Description and distribution of eggs and larvae of the brown hakeling Physiculus maximowiczi in Japanese waters.

Abstract

The morphological features and the distribution of eggs and prelarvae of the brown hakeling Physiculus maximowiczi are presented based on specimens obtained from field and laboratory studies. The eggs are buoyant, spherical and colorless, and have an oil globule. The diameter of eggs and oil globule ranged from 0.93 to 1.00mm and from 0.25 to 0.30mm, respectively. The prelarva of 1.70mm in total length has a wide pigmented band on the dorsal part throughout the body except for the notochord tip. In the caudal part there is a pair of melanophore patches on both the dorsal and ventral parts. Such pigmentation occurs in the late stage of the embryo development and is very characteristic. Also, it is distinct enough to discriminate the eggs and larvae of the brown hakeling from the Pacific mackerel and threadfin hakeling which are collected with the brown hakeling in the same area and period. The eggs and larvae were mainly distributed in the eastern part of the Izu Islands and along the Boso Peninsula, central Japan, which is situated in the inner region of Kuroshio Current.