Induced spawning of tropical sea cucumber, Stichopus fusiformiossa by neurotransmitters: Challenges and way forward

It is imperative to develop aquaculture methods for the tropical sea cucumber, Stichopus fusiformiossa as it is an essential component for the pharmaceutical and traditional medicine industry in Malaysia. With sea cucumber stocks harvested freely, conservation efforts should be in place to overcome future depletion or loss of populations in the wild. This study represents the first report to induce spawning of S. fusiformiossa using conventional methods (thermal shock, desiccation, microalgae stimulation) and neurotransmitter injections (serotonin, 1-methyladenine, epinephrine, norepinephrine) in an indoor based aquaculture system. Post induction, the sea cucumbers were observed for 8 hours. They displayed classic sea cucumber pre-spawning behaviours, namely, raising their head, swaying the anterior (side to side, back and forth, head spinning/circling) and prominent visibility of the gonopore. All neurotransmitters used successfully triggered the pre-spawning behaviours, with the group induced with 1-methyladenine remaining active throughout the observation period. During the first 10 minutes (0 hr) of neurotransmitter injection, 1-methyladenine induced group had more than 50 % of the animals with visible gonopores. Generally, body-raising behaviour was observed across all treatments at 0 hr. On the other hand, swaying behaviour was displayed more frequently in all neurotransmitter induced groups, although it remained below 40 % in each case. No swaying action was revealed in the group with raised temperature and microalgae stimulation treated group. While all treatments showed varying degrees of promising pre-spawning behaviour, none spawned during the observation duration. Histology of male and female gonad development stages were also examined randomly. This study describes challenges faced during spawning induction and general maintenance of stichopodid sea cucumbers which potentially undergo autolysis or melting of their external body wall due to physical stress. Utilization of neurotransmitters was unsuccessful; however, the findings from this study paves way for further avenues of research to elucidate the spawning induction techniques of S. fusiformiossa.