Experiments on the Lateral Line System of Anurans

Abstract

It has been claimed that in fishes, ordinary epithelial cells are transformed into lateral line sense organs under the influence of the regenerating lateral line nerve. However, in 19 Rana clamitans tadpoles observed frequently under the compound microscope for as long as 200 days, no new sense organs developed in association with the regenerating lateral line nerve fibers growing under skin not originally containing these organs. In another series of experiments living lateral line sense organs were observed during the regeneration of tail tips following tail-tip amputation in 53 Rana tadpoles. Thirty-two were hypophysectomized animals, which, due to the reduction of skin pigmentation, are of great value in making observations upon the sense organs, peripheral nerves and blood vessels. Twenty-one were normal tadpoles. In 17 control cases the lateral line nerve supplying the regenerating series of organs was allowed to regenerate normally. In the 36 experimental cases the lateral line nerve was transected anterior to the level of tail-tip amputation and was resectioned sufficiently often to prevent re-innervation of the posterior portion of the stump and the regenerating series of organs. Further evidence that there is considerable independence of the sense organs of their nervous connections is demonstrated by a third type of experiment. Living, denervated, lateral line sense organs of the dorsal tail fin were observed and compared with normally innervated organs on the opposite side over extended periods of time. Sixty-seven experiments, involvingrepeated observations on a total of 2,313 lateral line sense organs were followed for 6-142 davs. on a total of 2,313 lateral line sense organs were followed for 6-142 davs. These included 37 experiments on hypophysectomized Rana species and 30 on normal Rana clawzzitans tadpoles.