Opaepele vavilovi, Lunina, Anastasia A. & Vereshchaka, Alexander L., 2010

Lunina, Anastasia A. & Vereshchaka, Alexander L., 2010, A new vent shrimp (Crustacea: Decapoda: Alvinocarididae) from the Mid-Atlantic Ridge *, Zootaxa 2372, pp. 69-74 : 70-73

Opaepele vavilovi sp. nov.

( Figs. 1 A–D, 2A–H)

Material examined. Holotype female, cl 8.1 mm, Mid-Atlantic Ridge, Broken Spur vent site, Station 4797, 25.VIII.2005 (Zoological Museum, Moscow State University, Ma 3338). Paratypes: 4 females: cl 10.9, 7.7, 6.0, 4.5 mm; 1 male: cl 6.2 mm, all from Mid-Atlantic Ridge, Broken Spur vent site, Station 4797, 25.VIII. 2005 (Zoological Museum, Moscow State University, Ma 3339). The following paratypes will be deposited in the Oxford Zoological Museum: cl 7.7 mm and 10.9 mm.

Description. Carapace setose in anterior two-thirds of ventral margin; rostrum subtriangular in crosssection, subacute, dorsally convex, ventrally slightly concave, bearing six inconspicuous notches ( Fig. 1 A), reaching as far as mid-length of first segment of antennular peduncle; blunt dorsal carina conspicuous along anterior rostral margin; antennal tooth reaching 0.67 of rostrum length and overreaching cornea, with mediodorsally directed tip ( Figs. 1 B–C).

Pleura of first to third abdominal somites broadly rounded; fourth somite with posterolateral angle produced ( Fig. 1 D); fifth somite with posterolateral tooth. Sixth somite 1.5 as long as high.

Telson ( Fig. 1 E) elongate, almost orthogonal, 2.6 times as long as wide in its widest proximal margin, distal margin slightly narrower; dorsal margin armed with six pairs of spines of nearly equal size, three anteriormost pairs more medially placed; posterior margin slightly concave, armed with six pairs of spines.

Antennal scale nearly twice as long as wide, distolateral spine somewhat blunt, reaching 0.25 length of blade; anterior margin of scaphocerite broadly rounded. Antennal peduncle reaching to 2/3 length of scaphocerite, basal segment with ventral distal and median teeth.

Mandible with broad incisor, bearing 2 short and 3 long terminal teeth; palp with distal segment bearing plumose setae distally, longest positioned at middle of segment and exceeding it by 1.1 times its length. First maxilla distal endite covered with long, plumose setae along 0.2 of proximal margin and 0.75 of distolateral margin; palp bearing very long plumose mediodistal setae, reaching tip of endite. Second maxilla with narrow palp reaching end of distal endite; scaphognathite with rounded anterior lobe, as wide as long, and narrow triangular posterior lobe covered with shorter setae in its proximal part and very long terminal setae equal in length to entire scaphognathite. Endopod of first maxilliped shorter than palp, bearing two rows of setae on its dorsal and ventral sides; palp abruptly narrowing at about distal јoint; epipod with distinct proximal heel, about three times as long as wide in its proximal side. Second maxilliped ( Fig. 2 A) covered with plumose setae; distal segment separated from penultimate by oblique suture and bearing dense group of strong setae along 0.80 of its distomedial side. Third maxilliped ( Fig. 2 B) slightly longer than antennal scale, ischiomerus bearing long stout spine at articulation with carpus, propodus with a row of strong setae along 0.80 of distoventral side, dorsal margin covered with dispersed, slender setae.

First pereopod ( Fig. 2 C) with ischium and merus separated by oblique junction and covered with scattered setae along ventral side; carpus curved at 0.3 of its proximal side; movable finger directed inward; propodus flattened, bearing setae along cutting edge; width of fixed finger in lateral view 3.4 times that of dactylus; ischium 0.4 times, merus 1.4 times, propodus and dactylus 1.4 times as long as carpus, respectively. Second pereopod ( Fig. 2 D) covered with long setae; ischium and merus separated by oblique junction; chela with fingers subequal in size and armed with rows of spines directed distally; ischium 0.8 times, merus 1.6 times, propodus 1.1 times, and dactylus 0.7 times as long as carpus, respectively. Third pereopod ( Figs. 1 E–F) with ischium and merus separated by a distinct transverse junction and covered with a few, short setae on medial margins; carpus 1.5 times as short as merus, with a distolateral process; propodus with 17 proximal spines; dactylus 1/14 length of propodus, with one apical and four subterminal ungui. Fourth pereopod ( Fig. 2 G) similar in size and form to third pereopod; carpus 1.8 times as short as merus, with a distolateral process; propodus with several, proximal spines; dactylus with one apical and 3 subterminal ungui. Fifth pereopods unknown, broken off in all specimens, probably similar to third and fourth pereopods.

Second to fourth pleopods, each with appendix interna, reaching to about 0.25 of endopod length and hidden amongst stouter, much longer setae in both sexes. Appendix masculina almost as long as appendix interna, bearing eight strong apical setae.

Uropodal exopod somewhat longer than endopod, with distinct diaeresis, movable spine five times as long as fixed distolateral tooth.

Etymology. The new species is named after the Russian oceanographic research vessel “Akademik Sergej Vavilov”.

Colour. Pinkish (based on freshly dead specimens brought to the surface).

Variations. In the paratypes, the rostrum bears from five to eight small dorsal notches; whilst the posterior margin of the telson harbours 10–12 spines.

Remarks. Opaepele vavilovi sp. nov. differs from the other two species in the genus by having (1) a rostrum armed with small dorsal notches (vs. small teeth in O. loihi and smooth in O. susannae ), (2) a concave or straight posterior margin of telson (vs. convex in O. loihi and O. susannae ), and (3) the ischia and merii of the second through to fourth pereiopods armed with several spines (vs. unarmed in O. loihi and O. susannae ). Further, minor differences between the three species of Opaepele are detailed in Table 1.

TABLE 1. Morphological differences between the species of the genus Opaepele .

Characters Opaepele loihi Opaepele susannae Opaepele vavilovi sp. nov.

Figures

FIGURE 1. Opaepele vavilovi nov. sp. Holotype female (cl 8.1 mm): A, rostrum, lateral view; B, carapace and cephalic appendages, lateral view; C, anterior part of carapace and cephalic appendages, dorsal view; D, abdominal somites, lateral view; E, telson. Scale bars = 1 mm.

FIGURE 2. Opaepele vavilovi nov. sp. Holotype female (cl 8.1 mm): A, second maxilliped; B, third maxilliped; C, first pereopod; D, second pereopod; E, third pereopod; F, third pereopod, dactylus and distal part of propodus; G, fourth pereopod; H, appendix masculina and appendix interna. Scale bars = 1 mm.