Leucothoe orkneyi Holman & Watling, 1983

Krapp-Schickel, Traudl & Broyer, Claude De, 2014, Revision of Leucothoe (Amphipoda, Crustacea) from the Southern Ocean: a cosmopolitanism concept is vanishing, European Journal of Taxonomy 80, pp. 1-55 : 31-38

Leucothoe orkneyi Holman & Watling, 1983

Figs 15-18

Leucothoe orkneyi Holman & Watling, 1983: 231-233 , figs 12-14.

Diagnosis

Eyes medium, round. Mandibular palp long and narrow, art. 3 1/2-1/3 length of art. 2 (in original description verbally reported 1/3, but illustration shows 1/2). Cx 1 l:w subequal. Cx 3 subtrapezoidal, inferior margin serrate. Gn 1 carpus distal part about 8-9 x longer than wide, propodus ratio l:w = 6, dactylus reaching about 1/5 of propodus length. P 5-7 basis oval and not much broadened, with regularly rounded hind margin, ratio l:w 1.8 to 1.5; posterior margin strongly serrate (not mentioned in original description). Ep 2 posterodistally with upturned acute tip, Ep 3 with posterodistally rounded. T l:w = <3.

Type locality

Scotia Sea, east of South Orkney Islands; Eltanin 12, sta. 1079; 61°26’S, 40°55’W; 593- 598 m.

Material examined

Australian Museum, Sydney

P. 25494: Ross Ice-Shelf, McMurdo Sound, White Island, tide crack; 25 Jan. 1977; [approx. 78°08’S, 167°24’E]; 67 m depth; on rocky bottom encrusted with bryozoans and hydroids: 1 spec. 4 mm.

Belgian-Dutch Antarctic Expeditions

( RBINS, Brussels, EABN 1966-67, coll. M. Steyaert & M. Meisch, RBINS I.G. 23694)

EABN 1966-67: sta. 232; 25 Jan. 1967; Breid Bay, Baie Léopold III; 70°17’00”S, 24°15’E; 300 m, bottom trawl: 1 spec. 6 mm.

British Antarctic Survey, Cambridge

James Clark Ross 179: sta. BIO4 – EBS-3D-E; Amundsen Sea; 74.390880°S, 104.767260°W; 506 m; Epibenthic Sled-Epinet: 1 spec. 4.5 mm, slide.

NIWA, Wellington

NIWA 20875: Tangaroa sta. TAN0402/231; 4 Mar. 2004; off Balleny Islands; 67.4205017°S, 163.9391632°E to 67.4205017°S, 163.9391632°E; 111 m: 4 spec. 3.5-5 mm.

Polarstern cruises

( RBINS, Brussels, ANT XIII /3 ( EASIZ I), coll. C. De Broyer & G. Chapelle, RBINS I.G. 28252; ANT XV/3 ( EASIZ II), coll. C. De Broyer & Y. Scailteur, RBINS I.G. 28252; ANT XXII /3 ( ANDEEP III), coll. C. De Broyer & B. Danis, RBINS I.G. 32565.)

ANT XIII /3 ( EASIZ I): sta. PS39/005; 6 Feb. 1996; eastern Weddell Sea; SW of Kapp Norvegia; 71°40.40’S, 12°44.30’W; 229 m; dredge; Rauschert coll.: 3 spec. 4-6 mm.

ANT XIII /3 ( EASIZ I): sta. PS39/006; 7 Feb. 1996; eastern Weddell Sea; 71°30.80’S, 13°31.44’W; 300 m; dredge; Rauschert coll.: 2 spec. 3-5 mm.

ANT XIII /3 ( EASIZ I): sta. PS39/007; 8 Feb. 1996; eastern Weddell Sea; 71°28.60’S, 13°45.10’W; 279 m; dredge; Rauschert coll.: 1 spec. 4 mm.

ANT XIII /3 ( EASIZ I): sta. PS39/016; 15 Feb. 1996; eastern Weddell Sea; 73°51’S, 22°24’W to 73°51’S, 22°25’W; 246-252 m; dredge; Rauschert coll.: 1 spec. 4 mm.

ANT XIII /3 ( EASIZ I): sta. PS39/017; 16 Feb. 1996; eastern Weddell Sea; 73°19’S, 21°16’W, 447 m; dredge; Rauschert coll.: 4 spec. 2-5.2 mm.

ANT XIII /3 ( EASIZ I): sta. PS39/024 MG 26; 21 Feb. 1996; eastern Weddell Sea; 71°8.10’S, 11°31.90’W, 118 m; Multibox Corer: 1 spec. 5 mm.

ANT XIII /3 ( EASIZ I): sta. PS39/002 MG 27; 22 Feb. 1996; eastern Weddell Sea; 71°19’04”S, 12°24’48”W; 182 m; Multibox Corer: 3 spec. 3 mm.

ANT XIII /3 ( EASIZ I): sta. PS39/002 MG 28; 22 Feb. 1996; eastern Weddell Sea; 71°19’06”S, 12°22’48”W; 159 m; Multibox Corer: 2 spec. 4, 5 mm.

ANT XIII /3 ( EASIZ I): sta. PS39/002 MG 29; 22 Feb. 1996; eastern Weddell Sea; 71°18’36”S, 12°25’24”W; 181 m; Multibox Corer: 2 spec. 2,5 mm and 3,5 mm.

ANT XIII /3 ( EASIZ I): sta. PS39/002 MG 30; 22 Feb. 1996; eastern Weddell Sea; 71°19’12”S, 12°27’W; 253 m; Multibox Corer: 1 spec. sex? 5 mm (with red eyes).

ANT XIII /3 ( EASIZ I): sta. PS39/025 MG 31; 23 Feb. 1996; eastern Weddell Sea; 71°23’06”S, 14°19’48”W; 628 m; Multibox Corer: 1 spec. 5 mm.

ANT XIII /3 ( EASIZ I): sta. PS39/026; 24 Feb. 1996; eastern Weddell Sea; 71°29’S, 14°19’W to 71°29’S, 14°19’W; 210-214 m; dredge 21; Rauschert coll.: 6 spec. 3-6.5 mm.

ANT XIII /3 ( EASIZ I): sta. PS39/032; 04 Mar. 1996; eastern Weddell Sea; 70°28’S, 8°15’W to 70°28’S 8°15’W; 283-286 m: 9 spec. 4-6 mm.

ANT XV/3 ( EASIZ II): sta. PS48/039; 29 Jan. 1998; eastern Weddell Sea; 70°52.8’S, 10°31.4’W; 237 m; Agassiz Trawl: ♂ 6 mm.

ANT XXII /3 ( ANDEEP III): sta. PS67/133-2-EBS; 16 Mar. 2005; western Weddell Sea, Powell Basin; 62°46.49’S, 53°3.50’W; 1584 m; EBS-Epinet: 2 juv. 4 mm; 20 spec. 4-5 mm; EBS-Supranet: 1 spec. 5 mm.

Polish Antarctic Expeditions ( LPBO-UL, Łódź)

3rd Polish Biol. Ant. Exp. 1974: sta. PABE III- 46; 4 Nov. 1974; Enderby Land, Alasheyev Bight, Opasnaya Bay; 67°30’S, 45°40’E; 40 m: 1 spec. 6.5 mm.

9th Polish Ant. Exp.1985: sta. OC 419; 18 Jan. 1985; King George Island, Admiralty Bay, section 1; 62°09,0194’S, 58°26,510’W; 380 m; Van Veen Grab: 1 ad. 5 mm.

9th Polish Ant. Exp. 1985: sta. OC 481; 23 Jul. 1985; King George Island, Admiralty Bay, Section I, 62°09.154’S, 58°26.929’W, 205 m, Van Veen Grab: 1 ad. 5 mm.

9th Polish Ant. Exp. 1985: sta. OC 486; 10 Aug. 1985; King George Island, Admiralty Bay, section I; 62°09,067’S, 58°26,797’W; 270 m; Van Veen Grab: 1 spec.

9th Polish Ant. Exp. 1985: sta. OC 517; 30 Oct. 1985; King George Island, Admiralty Bay, Section I; 62°09.149’S, 58°26.927’W; 212 m, Van Veen Grab: 1 spec. 4 mm.

9th Polish Ant. Exp 1985: sta. OC 520; 3 Nov. 1985; King George Island, Admiralty Bay, section I; 62°09’S, 58°25’W; 335 m; Van Veen Grab: 2 spec.

Victoria Museum, Melbourne

J 38265 : Aurora Australis sta. AA93 127; MacRobertson Shelf, edge of Nielsen Basin; 67°16’07”S- 67°16’28”S, 65°25’14”E- 65°25’45”E; depth? [85 m?]: 1 spec. 3mm.

J 38266 : Aurora Australis sta. AA93 131; off Mac Robertson Land, northern end of Fram Bank; 67°05’02”S- 67°05’14”S, 68°58’48”E- 68°58’31”E; depth? ¨[208 m?]: 1 spec. 3mm.

J 38268 : Aurora Australis sta. AA93 158; Eastern Prydz Bay, off the Larsemann Hills; 68°54’53”S- 68°54’49”S, 76°37’02”E- 76°37’43”E; depth? [660 m?]: 4 spec. 3-4mm.

Redescription

Length

4-9 mm.

Head

Anterior margin rounded, anterodistal margin rectangular with rounded corner. Mid-cephalic keel with acute projection, extending past epistome. Rostrum small.

Eyes small, round, red colour remaining some time in alcohol ( Holman & Watling 1983: 231).

Antenna 1 one third of body length, flagellum 7-articulate, peduncle art. 1 width proximally less than twice article 2, disto-inferiorly with acute tooth, length art. 1 subequal to art. 2, art. 3 about 1/3 of art. 2, acc. flagellum not seen. Peduncle art. 3 + flagellum subequal to peduncle art. 2.

Antenna 2 subequal in length with antenna 1, peduncle art. 4> art. 5, flagellum 6 arts.

Mouthparts: Mandibles lacking molars, incisor and lacinia mobilis dentate; palp 3-articulate, art. 2 with 6 long lateral and 4-5 distal setae, art. 3 with 2 distal setae, 1/3 length of art. 2. Maxilliped IP small, ventrally fused, OP reaching about 1/5 of inner margin of palp art. 1; palp articles similar in length, all clearly longer than wide.

Peraeon

Cx 1 smooth, length and width subequal; anterior margin smooth, facial setae absent.

Gn 1 basis somewhat widened, lacking setae; ischium smooth; carpus basis about half as long as propodus, distal part linear and extremely narrow (width not much differing, about 9 long); propodus straight, 7-8 x as long as wide, palm minutely dentate with 12 short and up to 8 longer setae; dactylus smooth, reaching about 1/5 propodus length.

Cx 2 subquadrangular, about as long as wide, much wider than Cx 3, distally smooth; anterior margin straight, anterodistal corner rectangular, inferior and posterior margin straight, facial setae absent.

Gn 2 basis not inflated, on both margins up to 14 short setae and on anterior margin one longer one; carpus reaching about 1/3 propodus length, curved, distally truncate, with small serration, densely setose; propodus anterodistally with short acute prolongation and bundle of setae, posterior margin with many low humps, palm convex, proximally near dactylus-end widening with a characteristic blunt corner; one row of facial setae below the middle line; dactylus curved, both margins smooth, bare, reaching more than half of propodus length.

Cx 3 length> width, anterior and posterior margin straight, distally rounded and irregularly serrate, facial setae absent.

Cx 4 wider than long, smooth, bare, anterior margin scarcely convex, distal margin rounded, posterior margin shorter than anterior one, not excavate, facial setae absent.

P 3, 4 basis slender, a bit wider than merus; merus anterodistally lengthened; dactylus reaching more than half length of propodus.

Cx 5-7 facial setae absent.

P 5-7 similar, bases l:w ratio about 1.9 to 1.5, anterior margins with slight serrations and small weak spines, posterior margins strongly serrate (not mentioned in original description).

Pleon

Ep 1-2 with spines on distal margin, Ep 3 distally bare, but some short setae on posterior margin. Ep 1 posteroventral corner rounded, Ep 2 posteroventral corner acutely produced, Ep 3 posteroventral corner blunt and rectangular.

Uropods: U 2 the shortest, with unequal rami (ratio 1.5), the shorter one shorter than peduncle.

Telson ratio l:w> 3, tip tridentate because of two indentations near distal end, with a short seta inserted in each one.

Distribution

Circum-Antarctic (61°- 73°S, 8°- 58°W and 24°- 167°E; type material 60°35’S, 45°30’W).

Depth range

11-1584 m.

Remarks

The material examined here matches the description and figures of Holman & Watling quite well, but our specimens are always considerably smaller, found at shallower depth and their peraeopod bases are posteriorly serrate. Moreover the original description tells about specimens of 4.5-6.5 mm from 61°27’S, 41°55’W, while others from a similar area were between 6.5 and 9 mm, both localities from about 600 m depth. On p. 230-231 (loc. cit.) the authors wrote: “[...]of P 7, the basis of which appeared broadly rounded. Some slight variability in the degree of expansion of this article was seen [...], so its diagnostic value is questionable.”

Thus it could very well be that this material consists of a group of closely related and morphologically extremely similar species.

Holman & Watling (loc. cit.) compare their new species to L. tridens Stebbing, 1888 , L. miersi Stebbing, 1888 , L. trailli Thomas, 1882 , L. commensalis Haswell, 1880 , L. diemensis Haswell, 1880 , L. assimilis J.L. Barnard, 1974 and L. hyhelia J.L. Barnard, 1970 , which all differ from this new species in the shape of the first gnathopod. L. panpulco J.L. Barnard, 1961 and L. uschakovi Gurjanova, 1951 (up to 34 mm maximal length, 3000 m, see redescription in Krapp-Schickel & Vader 2012) have different bases on P 5-7, L. ctenochir K.H. Barnard, 1916 has a very characteristic palm on Gn 2.

Figures

Fig. 15. Leucothoe orkneyi Holman & Watling, 1983: Hd = head; A 1, 2 = antenna 1, 2; Gn 1 = first gnathopod; Gn 1’ = dactylus and propodus of first gnathopod enlarged.

Fig. 16. Leucothoe orkneyi Holman & Watling, 1983: Gn 2, Gn 2’ = second gnathopod from both sides; P 3, 4 = peraeopod 3, 4.

Fig. 17. Leucothoe orkneyi Holman & Watling, 1983: P 5-7 = peraeopod 5-7; Ep 1-3 = epimeral plates 1-3; U 1-3; uropod 1-3; T = telson.

Fig. 18. Distribution of Leucothoe orkneyi. Hydrographic fronts as in Fig. 5. TL = type locality.