Studies on Sharks―VI Reproduction of Galeorhinus japonicus
Year: 1973
Type: article
Abstract: We made observations of Galeorhiuus japonicus, caught in the East China Sea and landed at the Nagasaki fish market. In this species, only the right ovary is fun ctional, and usually 8 to 22 fully developed ova are ovulated during the ovulating season. This species belongs to the viviparous non-placental category, the external yolk-sac disappearing immediately before parturition. During the gestational stage, the uterine compartments are formed. In the early gestational stage the uterine compartments are oriented transversely but as the gestation advances the compartments become more longitudinally oriented. The number of embryos contained in the both uteri is 8 to 22, depending upon the size of the shark. The nutrition of embryos depends mainly upon the contents of their yolk-sac. However, the greater the increase in internal yolk, the more the external yolk disappears. The intestinal activity begins when the embryos grow to about 70 mm in total length, and the intestine also functions as an embryonic organ of nutrition. This species grows to a maximum length of about 1.05 m in male and 1.2 m in female and the sexually mature male is about 85 cm long, while female ranges from 84 cm to 102 cm in total length, the variation in the female individuals being very large. The parturition season is June when the embryos, about 210 mm to 250 mm in total length, are born prolifically. The ovulation, mating and fertilization occur mainly from June fo August. The gestation period is approximately 10 months.
Authors: Che-Tsung Chen, Kazuhiro Mizue
Language: Japanese
Subfield: Nature and Landscape Conservation
Field: Environmental Science
Domain: Physical Sciences
SDG: Life below water
Open Access status: green
OpenAlex ID: W200747300