Family ARCTURIDAE Dana, 1849

Parastacilla torus

© Copyright from King 2000.

Museums

Regional Maps

• Arcturidae Dana, J.D. 1849. Conspectus crustaceorum quae in orbis terrarum circumnavigatione, Carolo Wilkes e classe Reipublicae, Foederate Duce, lexit et descripsit (continued). American Journal of Science 2: 424-428 [424].

Introduction

Arcturids are marine benthic or epizoic isopods. The family is cosmopolitan but is rare in tropical waters.Arcturidae were restricted by Poore (2001) to valviferans with the mouthparts hidden laterally by plates of the head and pereonite 1and the exopod of the male pleopod 1 with a lateral notch, usually supporting two or more long plumose setae. Most are strongly geniculate between pereonites 4 and 5, the anterior segments held prominently erect but this is not always the case. Pleonite 4 is usually longer than more anterior pleonites, especially in males where it can be very thin. Pereopods 2–4 are usually cylindrical and held close under the mouthparts at rest but are expanded as a filter-basket of long setae for feeding. These limbs can be absent or not so modified.

The genus Arcturus is unlikely to occur in Australia but is listed below to include four nomina nuda described from NSW but for which types no longer exist.

Diagnosis

Body more or less cylindrical, without coxal dorsal plates or pleonal epimera, weakly or strongly geniculate between pereonites 4 and 5, anterior segments usually held prominently erect. Pereonite 4 at least 1.5 times as long as pereonite 3 (in males often much longer). Mouthparts and pereopod 1 enclosed in lateral view by lateral plates of head and pereonite 1. Pereopod 1 dactylus with unguis, or without unguis. Pereopod 1 gnathopod-like; pereopods 2–4 usually cylindrical, usually with even rows of long filter-setae, differentiated from ambulatory pereopods 5–7; pereopods 3 and 4 rarely absent; with prominent dactyli, unguis short (or dactylus lost in some pereopods). Uropodal exopod (smaller ramus) tapering (with terminal seta or setae only) (rarely absent). Pleopod 1 peduncle more elongate than rami, longer than on pleopods 2 and 3; exopod of male laminar, with proximolateral notch with 3 or 3 long setae. Basally as wide or wider than endopod.

General References

Poore, G.C.B. 2001. Isopoda Valvifera: diagnoses and relationships of the families. Journal of Crustacean Biology 21: 205-230

History of changes