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The complete larval development of Ibacus ciliatus from hatching to the nisto and juvenile stages using jellyfish as the sole diet

Wakabayashi, Kaori, Nagai, Satomi, Tanaka, Yuji
Aquaculture 2016 v.450 pp. 102-107
Decapoda, Scyphozoa, body length, clams, crustacean culture, diet, energy, fish, hatching, instars, juveniles, larvae, larval development, lobsters, metamorphosis, molting, mussels, nutritive value, rearing, survival rate, zooplankton
Phyllosomas of scyllarid lobsters are known to associate with jellyfish in the wild, suggesting that they prey on a wide variety of gelatinous zooplankton species. To investigate the potential of utilizing jellyfish as a diet for Ibacus ciliatus phyllosomas in culture, 22 newly hatched phyllosomas were reared individually and fed with the jellyfish Aurelia aurita and Chrysaora pacifica throughout the rearing period. Of the 18 phyllosomas that survived to stage VII, nine directly metamorphosed into the nisto stage 66.8days (range: 65–70) after hatching. Among them, five nistos successfully molted into the juvenile stage 85.0days (range: 83–87) after hatching. On the other hand, eight of the phyllosomas at stage VII molted through an extra instar. Four metamorphosed into the nisto stage 79.3days (range: 76–82) after hatching; however, these nistos failed to molt into the juvenile stage. Significant differences of the body length between the phyllosomas with and without an extra instar were observed after stage V. The addition of an extra instar in phyllosomas at stage VII may have been caused by the insufficient nutritional conditions during the earlier stages. Complete larval development from hatching to the juvenile stage in I. ciliatus was observed for the first time. Our method of using jellyfish as diet may be useful for improving the aquaculture techniques of I. ciliatus, and other species.Statement of relevancePhyllosoma has been known as a gelatinous zooplankton feeder in the wild. The most important finding in the present paper is that phyllosomas of the scyllarid lobster I. ciliatus can grow into the juvenile stage with feeding on jellyfish. The previous studies have tried to rear I. ciliatus phyllosomas with feeding clams or mussels, and observed that phyllosomas successfully metamorphosed into the nisto stage. However, no one has achieved to obtain the juveniles in culture. We utilized jellyfish as diet for phyllosomas. Consequently, the complete larval development from the newly hatched phyllosoma to the juvenile stages was observed for the first time. Jellyfish has been successfully applied as diet for phyllosoma only in the scyllarid lobster Ibacus novemdentatus until today, so that the present experiment is the second successful achievement. This result suggests that growth and survival rates of scyllarid lobster phyllosoma may be improved by use of jellyfish as diet for phyllosoma in their hatchery.Although the nutrition level of the gelatinous zooplankton has been known to be low, survival and growth rates of phyllosoma which fed on gelatinous zooplankton have been higher than those of phyllosoma which fed on other diet containing much nutrition. Similar results have been obtained in several species of fish. Therefore, we emphasize in this manuscript that the utilization of jellyfish as a nutritional resource for the fish and crustacean aquaculture should be further studied.It is considered that the extra molting may be added under conditions where larvae are unable to obtain sufficient energy reserves for growth and metamorphosis. Such conditions are mainly caused by inadequate nutritional quality; however, there is limited information of the critical timing at which the addition of the extra molting is determined. In our experiments, significant differences of body length between the phyllosomas having an extra molting and the phyllosomas without extra molting were started to be observed during the early stage of phyllosomas. Our results suggest that, in decapod crustaceans, the mortality of decapodid and juvenile stages may be affected by insufficient energy reserves during the early larval stages.