Epithelial System of the Male (Part II) - Sensilla: Cephalic and Phasmid Sensilla

Cephalic sensilla of the male -Phasmids of the male -Back to Contents

Cephalic sensilla of the male

In the adult male, each of the four cephalic sensilla contains the sensory ending of an additional male-specific CEM (D/V L/R) neuron (Sulston et al, 1983 showed that although CEM neurons born in both sexes, they undergo programmed cell death in the hermaphrodite during late embryogenesis). These neurons share sheath (CEPshD/VL/R) and socket (CEPsoD/VL/R) cells with the CEP neurons of the sensillum (see Ward et al., 1975, Figs14 and 33). The non-sex-specific CEPs end in the cuticle and are considered mechanosensory in modality. By contrast, CEM endings are exposed to the environment suggesting the neurons may function as chemosensors. It has been suggested that the CEMs function in male attraction or chemotaxis to hermaphrodites.

Phasmids of the male

Phasmids are found in both sexes on the lateral sides of the tail (MaleEpiFIG27A,B; see PHASMID IMAGE GALLERY- EPITHELIAL SYSTEM - HERMAPHRODITE HANDBOOK). The interfacial cells that contribute to the phasmid and phasmid organization changes several times during development. In the L1, the two neurons of the left and right phasmid, PHAL/R and PHBL/R, are surrounded by seam cells T(L/R) which function as socket cells, linking the phasmid sheath cell (PHshL/R) and the hyp by adherens junctions. In L2, the T cells are replaced by their great-granddaughters, the phasmid socket cells (PHso1L/R and PHso2L/R; MaleEpiFIG28C). PHso1L/R connect to PHshL/R and to the neuron but not the hyp. PHso2L/R connect to the hyp and PHso1L/R but not PHshL/R.

In the adult male Phso2(L/R) function as a true socket cells whereas PHso1(L/R) protrude into the sheath. PHso1(L/R) have a branched morphology and have been referred to as "wing" cells possibly because they resemble wing amphid neurons of the head in this regard (AWA, AWB and AWC described in Perkins et al., 1986). PHso1(L/R) cells also may contain a variable number of basal bodies (0-2), usually a feature of a sensory neurons, but not a glial cell (MaleEpiFIG29A,B). As these cells show no other signs of a neuronal cell fate (no axon, no synapses), they are classified as glial cells. In hermaphrodites the phasmid modulate chemorepulsion behavior (Hillard et al., 2002). Whether the changes observed in male phasmids alter their function in this sex is not known.