Family SPHAEROMATIDAE Latreille, 1825

Oxinasphaera bisubula

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Family SPHAEROMATIDAE Latreille, 1825

Compiler and date details

Gary C.B. Poore, Helen M. Lew Ton & Niel L. Bruce

Introduction

The Sphaeromatidae or marine pill-bugs are probably the most commonly encountered family of isopods on rocky shores and in shelf waters. The family is noted for its strong sexual dimorphism (males usually more sculptured and ornamented than females) and the unusual habit, in many species, of brooding juveniles in internal pouches of the adult female (Harrison 1984). There are numerous species in about 100 genera. Hansen's (1905) division of the family into three groups (Eubranchiatae, Hemibranchiatae and Platybranchiatae) has been used until recently and is the basis for the keys developed by Hale (1929); the keys are still useful to identify southern Australian species. Iverson (1982) replaced this scheme with five subfamilies (Ancininae, Cassidininae, Dynameninae, Sphaeromatinae and Tecticipitinae) for which he provided a key and lists of genera. Harrison (1984) also listed all genera known and discussed the morphology of the brood pouch of each. Following Bruce (1993), we recognise the Ancinidae and Tecticipitidae as separate families. Harrison & Ellis (1991) provided a practical worldwide key to the genera then known, but much has been described from Australia since then.

The Australian fauna is particularly rich compared to other regions and is notable for strong radiation in some genera, e.g. Paracassidina Baker and Oxinasphaera Bruce (Bruce 1994, 1997). Despite the number of genera and species already recorded from Australian waters, we estimate that the sphaeromatid fauna is likely to be, at the least, double that which is already known.

The genus Cymodoce Leach is in a very confused state. In a review of the genus, Harrison & Holdich (1984) clarified the status of some species previously assigned to it. The following were assigned with 'some doubt' to Cymodoce, but are included in that genus in this Catalogue: Cymodoce bidentata bidentata Haswell, 1882; C. bidentata tasmanica Baker, 1929; C. convexa Miers, 1876; C. coronata coronata Haswell, 1882; C. coronata fusiformis Baker, 1929; C. coronata intermedia Baker, 1929; C. mammifera Haswell, 1881; and C. inornata Whitelegge, 1902.

The Australian records of Cymodoce convexa Miers, 1876 and C. unguiculata Barnard, 1914 were considered doubtful by Harrison & Holdich (1984), but they did not exclude them from the Australian fauna.

Diagnosis

Capable of rolling into a sphere or folding over (i.e. head to pleotelson). Head not fused to pereonite 1; coxal plates 2–7 usually indicated dorsally; pleon usually of three parts: short and narrow pleonite 1; partially or completely fused pleonites (2–5 visible in dorsal view, indicated by lateral suture lines); vaulted pleotelson. Frontal lamina and clypeus fused. Mandible stout; incisor usually with multicusped incisor; lacinia mobilis present on left, multicusped; spine row present; molar process trituritive or a chitinised lobe. Maxillipedal endite elongate, setose. Pereopods ambulatory. Pleopods 1–3 with plumose marginal setae; pleopod 5 exopod with distal scale patches. Uropods anterolateral; exopod free when present; endopod fused with peduncle. Sexual dimorphism often pronounced. Young often brooded in invaginated pouches of ventral body wall.