The Research Institute for Marine Fisheries (RIMF, Vietnam) and University of the Sunshine Coast (USC, Australia) have been addressing these problems through artificial induction of oocyte maturation and spawning. From 2016 – 2019, under the PhD program, a staff of RIMF, Mr. Hoang Dinh Chieu has been studying the stimulation of sea cucumber spawning and oocyte maturation at USC by neurohormones extracted from sea cucumber radial nerve system.
Artificial induction of oocyte maturation followed by in vitro fertilization represents an innovative approach that could help increase production. The inducers of oocyte maturation are naturally synthesised within neural tissue, which in sea cucumbers includes radial nerve cords. In this study, we found that mature female radial nerve extract (RNE; 233 µg/ml) induced in vitro oocyte maturation at 98.9% efficiency in sea cucumber Holothuria leucospilota, based on germinal vesicle breakdown. RNE-matured oocytes were then fertilized (99%) with conspecific sperm, and larvae developed to late auricularia stage (25 days post-fertilisation). These detailed results can be seen in the publication here: https://doi.org/10.1016/j.aquaculture.2018.05.032
Furthermore, we have found a sea cucumber neuropeptide called RGP (relaxin-like gonad-stimulating peptide) that when produced as a recombinant and injected into mature individuals, could induce spawning behavior (head waving) and spawning within 1 hour. The RGP neurohormone is similar to a relaxin neurohormone in humans that we use for functions such as relaxing the uterine muscle wall and increasing sperm production. The sea cucumber juveniles from the spawning stimulation bioassay have been growing normally. These detailed results can be seen in the publication here: https://doi.org/10.3389/fgene.2019.00077
Stimulation of spawning in sea cucumber Holothuria scabra using RGP neurohormone.
Video of spawning stimulation in Youtube: https://www.youtube.com/watch?v=48P420pHnoQ
Our results provide a key finding for the development of a break-through new artificial breeding approach in sea cucumber aquaculture. After these successes, we are testing RGP neurohormone in another commercially important sea cucumber Holothuria fuscogilva at the Research Institute for Aquaculture No.3 (RIA3) through the Aus4Innovation program. This project is managed by CSIRO (The Commonwealth Scientific and Industrial Research Organisation, Australia) in partnership with MOST (Ministry of Science and Technology, Vietnam) and implemented by USC, RIA3 and RIMF. Link: https://research.csiro.au/aus4innovation/winners-of-aus4innovation-partnership-grants-announced