| 1Sea cucumber, Apostichopus japonicus (Selenca), tolerates salinity fluctuationsinhaibting intertide zone. This study deals with growth, food intake, food conversionand the bioenergetic reponses of red variant (wet weight of2.60±0.11g) and greenvariant (wet weight of2.56±0.08g) Apostichopus japonicus to different salinities of22,26,30,34, and38‰at16.5±0.5oC. The results showed that salinity hadsignificant effect on specific growth rate (SGR) of both green and red variants A.japonicus (P <0.01). Both color variants of sea cucumber had highest SGR at30‰,and then decreased when salinity below or above this point. Maximum SGR (thegreen1.07±0.08%d1, the red1.14±0.09%d1, respectively) is related withmaximum food intake (FI) and highest food conversion efficiency (FCE)(P <0.05)occurring at30psu. Only under22‰green variant grew faster than red variant (P <0.05), and under other four salinity treatments there was no significant differencebetween SGR of two color variant holothruians (P>0.05). Adaptable salinity scopefor green and red variants sea cucumber survival is18.5~39‰and20.9~38.6‰,respectively. Salinity can affect FCE of both variants sea cucumber should be related with Oxygen consumption rate (OCR) fluctuation with salinity. The average energybudget formula of sea cucumber at30‰was:100C=6G+42F+3U+49R for redvariant, and100C=6G+45F+3U+46R for green variant (C: energy ingested, G:energy for growth, F:energy loss as feces, U: energy used for ammonia excretion, R:energy loss for respiration). Sea cucumber had maxium energy ingested (C) andhighest proportion of energy for growth (G) at30‰, and then decreased whensalinity is above or below this salinity. Both red and green variants of A. japonicusdeposited for growth were very low, and the energy loss in feces and energy forrespiration accounted for the majority of assimilation energy. The result clearlyshowed that the optimum condition for farming green and red variants A. japonicus,both with respect growth and energy allocation, is the salinity scope of26~30‰.2In order to investigate the effect of light intensity on growth, food utilization, andenergy budget of red and green variants of sea cucumber A. japonicus,96green(6.28±0.02g) and96red (6.34±0.04g) were reared under six light intensities (0,50,300,1000,2000,3500lx) for60days at16°C. The results showed that light intensityhad a significant impact on specific growth rate (SGR)(P <0.01) for both variants ofA. japonicus. Within scope set light intensity50~3500lx, SGR of sea cucumber hadminus relationship with illumination intensity, sea cucumber grew slower as lightchange stonger. Under50lx both red and green variants of sea cucumbers grewfastest (P <0.05) among six treatments. Maximum SGR is related with maximumfood intake (FI) and highest food conversion efficiency (FCE)(P <0.05) occurring at 50lx. Stronger light intensity can restrain the FI and reduce the efficiency of foodcontribution to growth. FCE is lower under stronger intensity might be related withoxygen consumption rate (OCR). Result showed that OCR would obviously change aslight intensity (P <0.05). Minimum OCR occurred under50lx, suggesting minimumenergy be consumed on respiration and most be transformed as body weight. Energymetabolism would change obviously as light intensity (P <0.05). Under50lx averageenergy budget formula of red variant A. japonicus was100C=7G+51F+3U+39R,green variant A. japonicus was100C=7G+51F+3U+39R. which showed seacucumber spent only a small part of energy for growth.3To investgate effect of temperature on growth, food intake, food conversion andenergy budget of red and green color variants Apostichopus japonicus, juvenile seacucumber (initial body weight red variant5.62±0.12g, green variant5.39±0.09g)were aquacultured under8,12,16,20and24°C for60days. The result showedtemperature significantly affected growth of both color variants A. japonicus (P <0.05). For green and red variant A. japonicus can obtain maxium specific growth rate(SGR) at a temperature scope about16-20°C (green variant15.8°C, red variant18.6°C) due to higher FI and FCE (P <0.05). Green color variant had faster growthrate than red color variant under8°C (P <0.05), which indicated green color variant ismore adaptable for slightly lower water temperature. Lower oxygen consumption rate(OCR) under appropriate temperature to be helpful to higher FCE also attributed tohigher growth rate (P <0.05). Average energy budget of A. japonicus at16°C is: 100C=6G+42F+3U+49R for red variant，100C=6G+45F+3U+46R for green variant。,which showed red and green variants of A. japonicus deposited for growth were verylow, and the energy loss in feces and energy for respiration accounted for the majorityof assimilation energy at16°C. Under8°C red color variant sea cucumber desopitedenergy for growth is even minus, which indicated this temperature (<8°C) is too lownot adaptable for red variant A. japonicus growth. The result clearly showed thatoptimum condition for farming green and red variants A. japonicus, both with respectgrowth and food conversion, is the temperature scope of16-20°C.4This article comprehensively analyzed biological status of red variant and greenvariant of A. japonicus from ecology, heredity and morphology, and forecast red A.japnicus aquaculture future in north China. Study now fully showed that red variantand green variant of A. japonicus should think as two subspices of a specie A.japonicus. There are four basis to draw this consulion. First, there are morphologyisolation between two variants of A. jpaonicus. This two color variant had differentcolor on ventral side and this color difference can be inherited by the offspring.Secondly, there is ecology isolation between green variant and red variant seacucumber. Low water temperature and lower salinity would obviously restrainedgrowth rate of red variant sea cucumber, even the survival rate. It suggested redvariant had different ecological factor such as temperature and salinity to live. Thirdly,green variant had geographical isolation from red variant sea cucumber. Red variant islimited distributed only Oshika Peninsula and Saiki Bay, which is affected by Kuroshio and had higher constant temperature and salinity. The green variant A.japonicus distributed intertidal zone from Russia Haishenwai along Japan Sea, KoreaPeninsula, Shandong Peninsula, Liaodong Peninsula. Finally there is different geneticcomposition between two variant A. japonicus, and green variant can hybridize withred variant. It suggested that two variant can exchange gene and didn’t formreproduction isolation. As different color variant of A. japonicus they had constantheredity and not even to reproduction isolation. Whatever how much morphologyisolation between them, it should be considered as two subspecies of A. japonicus.Aquaculture practice proved after several generations, A. japonicus parentsgermplasm degenerated, and offspring became weak to illness and less than normaland grew slowly. To change this situation red variant of A. japonicus is introducedinto China. After temperature, salinity and light intensity experiment, data showedthat red variant sea cucumber can adapt water factor of north Huanghai. It isnecessary to select adapt site considering far away form lower salinity water insummer rain and water temperature of bond bottom is no less than4℃. |
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