参，其原因可能是紫刺参的肠道胰蛋白酶活性和超氧化物歧化酶活性更高。当水温为18 °C、22 °C和26 °C时，三种色型刺参中青刺参的溶菌酶活性最高，而紫刺参最低，表明青刺参和白刺参较紫刺参对于热胁迫更为敏感。水温为10 °C、14 °C、18 °C和22 °C时，白刺参的摄食率和摄入能量较青刺参与白刺参低，表明白刺参的摄食活动不活跃。综上所述，三种色型刺参的最适温度均为~18 °C，紫刺参对于热胁迫的耐受性较好，值得进一步研究。
将青色、白色和紫色刺参（1.0 ± 0.1 g）分别在盐度22、26、30、34和38条件下饲养60天，测定盐度对刺参生长、能量收支以及生理酶活的影响。结果显示，三种色型刺参均可以在盐度22~38条件下存活。盐度对刺参生长、能量收支以及生理酶活有显著影响（P<0.05）。刺参的特定生长率、摄食率、食物转化效率以及摄入能量和生长能比例均在盐度30时达到峰值。在盐度22和38时，刺参的生理酶活性会发生显著变化，表明低盐和高盐会影响刺参的生理代谢。青刺参在盐度22时，生长率显著高于白刺参和紫刺参。在盐度为30、34和38时，紫刺参生长率最高，青刺参次之，而白刺参生长率最低。青刺参在盐度22时，将更多的能量分配用于生长和呼吸。盐度为34和38时，紫刺参的生长能和呼吸能更高。相比于青刺参和白刺参，紫刺参的胰蛋白酶和超氧化物歧化酶活性在盐度30、34和38时显著更高，从而支撑了其较高的特定生长率和食物转化效率。这些结果综合显示，在盐度耐受范围内，青刺参对低盐的耐受性较好，而紫刺参对高盐的耐受性较好。
维生素C在刺参的生长和免疫过程中有着重要的作用。以Vc磷酸酯l-Ascorbyl-2-polyphosphate（LAPP）为添加剂配制6种不同维生素C含量的饲料（0、50、100、200、400和800 mg维生素C等价物kg-1饲料）分别饲养青色、白色和紫色三种色型刺参60天，并测定其生长、能量收支和非特异性免疫酶活性。结果显示，饲料维生素C含量对刺参的生长有显著影响（P <0.05）。青刺参和紫刺参在饲料维生素C含量为200 mg kg-1时特定生长率、摄食率以及生物转化效率最高，而白刺参在100 mg kg-1时达到峰值，表明白刺参的维生素C需求低于青刺参和紫刺参。这可能是因为白刺参较低的生长率和代谢率——其特定生长率、摄食率和食物转化效率效率以及各项免疫指标均低于青刺参和紫刺参。当饲料维生素C含量≥200 mg kg-1时，刺参体腔液丙二醛含量显著降低（P <0.05）。超氧化物歧化酶、过氧化氢酶和溶菌酶活性以及总抗氧化能力在维生素C含量为100~400 mg kg-1时均维持在较高水平。超氧化物歧化酶和过氧化氢酶活性以及总抗氧化能力与刺参特定生长率呈显著正相关（P <0.05），表明饲料中添加维生素C对刺参的生长和免疫大有裨益。白刺参和紫刺参的特定生长率、摄入能量以及生长能在饲料维生素C含量达到800 mg kg-1时显著降低（P <0.05），而青刺参的降低未达到显著水平。饲料维生素C含量达到800 mg kg-1时，刺参的免疫指标降低而体腔液丙二醛浓度略微升高，表明过高的维生素C含量对刺参的生长和免疫有负面作用。紫刺参的超氧化物歧化酶和过氧化氢酶活性高于青刺参和白刺参，指示其免疫状况更好。综合可考虑生长和免疫状况，白刺参的维生素C需求为~100 mg kg-1，青刺参和紫刺参的维生素C需求为~200 mg kg-1。;
A detailed literature review of physiological and ecological adaptability, and nutritional requirements of sea cucumber, Apostichopus japonicus was undertaken. A series of experiments were conducted to study the differences in physiological and ecological adaptability, and nutritional requirements of three color morphs of sea cucumber, A. japonicus--- green, white, and purple color morphs. Such information could be helpful in improving aquaculture technology and management for these three morphs of A. japonicus. The main results are as follows:
1. Effect of temperature on growth, energy budget and physiological performance of different color morphs of sea cucumber, Apostichopus japonicus
As an intertidal species, the sea cucumber Apostichopus japonicus (Selenka), tolerates diel and seasonal temperature fluctuations. This study was conducted to compare the performance of green, white, and purple color morphs of A. japonicus at different water temperatures to help improving aquaculture technology and management. In this study, three color morphs of juvenile A. japonicus (1.5 ± 0.1 g) were cultured at 10 °C, 14 °C, 18 °C, 22 °C and 26 °C for 60 days. The influence of temperature on the growth, energy allocation and physiological performance of A. japonicus was determined. The results indicated that temperature had a significant effect on growth, energy allocation and the physiology of sea cucumbers (P <0.05). Specific growth rates, feed conversion efficiencies and the proportion of energy allocated to growth of all three color morphs of A. japonicus were optimal at 18 °C, while ingestion rates and energy intake reached a maximum at 22 °C. Oxygen consumption rate and lysozyme activity increased in sea cucumbers as temperature increased. Activities of the enzymes superoxide dismutase, hexokinase and trypsin generally reached a maximum in all three color morphs of A. japonicus at 18 °C. The purple morph of A. japonicus had a higher growth rate, food conversion efficiency, and proportion of energy allocated to growth than green and white morphs at 18 °C and 22 °C. This can be explained by the much higher trypsin activity in the intestine of purple morph, which may also be the main reason for the high superoxide dismutase activity in the purple. At temperatures of 18 °C, 22 °C and 26 °C, the green morph had the highest level of lysozyme activity and purple morph had the lowest. These results indicated that the green and white color morphs may be more susceptible to thermal stress than the purple. Ingestion rates and energy intake of white morph were low compared with the green and purple at 10 °C, 14 °C, 18 °C and 22 °C, suggesting that white A. japonicus feed less actively. In conclusion, the optimum temperature for culture of the three color morphs was around 18 °C, and the purple had a better tolerance of thermal stress, which deserves further study and application.
2. The effect of salinity on the growth, energy budget and physiological performance of different color morphs of sea cucumber, Apostichopus japonicus
The sea cucumber Apostichopus japonicus (Selenka) tolerates salinity fluctuations when inhabiting the intertidal zone and culture ponds. Color variation is a distinct characteristic of A. japonicus, and a new color morph, purple A. japonicus was recently found on the coast of Rushan, Weihai City. In this study, green, white and purple morphs of juvenile A. japonicus (1.0 ± 0.1 g) were cultured at salinities of 22, 26, 30, 34 and 38 for 60 days. The influence of salinity on the growth, energy allocation and physiological performance of A. japonicus was determined. The results indicated that the three color morphs tested could survive within the salinity range of 22–38. Salinity had a significant effect on growth, energy allocation and the physiological performance of sea cucumbers (P <0.05). Specific growth rates, ingestion rates and feed conversion efficiencies of A. japonicus were generally optimal at a salinity of 30. Similar results were obtained for energy ingested, and the proportion of energy allocated to growth. Significant changes in enzyme activities of sea cucumbers mainly occurred at salinities of 22 and 38, indicating that metabolism was affected by low and high salinities. Green A. japonicus grew faster than the white and purple color morphs at a salinity of 22. Growth rates were highest in purple, then green and lowest in white color morphs at salinities of 30, 34 and 38. At a salinity of 22, the green allocated more energy to growth and respiration. The purple morph allocated more energy to growth and respiration when water salinity reached 34 and 38. At salinities of 30, 34 and 38, the purple morph had higher trypsin and superoxide dismutase activities, which supported the higher specific growth rate and food conversion rates compared with the green and the white color morphs. The results clearly showed that the green color morph performed better at low salinities, while the purple was better adapted to high salinities within the tolerance range.
3. Effects of dietary protein levels on the growth, energy budget, and physiological and immunological performance of different color morphs of sea cucumber, Apostichopus japonicus
Protein is a necessary nutrient for the sea cucumber, Apostichopus japonicus, an important commercial species in China, South Korea and Japan. In this study, the dietary protein requirements of two newly discovered color morphs—white and purple was investigated and compared with the common, green morph. The green, white and purple morphs were fed a diet with five different protein levels (1, 6, 11, 16 and 21%) for 60 days with a mixture of soybean meal and fish meal (1:1) as the protein source, and their growth, energy budget, physiological and immunological performance were measured. Results showed that dietary protein levels had a significant effect on the growth performance of A. japonicus (P <0.05). 6="" the="" maximum="" specific="" growth="" rate="" and="" proportion="" of="" energy="" allocated="" for="" occurred="" at="" dietary="" protein="" levels="" food="" conversion="" efficiency="" was="" highest="" indicating="" that="" optimum="" level="" these="" color="" morphs="" is="" .="" apparent="" digestibility="" coefficients="" dry="" matter="" crude="" but="" ingestion="" decreased="" with="" increasing="" due="" perhaps="" to="" sea-mud="" content="" diets.="" free="" ammonia="" malonaldehyde="" in="" coelomic="" fluid="" increased="" which="" can="" be="" explained="" by="" enhanced="" metabolism.="" trypsin="" activity="" significantly="" when="">16%, indicating that the protein content was beyond the digestive ability of sea cucumber, and that excess protein in the diet inhibits protein digestion. Catalase (CAT) and glutamic–oxaloacetic transaminase activity was positively and significantly correlated with SGR, indicating that rapid growth was supported by a robust immune system and effective protein metabolism. At a 1% dietary protein level, the purple color morph had significantly higher SGR, FCE, ACPD and CAT activity, and allocated more energy for growth than the green morph, indicating that the purple morph may be better adapted to a low protein diet than the green morph. The white morph had lower SGR, FCE, superoxide dismutase (SOD) and CAT activity, and allocated less energy to growth, but had a higher excretion energy and higher free ammonia content in coelomic fluid than the green or purple morphs, indicating a difference or physiological defect in protein metabolism in the white morph.
4. Effects of dietary ascorbic acid levels on the growth, energy budget, and immunological performance of different color morphs of the sea cucumber, Apostichopus japonicus
Ascorbic acid plays an important role in the growth and immunity of the sea cucumber, Apostichopus japonicus, a valuable commercial species in China, South Korea, and Japan. In this study, the dietary ascorbic acid requirements of two newly discovered color morphs of A. japonicus, white and purple, were investigated, and compared with that of the common green morph. Six diets were formulated containing 0, 50, 100, 200, 400, and 800 mg ascorbic acid equivalent kg-1 diet, as l-ascorbyl-2-polyphosphate. The color morphs were fed the diets for 60 days, and their growth, energy budget, and immunological performance recorded. Results showed that dietary ascorbic acid levels had a significant effect on the growth performance of A. japonicus (P <0.05). The green and purple morphs had the maximum specific growth rate (SGR), ingestion rate (IR), and feed conversion efficiency (FCE) at a dietary ascorbic acid level of 200 mg kg-1, while maximum values for the white morph were recorded at 100 mg kg-1, indicating that the white morph had a lower ascorbic acid requirement than the green and purple morphs. This could be explained by the lower growth and metabolic rates of the white morph, with lower SGR, IR, and FCE values plus immune indicators than the green and the purple morphs. Malonaldehyde (MDA) content in coelomic fluid decreased significantly when dietary ascorbic acid was ≥200 mg kg-1 (P<0.05). Superoxide dismutase (SOD), catalase (CAT), and lysozyme activities, plus total antioxidative capacity (T-AOC) leveled out at 100–400 mg kg-1. SOD and CAT activities plus T-AOC were significantly and positively correlated with SGR (P <0.05), indicating that supplemental dietary ascorbic acid had a beneficial effect on growth and immunity. SGR, energy intake, and the proportion of energy allocated to growth decreased significantly in the white and purple morphs when ascorbic acid levels reached 800 mg kg-1 (P <0.05); as did those of the green morph, but not significantly so. Immune indicators decreased and MDA content increased slightly at the 800 mg kg-1 level, indicating that high dietary ascorbic acid does not benefit growth or immunity. SOD and CAT activities were higher in the purple morph than the green and white morphs, indicating its superior immune system condition. Considering optimum growth and immunity, the ascorbic acid requirement of A. japonicus was ~100 mg kg-1 for the white morph and 200 mg kg-1 for the green and purple morphs.