The mode of action of neuropeptide in gametogenesis and application to artificial induction of gonad development in bivalves

Representative Organization: Tohoku University

2015/04/01 - 2016/03/31

Onagawa Bay and other experimental waters

Others

We performed GnRH administration with marine bivalves (e.g., Japanese scallop, Manila clam) to confirm in vivo effect of the neuropeptide. We also carried out molecular identification of sex differentiation marker genes and the steroidogenic genes that are supposed to be under the control of GnRH from Japanese scallop by using PCR and in silico cloning with next-generation sequencing. In addition, we established organ culture system with scallop gonad to analyze in vitro effect of the neuropeptide. While, we tried to establish the technique of artificially induced spawning in bivalves by using serotonin injection with the antibody of oocyte maturation arresting factor (OMAF) that inhibitory regulates oocyte release in bivalves.

We have cloned the genes encoding gonadotropin releasing hormone (GnRH) from various marine bivalve species so far. In order to develop the artificially induced maturation meditated with GnRH, we previously performed GnRH peptide administration into Japanese scallop. As a result, the GnRH administration accelerated spermatogenesis in males while it inhibited oocyte growth in females. In this year, we performed GnRH administration into Manila clam to confirm whether GnRH can also accelerate gonad development in a clam. However, we were faced with high mortality of the administrated clams. Since it might be caused by administration method, we will need to optimize the method for next year. In addition, we assessed the in vitro effect of GnRH with scallop gonad by organ culture study. The result was that the media containing GnRH could induce oviposition in the piece of scallop ovary. Currently, we are working on the influence to the steroidogenic genes stimulated by GnRH. Meanwhile, to develop the technique for controlling sex of bivalves, as a first step, we tried to identify sex differentiation marker genes for both sexes. In the result, we cloned one gene for testis marker and one gene for ovary marker at present. In addition, to develop the technique for controlling spawning of bivalves, we have studied oocyte maturation arresting factor (OMAF) which inhibits oviposition in Japanese scallop. In this year, we performed artificial induction of spawning with Manila clam by serotonin injection with OMAF antibody that can absorb OMAF. The result showed that the injection of serotonin could induce spermiation, while the injection with OMAF antibody did not show stimulative effect on spawning. It is noteworthy to mention that there were very few clams which could spawn by serotonin injection. This may be due to the maturity of clams. The mature clams should be used for further experiment in next year to confirm precise effect of OMAF on spawning.

FY2015 The mode of action of neuropeptide in gametogenesis and application to artificial induction of gonad development in bivalves