COMPARATIVE SPERMATOZOAL ULTRASTRUCTURE OF THE 3 DROMIACEAN FAMILIES EXEMPLIFIED BY HOMOLODROMIA-KAI (HOMOLODROMIIDAE), SPHAERODROMIA-LAMELLATA (DROMIIDAE), AND DYNOMENE TANENSIS (DYNOMENIDAE) (PODOTREMATA, BRACHYURA)

The monophyletic Dromiacea, including Sphaerodromia lamellata, Homolod romia kai, and Dynomene tanensis, here studied, have the following cha racters: (1) operculum perforate, but lacking the thoracotreme apical button; (2) opercular projections into the subopercular material, diag nostic of homolids, absent: (3) operculum discontinuous with the capsu le, unlike raninoids; (4) operculum moderately thick, not extremely th in as in the cyclodorippoids Tymolus and Xeinostoma; (5) operculum not extremely wide, contrasting with the great width in cyclodorippoids: (6) periopercular rim and (7) accessory opercular ring absent, being v ariably present in eubrachyurans; (8) subopercular protuberance throug h operculum well developed (synapomorphy), weak in homolids; (9) true acrosome ray zone absent; (10) peripheral border of outer acrosome zon e herder not ragged, unlike some xanthoids: (II) anterolateral pale zo ne of acrosome contents present (autapomorphy): (12) xanthid ring abse nt; (13) subacrosomal chamber or perforatorium extending preequatorial ly, unlike Ranina ranina: (14) head of perforatorium bilateral (autapo morphy); (15) corrugations of the wall of the perforatorial chamber ab sent; (16) centrioles apparently absent; (17) posterior median process of the nucleus absent; (18) thickened ring (typical of Eubrachyura) a bsent; (19) concentric lamellae (typical of Thoracotremata) in the out er acrosome zone absent; (20) capsular chambers absent: and (21) capsu lar flange absent. unlike Ranina ranina and Raninoides sp. Spermatolog ically Sphaerodromia lamellata appears closer to the dynomenid Dynomen e tanensis than it is to the mutually paraphyletic Dromidiopsis edward si and Stimdromia lateralis. The spermatozoon of Homolodromia kai (Hom olodromiidae) shares a striking putative synapomorphy with Paradynomen e tuberculata: a Range-like lateral extension of the lower acrosome zo ne; both species appear to lie within a dromiid clade. Neither the Dro miidae nor the Dynomenidae appear monophyletic spermatologically. The spermatozoal evidence is discussed in the light of a brief review of n on-spermatozoal morphology. General morphology and spematozoal ultrast ructure both strongly endorse monophyly of the Dromiacea.