APOPTOSIS AND ROLE OF CASPASE IN DEVELOPMENT OF MERETRIX MERETRIX LARVAE
文蛤(Meretrix meretrix)幼虫发育过程中细胞凋亡和Caspase 功能分析

Apoptosis plays an important role in larval development of species. Taking clam Meretrix meretrix as an example, to the apoptosis and function of caspase in bivalve larvae development and metamorphosis were studied. Apoptosis was detected in larvae at different stages with TUNEL labeling (Terminal-deoxynucleotidyl transferase mediated dUTP Nick End Labeling). The distribution of activated caspase in larvae was examined with CaspACETM FITC-VAD-FMK In Situ Marker. The pan-caspase inhibitor (Z-VAD-FMK) was used to analyze the function of caspase in 4-day-old and 5-day-old larvae post fertilization. Dimethyl sulfoxide (DMSO), the solvent of the inhibitor, was added to seawater as control. According to the effect on metamorphosis, the function of caspases in larvae was analyzed. The results reveal that the main apoptosis event occurred in the velum of pediveliger before metamorphosis, indicating that the degradation of velum might be the process of apoptosis. The activated caspases were observed in the larvae from trochophore to pediveliger, suggesting the caspases are involved in the whole developmental process. Having detected no signal in the velum, we proposed that the apoptosis in velum might be caspase-independent. The 4-day-old and 5-day-old larvae under treatment of caspase inhibitor showed significant lower metamorphosis rates than that in the DMSO control group (P<0.05). The results indicate that the caspases had functioned in early and later stages of metamorphosis, and also that DMSO could be an inducer in larvae metamorphosis.