瀬戸内海の硬骨魚の半規管に関する形態計測学的研究 : 特に運動能との関係 <原著>

Few studies on the relationship between the ability of movement and membranous labyrinth, especially semicircular canals, have been reported in fishes so far. It is conceivable that the extent and direction of movement in fishes are related to the morphology and fuction of semicircular canals. Thus, I measured the angle and length of semicircular canals and each part of the head from seven species of fishes (Mugil cephalus, Scomber japonicus, Trichiurus lepturus, Trachurus trachurus, Sillago sihama, Sebastes inermis, Paralichthys olivaceus) collected in the Seto Inland Sea in Japan, and investigated the relationship between the movement ability and the morphology of semicircular canals. In addition, the morphology of semicircular canals of lampreys, Lampetra japonica, was examined with scanning electron microscopy. The present study is summarized as follows : (1) sizes of the heads in the fishes are directly proportional to those of the semicircular canals, but the latter sizes are constant when the head is more than 180 mm in length ; (2) The angle and morphology of semicircular canals are different between the fishes examined, suggesting a close relationship between the organ morphology and the movement ability, that is, the angle of semicircular canals shows almost 90° (right angle) among the fish with brilliant movement ability, while in contrast, that among the fish with poor movement ability shows quite different angle ; and (3) In lampreys, a sensory cell of the saccular macula possesses a single kinocilium and many stereocilia showing step-like arrangements. The kinocilia of sensory cells in the semicircular canals are located in the proximal part, and both the saccular macula and the utricular macula are present in the membranous labyrinth.