Leucothoe longimembris, Krapp-Schickel & Broyer, 2014

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 : 17-21

Leucothoe longimembris sp. nov.

urn:lsid:zoobank.org:act:935721E6-F9D5-4E0A-9AAD-5DEE628627EB

Figs 5 , 8-10

Diagnosis

A 1> A 2, eyes absent, Cx 1-5 all ending ventrally at about the same level. Basis P 5-7 slim, broadest not medially but proximally; both margins of bases weakly serrated. Ep 2, 3 posterodistal corner lengthened and pointed. U 1 rami subequal, U 2 rami unequal, ratio 2:1, U 3 rami subequal, about 2/3 of peduncle.

Etymology

Many articles (in Latin membrum, abl. plural membris) like antennae, Gn 1, but especially the bases of the peraeopods 5-7 are unusually elongated (= longis) and this character is different from all other species hitherto known from the Antarctic or sub-Antarctic regions. The chosen specific name is used as non-flexible apposition.

Type material

Holotype ♀ ov. 15 mm ( RBINS, I.G. 32565 / INV. 103462), Polarstern ANT XXII-3 ( ANDEEP 3 ); sta. PS67/74-6 EBS; 20 Feb. 2005; eastern Weddell Sea; 71°18.35’S, 13°57.71’W; 1030 m; epibenthic sledge; coll. C. De Broyer & B. Danis.

Description

Length 15 mm.

Head

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

Eyes absent.

Antenna 1 nearly half of body length, flagellum with 21 articles, 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 1/4 of art. 2, acc. flagellum not seen. Peduncle art. 3 + flagellum shorter than peduncle arts 1+2.

Antenna 2 shorter than antenna 1, peduncle art. 4> art. 5, flagellum 7 arts.

Mouthparts: Mandibles lacking molars, incisor and lacinia mobilis dentate; palp 3-articulate, art. 2 with many lateral setae of different length, art. 3 with 2 distal setae, more than half length of art. 2. Maxilliped IP small, 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.

Gn 1 basis slender, not inflated, both margins with short setae; ischium smooth; carpus basis about half as long as propodus, distal part linear and extremely narrow, about 10 x longer than wide; propodus straight, about 6 x as long as wide, palm with short setae; dactylus smooth, reaching about 1/3 propodus length.

Cx 2 subquadrangular, about as long as wide, twice as wide as Cx 3, distally smooth; anterior margin and anterodistal corner regularly rounded, inferior margin straight, posteriorly somewhat excavated, facial setae absent.

Gn 2 basis not inflated, on both margins short setae; carpus reaching about 1/3 propodus length, curved, distally serrated, setose; propodus anterodistally with short, acute prolongation, posterior margin with many low humps, palm convex, proximally near dactylus-end no corner; facial setae not seen; dactylus curved, both margins smooth, bare, reaching about 2/3 of propodus length.

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

Cx 4 length shorter than width, smooth, bare, anterior margin nearly straight, distal margin rounded, posterior margin shorter than anterior one, not excavate, facial setae absent.

P 3, 4 basis very narrow, wider than delicate merus; dactylus reaching nearly half length of propodus, all margins naked.

Cx 5-7 facial setae absent.

P 5-7 similar, bases length:width ratio about 2.5 (P 5), 2.3 (P 6) and 2.6 (P 7), both margins with very slight serrations. Merus in P 5-7 with posterodistal corner lengthened.

Pleon

Ep 1-3 bare. Ep 1 distally rounded, Ep 2, 3 posteroventral corner acutely upturned.

Uropods: U 2 the shortest, with very unequal rami (ratio about 1:2), the shorter one shorter than peduncle. U 1 and U 3 with subequal rami.

Telson ratio l:w = 3, tip five-dentate because of four indentations near distal end.

Remarks

The new blind species is similar to the (also blind) deep-sea species L. ayrtonia Bellan-Santini, 1997 (5 mm) and L. atosi Bellan-Santini, 2007 (12 mm), found in the Mid-Atlantic Ridge at 37°N, 31°W at a depth of 850 m, and at the Barbados Trench, 10°N, 58°W at a depth of 1947 m respectively. Differences from L. ayrtonia are in the large rostrum, Cx 4 with posterodistal acute corner, Ep 3 quadrate with small tooth, from L. atosi are in much shorter antennae, blunt posterodistal corner at Ep 2, less unequal U 2 and broader telson. Also L. ushakovi Gurjanova, 1951 (type from Greenland at a depth of 3892 m, specimens from 8-34 mm length; see Krapp-Schickel & Vader 2012) has P 5-7 bases not medially, but proximally widest and is blind; differences with L. longimembris are are the setose bases of Gn 1, 2 and very unequal rami in U 2 in the here described material (vs. naked bases and less unequal rami in L. ushakovi ), a longer Gn 1 dactylus and a five-dentate slender telson here (vs. short dactylus and threedentate broader telson in L. ushakovi ).

Figures

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.

Fig. 8. Leucothoe longimembris sp. nov., holotype ♀ 15 mm. A 1, 2 = antenna 1, 2; UL = upper lip; Mx 1, 2 = maxilla 1, 2; Md, Md’ = mandible from both sides; Mxp = maxilliped.

Fig. 9. Leucothoe longimembris sp. nov., holotype ♀ 15 mm. Cx 1-4 = coxa 1-4; Gn 1, 2 = gnathopod 1, 2; P 3, 4 = peraeopod 3, 4.

Fig. 10. Leucothoe longimembris sp. nov., holotype ♀ 15 mm. Cx 5-7 = coxa 5-7; P 5-7 = peraeopod 5-7; Ep 1-3 = epimeral plate 1-3; U 1, U 3 = uropod 1, 3; T = telson; T’ = telson distally enlarged.