File:American malacological bulletin (1988) (18156377625).jpg

Title: American malacological bulletin
Identifier: americanmal6719881990amer (find matches)
Year: 1983 (1980s)
Authors: American Malacological Union
Subjects: Mollusks; Mollusks
Publisher: (Hattiesburg, Miss. ?) : (American Malacological Union)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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Fig. 11. Electron micrograph of a sensory nodule from a hair of Mopalia muscosa. In nodules, the dendrites (d) lose their typical organization; their mitochondria are twisted and the microtubules are no longer in parallel arrays (arrowheads). Large electron-lucent vacuoles (ve) lie around the periphery within the surrounding cells. 1982; Leise, 1986). In most cases, dorsal nodules are subja- cent to spicules. The ventral girdle in all chitons produces overlapping spicules (Blumrich, 1891; Pilsbry, 1892, 1893; Knorre, 1925; Fischer-Piette and Franc, 1960; Hyman, 1967) and in many cases these spicules also contact sensory nodules (Table 2). Two exceptions are Placiphorella velata and P. stimpsoni, in which the ventral spicules contact stalked cells that are much like those in the dorsal hairs. These cells too will probably prove to be sensory neurons upon further study. Curiously, in P. velata the marginal spicules are associated with typical stalked nodules (Plate, 1902; Leise, 1983). Of the chitons I studied, in only two species did I find claviform nodules without innervated papillae: Eudoxochiton nobilis and Plaxiphora obtecta. These animals were fixed in 5% formalin (see Leise, 1983) which does not preserve cellular ultrastructure as well as the combination of glutaraldehyde and osmium tetroxide. Thus, it is possible that the slender (1-2 fim in diameter) epidermal nerves were not preserved well enough for me to recognize them. It would be most surpris- ing if these two species alone show no innervated epidermal sensory organs. FUNCTIONS OF CHITON HAIRS The functions of chiton hairs are not well understood although plausible hypotheses abound. Hyman (1967) describes chiton hairs as armature, although chitons bear- ing hairs are successfully preyed upon by starfish (Mauzey etal., 1968; Paine, 1980), seagulls (Moore, 1975), fish (Ronald Shimek, pers. comm.) and humans. The girdle could be tox- ic or distasteful but it does not provide sufficient protection
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Fig. 12. Longitudinal 1 /jtm section through the base of a trichogenous papilla (tp) of Katharina tunicata. One nerve (ne) emerges from the base of the papilla then continues into the dermis (de) (from Leise, 1983). Many cells of these papillae also produce granules, which can be seen here in their various stages of condensation. Eventually, granules are extruded into the cuticle.

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