Annual Reproductive Cycle of Acheilognathus majusculus, a Korean Endemic Species

Abstract

An experiment was conducted to investigate the annual reproductive cycle of a Korean endemic species, Acheilognathus majusculus, from Jeokseong-myeon located in Seomjin River. The reproductive cycle is examined histologically regarding water temperature and day length of the habitat, the gonadosomatic index (GSI), the female ovipositor length index (OLI), monthly variation in egg diameter distribution, and developmental characteristics of female and male gonads. The maximum GSI was found in 19.21±2.32 and 6.90±0.53 for female and male respectively when water temperature (14℃) and day length (11.1hr) began to rise. On the other hand, the minimum level was reached during August (1.87±0.67 for female and 0.88±0.50 for male). No samples represent with measurable ovipositor between September and November, while the longest ovipositor length index was in April (79.68±4.69%). We compared and calculated the stages of testis and ovary development process in order to determine the germ cell development characteristics and the reproductive cycle. According to the result, we classified the female Acheilognathus majusculus reproductive cycle into four stages: Ripe (April) and spawning phase (May to June), degenerative phase (July), growing phase (August to December), and mature phase (January to March). The annual reproductive cycle of male Acheilognathus majusculus was categorized into five stages viz. Ripe and spawning phase (May to June), degenerative phase (July to August), resting phase (September to November), growing phase (December to February), and mature phase (March to April).

Annual Reproductive Cycle of Acheilognathus rhombeus, in Korea

“…The level of the highest GSI value in males differed among the Acheilognathinae subfamily fishes and was lower than that of females. There was coincidence with the timing of the peak of GSI in both females and males in majusculus (Lim & Lee, 2017).…”

“…respectively (An, 1995;Baek et al, 2003;Jeong et al, 2006;Jin et al, 2008;Lim & Lee, 2017;Shimizu et al, 1987). The level of the highest GSI value in males differed among the Acheilognathinae subfamily fishes and was lower than that of females.…”

“…The maturing phase of male with meiotic cells and spermatozoa in seminiferous tubules was observed from June to November, the frequency of spermatozoa was 20% in June, 40% in July, 55% in August, 70% in September, 75% in October and 75% in November. From August to Korean A. rhombeus (October), respectively (An, 1995;Baek et al, 2003;Jeong et al, 2006;Jin et al, 2008;Lim & Lee, 2017;Shimizu et al, 1987). These differences in GSI are likely due to genetic differences between species.…”

“…Asynchronous development has various types of oocytes within the ovary, a characteristics of multiple-spawning fish species (Shimizu et al, 1994). Rhodeus uyekii (An, 1995) and Acheilognathus signifer (Baek et al, 2003) and A. majusculus (Lim & Lee, 2017) are asynchronous development type with multiple spawning habit, while A. koreensis is a group-synchronous development type with single spawning habit (Jeong et al, 2006). A. rhombeus showed various types of oocytes within the ovary during the spawning phase in October and represent the typical asynchronous development of oocytes.…”

“…A few studies have been reported on the reproduction of Acheilognathinae subfamily species: reproductive cycle of Rhodeus uyekii (An, 1995), sexual maturation and spawning season of the Korean Bitterling, Acheilognathus signifier in upper reaches of the Hongchen River (Baek et al, 2003), abnormality of reproduction and organ structure of the Oily Bitterling, Acheilognathus koreensis from Isa Stream (Jeong et al, 2006), change of external reproductive parameters according to sexual maturation of the Striped Bitterling, Acheilognathus yamatsutae (Jin et al, 2008), and annual reproductive cycle of Acheilognathus majusculus, a Korean endemic species (Lim & Lee, 2017).…”