Australian Isopoda: Families

S.J. Keable, G.C.B. Poore & G.D.F. Wilson


Gnathiidae Leach, 1814

Gnathides Leach, 1814: 432.

Gnathiidae. -Cohen & Poore, 1994: 291. -Roman & Dalens, 1999: 225.

Description. Body. Body shape without loss or gross modification of appendages on one side of the body; in dorsal view without peduncular articles of antenna 1 or 2 contiguous with coxal margins.

Head. Head not capable of lateral rotation (laterally encompassed, abutting or fused to pereonite 1). Antenna 1 inserting on head anteriorly and/or dorsally to antenna 2, minute or well developed; not as follows: reduced to 2 articles with second article expanded and scalloped. Antenna 2 well developed. Mandible projecting anteriorly and together forceps-like (males), or not projecting anteriorly and together forceps-like (females); palp absent.

Pereon. Coxae extending ventrally and laterally to overhang the coxa-basis articulation of the pereopods. Pereopods 5 pairs readily apparent, pereopod 1 modified as pylopod ventrally overlying mouthparts, pereopod 7 absent; 1-3 or 1-7 not prehensile. Pereopods 5-7 without flattened setose articles andor dactyls modified or absent.

Pleon / Pleotelson. Pleonites and pleotelson not arranged as follows: pleonites 1-5 fused but with conspicuous lateral sutures, pleotelson fused to pleonites 1-5; pleonites 1-5 fused but with conspicuous lateral sutures, pleotelson not fused to pleonites 1-5; pleonites 1-5 fused without conspicuous sutures, pleotelson not fused to pleonites 1-5; pleonites 2-5 fused but with partial (usually lateral) sutures, pleotelson wholly or partly fused with pleonites 2-5; pleonites 3-5 fused without lateral sutures, pleotelson fused with pleonites 3-5, pleonites 1 and 2 free but may be only small rings or cuticular bars visible ventrally. Pleonite 5 subequal to or shorter than any of pleonites 1-4. Pleopods 5 pairs present. Pleopod 2 of males not consisting of an enlarged peduncle with a geniculate endopod and a small muscular exopod. Uropods positioned proximally on pleotelson; distinct from pleopods, not forming operculum over pleopodal chamber (although may be folded ventrally below pleotelson). Peduncle not forming an elongate clavate article with rami reduced or absent. Endopod not claw-like (acute and recurved) andor posteroventral in position. Exopod not folded dorsally over pleotelson.

Remarks. The mandibles are enlarged and project anteriorly like forceps in adult male Gnathiidae but are absent in females. See Martin & Davis (2001) for discussion of the placement of this family in a suborder.

Distribution and generic composition. See Kensley et al. (1996).





Cite this publication as: 'S.J. Keable, G.C.B. Poore & G.D.F. Wilson (2002 onwards). 'Australian Isopoda: Families. Version: 2 October 2002. http://crustacea.net'.