Ali Fakhri

The sea cucumber Holothuria (Mertensiothuria) leucospilota is an endemic export species in the Persian Gulf and despite its high economic value, no studies have been conducted on its reproductive biology in this region. The aim of the present study was to characterize the reproductive biology of H. leucospilota using gonadal tissue indices and steroid sex hormones (for the first time in a sea cucumber). Spawning was observed only once in this species. The annual reproductive cycle of H. leucospilota can be divided into six stages including rest (recovery), growth, advanced growth, maturity, spawning and post-spawning. These stages were simultaneous among the population. The onset of gametogenesis coincided with the end of January and continued until the end of July. From May to July, most individuals of the population were mature and ready to spawn. Spawning finally occurred in August when the water temperature reached its maximum. However, spawning continued until early October. In general, according to the present study, the breeding season of H. leucospilota is the summer in the Persian Gulf when the temperature reaches its maximum. Most individuals were in the resting phase between late October and early January, during which it was impossible to determine their sex.