The function of the ampullae of Lorenzini, with some observations on the effect of temperature on sensory rhythms

Abstract

The recognition of the morphological and developmental relationship of the vertebrate auditory organ and the lateral-line system of fishes and aquatic Amphibia rests on the foundation of a large volume of com­ parative researches. The main outlines of this generalization were already laid down forty years ago, and Cole’s work on the cranial nerves and lateral sense organs of fishes (1898) contains a comprehensive treatment of the history of the subject. The acustico-lateral or neuromast system embraces, in addition to the labyrinth and the lateral-line canals, the pit organs found to a greater or less extent in most fishes, the vesicles of Torpedo , and the ampullary canal system of Selachians and Holocephali. Concerning these Cole wrote: “The history of our knowledge of the phylogeny of the sensory canals is coincident with three discoveries—the discovery that the‘mucus’ canals contain sense organs, the discovery of Savi’s vesicles, and the dis­covery of the ampullae of Lorenzini.... We now know that all three types belong to the lateral line system, and I shall suggest that they represent three stages in the development of a canal—the most superficial condition, represented by the pit organs and Savi’s vesicles; the full development, represented by the canal; and the intermediate type, forming neither a Savi vesicle nor yet a canal, represented by the ampullae of Lorenzini” (p. 187). This conception has remained valid to the present day. The ampullae of Lorenzini, with which I am here principally concerned, are briefly described in current text-books as transitional or specialized neuromasts, and the implication always is that structurally and functionally they do not differ significantly from the neuromasts of the lateral-line canals. For example, in their recent exhaustive treatise on the vertebrate nervous system Kappers, Huber and Crosby (1936) state with reference to the lateral-line canals, the Savi vesicles and the ampullae of Lorenzini: “thus in the various animals there is a transition between an open and a closed system for perceiving vibrations" (p. 438).