Family ARCTURIDAE Dana, 1849

Parastacilla torus

Museums

Museum list

Regional Maps

Family ARCTURIDAE Dana, 1849

Introduction

Arcturids are marine benthic or epizoic isopods. The family is cosmopolitan but is rare in tropical waters. There are many species in 16 genera. More than 20 other so-called arcturid genera and numerous species are placed by us in Antarcturidae. To date, all existing literature treats the Arcturidae as including the Antarcturidae as well. The monotypic family Amesopodidae Stebbing, 1905 is included in the synonymy of Arcturidae. Its single species is a marine epizoan. All Australian specimens have been taken on the hydroid Lytocarpus philippinus (Kirchenpaurer). It is found in Sri Lanka as well as in tropical Australia (Stebbing 1905).

The diagnosis is from Poore (2001).

Diagnosis

Body 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). Head and pereonite 1 fused. Pereonite 4 at least 1.5 times as long as pereonite 3 (in males often much longer). All pleonites fused into pleotelson. Body smooth or slightly sculptured, or variously spinose or rugose; pleotelson without dorsolateral ridges ending in mediodorsal posterior spine. Dorsal coxal plates 2–7 obsolete, bases of pereopods exposed, or 2–7 obsolete and with expanded marginal tergites (Arcturinoides only). Mouthparts and pereopod 1 enclosed in lateral view by lateral plates of head and pereonite 1. Eyes well developed, or reduced or lost (rare).

Antenna 2 flagellum of 2–3 articles plus distal claw. Pereopod 1 a gnathopod, pereopods 2–4 elongated, differentiated from ambulatory pereopods 5–7 (some of pereopods 2–4 rarely absent). Pereopod 1 dactylus evenly curved along anterior margin, evenly tapering if present. Pereopods 2–4 with paired long setae along posterior margins evenly and well developed; with prominent dactylus, unguis short (or dactylus lost in some pereopods); pereopod 4 similar to pereopod 3. Pereopods of males without dense fur of fine setae. Uropodal exopod (smaller ramus) tapering (with terminal setae only), more than half as long as endopod (usually).

Oostegites 1–4 functional, 5 absent, or 1–5 functional (Arcturus only); 1–4 not supported by coxal lobes. Penes fused as a single penial plate; penial plate apically simple or barely slit. Pleopod 1 peduncle more elongate than on other pleopods; with marginal setae on rami longer than or equal to length of rami. Pleopod 1 exopod of male laminar; with lateral excavation. Pleopod 2 of male with appendix masculina about as long as endopod (or longer), basally as wide or wider than endopod.