SENSORY NEUROANATOMY OF A SKIN-PENETRATING NEMATODE PARASITE - STRONGYLOIDES-STERCORALIS .1. AMPHIDIAL NEURONS

The Strongyloides stercoralis infective larva resumes feeding and deve lopment on receipt of signals, presumably chemical, from a host. Only two of the anterior sense organs of this larva are open to the externa l environment. These large, paired goblet-shaped sensilla, known as am phids, are presumably, therefore, the only chemoreceptors. Using three -dimensional reconstructions made from serial electron micrographs, am phidial structure was investigated. In each amphid, cilialike dendriti c processes of 11 neurons extend nearly to the amphidial pore; a twelf th terminates at the base of the amphidial channel, behind an array of lateral projections on the other processes. A specialized dendritic p rocess leaves the amphidial channel and forms a complex of lamellae th at interdigitate with lamellae of the amphidial sheath cell. This ''la mellar cell'' is similar to one of the ''wing cells'' or possibly the ''finger cell'' of Caenorhabditis elegans. Each of the 13 amphidial ne urons was traced to its cell body. Ten neurons, including the lamellar cell, connect to cell bodies in the lateral ganglion, posterior to th e nerve ring. The positions of these cell bodies were similar to those of the amphidial cell bodies in C. elegans. Therefore, they were name d by using C. elegans nomenclature. Three other amphidial processes co nnect to cell bodies anterior to the nerve ring; these have no homolog s in C. elegans. A map allowing identification of the amphidial cell b odies in the living worm was prepared. Consequently, laser ablation st udies can be conducted to determine which neurons are involved in the infective process. (C) 1995 Wiley-Liss, Inc.