Sex attraction and copulation in Chiloplacus symmetricus (Nematoda: Acrobelinae)

Abstract

Sex attraction was observed in the free-living nematode Chiloplacus symmetricus. Males were strongly attracted to female secretions but females did not respond to male secretions. Males were not attracted to 4th-stage female juvenile secretions and 4th-stage male juveniles were unresponsive to adult female secretions. Hence, only adult females produce sex attractants and only adult males respond to them. Males orienting to female secretions show different behavioural responses involving numerous non-directional turnings (klinokinesis) as well as a direct approach (klinotaxes). During copulation, the male coiled its posterior end around the female while the spicules probed for the vulval opening. The female took no active part in pairing.