Timing of the reproductive cycle of Holothuria (Mertensiothuria) leucospilota (Brandt, 1835) from the Persian Gulf based on evaluation of gonad histomorphology and sex hormones

Sea cucumber Holothuria (Mertensiothuria) leucospilota is a native export species in the Persian Gulf, and despite its high economic value, no study has been conducted on its reproductive biology in this region. The aim of the present study was to describe the reproductive biology of H. leucospilota using gonad tissue indices and steroid sex hormones (for the first time in sea cucumbers). Spawning was observed only once in this species. The annual reproductive cycle of H. leucospilota can be divided into six stages including resting (recovery), growth, advanced growth, mature, spawning and spent. These stages were simultaneous among the population. The beginning of gametogenesis coincided with the end of January and continued until the end of July. From May to July, the majority of individuals in the population were mature and ready to spawn. Spawning finally took place in August when the water temperature reaches its maximum value. However, spawning continued until the beginning of October. In general, according to the present study, the reproductive season of H. leucospilota is the summer of 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 distinguish the sex of them.