ULTRASTRUCTURE AND PRESUMED FUNCTION OF THE PLEURAL DERMAL GLANDS IN THE ATYPICAL MALE OF THE PARASITIC COPEPOD PACHYPYGUS-GIBBER (CRUSTACEA, NOTODELPHYIDAE)

The topography, external structure, and ultrastructure of hitherto unknown exocrine dermal glands are described in one of the two adult male forms of the ascidicolous marine copepod Pachypygus gibber. The glands are located in the pleural lateroventral zone of the cephalosome. They are composed of three cells: secretory cell, intermediary cell, and canal cell. The secretory cell undergoes transformations involving four successive phases. The final phase leads to an autolysis of the cellular components with emptying of the cell content. An interesting feature is the spatial association of the glandular cells and their pores with sensory cells and their pores, the latter being considered as a chemoreceptor organ. The secretion is therby in direct contact with dendritic ends devoid of cuticular cover, which protrude outside the copepod via the sensory pores. The various characteristics of this "sensory-glandular" complex, present exclusively in the atypical male (which has an additional free planktonic phase as an adult), lead to the hypothesis of a functional cooperation between the glandular apparatus and the sensory organ.