Studies on embryo development and larval feeding of clam Paphia textile

The present study investigated the embryonic development, growth, metamorphosis, locomotory patterns, and feeding behaviors of Paphia textile larvae, offering dietary suggestions based on observed patterns. The larvae were subjected to a dietary regimen consisting of nine microalgae species at various developmental stages (1, 4, 7, 10, 13, and 16 days post-hatching). One hour after each feeding session, their feeding patterns were carefully documented. To assess digestion, larvae that had consumed the microalgae were filtered, rinsed, and placed in filtered seawater. The embryonic development of P. textile encompassed distinct stages, including the fertilized egg, emergence of the first and second polar bodies, progression through the 2–32 cell stage, morula stage, blastula stage, gastrula stage, trochophore stage, and ultimately the D-larvae stage. Movement patterns revealed that the larvae primarily utilized their cilia for locomotion and feeding. From a transverse perspective, they moved clockwise, tracing an irregular circular path. Vertically, they exhibited spiral movements, ascending or descending as needed. As they entered the late stage, they transitioned to using reciprocal expansion of their axe feet for crawling and filtering food through their gills. Throughout their development, the larvae were fed a variety of microalgae species, including Chlorella vulgaris, Nannochloropsis oculata, Pavlova viridis, Dicrateria zhanjiangensis, and Isochrysis galbana. At 4 days old, they began consuming Dunaliella salina, and at 7 days, they incorporated Platymonas subcordiformis into their diet. By 10 days of age, they had expanded their food choices to include Chaetoceros muelleri. However, it was noted that larvae frequently suffered from indigestion or incomplete digestion when fed excessive amounts of C. vulgaris and N. oculata. Therefore, it is recommended to commence the larval culture of P. textile using P. viridis, D. zhanjiangensis, and I. galbana as the primary dietary sources. Furthermore, a feeding strategy emphasizing small, frequent meals is recommended to promote optimal digestion and larval health. •The larvae were able to feed on Chlorella vulgaris, Nannochloropsis oculata, Pavlova viridis, Dicrateria zhanjiangensis, and Isochrysis galbana throughout their development.•They began feeding on Dunaliella salina at 4 days of age, Platymonas subcordiformis at 7 days of age, and Chaetoceros muelleri at 10 days of age.•However, the larvae struggled