Rhinoecetes makritrichoma, 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 : 111-114

Rhinoecetes makritrichoma sp. nov.

Figures 7–8

Type fixation. Holotype, ♂, here designated.

Etymology. Greek for long (makris) and animal hair (trichoma) referring to the network of unusually long setae on eye lobes, coxae and pereopods.

Material examined. Holotype, ♂, 3.2 mm. Off Green Is., Rottnest Is., Western Australia, 32°01’S 115°30’E, 14 m, fine sand, stn WA-236, J.K. Lowry, 21 December 1983, AM P34972.

Paratypes. Same sample as holotype, AM P 101860 (many specimens) . Same sample as holotype, AM P 101861 (3 ♂♂ and 7 ♀♀) . Same sample as holotype, NHMD-233135 (12 specimens) . Same sample as holotype, WAM C73463 (10 specimens) . Geordie Bay, Rottnest Is. , Western Australia, 31°59.5’S 115°35’E, 10 m, airlifted sand, stn WA-229, R Springthorpe, JK Lowry, 20 December 1983, AM P34974 (1 ♀, 2 juv.) . Western Australia, Seven Mile Beach, Dongara, south of Geraldton , 29°15’S 114°55’E, V. Wadley, 7 January 1988, WAM C73441 (1 ♂ with 1 ♀ abode attached, 1 juv.) .

Description (♂). Head as long as pereonites 1 and half of 2 combined along dorsal midline; mid-anterior depression deep, encompassing approximately 3/4 head length. Rostrum slightly down curved, acutely pointed, in dorsal view reaching beyond apices of eye lobes with entire length. Eye lobes in lateral view strongly tapering towards blunt apex; apex with very long single, simple seta.

Antenna 1 approximately as long as head and pereonites 1–4 combined, reaching 3/4 along article 4 of antenna 2; flagellum of 4+ articles, as long as peduncle articles 2 and 3 combined. Antenna 2 about as long as head, pereonites and pleonites combined; ventral projection of peduncle article 2 apparently about 0.1 longer than broad at base ( Fig. 8 vp in slightly oblique view, partly obscured), with broadly rounded apex, with lateral and apical fringe of long simple setae; peduncle article 4 with few scattered ventral and dorsal simple setae; article 5 distal half with tufts of long simple setae ventrally and scattered setae dorsally; article 5 length 0.7 of article 4; flagellum articles 1 and 2 with several slender, straight robust setae.

Mouthparts, mandible palp article 1 with 2 lateral, 3 medial and 1 apical long setae.

Gnathopod 1 propodus length 4.0 width, with 2 mid-posterior robust setae. Gnathopod 2 propodus length 1.8 greatest width. Pereopods 3–4 basis with row of very long setae along distal half of anterior margin, posterior margin without setae; merus with mid-anterior and anterodistal long setae, posterior margin with dense row of long setae. Pereopods 5–6 basis distal third of anterior margin with dense group of 10–12 very long setae, posterior margin with 1 or 2 long setae; merus mid-posterior margin with dense group of long setae.

Uropod 1 peduncle dorsolaterally with 2 simple setae and tuft of very long setae distally, ventral apical margin with finely fimbriate corona; outer ramus straight, approximately 0.6 dorsal length of peduncle, lateral margin with 2 (3) robust setae; inner ramus 0.8 length of outer ramus, straight. Uropod 2 peduncle 0.44 length of peduncle of uropod 1, with finely fimbriate corona (not illustrated); ramus 0.5 length of peduncle, 0.5 length of uropod 1 inner ramus, reaching about middle of peduncle uropod 3. Uropod 3 peduncle with angularly pointed median projection carrying a few simple setae apically; ramus with 2 long simple setae. Telson width approximately 1.3 length, apex evenly convex.

Female. Generally as male, but pereopods 5 and 6 basis with much less dense bunch of anterior setae. Pereonite 7 ventrally with straight, forward pointing sternal papillae, nearly twice as long as broad at base ( Fig. 8 F sp).

Size. Largest ♂, 3.2 mm; largest ♀, fully developed oostegites, 2.8 mm.

Colour and biology. No observations.

Distribution. Western Australia, Rottnest Island, 10– 14 m.

Remarks. Of the 17 species of Rhinoecetes now known from Australia four, R. brevicornis Just, 2012a from the south-east coast, R. meridianus Just 2012a from the Bass Strait region, R. annae Just 2012b from around Darwin in the Northern Territory, and the new species R. sinuduopopulus (above) share with R. makritrichoma sp. nov. simple setae only on the peduncle of uropod 1. The first-mentioned differs from R. makritrichoma and R. sinuduopopulus by its short, broad rostrum, in longer and more straight robust setae on antenna 2 flagellum, ventral projection of antenna 2 article 2 elongate, and in being considerably larger (♂ 6.9 mm, ♀ 6.0 mm). Rhinoecetes meridianus differ from the two Western Australian species by the truncate eyelobes in lateral view, the longer and straighter robust setae on flagellum of antenna 2. Rhinoecetes annae is of the same size as the new species, but it differs from R. makritrichoma and R. sinuduopopulus by its broad apically rounded eyelobes in lateral view, the longer antenna 1 relative to antenna 2, and the strong denticles on the ventral apical corona of uropod 1 compared with finely fimbriate corona in the new species. Finally R. makritrichoma differs from the other four species by its unusual network of long coxal and pereopodal setae.

Figures

FIGURE 7. Rhinoecetes makritrichoma sp. nov. Holotype, ♂, except M, ♂ paratype. a2 flag, antenna 2 flagellum enlarged; cdv, cephalon dorsal view; clv, cephalon lateral view; up1 vv, uropod 1 peduncle ventral view; us, urosome. Habitus scale: 1 mm.

FIGURE 8. Rhinoecetes makritrichoma sp. nov. Holotype, ♂, except F, ♀ paratype; M, ♂ paratype. gp1, gnathopod 1; gp2, gnathopod 2; md plp, mandible palp; p3, pereopod 3; p5, pereopod 5; sp, sternal papilla (left lateral view), 6 and 7, pereonites 6 and 7; vp, ventral projection of article 2 of antenna 2.