ON THE STRUCTURE OF THE CEPHALIC CUTICLE IN FREE-LIVING NEMATODES OF THE FAMILY LINHOMOEIDAE (NEMATODA, CHROMADORIA, SIPHONOLAIMOIDEA)

Cephalic cuticular structures of 3 linhomoeid species from the White Sea were studied by transmitting and scanning electron microscopy. The somatic cuticle of Desmolaimus zeelandicus has no fluent thickening towards mouth, but sharply turns into a mouth cuticular ring(MCR). There is a hoop of solid homogenous cuticle inside the MCR. The stomatorhabdions are free of oesophageal tissue and demarcate themselves sharply from the MCR. In Terschellingia longicaudata cephalic cuticular structures represent a simplified variant of the former type. In Eleutherolaimus sp. elements of linhomoeid and monhysteroid stoma are combined: fluent thickening of the somatic cuticle in the cephalic region and illegible MCR with a homogenous cuticle hoop inside. The structural type of Eleutherolaimus is considered to be plesiomorphic within the Linhomoeidae.