Family ENTONISCIDAE Kossmann, 1881

Tiarinion texopallium

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Family ENTONISCIDAE Kossmann, 1881

Introduction

Members of the Entoniscidae are internal parasites of anomuran and brachyuran crabs and rarely of caridean shrimps. There is a high degree of host specificity. Female entoniscids are typically surrounded by a host response sheath and are connected to the external environment via a furrow or hole in the carapace of the host. Most entoniscids are parasitic castrators although complete castration may depend on the status of the host and duration of the infestation (Veillet 1945). In some cases male feminisation may occur. Entoniscids are highly sexually dimorphic; females are grossly distorted and dwarf males are more typically isopod-like. Sixteen genera and at least 37 species are known (Shields & Earley 1993; Shields & Ward 1998). Only two species have been described from Australia, but Shields & Earley (1993) suspected many other species await description. Shiino (1942) provided a key to the species in Japan and several of these may have hosts that occur in Australia.

The concept of a 'gruppe' within Bopyridae based on Entoniscus was introduced by Müller (1871), but the family name was first formalised by Kossman (1881).

Diagnosis

Female: body either worm-like or highly lobose, asymmetrical; somites visible only middorsally if at all. Cephalon hemispherical; oral cone (mandible and lamellar maxilliped only) produced anteriorly or posteriorly. Pereopods of 4 or 5 pairs, vestigial if present, located on dorsal thorax. Oostegites variable in size; oostegite 1 highly developed as a hood projecting anteriorly over cephalon; others small, often fused; brood pouch asymmetrical or bilateral. Gills simple or complex. Pleopods small or absent. Uropod distinct or absent. Pygidium simple. Male: Narrow, with pereonite 1 fused to cephalon. Pereopods simple, 3 to 5 segments. Abdomen without ornamentation, telson bifid with or without rami.