Family IDOTEIDAE Samouelle, 1819

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Family IDOTEIDAE Samouelle, 1819

Introduction

Idoteids are common inhabitants of marine intertidal and shallow subtidal environments where they are found attached to seagrasses or macroalgae. Some species are known locally as sea centipedes because of their narrow shape and similar legs. There are numerous species in most seas except in polar regions. Poore & Lew Ton (1993) provided keys to the southern Australian and New Zealand species (few are known from the tropics). Brusca (1984) discussed the phylogeny of the Idoteidae and Holognathidae together (as Idoteinae) and this work is a key source for identification of the non-Australasian genera, phylogeny and biogeography. The diagnosis is from Poore (2001).

Diagnosis

Body straight, more or less flattened or semicylindrical, or strongly vaulted; tapering posteriorly. Head and pereonite 1 free, or fused (Crabyzos, Lyidotea only). Head more or less semi-cylindrical. Pereonite 4 of similar length to pereonite 3. Pleonites 1–2 articulating with each other and fused pleotelson, or pleonite 1 articulating with fused pleotelson, or all pleonites fused into pleotelson (other pleonites sometimes indicated laterally or dorsally). Body smooth or slightly sculptured, or variously spinose or rugose. Dorsal coxal plates 2–7 more or less ventrally expanded over bases of pereopods (coxal plates often very reduced), or 5–7 expanded over bases of pereopods and tergites marginal on pereonites 2–4 (Synidotea only), or 2–7 obsolete and with expanded marginal tergites (Synischia only). Eyes well developed, or reduced or lost.

Antenna 2 flagellum multiarticulate, or clavate (usually with minute terminal article(s)). Maxillipedal epipod as long as or longer than wide. Pereopod 1 slightly differentiated from pereopod 2, its propodus broader than in pereopod 2. Pereopods 2–4 with irregular fine setae and marginal robust setae; with prominent dactylus, unguis short; pereopod 4 similar to pereopod 3. Pereopods of males with dense fur of fine setae. Uropodal exopod (smaller ramus) ovate, fringed with setae (if present) (usually absent), more than half as long as endopod.

Oostegites 1–5 functional, or 1–4 functional, 5 absent (Synidotea only). Penes fused basally as a penial plate but divided over most of length, or fused as a single penial plate (Synidotea only), or paired, elongate (Lyidotea only). Pleopod 1 peduncle short (similar to other pleopods); with marginal setae on rami much shorter than length of rami. Pleopod 1 exopod of male laminar. Pleopod 2 of male with appendix masculina about as long as endopod, basally less than half width of endopod.