COMPARISON OF CRUSTACEAN AND INSECT MECHANORECEPTIVE SETAE

Mechanosensitive cells of crustacean setae show important cytological differences compared with those of insects. The mechanosensitive cells in arthropod setae can be classified in 2 groups, which are structura lly and functionally different. The typical mechanosensitive cells of insect setae show a tubular body at the tip of their dendrites, wherea s mechanosensitive cells of aquatic crustaceans never show such a stru cture and are characterized by a 9 + 0 cilium, a large ciliary root an d a scolopale cell. Among crustaceans, mechanosensory cells with a tub ular body are observed only in terrestrial isopods. Therefore, it seem s that the type of mechanosensitive cell associated with an arthropod seta is linked more to the physical environment than to the systematic group. It is also linked to differences in the kind of mechanosensiti vity of the 2 types of cells: dendrites with a tubular body are compre ssion-sensitive, whereas dendrites with a 9 + 0 type cilium would be s tretch-sensitive, The presence of one type of cell in the terrestrial organisms and of the other in the aquatic animals may be explained by the physical characteristics of the environment. (C) 1997 Elsevier Sci ence Ltd.