Rhiganthura capricornica, Poore, Gary C. B., Lew, Helen M. & Ton, 2002

Poore, Gary C. B., Lew, Helen M. & Ton, 2002, Expanathuridae (Crustacea: Isopoda) from the Australian region, Zootaxa 82, pp. 1-60 : 55-56

Rhiganthura capricornica n. sp. ( Figs 34–36 )

Material examined.– Holotype. Australia. Queensland, Heron I., Blue Pools (23°27'S, 151°55'E), N.L. Bruce, 17 Jan 1979, QM W16290 (juvenile, with 2 slides). Paratypes. Type locality, QM W8118 (2 juveniles). Heron I., “Canyons”, 7 m, N.L. Bruce, 8 Dec 1979, QM W16291 (1 juvenile, 1 slide). Heron I., central lagoon, 2 m, N.L. Bruce, 19 Nov 1979, QM W8750, (1 juvenile). Heron I., reef flat in front of research station, N.L. Bruce, 15 Jan 1979, QM W8088 (1 manca); W8115 (2 mancas).

Description: Juvenile. Head wider than long, with prominent broad rostrum between bases of antennae 1; eyes anterolateral. Pereonite 1 laterally swollen, 3 narrower than others, 5 the longest and 7 half length of pereonite 6. Pleonite 1 short, almost invisible dorsally, pleonites 2–4 of approximately equal length, 5 1.5 times as long, 1–5 about as long as pereonites 6+7, pleotelson as long as pereonites 5–7; pleonite 6 with marginal row of setae. Telson base 0.6 width of widest point, half way along; apical half tapering, with dentate margins, with marginal dorsal setae and its apex with 7 longer setae on each side.

Antenna 1 peduncle with shorter and progressively narrower articles; flagellum longer than last peduncle article, of short article 1, article 2 longer, 3 and 4 minute, last 2 each with 1 aesthetasc. Antenna 2 peduncle longer than antenna 1, articles 4 and 5 longer than wide; flagellum of 5 articles.

Mandible with produced simple incisor, lamina dentata denticulate, molar process obscure; palp of 1 article with 1 distal seta. Maxillipedal endite reaching to end of fused palp articles 1+2, rounded, with 2 distal setae; palp articles 1+2 fused, article 2 with 1 mesial seta, article 3 longer and with 2 simple mesial setae, article 4 rounded and with 2 mesial setae, article 5 short and with 4 apical setae.

Pereopod 1 subchelate, with stout proximal articles; merus cupping carpus and propodus, with blunt tooth on posterior margin; carpus with blunt teeth and 1 seta on posterior margin; propodus swollen, palm axial with blunt marginal teeth, 2 short setae, mesial face with 3 setae distally; dactylus palm with 3 rounded teeth, unguis about one­third its length. Pereopod 2 much more slender than first; merus cupping triangular carpus; carpus with 2 setae on posterior margin; propodus weakly swollen, palm with weak proximal teeth, 2 short spiniform seta (1 minute) and another pectinate seta distally. Pereopod 3 similar to pereopod 2. Pereopods 4–6 similar; carpus triangular with 1 spiniform seta; propodus with 2 posterior marginal spiniform setae; dactylus curved, unguis one­third length. Pereopod 7 carpus more elongate than in more anterior pereopods; propodus with 4 anterodistal double­pectinate setae.

Pleopod 1 with rami together operculiform, endopod half as wide as exopod and longer, distally setose; exopod 1.8 times as long as wide, marginally setose. Pleopods 2–5 about three­quarters as long as pleopod 1; endopods more rectangular and narrower than exopods, distally truncate and setose; exopods distally and laterally setose. Uropodal endopod as long as peduncle, reaching to end of telson; endopod 1.5 times long as wide, marginally dentate, distally and laterally setose; exopods not meeting in midline, each with proximal ventral lobe, ventrally crenellate, dorsal lobe extending posteriorly as dentate spike more than twice length of ventral lobe.

Female and male. Unknown.

Size: To 3.2 mm.

Distribution: Heron I., southern Great Barrier Reef, Australia; lagoon sediments.

Remarks: The only other described species of the genus is Rhiganthura novaezealandiae Kensley, 1978 from New Zealand. The two species are very similar but the new one differs in the possession of a 1­articulate mandibular palp (2 articles in the type species), and a visible terminal article of the maxillipedal palp. There may be differences in the uropods and telson but Kensley’s (1978a) figures are not sufficiently detailed.

Figures

FIGURE 34. Rhiganthura capricornica n. sp. Holotype, QM W 16290. Scale bar = 1 mm.

FIGURE 35. Rhiganthura capricornica n. sp. Holotype, QM W 16290.

FIGURE 36. Rhiganthura capricornica n. sp. Holotype, QM W 16290.