On the thyroid gland of some Japanese teleosts

Abstract

In this paper the author has newly described on the thyroid gland of Japanese teleosts, mackerel, yellow skin tuna, Pacific marlin, Japanese parrot fish, cold porgy and smooth lump sucker. Moreover, the external morphology and histology of some Japanese teleosts have been discussed including the data of other fish.
1) The external morphology of thyroids of yellow skin tuna and Pacific marlin were closely similar to those of tuna and sail fish reported in the previous paper, respectively. The thyroids of these fish lied on the bifurcated regions of the 1st and 2nd afferent branchial arteries which derive from the ventral aorta, and Were the compact masses consisting of anterior and posterior lobes. A nearly identical shape of thyroid was observed in the glands of mackerel, frigate mackerel, dolphin (or dorado), yellow tail, etc.
2) The thyroids of Japanese parrot fish and cold porgy existed as a single mass and both of anterior and, posterior lobes were distinguished clearly. In smooth lump sucker the thyroid consisted of only a single mass. It has been considered that these matters are under the control of the condition of afferent bronchial arteries which derive from the ventral aorta.
3) The wet weight of thyroid mass per 1 kg of body weight ranged from 9. 00mg (minimum) of a mackerel to 52. 50mg (maximum) of a smooth lump sucker and represented 29.07mg as an average value of ten species of fish ; namely, tuna, sail fish, yellow tail, Hiramasa, mackerel, yellow skin tuna, Pacific marlin, Japanese parrot fish, cold porgy and smooth lump sucker.
4) Among six species of fish reported in this paper, only the thyroid of cold porgy showed a hyperfunctioning figure. On the other hand, the thyroids of remaining five species of fish appeared to be in the condition of norml activity. In some fish which have compact masses of thyroid, the state of their thyroid activity could not be decided only by their histological figures.