サケ幼魚の発生に対するチロキシン及びチオウレアの影響
1955 年 4 巻 1-3 号 p. 83-93
詳細
1955 年 4 巻 1-3 号 p. 83-93
In the A-series, thirty chum salmon alevins were immersed in the solution of 1/1, 000, 000 of thyroxine and 1/3, 000 of thiourea, respectively, for six weeks immediately after hatching, and in the B-series, thirty alevins were immersed in the solution of 1/1, 000, 000 of thyroxine for seven weeks, one week after hatching, the effects of these treatments to salmon larvae were observed. The same number of control groups were held in tapwater under identical conditions.
The following results were obtained:
1. In the both series of treated larvae, a marked inhibition in weight increase namely, the growth rate and also a delaying of the rate of absorption of yolk sac were observed. In the body form of the larvae treated by thyroxine, the broadening of the head, such as protrusions on the top of the head as well as posterior edge of the opercular and enophthalmos like conditions, was observed. But the developments of thetrunks, caudal, and fins, except elongated pectoral fins, were very poor. These modifications were more remarkable in the B-series.
The marked changes were not observed in the larvae treated by thiourea, besides the immature characteristic which were somewhat kept in the body form.
2. In the both series, the colorlation of the larvae treated by thyroxine showed a pallor, namely, premature silverication, which was produced by the deposition of excessive guanine. On the other hand, the coloration of the larvae treated by thiourea showed no change.
3. In the control fish, the histology of the thyroid gland showed a figure of functional and hyperactivity with cuboidal epithelium and vacuolized colloid.
On the contrary, the thyroid gland of the larvae treated by thyroxine in the both series appeared in the hypofunctioning figure with flattened epithelium and dense colloid.
While the thyroid of the larvae treated by thiourea revealed pathological hyper functioning with obvious hypertrophic columnal epithelium, number increase and size decrease of follicles, and lack of colloid. Furthermore, hypertrophic cells of pituitary also observed in the thiourea treated fish.
