The Effects Of Environmental Factors On Behavior And Growth Of Sea Cucumber Apostichopus Japonicus

Two temperature levels of15℃and21℃combined with three photoperiod (12L:12D,24D724L) treatments were used to investigate the effects of temperature and photoperiod on the daily activity rhythm of adult (52.01±5.14g) and juvenile (10.68±3.52g) sea cucumber (Apostichopus japonicus). We also investigate the effects of temperature and light intensity on the activity time budgets of sea cucumber, and the difference between adult and juvenile A. japonicus. The result showed that A. juponicus was a typical nocturnal animal, there was a peak of feeding and moving at periods of2:30-4:00and18:30-22:00, the other peaks of activity occurred at12:30-14:00under the21℃treatment, there also were two peaks of activity occurred at2:30-4:00and18:30-22:00under15℃treatment.Temperature was an important factor affecting behaviors of A. japonicus under the same photoperiod. The feeding activity proportion of A. japonicus under15℃treatment is significantly higher than the proportion under21℃. Light-intensity was an important factor affecting the animal behavior under15℃, the feeding and moving behavior proportion of A. japonicus under the dark treatment were significantly higher than that under light treatment.There were significant differences of activity budget between the adult and juvenile A. japonicus. The feeding and activity behavior proportion of adult A. japonicus were significantly higher than the juvenile under the21℃treatment, and the result under15℃was opponent.We designed six types of sediments easily found in natural sea including sand (S), muddy (M), small rock (SR), large rock (LR), muddy with eelgrass planted (SG), and large rock with benthic algae planted (AR). Sea cucumber’s selections for different types of sediment are significantly different, they negatively selected sand and muddy sediments, and positively selected three types of sediments including small rock, large rock and large rock with benthic algae planted on, and utilizations of sea cucumber for these three types of sediments were significantly higher than the other types.Light-intensity played an important role on affecting the patch selection of A. japonicus. When lighted, the proportion of sea cucumbers selected large rock, muddy with eelgrass planted, and large rock with benthic algae planted. On the contrary, under darkness, the number of sea cucumber attached the wall of aquarium was largely increased. There were significant differences between the adult and juvenile A. japonicus. Juvenile individuals selected more small rocks and muddy sediments, but adults selected more large rock sediment.As our results, eelgrass has significant effects on improving environmental quality for sea cucumber, it keeps ammonium nitrogen of the water body under a low density and the GSH and T-SOD in coelomic fluid of A. japonicus low and stable. Also, eelgrass co-culture with sea cucumber benefits the final weight and GL/BL of A. japonicus.