• Development and Reproduction
• /
• v.25 no.4
• /
• pp.299-303
• /
• 2021

The ascidian Halocynthia aurantium (sea peach), a marine invertebrate, belongs to the same genus of the phylum Chordata along with the ascidian Halocynthia roretzi (sea pineapple), which is one of the model animals in the field of developmental biology. The characteristics of development and reproduction of H. aurantium are not yet known in detail. In order to find out the spawning period of H. aurantium, we investigated development of the gonads during the annual reproductive cycle. Testis and ovary were both in the bisexual gonads (ovotestes) of H. aurantium, which is a hermaphrodite like H. roretzi. In H. aurantium, the right gonad was longer and slightly larger than the left gonad throughout the year. In each gonad, the number of the testis gonoducts was slightly higher than that of the ovary gonoducts. These features were similarly observed in H. roretzi. However, the number of the testis gonoducts and the ovary gonoducts in each gonad of H. aurantium was about half that of H. roretzi. The gonads of H. aurantium contracted during the winter and summer seasons. The gonads decreased to the smallest size around February, and then started to increase again in March. The gonads were most developed in September of the year. Therefore, it is estimated that the spawning of H. aurantium begins around this period.

• Korean Journal of Ichthyology
• /
• v.5 no.2
• /
• pp.226-234
• /
• 1993

Cobitis sinensis-longicorpus complex considered as hybrid origin between C. sinensis and C. longicorpus coccurred ommonly in the upper streams of the Nakdong River, Korea. Histological examinations of their gonad were accompanied with 272 individuals of C. sinensis-longicorpus complex collected. Most of fishes collected were females, however, only 6 individuals were found males. The ovarian tissues of females are completely fertile undergoing normal oogenensis. In the male gonads, testicular lobule structure with abnormal vacuolar tissues were observed. Spermatogonia and spermatocytes were also observed of their testis however spermatids or sperms were not shown in their developmental stages. From these facts, we infer that female population of C. sinensis-longicorpus complex may be unique reproductive hierarchy accomplishing their reproduction with participation of males of their closely related bisexual species.

• Korean Journal of Ichthyology
• /
• v.33 no.1
• /
• pp.37-42
• /
• 2021

This study sought to reveal spawning period and sex inversion of black seabream, Acanthopagrus schlegelii collected off the coast of Tongyeong, Korea. The monthly gonodosomatic index (GSI) showed the same pattern of between both sexes, and it was estimated that black seabream spawned once a year (between April and May). Histological examination revealed the transition from male to female sex, size of fork length bisexual gonad with ovarian (primary hermaphrodite; progress from male to female, MF) was seen at 20.5 to 39.6 cm and bisexual gonad with testicular (post hermaphrodite; female development and Male degeneration, FM) was seen at 26.4 to 50.2 cm. The egg diameters was in the range of 0.02 to 0.60 mm, with the smallest average egg diameter of 0.09 mm in February, the highest average egg diameters of 0.43 mm in August, and the range of fecundity was number of eggs 277,148 (33.9 cm) to 2,772,421 (34.1 cm).