Morphological Characteristics of the Lateral Line Receptors of Hynobius leechii (Urodela: Hynobiidae)

Abstract

Morphological characteristics of the lateral line receptors, specifically the superficial neuromast, the pit organ, and the ampullary organ, are described and compared among larval, metamorphosed, and both female and male adult Hynobius leechii. The distribution and morphologies of the lateral line receptors are similar to those of other urodeles. During the transition from a larval to an adult salamander, the number of receptors is generally reduced, but their sizes increase. Other morphological changes also occur, such as the development of a more distinct mantle cell boundary at the epidermal surface of the adult ampullary and pit organs. In particular, we found kinocilia on the sensory hair cells of the ampullary organs of both larval and adult salamanders, and, for the first time, we describe two different morphologies of the pit organ in urodeles. The detailed description of the pit organ represents only the second study of its kind in urodeles. However, our comparison of lateral line receptors between larval and adult salamanders is the first of its kind for salamanders that utilize external fertilization.