FIGURE 13.1 A star-nosed mole (Condylura cristata) and tentacled snake (Erpeton tentaculatus). (A) Star-nosed moles have large forelimbs, small eyes, and a nose ringed by 22 appendages or rays. (B) A colorized scanning electron micrograph shows the snake’s scaled tentacles. [Note: Figure can be viewed in color in the PDF version of this volume on the National Academies Press website, www.nap.edu.]
The details of how and why each species evolved appendages are very different, but the lessons from investigating their biology are similar. In each case, an integrative approach combining neurobiological, behavioral, and ecological facets is necessary to best understand the sensory system. In the spirit of such an approach, it is hoped that the reader will view Movies S1, S2, S3, S4, S5, and S6 of Supporting Information in Catania (2012) when reading the descriptions of behavior.
SENSORY ORGANS AND INNERVATION OF THE STAR
The star is a little over 1 cm across and composed of 22 epidermal appendages or rays. Thus, it is a skin surface and not a specialization for olfaction. The rays are numbered from 1 to 11, starting with the dorsal-most ray and ending ventrally with a small ray in front of the mouth (Fig. 13.2A). Each ray is covered with small domes called Eimer’s organs (Eimer, 1871; Van Vleck, 1965) (Fig. 13.2B). Such mechanosensory organs are found on the noses of most moles (Quilliam, 1966; Shibanai, 1988; Catania, 2000b) and are anatomically similar to small, domed push rods found on the snout of distantly related monotremes (Andres et al., 1991; Iggo et al., 1996; Manger and Pettigrew, 1996; Proske et al., 1998). In star-nosed moles, each organ is about 40–60 μm in diameter and has a small