Timing of the reproductive cycle of Holothuria from the Persian Gulf based on evaluation of gonad histomorphology and sex hormones

The sea cucumber Holothuria (Mertensiothuria) leucospilota is a species native to the Persian Gulf that is commercially exported. Despite its high economic value, no study has been conducted on the reproductive biology of this species 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 to occur only once per year in this species. The annual reproductive cycle of H. leucospilota can be divided into six stages that include resting (recovery), growth, advanced growth, mature, spawning and spent. These stages were observed to occur simultaneously among the study 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 reached its maximum value. However, spawning continued until the beginning of October. In general, the reproduction season of H. leucospilota from the Persian Gulf is the summer, 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.