Studies On The Technique For Artificial Breeding Of Phascolosoma Esculenta

Phascolosoma esculenta,belonging to Sipuncula,Phascolosomatidea,Phascolosomatifo-rmes,Phascolosomatidae,is the endemic spieces of China,it is also in the larger yield of species of Sipunculain China.P.esculenta is mainly grown in middle and high tide area of intertidal zone;it has been cultured in China with high economic value.However,with the decrease of natural resources,the studies on the cultivation biology becomes more and more attractive.At present,the seeds for aquaculture of P.esculenta mainly depend on collecting wild seeds.As gradual decay of natural resources and continuous expansion of artificial breeding scale,the seeds for aquaculture will become increasingly,it is alreadly imperative to conduct artificial propagation.This paper reported the artificial breeding technique of P.esculenta,and observed the breeding biology,artificial culture and oxytocin,etc.The main results are as following:Observing the development of germ cell and morphological characteristics of P.esculenta,the study of ratio of female and male,fecundity,spawning and fertilization rate was conduct.The results showed that the average weight of P.esculenta parents spawning was 4.61 g,and the ratio of female and male was 1:1 in Ningde;The fecundity increased with growing weigh,while the relative fecundity decreased when the individual weight reached a certain size(each greater than 5g);From June 30 th to September 28 th,the period of parents spawning is 91 days and the total amount of eggs was 16.33 million.The amount of eggs was 7.525 million,6.995 million and 2.21 million in July,August and September,respectively,which is accounted for 46.1%,40.4% and 13.2% of the total amount,respectively.The quality of fertilized eggs from July to August was better than that in September.Hatching rates,larval survival rate and growth of Phascolosoma esculenta were compared under a gradient of different salinities.The results showed that:(1)The range of suitable salinities was 15-30,and the rage of the most optimum salinities was 20-26,showing the tendency of low salinities tolerance;(2)survival activity indices were 9.8,78.3,60.9,12.6,12.2,and 10.7 respectively for the larvae at salinity 10、15、20、25~26、30、35;There were extremely significant differences among the groups.The survival time of the larvae was the longest at salinity 15 and 20,and the survival time was 7 days.(3)From the growth of larvae,the larvae length grew from 251.7μm to 542.9~568.5μm during 9 days of culture and the growth rate was 60.3~63.2μm/d.The fastest speed of growth rate was the group of natural salinity 25~26,and the slowest was the group of salinity 30,there was significant difference between the groups.The highest survival rate of larvae was the group of salinity 20,and the range of the suitable salinities was 15~26.A certain amount of P.esculenta parents were collected from the coastal sea along Fujian Ningde,and then got fertilized eggs through artificial induced spawning after parents intensive cultivation.At water temperature of 28.5~30.5℃ and salinity of 25~26,the hatched pelagospheric larvae began to metamorphoseto nymph by 9~13days,and became juveniles with the body length of 0.8~1.1mm after more than one month of larvae breeding,the larvae reached 4~5mm when cultured for 4 months.Through observation of larval peanut worm(Phascolosoma esculenta)fed by two kinds of marine micro algae(Platymonas subcordiformis and Chlorella sp)and brine shrimp flakes during the test,the results showed that larva peanut worm was omnivorous and could be better feeding,and could develop to benthic morphology.