Spawning induction of the high-value white teatfish sea cucumber, Holothuria fuscogilva, using recombinant relaxin-like gonad stimulating peptide (RGP)

Abstract

We have previously shown in Holothuria leucospilota the maturation-inducing role of the neurohormone relaxin-like gonad-stimulating peptide (RGP). Here, we report the induction of oocyte maturation and spawning in another holothuroid, the white teatfish, H. fuscogilva, with a species-specific recombinant RGP produced in the yeast expression system. The recombinant H. fuscogilva RGP (rwt_RGP) was bioactive in vitro, as demonstrated in germinal vesicle breakdown (GVBD) assays, and in vivo, stimulating spawning in H. fuscogilva at three doses tested (50, 100 and 150 μg/kg). The spawned gametes were viable, and here we report their development until the early juvenile stage. The rwt_RGP was also bioactive in H. scabra and in H. leucospilota. We also investigated the bioactivity of two forms of synthetic RGP, whose sequences were synthesised according to that of the H. fuscogilva. The peptides have linked B- and A-chains with one form having an amidation at the carboxy terminal of the B-chain. We observed bioactivity of both synthetic peptides, as evidenced by induction of GVBD in in vitro assays and by induction of spawning in fully grown H. leucospilota. Altogether, our results provide further evidence of the gonad-stimulating role of RGP in echinoderms. We have shown that our recombinant and synthetic RGPs are applicable among the Holothuria species, providing a reliable breeding method for the highly valuable cultured species of this class. Our findings have significance both for the survival of threatened sea cucumbers and for their sustainable aquaculture.