Improved method for culturing the swimming crab Portunus trituberculatus larvae to prevent mass mortality during seed production

Larvae of the swimming crab Portunus trituberculatus are traditionally cultured with rotifers, Artemia, and phytoplankton. However, abnormal morphology of last-stage zoeae caused by excessive nutritional intake, abnormal morphology of megalopae caused by indirect ingestion of phytoplanktons via rotifers during zoeal stages, and lack of essential nutrients due to starvation of Artemia cause mass mortality. To develop techniques addressing these issues simultaneously, we evaluated methods to prevent megalopal abnormalities while avoiding starvation of Artemia (experiment 1). Then, we evaluated the effects of Artemia feeding schedules on the occurrence of last zoeal abnormalities (experiment 2). In experiment 1, megalopal abnormality was prevented by rearing larvae with enriched Artemia supplemented with digestible Nannochloropsis, but without rotifers. However, the developmental rates were variable among individuals because of the large size of enriched Artemia for early zoeae, and last zoeal abnormality was induced because of excessive Artemia feeding, resulting in low survival. In experiment 2, newly hatched Artemia were only supplied during the first zoeal stage, and larvae were reared with low density Artemia and/or low salinity. These measures achieved high survival rate while suppressing the last zoeal abnormality. Our results suggest that P. trituberculatus larvae can be successfully cultured using only Artemia.