The external features and histological structures of endocrine glands of a Japanese cyprinid fish,
Gnathopogon elongatus (TEMMINCK et SCHLEGEL), obtained from the fresh-water region of Niigata City were observed and the following results were obtained. The materials used in this study seems to be matured adult fish before spawning season.
1. The pituitary gland is long ovoid in shape, and keeps touch with the area of optic chiasma with the connective tissue bundle. The pituitary of this fish may be regarded as a lepto-cranio-basic type.
The arrangements and histological figures of three glandular lobes of adenohypophysis are closely similar to those of a brackishwater cyprinid fish,
Tribolodon hakonensis taczanowskii, however these differ from those of carp and Funa (
Carassius).
2. The discreted thyroid follicles concentrate on the ventral aorta, as which form an anterior and a posterior lobe, but these are not recognized in the other internal organs. The histology of thyroid of this cyprinid fish shows a hypofunctioning figure.
3. The head kidney is apparently independent of the body kidney, and, in general, consists of the lymphoid tissue uniformly. The cardinal vein and its branches in the head kidney are enveloped in the layer of chromaffin cells, and these in turn are surrounded by the mass of acidophilic cells.
4. In the ovary the abundant ovarian eggs in the last stage of yolk globule are found. Therefore, many cyanophiles which are demonstrated in the pars principalis of pituitary seems to be the gonad stimulating cells.
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