Rhinoecetes dinoceros, 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 : 13-17

Rhinoecetes dinoceros sp. nov.

Figures 8–10

Type fixation. Holotype, male, here designated.

Etymology. The species is named for its dinosaur-like vaulted head and up-curved rostrum.

Material examined. Holotype, 3, 6.5 mm, Australia, New South Wales, Jervis Bay, south east of Huskisson, off Moona Moona Creek, 35°03’S 150°40’E, 14 m, silty sand with fine shell fragments, hand dredge, SCUBA, J. Just, P.B. Berents, R.T. Springthorpe, 18 November 1984, stn AU76, AM P87039.

Paratypes. Australia, New South Wales: Same collecting data as holotype, stn AU76, AM P87040 (2 3, 1 small specimen). Same collecting data as holotype, stn AU75, AM P87041 (3 young specimens with abodes, 8 juveniles). Same collecting data as holotype, stn AU75, AM P87042 (1 Ƥ with newly hatched juveniles, see Fig. 8 F). Same collecting data as holotype, stn AU75, AM P87043 (1 young with abode). Jervis Bay, off Moona Moona Creek, 35°03’S, 150°40’E, 8 m, fine sand with detritus to coarse shelly broadly rippled sand, just inside low rock reef covered with large brown algae, hand dredge on SCUBA, J. Just, P.B. Berents & R.T. Springthorpe, 15 November 1984, stn AU65, AM P87044. Jervis Bay, south east of Huskisson, off Moona Moona Creek, 35°03’S 150°40’E, 8 m, broadly rippled sand with some detritus, hand dredge, SCUBA, J. Just, P.B. Berents, R.T. Springthorpe, 16 November 1984, stn AU66, AM P87045 (1 young Ƥ). E of Malabar, 33°58’S 151°20.36’E, 75 m, sandy gravel, dredge, Australian Museum Shelf Benthic Survey, stn C6 S3, 22 May 1972, AM P22519 (2 small specimens). 1.6 km E of Malabar, 33°58.15’S 151°17’E, 66 m, dredge, Australian Museum Shelf Benthic Survey, stn III, 30 August 1973, AM P22521 (4 small specimens). 2 km E of Long Bay, 33°58.20’S 151°17.49’E, 127 m, Australian Museum Shelf Benthic Survey, stn IV, 30 July 1973, AM P22522 (21 specimens from adults to small young). 2 km E of Long Bay, 33°58.20’S 151°17.49’E, 127 m, dredge, Australian Museum Shelf Benthic Survey, stn IV, 9 December 1973, AM P22523 (1 Ƥ). 2.3 km SE of Malabar, 33°58.27’S 151°18.41’E, 134 m, dredge, Australian Museum Shelf Benthic Survey, stn V, 4 December 1973, AM P22524 (6 3, 4 ovigerous Ƥ). 2.3 km SE of Malabar, 33°58.27’S 151°18.41’E, 134 m, dredge, Australian Museum Shelf Benthic Survey, stn V, 29 January 1974, AM P22525 (2 Ƥ). 2.3 km SE of Malabar, 33°58.27’S 151°18.41’E, 134 m, dredge, Australian Museum Shelf Benthic Survey, stn V, 24 October 1973, AM P22526 (28 specimens, various sizes). Jibbon Point, 34°04’S 151°13’E, 50 m, sand, dredge, K. Sheard, 12 September 1943, AM P32001 (13 specimens). E of Port Jackson, 33°52’S 151°23’E, 80 m, epibenthic sled, FRV Kapala , stn K- 80-20-11, R.T. Springthorpe, 11 December 1984, AM P34969 (1 specimen). Byron Bay, 100 m NW of Julian Rocks, 28°61’S, 153°63’E, 15 m, shelly sand between rocks, S.J. Keable and R.T. Springthorpe, 4 March 1992, AM P84642 (1 ovigerous Ƥ, 1 young). Coral Sea, 29°57'S, 153°24'E, 75 m, muddy sand, van Veen grab, Galathea st. 545, 11 Nov. 1951, ZMUC-CRUS-20464 (1 young).

Victoria, Bass Strait: Eastern Bass Strait, 39°22.4’S 148°38.7’E, 73 m, muddy sand, dredge, G.C.B. Poore, HMAS Kimbla , cruise 79-K-1, stn BSS 38, 29 March 1979, NMV J9557 (1 Ƥ). Eastern Bass Strait, 94 km N of North Point, Flinders Island, 38°53.7’S 147°55.2’E, 71 m, medium sand, epibenthic sled, R. Wilson, RV Tangaroa , stn BSS 171, 17 November 1981, NMV J9559 (1 ovigerous Ƥ, 1 young). Eastern Bass Strait, 70 km N of North Point, Flinders Island, 39°03.9’S 147°55.4’E, 62 m, shelly sand, epibenthic sled, R. Wilson, RV Tangaroa, cruise 81-T-1, stn BSS 172, 17 November 1981, NMV J9560 (1 large 3 with abode). Same data as previous sample, NMV J9561 (1 small specimen). Central Bass Strait, 26 km SE of Aireys Inlet, 38°39.8’S 144°18.2’E, 79 m, very fine sand, R. Wilson, RV Tangaroa, cruise 81-T-1, stn BSS 181, 19 November 1981, NMV J9563 (1 Ƥ). Eastern Bass Strait, 40 km SSW of Lakes Entrance, 38°18.0’S 147°37.0’E, 55 m, muddy fine shell, epibenthic sled, M. Gomon and R. Wilson, RV Silver Gull, stn BSS 209, 31 July 1983, NMV J9564 (1 specimen).

Australia, Queensland, Moreton Bay: Middle Banks, 27°11’S 153°21’E, I. Poiner, July/ August 1982, QM W11558 (1 adult Ƥ, 4 mm).

Description (holotype, 3). Head about as long as pereonites 1 and 2 combined, with large overhanging brows; midanterior depression deep, encompassing approximately 1/3 head length; head in lateral view vaulted proximal to anterior depression. Rostrum moderately upturned, acutely pointed, in dorsal view reaching beyond apices of eye lobes with nearly its entire length. Eye lobes in lateral view upper margin sinuous, apex narrowly rounded, lower anterior margin with 1 long and several short simple setae. Pereon with scattered small simple setae.

Antenna 1 approximately as long as head and pereonites 1–4 and 1/3 of 5 combined, barely reaching to apex of antenna 2 peduncle article 4; flagellum of 5+ articles, approximately as long as peduncle articles 2 and 3 combined. Antenna 2 approximately as long as head, pereonites 1–7 and pleonites 1 and 2 combined; ventral projection of peduncle article 2 elongate [not fully observed], apex rounded, with fringe of long simple setae apically and laterally; articles 3–5 with groups of short setae; article 5 length 0.8 of 4; flagellum articles 1 and 2 with short robust setae.

Gnathopod 1 propodus length 3.0 width, with 3 midposterior slender robust setae. Gnathopod 2 propodus length 1.8 greatest width. Pereopods 3–4 basis with continuous row of long setae along anterior margin, posterior margins with a few long setae; merus with 4 tufts of long setae on posterior margin, distal lateral surface with a few long setae. Pereopods 5–6 basis anterior margin with row of long setae in distal half, posterior margins with a few unequally long setae. Pereopod 7 propodus mid posterior margin with 2 groups of short setae and tuft of long setae distally.

Uropod 1 peduncle with dorsolateral row of 4 small robust, distomedial corner with single short simple seta; outer ramus slender, slightly inward curved, approximately 0.6 length of peduncle, with lateral row of 7 robust setae, medial margin with row of simple setae; inner ramus 0.7 length of outer ramus, slightly inward curved, distolateral margin with a few simple setae. Uropod 2 peduncle approximately 0.4 length peduncle of uropod 1, ramus approximately half length of peduncle, not reaching beyond ramus uropod 3. Uropod 3 peduncle with rounded median projection carrying tuft of simple setae apically; ramus with row of 3 setae increasing in length towards the middle. Telson width approximately 1.35 length, distal margin broadly rounded.

Female. Left gnathopod 2 propodus of a single female has 3 robust setae ( Fig. 9 F). Pereonite 7 of ovigerous and spent females have elongate, forward curved sternal papillae ventrally.

Size. Largest 3, 8.0 mm; largest Ƥ, 7.6 mm.

Variation. In some specimens the rostrum is slightly more up-curved than in the holotype, but not as extreme as in the preceding species.

Colour and biology. Head translucent with rust-red reticulation, front margin cream; pereonites 1–2 redbrown, pereonites 3–6 white mottled; pereonite 7, pleon and urosome increasingly translucent. Frons brown with white mottling; mouthparts brown. Antenna 1 peduncle with longitudinal cream-yellow lines and irregular redbrown blotches; flagellum massively cream-yellow. Antenna 2 peduncle articles 3–5 with similar cream-yellow longitudinal lines bordered by red-brown; flagellum colourless.

At the type locality the species was found on silty sand with fine shell fragments. Individuals occupied a variety of micro molluscs and occasionally other suitable abodes, including a single specimen in a ‘borrowed’ Cerapus tube, to which is attached a front tube covered with shell fragments and occasional large sand grains. Recently released juveniles were observed having built their own tiny sediment tubes on the parent’s abode ( Fig. 8 F).

Remarks. The single specimen from Moreton Bay, Queensland, a female with fully developed oostegites, is referred to Rhinoecetes dinoceros sp. nov. on account of the identical head shape and rostrum ( Fig. 10 MB clv). The specimen is, however, about half the size of adult females from the Sydney area south to Bass Strait, Victoria, and the uropods are more like young immature specimens from southern localities. As with the preceding species, new material from Moreton Bay and the long stretch between there and Sydney is needed.

Rhinoecetes dinoceros sp. nov. is similar to R. rhinoceros sp. nov. (above) on account of the upturned rostrum, the deeply depressed anterodorsal surface of the head with large brows, and the slender, somewhat inward turned rami on uropod 1. It differs from the latter in the actual shape of the rostrum, the mid dorsally vaulted head in lateral view, the considerably more pronounced brows, a shorter uropod 2, and generally less densely setose pereopods.

Distribution. Eastern Australia, Moreton Bay, Queensland to Bass Strait, Victoria. 8– 80 m.

Figures

FIGURE 8. Rhinoecetes dinoceros sp. nov. Holotype, 3, except F, paratype Ƥ in abode (from Just, 1988, fig. 6 B). a flag, antenna 2 flagellum; c, head (dv, dorsal view, lv, lateral view); j, juveniles in microabodes; vp, ventral projection of antenna 2 article 2. Habitus scales for 3 and abode: 1 mm.

FIGURE 9. Rhinoecetes dinoceros sp. nov. Holotype, 3, except F, ovigerous Ƥ. gp 1, gp 2, gnathopods 1 and 2; gp 2, r, variant right gnathopod 2; p 4 and 6, pereopods 4 and 6; us, urosome with uropods.

FIGURE 10. Rhinoecetes dinoceros sp. nov. F, Ƥ with fully developed oostegites; MB, Ƥ of 4.0 mm, with fully developed oostegites, Moreton Bay (QM W 11558). c lv, head, lateral view; sp, sternal papillae; us, urosome with uropods.