Rhinoecetes karkharius, Just, 2019

Just, Jean, 2019, Siphonoecetini Just, 1983 (Crustacea, Amphipoda, Ischyroceridae) 13: Western Australian species of Bubocorophiina in Rhinoecetes, Cephaloecetes, Sinoecetes, Borneoecetes and Pararhinoecetes gen. nov., Zootaxa 4554 (1), pp. 101-140 : 120

Rhinoecetes karkharius sp. nov.

Figures 13–14

Type fixation. Holotype, ♂, here designated.

Etymology. The epithet is latinised Greek for shark. It refers to the locality Shark Bay.

Material examined. Holotype, Ƌ, 5.9 mm, Denham, Shark Bay , Western Australia, 25°56’S 113°32’E, ca. 50 m off shore, 0.75 m ( HW), sand and foraminiferans with scattered Penicillum and some detritus, hand dredge. J. Just, 20 March 1984, stn AU18, WAM C73450.

Paratypes. Same sample as holotype, WAM C73451 (2 ovig. ♀, 1 adult ♀). Denham, Shark Bay, Western Australia, Australia, 25°56’S 113°32’E, ca. 100 m off shore, 1.5 m ( HW), sand and foraminiferans with some detritus, hand dredge. J. Just, 20 March 1984, stn AU17, WAM C73452 (5 specimens) .

Description (♂). Head as long as pereonites 1 and 0.75 of 2 combined along dorsal midline; mid-anterior depression moderately deep, encompassing slightly more than 0.5 head length; front margin each side of rostrum with curved ‘brows’. Rostrum straight, acutely pointed, in dorsal view reaching well beyond apices of eye lobes. Eye lobes slightly truncate in lateral view, lower distal margin with 1–2 simple setae.

Antenna 1 approximately as long as head and pereonites 1–4 combined; flagellum of 7+ articles, as long as peduncle articles 2 and 3 combined. (Antenna 2 beyond peduncle article 3 not observed); ventral projection of peduncle article 2 as long as broad at base, tapering to rounded apex, with fringe of simple setae apically and laterally. Flagellum articles 1 and 2 with many slender robust setae (from paratype ♂).

Mouthparts, mandible palp article 1 with 2 groups of 2 and 3 ventral and 4 apical long setae.

Gnathopod 1 propodus length 3.0 width, with 2 mid-posterior robust setae. Gnathopod 2 propodus length 1.8 greatest width. Pereopods 3–4 basis with long and short setae along entire anterior margin, a few long setae on mid-posterior margin; merus with tuft of long setae on mid anterior margin and dense bunch of anterodistal long setae, posterior margin with 5–6 groups of unequally long setae. Pereopods 5–6 basis with dense bunch of long setae distally on anterior margin, posterior margin with a few short setae.

Uropod 1 peduncle dorsolaterally with single robust seta, a few simple seta proximally, tuft of simple setae distally, and 1 robust seta at mediodistal corner; ventral apical margin with minutely fimbriate corona; outer ramus nearly straight, approximately 0.5 lateral length of peduncle, lateral margin with 4 robust setae, medial margin with 3 smaller robust setae; inner ramus 0.8 length of outer ramus, straight. Uropod 2 peduncle approximately 0.4 length of peduncle of uropod 1, with minutely fimbriate corona; ramus 0.4 length of peduncle, 0.5 length of uropod 1 inner ramus, with simple setae at base of terminal robust seta, reaching to uropod 3 ramus. Uropod 3 peduncle with rounded median projection carrying a few simple setae apically; ramus with 4–5 long simple setae. Telson width approximately 1.1 length, apex evenly convex.

Female. Generally as male. Uropod 1 peduncle with a couple more robust setae. Pereonite 7 ventrally with straight, tapering sternal papillae ( Fig. 14 Fsp).

Size. Largest ♂ 5.9 mm; largest ♀ 5.0 mm, ovigerous with 6 ova.

Colour and abodes. Not known.

Distribution. Western Australia, Shark Bay (Denham), 1– 2 m.

Remarks. Rhinoecetes karkharius sp. nov. was found in the same habitat as R. caetus sp. nov. (above) in the shallow water at Denham in Shark Bay. The former differs from R. caetus by the strong brows either side of the short, straight rostrum (no brows, curved rostrum), a stout robust seta on mediodistal corner of uropod 1 peduncle (no seta), a medial row of small robust setae on the inner ramus of uropod 1 (no medial setae), and minutely fimbriate uropod 1 corona (denticulate corona).

Figures

FIGURE 13. Rhinoecetes karkharius sp. nov. Holotype, ♂, except M, paratype, ♂. a2 flag, antenna 2 flagellum; cdv, cephalon dorsal view; clv, cephalon lateral view; md plp, mandible palp; up1, uropod 1 peduncle ventral view; us, urosome; vp, ventral projection of article 2 of antenna 2. Scale for habitus: 1 mm.