Leucothoe antarctica Pfeffer, 1888

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 : 4-11

Leucothoe antarctica Pfeffer, 1888

Figs 1-5

Leucothoe antarctica Pfeffer, 1888: 54-57 , Taf. II: fig. 4.

sub Leucothoe spinicarpa variant 3 – Holman & Watling 1983: 228-229.

Diagnosis

Eyes large, round. Mandibular palp long and narrow, art. 3 about 1/3 length of art. 2. Cx 3 tongue-shaped rounded, smooth. Gn 1 propodus l:w = 4-5, dactylus reaching about 1/3-1/4 of propodus length. P 5-7 basis oval broadened, with regularly rounded hind margin, ratio l:w = 1.5 to 1.2; posterior margin at least in P 7 strongly serrate (not mentioned in Pfeffer’s description). Ep 2 posterodistally with rounded upturned corner.

Type material

Neotype ♀ ov. 5 mm, 2 slides ( RBINS, I.G. 31073 / INV. 103461). Polarstern ANT XIX/3 ( ANDEEP I), sta. PS61/067-1; 4 Feb. 2002; off Elephant Island, 60°55’53”S, 55°27’38”W to 60°55’09”S, 55°24’50”W; 115-182 m; bottom trawl.

Type locality

South Georgia, Royal Bay, near the Deutsche Polarstation 1882-1883 at Moltke Harbor, approx. 54°30’58”S, 36°00’45”W.

Additional material

Belgian-Dutch Antarctic Expeditions

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

EABN 1966-67, sta. 238, 3 Feb. 1967, Breid Bay, Baie Léopold, 70°19’S, 24°14’E; 200 m; bottom trawl: 1 juv.

Polarstern cruises

( RBINS, Brussels, ANT XIII /3 ( EASIZ I), coll. C. De Broyer & G. Chapelle, RBINS I.G. 28252; ANT XIX /3 ( ANDEEP I), coll. C. De Broyer, P. Dauby & F. Nyssen, RBINS I.G. 31073)

ANT XIII /3 ( EASIZ I), sta. PS39/24 MG 26; 21 Feb. 1996; eastern Weddell Sea; 71°08’06”S, 11°31’54”W; 118 m; Multibox Corer: 1 spec. 3.5 mm.

ANT XIX /3 ( ANDEEP I), sta. PS 61/047-1; 30 Jan. 2002; off Elephant Island; 61°4.18’S, 54°36.81’W, 189 m, bottom trawl: 1 spec. 4 mm.

ANT XIX /3 ( ANDEEP I), sta. PS61/067-1; 4 Feb. 2002; off Elephant Island; 60°55’53”S, 55°27’38”W to 60°55’09”S, 55°24’50”W; 115-182 m; bottom trawl: 1 spec. ♀ ov. 5 mm slide.

Polish Antarctic Expeditions ( LPBO-UL, Łódź)

9 th Polish Ant. Exp, sta. OC 412; 11 Jan. 1985; King George Island, Admiralty Bay, Ezcurra Inlet; 62°10’S, 58°32’W; 90 m; Van Veen Grab: 1 spec.

9 th Polish Ant. Exp, sta. OC 520; 3 Nov. 1985; King George Island, Admiralty Bay, section I; 62°09’S, 58°25’W; 335 m; Van Veen Grab: 1 juv.

Victoria Museum, Melbourne

? J 38267 [ Aurora Australis AA93 142], off Mac Robertson Land, north of Fram Bank; 66°48’ 46”S- 66°48’52”S, 70°24’59”E- 70°25’32”E; depth:?: 1 spec. 3 mm.

Redescription

Length

4-9 mm [Pfeffer: “ 5 mm ”].

Head

Anterior margin rounded, anterodistal margin rectangular with rounded corner. Mid-cephalic keel not prominent. Rostrum small.

Eyes large, round.

Antenna 1 a quarter of body length, flagellum 10-12-articulate, peduncle art. 1 width proximally less than twice article 2, disto-inferiorly without acute tooth, length art. 1 subequal art. 2, art. 3 about 1/4 of art. 2, acc. flagellum not seen.

Peduncle art. 3 + flagellum shorter than peduncle arts 1+2.

Antenna 2 subequal in length to antenna 1, peduncle art. 4> art. 5, flagellum 7-10 arts.

Mouthparts: Mandibles lacking molars, incisor and lacinia mobilis dentate; palp 3-articulate, art. 2 with 12 long lateral setae, art. 3 with 2 distal setae, 0.35 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.

Peraeon

Cx 1 smooth, length> width; anterior margin smooth, facial setae absent, inferior margin smooth [Pfeffer: “anterodistally rounded corner of about 70°”].

Gn 1 basis scarcely inflated, posterior margin with groups of short setae; ischium smooth; carpus basis more than half as long as propodus, distal part linear and extremely narrow, about 8 x longer than wide; propodus straight, about 4-5 x as long as wide [Pfeffer: “about 4 times”], palm minutely dentate with 8 short setae; dactylus smooth, reaching about 1/3-1/4 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 6 short or long setae; carpus nearly reaching half propodus length, curved, distally like a finger-tip rounded, densely setose; propodus anterodistally with short, blunt prolongation and a bundle of setae, posterior margin with many low humps, palm convex, proximally near dactylus-end no corner; facial setae medially and submedially present; dactylus curved, both margins smooth, bare, reaching somewhat more than half of propodus length.

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

Cx 4 length subequal to width or longer than wide, smooth, bare, anterior margin straight, distal margin rounded, posterior margin shorter than anterior one, not excavate, facial setae absent.

P 3, 4 basis very narrow, a bit wider than merus; dactylus reaching nearly half length of propodus, posterior margins with some short thin spines.

Cx 5-7 facial setae absent.

P 5-7 similar, bases l:w ratio about 1.5 (P 5) to 1.2 (P 7), anterior margins with very slight serrations and small weak spines, posterior margins in P 5, 6 smooth or serrated, in P 7 strongly serrate [not mentioned in Pfeffer]. Merus in P 5-7 with posterodistal corner lengthened.

Pleon

Ep 2 with spines on distal margin, Ep 1, 3 distally bare, but some small setae on posterodistal corner of Ep 3. Ep 1 distally rounded, Ep 2 posteroventral corner not acutely upturned, but produced with rounded corner, Ep 3 posteroventral corner blunt and rectangular.

Uropods: U 2 the shortest, with very unequal rami (ratio nearly 1:2), the shorter one shorter than peduncle.

Telson ratio length:width = 3, tip tridentate because of two indentations near distal end, with a short seta inserted in each one.

No sexual dimorphism known.

Distribution

Circum-Antarctic, from 54° to 71°S, from 11° to 58°W and from 24 to 70°E (type material: 54°S, 36°W).

Depth range

24- 335 m.

Remarks

Pfeffer (1888) compared his new species only with the Atlantic species Leucothoe articulosa (Leach, 1814) , insufficiently described and actually kept it – with question marks – as a synonym of L. spinicarpa (Abildbaard, 1789) ; there is, however, no doubt that it belongs to the “ spinicarpa -group”.

The original description and illustration of the single type are not very helpful (see Fig. 1 ), but at least the semicircular posterior margin of P 7 and the scarcely upturned rounded posterodistal corner in Ep 2 are visible in the drawing.

Holman & Watling (1983: 228-229, fig. 11d-e) discussed a so-called “ Leucothoe spinicarpa variant 3”; on p. 229 they wrote: “Cx 3 with smoothly rounded ventral margin, Cx 4 not excavate posteriorly. Gn 1 dactyl 1/5 length and approximately equal to width of propodus, latter 6 times as long as wide (here 5x). P 7 basis broadly expanded, Ep 3 with quadrate posterodistal corner. Distribution: tip of Antarctic Peninsula, 210-220 m [about 63°S, 58°W].”

By the combination of the key character states – P 7 basis broadly rounded, Gn 1 dactylus reaching about 1/4 of propodus, Cx 3 distally smooth, Ep 2 posterodistal corner only a little produced and rounded – L. antarctica clearly differs from all other members of the spinicarpa-group.

Figures

Fig. 1. Leucothoe antarctica Pfeffer, 1888: original illustration in Pfeffer 1888, fig. 4.

Fig. 2. Leucothoe antarctica Pfeffer, 1888, neotype ♀ 5 mm. Hd = head; A 1, 2 = antennae; Mx 1 = first maxilla; Mx 1’ = palp of first maxilla enlarged; Mx 2 = second maxilla; Md = mandible-body; Md’ = palp of mandible.

Fig. 3. Leucothoe antarctica Pfeffer, 1888, neotype ♀ 5 mm. Gn 1 = first gnathopod; Gn 1’ = dactylus, propodus and carpus of first gnathopod enlarged; Gn 2 = second gnathopod female; Gn 2’ = second gnathopod male; Mxp = maxilliped.

Fig. 4. Leucothoe antarctica Pfeffer, 1888, neotype ♀ 5mm. P 3-7 = peraeopod 3-7; P 7’ = basis of peraeopod 7 enlarged; Ep 1-3 = epimeral plates 1-3; U 1-3 = uropod 1-3; U 1’, U 2’ = uropods 1, 2 enlarged; T = telson, T’ = telson reduced; T’’ = tip of telson enlarged.

Fig. 5. Distribution of Leucothoe antarctica Pfeffer, 1888, L. campbelli sp. nov., L. longimembris sp. nov., L. macquariae sp. nov. and L. merletta sp. nov. The hydrographic fronts shown on the map are from north to south: the Sub-Tropical Front, the Sub-Antarctic Front, the Antarctic Polar Front and the Southern Antarctic Circumpolar Current Front. Mean position of the fronts according to Sokolov & Rintoul (2009). TL = type locality.