As the precursor of vitellin (Vn),vitellogenin (Vg) has initially been considered as a female-specific protein involved in vitellogenesis,while it was also present in males induced by hormones or organs manipulation.Distinct from vtg1 we previously found in female mud crab Scylla paramamosain,vtg2 was intriguingly detected in male testis under normal physiological conditions in this study.study. Sequence analysis showed that vtg2 and vtg1 were actually two isoforms of Vg caused by different types of alternative splicing.