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 prev alence and role of GTG in the Brachyura, the first gonopods of six spe cies of boreo-temperate and tropical brachyurans belonging to four fam ilies were examined morphologically and histologically, using the PAS- Alcian-blue staining protocol: Carcinus maenas, Portunus sebae, and Ov alipes ocellatus (Portunidae), Cancer irroratus (Cancridae), Grapsus g rapsus (Grapsidae), and Petrolisthes armatus (Porcellanidae). Discrete rosette type GTG were found in all species examined, although the lon gitudinal 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 pore s in the cuticle; staining properties of secretions at the duct openin gs to the ejaculatory canal matched those of the GTG. Neither GTG, duc ts, nor pores were observed in regions distal to the ejaculatory canal . These data indicate that the prime, if not exclusive, role of the GT G is in reproduction, and that GTG may therefore be considered accesso ry sex glands. Together with previous and current investigations such GTG have been observed in all eight brachyuran species examined from f ive families, and are thus probably ubiquitous within the Brachyura. T he organization and nature of the gland secretions differed between ta xa: alternating acid (AMPS) and neutral mucopolysaccharide (NMPS) laye rs in the three Portunidae, AMPS only in Cancer irroratus and NMPS onl y 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 investmen t (stored spermatophores) from opportunistic microbes following copula tion, and the reciprocal processes of sperm competition and paternity assurance. The NMPS secretions may function as a lubricant to reduce m echanical wear of the ejaculatory canal by the second gonopod during c opulation, and to reduce the viscosity of the ejaculate from the vas d eferens as it enters the narrow ejaculatory canal.