Family SPHAEROMATIDAE Latreille, 1825
Oxinasphaera bisubula
© Copyright from Bruce 1997.
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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 family Sphaeromatidae is commonly encountered in shallow-water marine environments. While they are morphologically diverse they are easily recognised, often by the compact shape but more reliably by the fusion of the pleonites and relatively simple walking legs. They are often brightly coloured and somewhat calcified, unlike cirolanid ‘sea lice’ for example. Few species attain lengths greater than 10 mm – many are smaller than this, 3–5 mm long, and about 30 mm is the greatest length found. The males of many species are ornately sculptured, showing considerable sexual dimorphism. Others can be smooth, even quite flat. Family diagnoses can be found in Bruce (1993) and Wetzer et al. (2018) and form the basis of the diagnosis here.
Sphaeromatidae are the largest family of free-living isopods with 99 genera of which six are exclusively freshwater (Wetzer et al., 2013, 2018). Species number almost 700, and numerous genera and countless species remain undescribed. Sphaeromatids are primarily shallow-water, with the majority of species found on the continental shelf. Only 20 species of Sphaeromatidae have been recorded from depth 400 metres of more (Bruce, 1994, 1997) and of these six extend to depths greater than 1000 metres, a number that remains unchanged to date. Sphaeromatidae are predominately found on hard substrata such as rocky shores, coral reefs as well as sedimentary sea-floor habitats. Hard substrata are rarely sampled in deep water, but museum collections indicate that there is diverse sphaeromatid fauna on such habitats in deep water that is, as yet, unreported.
Wetzer et al. (2013) showed that the family is monophyletic based on an analysis based on an 18S rDNA dataset. Attempts to divide Sphaeromatidae into groups started with Hansen (1905) who recognised what he termed the platybranchiate, hemibranchiate and eubranchiate genera, the three groups later raised to subfamilies by Hurley & Jansen (1977). “Platybranchiatinae” were characterised by the endopods and exopods of pleopods 4 and 5 lacking thickened transverse ridges, pleopods 3 and 4 without a transverse suture, and pleopod 5 exopod with a partial suture. “Hemibranchiatinae” were characterised by the endopods of pleopods 4 and 5 with thickened transverse ridges, pleopods 3–5 exopods usually with a transverse suture. “Eubranchiatinae” have endopods and exopods of pleopods 4 and 5 with thickened transverse ridges, pleopods 3 and 4 exopods usually without a transverse suture, and pleopod 5 exopod with partial or complete suture. Because these subfamily names are not based on a genus name, Iverson (1982) replaced them with Cassidininae Iverson, 1982, Sphaeromatinae Latreille, 1825 and Dynameninae Bowman, 1981 respectively. He listed 20, 20 and 31 genera in each subfamily respectively. The importance of the marsupium in sphaeromatid classification was discussed by Harrison (1984) but because generic identification depends almost entirely on adult male features the number of oostegites, and anterior and posterior brood pouches contribute little to generic diagnoses and nothing to the diagnoses here.
After discussion on the validity of these subfamilies (Bruce, 1995, 1997, 2003; Kussakin and Malyutina, 1993), Wetzer et al. (2018) used a 16S and 18S rDNA dataset from 44 species in 33 genera to show that the subfamilies are artificial.
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
Body oval, vaulted, or flat; head free from pereonite 1; pereonites 1–7 visible dorsally. Coxal dorsal plates 2–7 delimited from tergite by weak nonarticulating suture (sometimes not); dorsal coxal plate 7 similar, usually smaller, to dorsal coxal plate 6. Pleon with pleonite 1 usually present, often hidden dorsally; pleonites 2–5 mesially fused, indicated laterally by 0–3 sutures, occasionally fused to pleotelson. Antennular and antennal peduncles cylindrical, not part of margin of body, or flattened, defining anterior margin of body. Mandibular incisor process multicuspid; left incisor mobilis short, wide. Maxillipedal palp of 5 free articles. Pereopod 1 usually ambulatory. Pereopods 2–7 ambulatory. Uropods endopod fused to peduncle (lamellar, sometimes reduced or absent), exopod usually lamellar (sometimes absent or styliform).
General References
Bruce, N.L. 1993. Two new genera of marine isopod crustaceans (Flabellifera: Sphaeromatidae) from southern Australia, with a reappraisal of the Sphaeromatidae. Invertebrate Taxonomy 7: 151-171
Bruce, N.L. 1994. The Cassidininae Hansen, 1905 (Crustacea: Isopoda: Sphaeromatidae) of Australia. Journal of Natural History 28: 1077-1173
Bruce, N.L. 1995. The taxonomy and phylogeny of tube-tailed sphaeromatid isopods (Crustacea) with descriptions of new species and a new genus from southern Australia. Ophelia 43: 127-180
Bruce, N.L. 1997. A new genus of marine isopod (Crustacea: Flabellifera: Sphaeromatidae) from Australia and the Indo-Pacific region. Memoirs of Museum Victoria 56: 145-234
Bruce, N.L. 2003. New genera and species of sphaeromatid isopod crustaceans from Australian marine coastal waters. Memoirs of Museum Victoria 60: 309-370
Hansen, H.J. 1905. On the propagation, structure and classification of the family Sphaeromidae. Quarterly Journal of Microscopical Science 49: 69-135
Harrison, K. 1984. The morphology of the sphaeromatid brood pouch (Crustacea: Isopoda: Sphaeromatidae). Journal of the Linnean Society of London, Zoology 82: 363-407
Harrison, K. & Ellis, J.P. 1991. The genera of the Sphaeromatidae (Crustacea: Isopoda): a key and distribution list. Invertebrate Taxonomy 5: 915-952
Harrison, K. & Holdich, D.M. 1984. Hemibranchiate sphaeromatids (Crustacea: Isopoda) from Queensland, Australia, with a world-wide review of the genera discussed. Journal of the Linnean Society of London, Zoology 81: 275-387
Hurley, D.E. & Jansen, K.P. 1977. The marine fauna of New Zealand: family Sphaeromatidae (Crustacea: Isopoda: Flabellifera). Memoirs of the New Zealand Oceanographic Institute 63: 1-95
Iverson, E.W. 1982. Revision of the isopod family Sphaeromatidae (Crustacea: Isopoda: Flabellifera) I. Subfamily names with diagnoses and key. Journal of Crustacean Biology 2: 248-254
Wetzer, R., Bruce, N.L. & Pèrez-Losada, M. 2018. Relationships of the Sphaeromatidae genera (Peracarida: Isopoda) inferred from 18S rDNA and 16S rDNA genes. Arthropod Systematics & Phylogeny 76: 1-30
Wetzer, R., Pérez Losada, M. & Bruce, N.L. 2013. Phylogenetic relationships of the family Sphaeromatidae Latreille, 1825 (Crustacea: Peracarida: Isopoda) within Sphaeromatidea based on 18S-rDNA molecular data. Zootaxa 3599: 161-177
History of changes
| Published | As part of group | Action Date | Action Type | Compiler(s) |
|---|---|---|---|---|
| 13-Mar-2025 | CRUSTACEA Brünnich, 1772 | 01-Feb-2025 | MODIFIED | Dr Gary Poore |
| 05-Aug-2022 | 04-May-2011 | MODIFIED | ||
| 05-Aug-2022 | 29-Jun-2010 | MODIFIED | ||
| 12-Feb-2010 | (import) |