Changes in plasma vitellogenin and estradiol-17β levels during the gonadal development of the female Japanese common goby Acanthogobius flavimanus

Abstract

The Japanese common goby Acanthogobius flavimanus is an important target species for game fishing and costal fisheries in Japan. Here, we aimed to determine the annual reproductive cycle of the female Japanese common goby collected from the Taira River, Nagasaki, by histological observation and analyzing changes in vitellogenin (VTG) and estradiol-17β (E₂) plasma levels. Changes in gonadal development, gonadosomatic index (GSI), and plasma VTG and E₂ were investigated between June 2012 and February 2013. The GSI rapidly increased between December and January, when the water temperature dropped from 15 °C to 13 °C and the photoperiod was at its annual lowest. Vitellogenic oocytes appeared in the ovary just prior to the increase in GSI in November. Levels of VTG and E₂ rapidly increased in December and were correlated with ovarian development. Vitellogenic and mature oocytes were maintained in January and February, when plasma VTG and E₂ were high. These results showed that the vitellogenesis in the Japanese common goby started in November and that the main spawning season in Nagasaki began from January. Thus, initiation of ovarian development may be induced by decreased water temperature and shortening of day length, and maturation may proceed because of low temperatures.