Maturation of the Mudskipper Boleophthalmus pectinirostris Distributed in the Mud Flats of the Midori River, Kumamoto Prefecture

Abstract

Ovaries of the mudskipper, Boleophthalmus pectinirostris (N=327), collected from May 1988 to August 1989 were observed histologically, and the frequency distributions of the oocyte diameters were examined. In both 1988 and 1989, the fish spawned from May to July with intensive spawning in June. Yolk accumulating oocytes were grouped in an ovary into two developmental stages in well-matured ovaries. Moreover, some ovaries were filled with yolked oocytes together with postovulatory follicles in the spawning season. The aspects in the ovary indicate that the females spawn several times in a single spawning season. No specimens had oocytes which had developed over the migratory nucleus stage, indicating that the maturation after this stage proceeds in the spawning nest in the burrow. Some 1-year-old and most 2- and 3-year-old females participated in spawning. The minimum size of spawning females was about 90mm in standard length.