Reproductive biology of the commercial sea cucumber Holothuria fuscogilva in the Solomon Islands

Reproduction of Holothuria fuscogilva (Selenka, 1867) in the Solomon Island s was investigated over a 4 yr period (1994 to 1998) by macroscopic and mic roscopic examination of the gonad tubules, the gonad index (GI) method, his tological examination of gametogenesis, and spawning-induction trials. The gonad consisted of numerous tubules that dominated the coelom of gravid spe cimens. New tubules appeared in March, and grew in size and extent of branc hing until they reached their maximum size and maturity in August. Spawning occurred from August to October, with the majority of gametes released dur ing October, although it was only partial in many individuals. After spawni ng, the tubules appeared wrinkled and resorbed into the gonad basis. A five -stage gonad maturity scale based on the macroscopic appearance of the gona d tubules corresponded with discrete stages of gametogenesis identified by histology. Gametogenesis was initiated in mid-March, with oogenesis and spe rmatogenesis occurring in parallel, followed by the gl owing stage (May to July) which was mat ked by active gamete development. Successful induction of spawning during the brooding period corroborated the GI and histological data. The uniform growth of gonad tubules indicated that H. fuscogilva in the Solomon Islands does not conform to the progressive tubule recruitment model described for other holothurians. An important application of this st udy is that the appearance of gonad tubules, removed by biopsy, can be used to determine the gonad condition of wild adults or captive brood-stock.