Development of new aquaculture and seed production technology for commercially-important shrimp species: Research at JIRCAS
Shrimp culture is a significant component of the world’s fisheries industry, and is conducted widely in South/Southeast Asian countries. Penaeid shrimp species are mainly targeted in such endeavors, and among these, the whiteleg shrimp, Litopenaeus vannamei, constitutes more than 80% of the world’s total production. In order to support this very large shrimp farming industry, it is essential to produce sufficient quantities of juvenile shrimp. To this end, eyestalk ablation is frequently used in commercial hatcheries in order to induce ovarian maturation and spawning. However, eyestalk ablation exhibits adverse effects, such as increased mortality rates and deterioration of egg quality; moreover, it has received a great deal of criticism from the viewpoint of animal welfare by the general public. Therefore, it is urgent to develop a means of promoting maturation based on the understanding of the physiological functioning of the animal, in order to establish a more effective means of seed production for species such as L. vannamei.
With the goal of contributing to the promotion of a more sustainable shrimp farming industry, the Japan International Research Center for Agricultural Sciences (JIRCAS) is implementing a research project entitled “Development of advanced seed production and culture technology for economically-important shrimp species based on elucidation of reproductive mechanisms”. This project is being carried out with the aim of elucidating mechanisms of maturation, with the ultimate goal of developing reproductive-stimulating technology that could potentially replace eyestalk ablation.
Many aspects of crustacean reproduction and the associated mechanisms in shrimp remain unclear; however, it is well-known that ovarian maturation is regulated negatively by neurohormones such as vitellogenesis-inhibiting hormone (VIH). VIH is synthesized at the X-organ/sinus gland complex, a neurosecretory organ located in the eyestalks. It is then secreted into the hemolymph, after which it acts negatively on reproduction by inhibiting vitellogenin (Vg) synthesis. Vg, which is the precursor of the major egg yolk protein in oviparous animals, is synthesized at the hepatopancreas and ovary, secreted into the hemolymph, and then accumulated in developing oocytes.
Studies at JIRCAS have utilized L. vannamei as a model animal; the principle aim of research up to now has been focused on acquiring basic information necessary for understanding reproductive mechanisms in further detail. For example, we have developed measurement systems for VIH and Vg, and have examined their relative dynamics in context of molting and eyestalk ablation in L. vannamei (Kang et al. 2014). In another paper, we clarified the structure of multiple VIH genes present in L. vannamei, and elucidated their expression levels in the eyestalks in relation to molting and unilateral eyestalk ablation (Kang et al. 2018). The results of such research will be presented in detail during the presentation, along with discussion of other endocrine factors besides VIH that potentially control ovarian maturation in shrimp. The over-arching aim of this research is to provide useful technology to developing regions of the world where shrimp culture is an important industry.
|作成者||Bong Jung Kang|
|著者キーワード||Litopenaeus vannamei Shrimp Vitellogenesis-inhibiting hormone (VIH) Vitellogenin (Vg)|
|公開者||Japan International Research Center for Agricultural Sciences|