カワヤツメ(円口類)の内柱および甲状腺の形態

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The external and internal structure of the endostyle of ammocoetes larvae and thyroid gland of adult sea-lamprey, Lampetra (=Entosphenus) japonica, during its anadromous season are described. The endostyle of ammocoetes is situated between the first and fifth branchial pouches, and consists of five cavities. In the epithelium of endostyle six types of cells are distinguished; of these, the type III cells which form the lateral wall of the endostylar cavity seem to change into the cells forming the follicular epithelium of the adult thyroid gland. The thyroid of the adult lamprey is very small, and wet weight of the gland per g. of body weight is only 0.007mg. The gland is spindle-shaped and lies on the dorsal surface of the basibranchial artery; it extends from the bifurcated regions of the first to the fifth branchial arteries. The thyroid follicles can be divided roughly into three groups: (1) the follicles surrounded by high epithelium have a small lumen filled with small quantity of colloid, and are situated in the anterior and posterior regions of the gland, (2) the follicles surrounded by low epithelium have no smooth colloid in their lumens, (3) the lumens located in the central part of the gland have broad cavities. The thyroid follicles of the sea-lamprey seem to be of the holocrine type.
公益社団法人日本水産学会の論文