Cassidias australiensis, Bruce, 2003

Bruce, N. L., 2003, New genera and species of sphaeromatid isopod crustaceans from Australian marine coastal waters, Memoirs of Museum Victoria 60 (2), pp. 309-369 : 320-327

Cassidias australiensis sp. nov.

Figures 8–13

Material examined. Holotype. Male (4.0 mm), NW end of McCluer I., NT, 11°02´S, 132°58´E, 16 Oct 1982, hydroids etc. from bommies, G.C.B. Poore ( NMV J39703 ).

Paratypes. NT. Males (3.4–4.0 dissected, 4 each 3.5–4.0 [all crushed] mm), females (ovigerous 4.3 mm, dissected, non-ovigerous 2.6–4.2 dissected), immature (2.3–2.7 mm), 54 unmeasured immature, males and females, same data as holotype ( NMV J26384 , J39709 ). Female (non-ovigerous 3.2 mm), Table Head, Coburg Peninsula, 11 May 1983, mixed substrata, rocks and sponges, N.L. Bruce ( NTM Cr012315). Male, 25 females and immature, McCluer I., S end, 11°06´S, 133°00´E 17 Oct 1982, 8.0 m, hydroids etc., G.C.B. Poore ( NMV J26388 ). 4 males, c. 40 females and immature, McCluer I., NW end, 11°02´S, 132°58´E 16 Oct 1982, 8.0 m, yellow hydroids, J.K. Lowry ( NMV J26389 ). 13 males, c. 100 females and immature, Fannie Bay , Darwin , 11°24´S, 130°48´E, 26 Oct 1982, 8 m, hydroids etc, J.K. Lowry ( NMV J26386 ). WA. Females (ovigerous 3.0, non-ovigerous 3.1 mm), North-West Shelf, 19°29.7´S, 118°52.2´E, 24 Oct 1983, 37 m, sled, CSIRO, RV Soela ( WAM C28895 ) .

Description of male. Body about twice as long as greatest width, strongly vaulted, ovate, widest at pereonite 5; dorsal surfaces anteriorly smooth, becoming minutely granular towards posterior, scattered setae present on posterior of pereonites and on pleotelsonic process. Cephalon anterior margin with 2 transverse ridges, ventral rostral process weakly developed. Head and pereonite 1 subequal in length in dorsal view, pereonite 1 about 1.4 times as long as pereonite 2, unornamented; pereonites 2>3<4<5>6>7. Pleon about twice as long as pereonite 7, with evident sutures and sublateral ‘keys’. Pleotelson process proximal half with convex lateral margins distal portion with lateral margins straight, posteriorly subtruncate with weak median indentation; distal part with 2 distinct ranks of setae merging to one across posterior margin; in lateral view appearing distally narrowly rounded; ventral margin with deep exit channel, ventral margin wide and flattened with sublateral depression mesial to uropods.

Antennule peduncle article 1 1.9 times as long as wide, about 4.7 times as long as article 2, distal one-third of anterior margin with obscurely indented blade; both articles 1 and 2 finely pilose, posterior margin with sensory setae; article 3 about half as long as article 1 4 times as long as wide, twice as long as article 2; flagellum 7-articled, extending to posterior of pereonite 1, about 2.5 times as long article 3. Antenna peduncle articles 1 and 2 short, article 1 anterior margin with mass of setae, combined lengths about equal to that of article 5; article 3 about 0.8 times as long as article 4; article 4 about 0.7 as long as article 5, articles 3–5 collinear; flagellum about equal in length to peduncle, extending to anterior margin of pereonite 2, with 12 articles.

Epistome anteriorly acute, minutely granular, with weak lateral constriction; with distinct anteromedial nodule. Left mandible incisor with 4 cusps, lacinia mobilis with 3 cusps, spine row of 5 serrate curved spines; right mandible with 3 indistinct cusps, spine row of 2 broad-based multidigitate spines, 5 serrate spines; molar process round; palp articles 1 and 2 subequal in length, article 2 distolateral margin with 3 biserrate setae; article 3 with 11 biserrate setae, terminal seta being largest. Maxillule mesial lobe with 3 long, weakly pectinate RS and 2 shorter simple RS, lateral lobe with 11 peripheral RS on gnathal surface, twelfth seta set between these; most RS are weakly and bluntly serrate on distal part, proximal RS strongly serrate. Maxilla lateral lobe and middle lobe each with 7 and 6 curved finely serrate RS respectively, mesial lobe with 6 serrate and biserrate RS. Maxilliped endite lateral margin strongly convex, distal margin with 1 simple RS at sublateral angle, 4 curved CP RS, 3 sinuate CP RS; distomesial margin with 3 large stout CP RS, increasing in size proximally; palp slender, article 2 4 times as long as basal width; articles 3 and 4 with finger-like distomesial lobes; articles 2–5 with about 12, 13, 14 and 16 setae respectively.

Pereopod 1 basis about 2.9 times as long as greatest width, approximately twice as long as propodus; superior margin with few widely-spaced short simple setae; ischium about as long as propodus, twice as long as greatest width, proximal superior margin with 2 acute short simple RS, inferior margin with short setulose fringe; merus about 0.7 as long as ischium, 1.2 times as long as greatest width, superior distal angle with 2 acute biserrate RS, inferior margin with distally plumose setae set among setulose fringe; carpus approximately as long as wide, inferior margin 0.6 times as long as merus, with 2 distally plumose setae; propodus 2.5 times as long as greatest width, inferior margin with 3 stout serrate and 2 slender distally plumose setae; dactylus 0.6 times as long as propodus, unguis inferior margin with prominent serrate cuticular scales, secondary unguis recurved simple. Pereopods 2–7 subsimilar. Pereopods 2 and 3 similar to pereopod 1. Pereopod 2 basis 3 times as long as greatest width, inferodistal angle with single simple seta, superior margin with widely spaced small setae; ischium 0.7 times as long as basis, 3 times as long as greatest width, superior distal margin with 2 simple setae, inferior margin with short setulose fringe and 4 widely-spaced short simple setae; merus about half as long as ischium, superior distal angle with 1 long simple seta, inferior margin setulose with 2 long distally plumose setae, distal seta being twice as long as proximal seta; carpus anterodistal angle with single small simple seta, inferior margin setulose, with 4 setae, longest of which is simple, remainder distally plumose; propodus about as long as ischium, superior distal angle with 3 setae one of which is pappose, inferior margin finely setulose, with 3 RS; dactylus 0.6 as long as propodus. Pereopods 5–7 similar, longer and with more RS than pereopods 1 and 2. Pereopod 7 basis 4 times as long as greatest width, inferodistal angle with single simple seta, superior margin with 2 widely-spaced small setae, distally with 1 palmate seta; ischium 0.8 times as long as basis, 3.8 times as long as greatest width, proximal superior margin with 1 short acute RS, superior distal margin with 1 simple setae, inferior margin with 2 widely-spaced short simple setae; merus one-third as ischium, superior distal margin with 2 simple setae, inferior margin setulose with 3 simple RS; carpus 1.3 times as long as merus, anterodistal angle with 2 acute RS, 1 simple and 1 palmate seta, simple seta, inferior margin setulose, with 1 simple and one serrate RS, inferodistal angle with 4 serrate RS; propodus 1.7 times as long as ischium, superior distal angle with 1 simple and 1 palmate seta, inferior margin finely setulose, with 4 simple RS; dactylus 0.4 as long as propodus.

Penes twice as long as basal width, distally subtruncate; separated by 1.1 times basal width of penial process.

Pleopod 1 exopod and endopod with 26 and 12 PMS respectively; endopod 0.4 as long as exopod, 4 times as long as greatest width, proximal lateral margin weakly concave. Pleopod 2 exopod and endopod with 28 and 10 PMS respectively; appendix masculina 5 times as long as wide, bluntly rounded, mesial margin straight, lateral margin weakly convex. Pleopod 3 exopod and endopod with 28 and 13 PMS respectively. Pleopod 4 both rami with prominent thick ridges, exopod lateral margin with c. 10 fine setae, small proximal submarginal lobe. Pleopod 5 both rami with prominent thick ridges; exopod with 3 scale patches distal to suture, lateral margin with numerous short simple setae, distal margins with longer scale-setae; endopod with scale-setae on distal margin only. Uropod 3 times as long as wide.

Female. Body shape similar to that of male, but pleotelson process prominent, less developed; with fewer setae on dorsal surfaces. Uropod endopod 4 times as long as wide (including peduncular portion), distal margin subtruncate; exopod about 3 times as long as wide, distal margin concave. Brood pouch of 3 pairs of overlapping oostegites arising from pereonites 2–4.

Size. Adult males 3.4–4.0 mm, ovigerous females 3.0– 4.3 mm, non-ovigerous females 2.6–4.2 mm.

Etymology. All species of Cassidias have been named after the country from which they were collected (coincidentally all starting with the letter ‘a’), and I continue with that practice.

Distribution. NT, North-West Shelf, WA; 8– 37 m. The species has been recorded from hydroids, while field observations suggest that it is a commensal of gorgonian ‘corals’. A colour photograph shows a similar isopod from Indonesia, identified as Cassidias sp. , on a gorgonian ( Bruce, 1999).

Remarks. Neither Cassidias argentinea nor Cassidias africana have been described in detail. The male of Cassidias argentinea remains unknown, but the female differs from C. australiensis in being larger, with distally rounded uropods (in C. australiensis the female uropodal endopod is truncate, the exopod distally indented). Males of Cassidias africana differ in having the pleotelsonic process subacute rather than truncate and have a far longer uropodal endopod which is distally swollen giving a somewhat club-shaped appearance.

Figures

Figure 8. Cassidias australiensis sp. nov. A–F, male holotype, G–H, male paratype, remainder as indicated. A, dorsal view; B, lateral view; C, pleon, ventral view; D, pleotelson, posterior margin, posterior view; E, frons and anterior of head in ventral view; F, frons, female; G, antennule; H, antenna.

Figure 9. Cassidias australiensis sp. nov. All figs male paratype. A, maxilliped; B, maxillule, lateral lobe; C, maxillule mesial lobe; D, maxilla; E, left mandible; F, right mandible, distal part.

Figure 10. Cassidias australiensis sp. nov. A–C, pereopods 1, 2 and 7; D, dactylus, pereopod 1; E, penial processes; F, uropod, immature; G, oostegite 2.

Figure 11. Cassidias australiensis sp. nov. A–E, pleopods 1–5; F, coupling hooks, pleopod 1.

Figure 12. Cassidias australiensis sp. nov. All female except C, immature paratype. A, lateral view; B, dorsal view of pleon; C, dorsal view of pleon, immature; D, maxilliped; E, left mandible; F, maxilla; G, maxillule; H, uropod.

Figure 13. Cassidias australiensis sp. nov. SEMs. Male, McLuer Island, NT, NMV J26384. A, cuticle on pleon; B, left mandible; C, pereopod 1, dactylus; D, maxilla; E, mandible palp article 3; F, pleopod 5, exopod dorsal.