Gonopod tegumental glands: a new accessory sex gland in the Brachyura

It is not yet known whether gonopod tegumental glands (GTG) previously described in one species of brachyuran crab (Chionoecetes opilio) are a general feature in this large taxon. In order to determine the prevalence and role of GTG in the Brachyura, the first gonopods of six species of boreo-temperate and tropical brachyurans belonging to four families were examined morphologically and histologically, using the PAS–Alcian-blue staining protocol: Carcinus maenas, Portunus sebae, and Ovalipes ocellatus (Portunidae), Cancer irroratus (Cancridae), Grapsus grapsus (Grapsidae), and Petrolisthes armatus (Porcellanidae). Discrete rosette-type GTG were found in all species examined, although the longitudinal extent and location differed somewhat between taxa. The GTG were invariably grouped about the ejaculatory canal, and communicated with the lumen of the ejaculatory canal via ducts which traversed pores in the cuticle; staining properties of secretions at the duct openings to the ejaculatory canal matched those of the GTG. Neither GTG, ducts, nor pores were observed in regions distal to the ejaculatory canal. These data indicate that the prime, if not exclusive, role of the GTG is in reproduction, and that GTG may therefore be considered accessory sex glands. Together with previous and current investigations such GTG have been observed in all eight brachyuran species examined from five families, and are thus probably ubiquitous within the Brachyura. The organization and nature of the gland secretions differed between taxa: alternating acid (AMPS) and neutral mucopolysaccharide (NMPS) layers in the three Portunidae, AMPS only in Cancer irroratus, and NMPS only in Grapsus grapsus and Petrolisthes armatus. When combined with data on gonopod morphology and occurrence of spermatophore-less sealant in the ejaculate of various brachyurans, two plausible functions of the AMPS GTG secretions emerge: protection of the male's genetic investment (stored spermatophores) from opportunistic microbes following copulation, and the reciprocal processes of sperm competition and paternity assurance. The NMPS secretions may function as a lubricant to reduce mechanical wear of the ejaculatory canal by the second gonopod during copulation, and to reduce the viscosity of the ejaculate from the vas deferens as it enters the narrow ejaculatory canal. Received: 26 January 1998 / Accepted: 11 June 1998