국내 양식산 시베리안 철갑상어(Acipenser baerii)의 성 성숙 및 vitellogenin 유전자 발현 특징

Abstract

Sturgeons, frequently referred to as "living fossils" in the actinopterygian lineage, are potential candidates for aquacultural production especially with respect to the highly valued caviar products from females. For this reason, the induction of all-femaleness in sturgeons has been one of long-cherished wishes in order to improve the productivity of sturgeon farming. However, they have readily long life spans and achieve reproductive maturity late in life. It consequently hurdles the practical identification of phenotypic sex in their early life, and further their reproductive mechanisms have not been comprehensively illuminated yet. In line with our long-term goal to achieve all-femaleness of Siberian sturgeon (Acipenser baerii), the objective of this study was to provide a basis for sexual maturation of this species under farming conditions, based on the examination of morphological change of gonads along with vitellogenin gene expression in different year classes. The gonad development was not clearly visible in the eight-month-old individuals that had been produced in 2011, in which distinct gonadal tissues could be seen in none of individuals examined. At 1 year of age, fishes represented visible and sex-distinguishable gonads, although there was variation in the size and maturity of the gonads among individuals. Most 1-year-old females, showed immature, underdeveloped ovaries with a high portion of ovarian fat. The same-aged males displayed more significant development of testicular tissues than their female counterparts. Afterwards, the gonad developments in both sexes were progressively advanced with a time function of age, and such that the phenotypic sexing of the fish became highly feasible in both sexes from the year class of 2009. Based on the qRT-PCR, the basal expression levels of vitellogenin mRNAs in the fish produced in 2011 were negligible. However the hepatic mRNA expression of vitellogenin were modulated toward upregulation with ages and peaked at the fishes belonging to the year class of 2008. Then, the vitellogenin expression was significantly down-regulated in fully matured fishes belonging to the year class of 2003 irrespective of sexes.