Rhinoecetes rhinoceros, Just, Jean, 2012

Just, Jean, 2012, Siphonoecetini Just, 1983 (Crustacea, Amphipoda, Ischyroceridae) 9: New species in Rhinoecetes Just, 1983, Cephaloecetes gen. nov. and Neoecetes gen. nov. from the south-eastern Australian shelf, Zootaxa 3234, pp. 1-42 : 9-13

Rhinoecetes rhinoceros sp. nov.

Figures 5–7

Type fixation. Holotype, 3, here designated.

Etymology. The species is named for its strongly up-curved rostrum.

Material examined. Holotype. 3, 7.0 mm, Australia, New South Wales, Sydney, Pittwater, inside Palm Beach, 0.5 m, sandy mud and coarse terrestrial detritus in open Zostera bed, hand dredge on SCUBA, J. Just, P. Berents, R.T. Springthorpe, 24 September 1984, stn AU57, AM P87030.

Paratypes. New South Wales, Sydney: Same data as holotype, AM P86637 (3 with abode). Same data as holotype, AM P86638 (1 ovigerous Ƥ, 1 adult 3). Same data as holotype, AM P86639 (14 ovigerous Ƥ, 13 adult 3, many young and juveniles). Same data as holotype, AM P87036 (many abodes, a number with inhabitant). Pittwater, inside Palm Beach, 2–2.5 m, sand, shell fragments, much detritus in open Posidonia bed, hand dredge on SCUBA, J. Just, P. Berents, R.T. Springthorpe, stn AU56, 24 September 1984, AM P87037 (6 specimens, 1 abode aggregate of 3 and Ƥ). Pittwater, inside Palm Beach, 4 m, sand, some shell fragment, scattered sea-grass, some algae, hand dredge on SCUBA, J. Just, P. Berents, R.T. Springthorpe, stn AU58, 24 September 1984, AM P87038 (1 ovigerous Ƥ with abode). E of North Head, Port Jackson, Sydney 33°49’S, 151°18’E, 25.9 m, with Halme gigantea , Australian Museum Shelf Benthic Survey, 26 February 1974, AM P22503 (1 specimen). Pittwater, Palm Beach, 100 m S of W-side of Barrenjoey Head, 33°35’S 151°19.4’E, 4.5 m, Zostera bed, shells, mud, J.K. Lowry, R.T. Springthorpe, 30 November 1983, AM P34970 (2 3, 1 Ƥ, 6 young).

Queensland, Moreton Bay, Middle Banks: 27°11’S 153°21’E, ca. 8 m, grab, stn 3B, May 1982, QM W11559 (1 3, 3.8 mm). Off Tangalooma, Moreton Island, 27°11’S 153°21’E, ca. 14 m, grab, stn 6D, November 1982, QM W11661 (1 3, 3.8 mm).

Description (holotype, 3). Head as long as pereonites 1 and 2 combined along dorsal midline; midanterior depression deep, encompassing approximately 0.6 head length. Rostrum dipping steeply down then curving back up forming well over half circle, acutely pointed, in dorsal view reaching beyond apices of eye lobes with about 1/ 3 its length. Eye lobes rounded in lateral view, lower anterior margin with two simple setae. Pereon with few, scattered small simple setae dorsally.

Antenna 1 approximately as long as head and pereonites 1–5 combined, reaching to apex of antenna 2 peduncle article 4; flagellum (right) of 6+ articles (left flagellum, Fig. 5 habitus, appear damaged), approximately as long as peduncle articles 2 and 3 combined. Antenna 2 approximately as long as head, pereonites 1–7 and pleonites 1 and half of 2 combined; ventral projection of peduncle article 2 as long as broad at base, triangular, bluntly pointed, with fringe of long simple setae apically and laterally; articles 3–5 with dorsal, ventral and lateral groups of short simple setae, longest on article 5; article 5 length 0.85 of 4; flagellum articles 1 and 2 with short robust setae. Mouthparts, mandible palp article 1 with dorsal, ventral and apical groups of long setae.

Gnathopod 1 propodus length 3.0 width, left with 2 midposterior short robust setae (segment appears to have been damaged), right with 4 robust setae. Gnathopod 2 propodus length 1.9 greatest width. Pereopods 3–4 basis with dense row of long setae on anterior margin, tuft of long setae on lateral surface, and 2 groups on midposterior margin; merus with several groups of long setae along anterior and posterior margins. Pereopods 5–6 basis with dense row of long setae along distal half of anterior margin, posterior margins with several unequally long setae. Pereopod 7 propodus posterior margin with 4–5 groups of long setae.

Uropod 1 peduncle with dorsolateral row of small robust setae, mediodistal corner with single simple setae; outer ramus slender, slightly inward curved, approximately 0.6 length of peduncle, lateral margin with row of 6–7 robust setae, medial margin with row of simple setae; inner ramus 0.7 length of outer ramus, slightly inward curved, with 1 small simple setae distally. Uropod 2 peduncle approximately half length peduncle of uropod 1, with 2 dorsolateral simple setae; ramus approximately half length of peduncle, with 1 simple seta distally, reaching beyond uropod 3 ramus with about 1/3 its length. Uropod 3 peduncle with rounded median projection carrying tuft of simple setae apically; ramus with row of 5 simple setae increasing in length towards the middle. Telson width approximately 1.2 length.

Female. Left gnathopod 1 propodus with 4, right with 3 robust setae. Pereonite 7 ventrally with short, forward curving sternal papillae.

Size. Largest 3, 7.3 mm, largest Ƥ, 6.2 mm.

Variation. Two males from Moreton Bay, Queensland, are with some hesitation included in the paratype series of Rhinoecetes rhinoceros sp. nov. Head shape and rostrum are highly characteristic of that species ( Fig. 7 M), but the specimens are much smaller than males of similar development at the type locality at Sydney. Hence the Moreton Bay specimens are less setose and have fewer robust setae on the uropods.

More material from Moreton Bay and from the approximately 1000 kilometer coast line between Moreton Bay and Sydney is needed to ascertain the veracity of this decision.

Colour and biology. Body red-brown to dark brown with cream-white saddle on pereonites 3–6. Head creamwhite in dorsal depression. Antenna 1generally colourless translucent, with brown blotches dorsally at peduncular base. Antenna 2 peduncle article 3 whitish with brownish in posterior half; article 4 distal 1/4 cream-white, proximally more translucent with red-brown longitudinal bands reaching to white part. Smaller specimens less strongly coloured, tending to be translucent in posterior parts, but the general colour pattern is recognizable. Specimens occupy a range of suitable abodes, most commonly micro prosobranch shells. Abode aggregates of 3 and Ƥ observed.

Distribution. Eastern Australia, New South Wales, Sydney area, 2–4.5 m; Queensland, Moreton Bay, 8– 14 m.

Figures

FIGURE 5. Rhinoecetes rhinoceros sp. nov. Holotype, 3, except F, paratype, ovigerous Ƥ. a 2 flag, antenna 2 flagellum; c, head (dv, dorsal view, lv, lateral view); vp, ventral projection of antenna 2 article 2. Habitus scale for 3 and Ƥ: 1 mm.

FIGURE 6. Rhinoecetes rhinoceros sp. nov. Holotype, 3. gp 1, gnathopod 1 (l, left, r, right); gp 2, gnathopod 2; p 3 and 5, pereopods 3 and 5; us, urosome with uropods.

FIGURE 7. Rhinoecetes rhinoceros sp. nov. A, examples of abodes (AM 87063); F, paratype ovigerous Ƥ; M, 3 of 3.7 mm from Moreton Bay (QM W 11661). c, head (lateral view); gp 1, gnathopod 1 (l, left, r, right); sp, sternal papillae.