THE BEHAVIOR OF HETEROLEPIDODERMA SP. (GASTROTRICHA)

The behavior of Heterolepidoderma sp. was studied with the same approa ch as those already used for many species of ciliates. The ethogram we drew comprehends both helicoidal swimming (n = 20, r = 52.5 +/- 12.2 mu m, pitch = 512 +/- 101 mu m, (v) over right arrow = 215 +/- 43 mu m /sec), periodically interrupted by irregular patterns changing the dir ection of the swimming of random angles and creeping on the substrate. The latter behavioral state, very common for the species we studied, occurs along tracks formed by successive elements (circular, C, vs lin ear segments, S) joined to each other by two kinds of reactions, which change their trajectory. The surprising similarities and the unexpect ed differences between the behavior of this gastrotrich and those of t he ciliates already studied from this point of view are discussed, on the basis of the dimensional ranges and ecological niches shared by th ese two, definitely unrelated groups of organisms.