Study On Physiological Basis Of Polyculture Of Hemicentrotus Pulcherrimus With Apostichopus Japonicus In Sea Cucumber Pond

The explosive proliferation of macroalgae in sea cucumber ponds poses a serious threat to the survival of Apostichopus japonicus,and at the same time,it will cause damage to the whole ecological aquaculture system.Therefore,the control of algae explosive proliferation is of great significance to the culture of sea cucumber.In this study,we envisaged using Hemicentrotus pulcherrimus to control macroalgae in sea cucumber ponds,combined with molecular biology to identify the species and variation of macroalgae in sea cucumber ponds,and to identify the control objects;The feeding habits and physiological changes of H.pulcherrimus on common algae in sea cucumber ponds at different water temperatures were studied;Mixed feeding of A.japonicus with H.pulcherrimus in the same water,then we discussed the feasibility and optimum proportion of ployculture.The results will provide the basis and direction for the follow-up work of macroalgae control in sea cucumber ponds.1.Morphological and Molecular Biological Identification of Several Macroalgae in Sea Cucumber Culture PondsIn order to find out the species of macroalgae,the macroalgae in culture ponds of sea cucumber in Penglai area were investigated and sampled from March to August2018,and the annual hydrological changes of sea cucumber ponds in Penglai area were monitored.Ten species of macroalgae in sea cucumber ponds were identified as HYn(n=1,2…10).Combined with morphological observation and 18 S rDNA sequence analysis,HY1,HY4,HY5,HY8 and HY10 were identified at species level,and HY2,HY3,HY6,HY7 and HY9 were identified at genus level.It was clear that the most abundant and harmful algae in sea cucumber culture ponds were Leathesia difformis,Chaetomorpha moniligera and two species of Ulothrix and Enteromorpha,and their variation regularities have been found out.The results provide a basis and direction for the follow-up management of macroalgae in sea cucumber culture ponds.2.Study on Feeding Selection,Respiration and Excretion of Five Marcoalgae by H.pulcherrimus under Different Water TemperaturesH.pulcherrimus was choosed as the research object and the feeding choice to five macroalgae in sea cucumber ponds was studied.By means of breathing bottle method,the oxygen consumption and ammonia excretion rates of H.pulcherrimus fed on different algae at different temperatures(10.1?,15.6?,20.3?)were compared.The results showed that the feeding selectivity of H.pulcherrimus to five algae in order from large to small is Undaria pinnatifida,L.difformis,Ulva pertusa,Enteromorpha intestinalis,and C.Moniligera.The daily relative feeding and weight gain rate of H.pulcherrimus were significantly affected by temperature and algae species.When the water temperature was 15.6?,the daily relative feeding rate and weight gain rate were the highest.The group fed on U.pinnatifida was significantly higher than other groups.The group fed on C.moniligera had the lowest daily relative feeding rate and weight gain rate.Oxygen consumption rate of H.pulcherrimus increased gradually with the increase of water temperature in different groups.At the same temperature,the oxygen consumption rate of U.pertusa group was the highest.The ammonia excretion rate first increased and then decreased with the increase of water temperature,and at 15.6?,the rate was the highest.The results of this study will provide a foundation for the ecological breeding of H.pulcherrimus and for the construction of a green integrated aquaculture model in sea cucumber ponds.3.Effects of Different Algae and Ployculture Ratio on the Growth and Digestive Enzyme Activity of Sea Cucumber(A.japonicus)and Sea Urchin(H.pulcherrimus)The effects of different macroalgae and ployculture ratio on the growth and the digestive enzyme activities of A.japonicus and H.pulcherrimus were studied.The results showed that different macroalgae and ployculture ratio had a significant effect on the weight gain rate(WGR)and specific growth rate(SGR)of A.japonicus.In L.difformis group(H group),the SGR of sea cucumber in 3:1 ratio was largest(0.94±0.12%/d),whereas the SGR in 2:1 ratio reached 1.36 ± 0.04 % /d in U.pertusa group(L group)..The SGR of sea urchin decreased with the increase of its own density and at the same ployculture ratio,L group was significantly higher than H group.Trypsin and amylase activities of the intestinal of sea cucumber are affected by different algae and polyculture ratio.The activities of the two enzyme both showed a decreasing trend with the decrease of polyculture ratio,but the difference between L1 and L2 was not significant.The activity of trypsin and amylase in L group was higher than that in H group under the same ployculture ratio.Lipase is only affected by the polyculture ratio,showing a decreasing trend.According to the above results,when U.pertusa was used as bait,the suitable ployculture ratio of H.pulcherrimus and A.japonicus was 2:1,while the suitable ployculture ratio was 3:1 when L.difformis was used as bait.,The results of this study will provide data support for the establishment of integrated aquaculture model.of A.japonicus and H.pulcherrimus.