Bythocypris malyutinae Brandão, 2008, sp. nov.

Bythocypris malyutinae sp. nov.

(Figs. 19.Q, 27, 28, 29.A–F, M, N, P–W, 30.A, B, G, H, M–R, 31, 32)

Etymology. In honour of Dr. Marina Malyutina (Institute of Marine Biology, FEB RAS, Russia), who is a specialist on deep­sea Isopoda, and also works on the ANDEEP material.

Material. 19 live specimens. Holotype: 1 A M (SNB 0255), ANDEEP III, # 102–13–U, ZMH K­ 41294. Paratypes: 1 A F (SNB 0263), ANDEEP II, # 134–4–E, ZMH K­ 41293; 1 A F (SNB 0245), 1 (A­2) (SNB 0304), ANDEEP II, # 134–4–S, ZMH K­ 41295; 1 (A­1) (SNB 0083), 2 (A­1) (SNB 0313­4), ANDEEP II, # 135–4–E, ZMH K­ 41296; 1 A, 2 (A­1) (SNB 0657), 1 (A­3), ANDEEP II, # 135–4–S, ZMH K­ 41297; 1 A F (SNB 0249), ANDEEP III, # 102–13–E, ZMH K­ 41307; 1 A F (SNB 0256), ANDEEP III, # 102–13–S, ZMH K­ 41308; 1 A F (SNB 0110), 1 (A­1) (SNB 0254), ANDEEP III, # 102–13–U, ZMH K­ 41309; 1 (A­1) (SNB 0257), ANDEEP III, # 102–13, ZMH K­ 41310; 1 A F (SNB 0273), ANDEEP III, # 110–8–E, ZMH K­ 41311; 1 (A­1) (SNB 0274), ANDEEP III, # 110–8–S, ZMH K­ 41312; 1 (A­1) (SNB 0111), ANDEEP III, # 110–8– U, ZMH K­ 41313.

Distribution. Weddell Sea, Southern Ocean (Atlantic Sector), 4059.4 to 4895.0m.

Measurements (Fig. 28). Holotype, LV, L 1.88mm, H 1.02mm, RV L 1.88mm; H 0.88mm.

Paratypes, A LV, L 1.86–1.94mm, H 0.99–1.04mm; (A­1) LV, L 1.46–1.63mm, H 0.76–0.89mm; (A­2) LV, L 1.15–1.27mm, H 0.65–0.69mm.

Diagnosis. Valves quite large, subovate to sub­triangular, inequilateral in lateral view. Podomere VI of AII of male with 1 long claw, 1 sexually dimorphic, “6­segmented”, medium­sized, fused seta, and 2 or 3 simple medium­sized setae; podomere VI of AII of female with 1 long claw, simple, 1 medium­sized, fused claw, and 2 or 3 medium­sized setae. MxI with 5 to 10 strahlen and around 26 feathered setae. ApV with 6 to 11 strahlen and 5 to 8 feathered setae. Fu with 2 tiny setae on dorsal margin; 6 to 7 short setae, and 3 medium­sized setae (setae 2 and 4 longest) on ventral margin. Hemipenis with coiled vas deferens; strongly sclerotized, arched proximal lobe, and conical distal lobe, the last one armed distally with numerous chitinous spines.

— B. aff. malyutinae (herein); — B. sp. aff. B. mozambiquensis (herein); — B. mozambiquensis (from Maddocks 1969); — B. mozambiquensis? (dubious record from Maddocks 1969); "— B. eltanina and B. spiriscutica (from Maddocks 1969); — B. promoza (from Maddocks 1973).

Description. Valves quite large; elongate and inequilateral (anterior margin more broadly rounded than posterior margin) in lateral view. External surface smooth, radial pore canals simple, with or without rim. LV with rounded outline, ventral margin straight, with upswung posterior angle, smoothly rounded dorsal margin. RV fairly sinuous in outline, especially the ventral margin; with truncate anterior margin, and slightly concave anterodorsal and posterodorsal margins. Females higher in relation to length than males. Adductor muscle scars bythocytherid, with 3 anterior (subdivided) scars and 1 posterior (subdivided) scar. Zone of concrescence fairly narrow with numerous short, straight marginal pore canals. Carapace subovate in dorsal view.

AI robust with not very long setae; chaetotaty 1(0/0), 2(0/0:0­ 2 i), 3(.2­3/0), 4(.0­2/.1), 5(.2­5/.2), 6(.2­3/.2), 7(0/0:5). Exopodite of AII with 2 long and 1 short setae; podomere VI of male with 1 long claw, 1 sexually dimorphic “6­segmented” medium­sized fused seta, and 2 or 3 simple medium­sized seta; podomere VI of female with 1 long claw, 1 sexually dimorphic simple fused medium­sized claw, 2 or 3 medium­sized simple setae; chaetotaxy 1(0/0:0­ 2 i), 2(1/0: 1i), 3(0/.3­4.1c,1,0­1r), 4(0/.2r.1c,1), 5(.1.1c,1/1,1r,1c), female­6(0/:1c,2,1fc,1), male­6(0/:1c,1,1fs,1). Base of Md with 1 anterodorsal seta, masticatory process with 5 teeth plus several short setae; exopodite with 1 very long and 2 long feathered setae (one of the mandibles of one specimen with 1 very long and 3 long setae); podomere IV of palp with 2 or 3 medium­sized setae and 2 mediumsized plumose claws; chaetotaxy of palp 1(0­1/1: 1i), 2(.1.3­4/3: 1i), 3(.4­5./.1:1­2,1c), 4(.1­3./0:2­3c,2). MxI with 5 to 9 strahlen (!) and 25 or 26 feathered setae; each endite with 1 to 4 plumose claws and around 5 setae; palp with 3 dorsal and 2 ventral setae, and 1 modified plumose claw. ApV with 6 to 11 strahlen and 5 to 10 feathered setae, podomere II might or might not be fused to podomere III; chaetotaxy 1(.1.2­3.3/0), 2(0/.2), [+or not]3(0/1), 4(0/.1­2), 5(0/0:.1,1c,1). Exopodite of ApVI and Ap VII with 2 medium­sized setae; one Ap of 1 specimen (SNB 0110) with 2 instead of 1 seta on podomere 4; chaetotaxy 1(.1.1.2/0), 2(0/.2), 3(0/.1), 4(0/.1­2), 5(0/0:1,1c,1). Fu with 2 rudimentary setae on dorsal margin; ventral margin with 4 or 5 short proximal setae, 1 medium­sized thin setae, 2 medium­sized robust setae, and 1 short distal seta. One short seta between Fu rods. Genital lobe subtriangular, or suboval with tubularly extended distal margin. Hemipenis with coiled vas deferens; strongly sclerotized, sub­rectangular, arched, short proximal lobe; and subconical distal lobe armed distally with numerous chitinous spines.

Remarks. Bythocypris malyutinae sp. nov. presents both bythocypridid and bairdiid characthers. It is a typical bythocypridid in: (1) carapace (subtriangular, thin and smooth), (2) antenna I with not very long setae; (3) genital lobe with short internal tube; (4) adductor muscle scars arranged in three anterior and one posterodorsal rows. Otherwise, the antenna II in B. polarsterni sp. nov. presents one claw (in females) or seta (in males) fused to podomere VI, which Maddocks (1969, 1972, 1973, 1976, 1991, 1995) considered to be diagnostic of the family Bairdiidae. Actually, females of Bythocypris eltanina Maddocks, 1969 also present a fused claw on this podomere (Maddocks, 1969, Fig. 48.D). In the provided illustration of the male specimen (Maddocks, 1969: 48.C), it is unfortunately not possible to distinguish the insertion of the “segmented” claw from the other several setae the podomere VI.

The immense morphological variation observed in the valves and soft parts probably indicates that several species might be included in the names B. malyutinae sp. nov., Bythocypris sp. 1 aff. B. malyutinae (see description below) and Bythocypris sp. 2 cf. B. mozambiquensis (see description below), as herein defined: (1) the valves can be sub­oval (Figs. 29.I, 30.A, B) to subtriangular (Figs. 29.L, 30.F, B), with more (Fig. 30.E, F) or less (Fig. 29.C, D) protruding posterior angle; (2) the hemipenis presents variation on the distal lobe (width, and relative length of spiky distal area) (Fig. 30.G, H); (3) genital lobe can be subtriangular, sub­oval with a thin tubular extension, or sub­oval with a thick tubular extension; (4) vibratory plate of maxilla I with 5 to 10 strahlen; (5) vibratory plate of appendage V with 6 to 14 strahlen; (6) chaetotaxy of most podomeres of appendages (except AI podomere I, VII; AII podomere I, II; Md palp podomere I, ApV podomere IV, Ap VI exopodite, podomere II, IV; ApVII podomere I, III, IV) and Fu is very variable among the 13 adults examined. In particular, the highly variable number of strahlen on the vibratory plates of the maxilla I and the appendage V are strong evidence for the presence of different species. Furthermore, Hartmann (1968: 458), stated that the morphology of the genital lobe of Bairdioidea have systematic importance, since it is characteristic for each species. Unfortunately, even after the careful study of the chaetotaxy of the 16 available adults (3 males, 10 females), no consistent character defining the different species could be found. Therefore, only one new species is named (B. malyutinae), and the more extreme forms are left in open nomenclature (including Bythocypris sp. 1 aff. B. malyutinae, and Bythocypris sp. 2 cf. B. mozambiquensis).

Bythocypris malyutinae sp. nov. belongs to the Bythocypris mozambiquensis group, which includes B. mozambiquensis Maddocks, 1969, B. eltanin Maddocks, 1969, B. spiriscutica Maddocks, 1969 and B. promoza Maddocks, 1973. Some differences can be observed between B. promoza (Maddocks, 1972, Figs. 1 –3) and B. malyutinae: (1) podomere V of AII in B. promoza conspicuously more elongate (Maddocks 1972: Fig.1 C) than B. malyutinae sp. nov; (2) male modified seta of podomere VI of AII is “segmented” from the mid­length to the distal tip in B. promoza and is “segmented” just in the mid 1/3 of its length in B. malyutinae; (3) B. promoza lacks claws on Md palp, while B. malyutinae has 1 mediodistal claw on podomere III and 2 distal claws at podomere IV; (4) B. promoza lacks feathered setae on MxI palp and endites; (5) the former sp. shows 12 strahlen (instead of 6 to 11) and 6 tiny posterior setae (instead of 5 to 10 medium­sized setae); (6) the former sp. has more elongate podomeres on Ap V to VII; (7) B. promoza has fewer setae on Fu (4 anterior, long setae plus 3 tiny setae, instead of 2 tiny dorsal, plus 8 or 9 setae on ventral margin); (8) the hemipenis of B. promoza lacks the large tubular spiny distal lobe.

Based on 103 empty valves and 2 juveniles (with soft parts), Maddocks (1969: 99–102) described Bythocypris mozambiquensis Maddocks, 1969 from a total of 16 samples from the Mozambique Channel (14 samples, 1140 to 3850m), Southwestern Pacific (3 samples, 1930 to 3475m) and Gulf of Mexico (1 sample, 1335m). As that author stated, it is possible to observe that, “there is an extraordinary amount of variation among forms assignable to this species” (1969: 100). In my opinion, most probably all these specimens studied by Maddocks comprise more than one sp., but this fact is masked by the total absence of soft parts. Because of that, the following comparison will be related to the holotype and other paratypes included by Maddocks in the “typical form” (Maddocks 1969, Fig. 46.E, G, K, M). Bythocypris malyutinae sp. nov. differs from B. mozambiquensis, because the former species: (1) is larger (Fig. 28), adult length 1.78 to 1.94mm, instead of 1.40 to 1.50mm (Maddocks 1969: 99–100); (2) present smoothly rounded lateral outline, with rounded anterior margin, instead of an angulate outline with truncate anterior margin; (3) is less high in relation to length.

Overall, B. malyutinae presents a similar valve outline to Bythocypris eltanina Maddocks, 1969 (except that the new species has a more rounded dorsal margin) but differs considerably in hemipenis (Fig. 30. G–L herein; Maddocks 1969, Fig. 48.G).

The new species described herein differs from: (1) B. reniformis, B. affinis, and B. prolata by its more subtriangular lateral view; (2) B. elongata in being higher in relation to length, with more smoothly rounded dorsal margin, and more sinuous LV outline; 3) B. spiriscutica has a more ovate outline, with less distinct posterior angle.