The hair-peg organs of the shore crab,Carcinus maenas (Crustacea,Decapoda): Ultrastructure and functional properties of sensilla sensitive to changes in seawater concentration |
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Authors: | Dr Manfred Schmidt |
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Institution: | (1) Zoologisches Institut, Johann Wolfgang Goethe-Universität, Frankfurt, Germany;(2) C.V. Whitney Laboratory, University of Florida, 9505 Ocean Shore Blvd., 32086 St. Augustine, Florida, USA |
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Abstract: | Summary The hair-peg organs of the shore crab, Carcinus maenas, are modified hair-sensilla. A small hair shaft (peg) is surrounded by a tuft of solid cuticular bristles (hairs). Each hair-peg organ is innervated by 6 sensory neurons, 2 of which have scolopidial (type-I) dendrites. The outer segments of all dendrites pass through a cuticular canal extending to the articulated hair base in which the 2 type-I dendrites terminate. The other 4 (type-II) dendrites reach the clavate tip of the hair shaft and have access to a terminal pore and a large sickle-shaped aperture. Three inner and 8–12 outer enveloping cells belong to a hair-peg organ. The innermost enveloping cell contains a scolopale, which has desmosomal connections to the ciliary rootlets of the type-I dendrites. An inner and an outer sensillum lymph space are present. The ultrastructural features of the dendrites and the cuticular apparatus indicate that the hair-peg organs are bimodal sensilla, comprising 2 mechano- and 4 chemosensitive sensory neurons. Extracellular recordings from the leg nerve indicate that the chemosensitive neurons of the hair-peg organs respond to changes in seawater concentration in the physiological range of Carcinus maenas.Supported by the Deutsche Forschungsgemeinschaft (SFB 45/A1; W. Gnatzy) |
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Keywords: | Sensilla Mechanoreceptors Chemoreceptors Sea water Shore crab Carcinus maenas (Crustacea Decapoda) |
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