Australian Isopoda: Families

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

Arcturidae Dana, 1849

Arcturidae Dana, 1849: 424. -Poore, 2001b: 222.

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; in lateral view flexed between pereonites 4 and 5, or strongly geniculate between pereonites 4 and 5 (especially in male), or straight, more or less flattened or semicylindrical (Arcturinoides only). Body surface smooth or slightly sculptured, or variously spinose or rugose.

Head. Head not capable of lateral rotation (laterally encompassed, abutting or fused to pereonite 1); fused to pereonite 1. Eyes well developed, or reduced or lost (rare). 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; flagellum of 2-3 articles plus distal claw. Mouthparts not forming suctorial cone or proboscis; with pereopod 1 enclosed in lateral view by lateral plates of head and pereonite 1. Mandible not projecting anteriorly and together forceps-like; palp absent.

Pereon. Pereonite 4 at least 1.5 times as long as pereonite 3 (in males often much longer). Pereonites 6-7 pereonite 7 distinct dorsally, free. Coxae extending ventrally and laterally to overhang the coxa-basis articulation of the pereopods, or not extending ventrally and laterally to overhang the coxa-basis articulation of the pereopods; 2-7 obsolete, bases of pereopods exposed, or 2-7 obsolete and with expanded marginal tergites (Arcturinoides only). Oostegites 1-4 functional, 5 absent, or 1-5 functional (Arcturus only); 1-4 not supported by mesial coxal lobes. Pereopods 6-7 pairs readily apparent; 1-3 or 1-7 not prehensile; 1 a gnathopod, 2-4 elongated, differentiated from ambulatory 5-7 (pereopods 3 and 4 rarely absent); without dense fur of fine setae in males. Pereopod 1 dactylus evenly curved along anterior margin, evenly tapering. Pereopods 2-4 with paired long setae along posterior margins evenly and well developed; 2-4 dactylus prominent, unguis short (or dactylus lost in some pereopods). Pereopod 4 similar to pereopod 3. Pereopods 5-7 without flattened setose articles andor dactyls modified or absent. Penes fused as a single penial plate; penial plate apically simple or barely slit.

Pleon / Pleotelson. Pleonites and pleotelson with pleonites 1-5 and pleotelson fused. Pleopods 5 pairs present. Pleopod 1 peduncle longer than peduncle on pleopods 2-5; marginal setae on rami longer than, or equal to, length of rami; exopod of males laminar, lateral excavation present. Pleopod 2 of males not consisting of an enlarged peduncle with a geniculate endopod and a small muscular exopod; appendix masculina about as long as endopod (or longer), basally as wide or wider than endopod. Pleotelson without dorsolateral ridges ending in mediodorsal posterior spine. Uropods positioned proximally on pleotelson; folded ventrally below pleotelson, forming operculum enclosing pleopodal chamber. 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, tapering, with terminal setae only, more than half as long as endopod or very short, bearing a single prominent robust seta (endopod also with robust apical seta) (usually).

Distribution and generic composition. Globally widespread in shallow and shelf depths especially in cooler waters (Poore, 2001b). See Kensley et al. (1996) but note that Poore (2001b) considers the family to contain the following genera with numbers of included species in parentheses: Agularcturus Kensley, 1984 (1); Amesopous Stebbing, 1905 (1); Arctopsis Barnard, 1920 (1); Arcturella Sars, 1897 (15); Arcturina Koehler, 1911 (5); Arcturinella Poisson and Maury, 1931 (1); Arcturinoides Kensley, 1977 (2); Arcturopsis Koehler, 1911 (3); Arcturus Latreille, 1829 (24); Astacilla Cordiner, 1793 (27); Edwinjoycea Menzies and Kruczynski, 1983 (1); Idarcturus Barnard, 1914b (3); Neastacilla Tattersall, 1921 (35); Parastacilla Hale, 1946 (2); Parapleuroprion Kussakin, 1972 (1); Spectarcturus Schultz, 1981 (1) (123 described species in all).

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