Cristatotanais contoura, Błażewicz-Paszkowycz, Magdalena, Bamber, Roger N & Cunha, Marina R, 2011

Błażewicz-Paszkowycz, Magdalena, Bamber, Roger N & Cunha, Marina R, 2011, New tanaidomorph Tanaidacea (Crustacea: Peracarida) from submarine mud-volcanoes in the Gulf of Cadiz (North-east Atlantic), Zootaxa 2769, pp. 1-53 : 14-20

Cristatotanais contoura sp. nov.

Figs 7–9

Type material. 1Ƥ, Holotype ( BMNH.2010.300), 13 allotype ( BMNH.2010.301), 119 paratypes ( BMNH.2010.302-401), Station CA 546, Captain Arutyunov mud-volcano, 35º39.692’N 07º20.046’W, 1345 m depth, mud-breccia and gas-hydrate, TV-grab, 0 6.08.2004, coll. MRC.

Other records. 7 specimens, same data as holotype; 23 specimens, Stn CA392, Captain Arutyunov mud-volcano, 35º39.656’N 07º20.018’W, 1320 m depth, mud-breccia, Gravity corer, 09.07.2002; 2 specimens, Stn CA 393, Captain Arutyunov mud-volcano, 35º39.740’N 07º19.942’W, 1327 m depth, mud-breccia, TV-grab, 09.07.2002; 1 specimen, Stn AV394, Aveiro mud-volcano, 35º52.225’N 07º26.243’W, 1098 m depth, marl and mud-breccia, Gravity corer, 11.07.2002; 2 specimens, Stn YU 524, Yuma mud-volcano, 35º24.973’N 07º05.461’W, 960 m depth, marl and mud-breccia, TV-grab, 02.08.2004; 33 specimens, Stn CA 543, Captain Arutyunov mud-volcano, 35º39.688’N 07º19.981’W, 1345 m depth, mud-breccia and H2S, Gravity corer, 06.08.2004; 1 specimen, Stn CA 544, Captain Arutyunov mud-volcano, 35º39.707’N 0 7º20.012’W, 1330 m depth, mud-breccia and gas-hydrate, Gravity corer, 06.08.2004; 442 specimens, Stn CA 547, Captain Arutyunov mud-volcano, 35º39.701’N 07º20.037’W, 1344 m depth, mud-breccia and gas-hydrate, TV-grab, 06.08.2004; 19 specimens, Stn CA 548, Captain Arutyunov mud-volcano, 35º39.708’N 07º20.034’W, 1345 m depth, mud-breccia and H2S, Kasten corer, 06.08.2004; 1 specimen, Stn Mer 575, Mercator mud-volcano, 35º17.903’N 06º38.715’W, 355 m depth, mud breccia, Boxcorer, 26.07.2005; all coll. MRC.

Description of female: body ( Fig. 7 A, B) attenuate, holotype 5.6 mm long, 8.5 times as long as wide. Cephalothorax subrectangular, narrowing strongly towards rostrum, 1.3 times as long as wide, slightly longer than pereonites 1 and 2 together, naked, rostrum slight, eyes and eyelobes absent. Pereonite 1 shortest, pereonites 2, 3 and 6 subequal, twice as long as pereonite 1, pereonites 4 and 5 each 1.2 times as long as pereonite 2 (all pereonites respectively 2.7, 1.3, 1.2, 1.0, 1.0 and 1.25 times as wide as long). Each pleonite 3.3 times as wide as long and bearing pleopods. Pleotelson semicircular, as long as last two pleonites together, with one midlateral and one posterolateral seta on each side ( Fig. 9 H).

Antennule ( Fig. 8 A) proximal article 1.8 times as long as wide, as long as articles 2 and 3 together, outer margin with simple seta and two penicillate setae in distal half; second article as long as wide, outer margin with simple seta and two penicillate setae; third article 0.6 times as long as second article, with two simple and one penicillate distal setae; fourth article tapering, twice as long as third article, with six distal setae.

Antenna ( Fig. 8 B) proximal article compact, second article 1.6 times as long as first and as long as wide, with dorsodistal seta; third article as long as first, with dorsodistal seta; fourth article longest, three times as long as third article, 3.5 times as long as wide, with two simple and three penicillate distal setae; fifth article twice as long as third, tapering; sixth article one fifth as long as fifth article, with four distal setae.

Labrum ( Fig. 8 D) rounded, naked. Mandibles not found. Labium ( Fig. 8 F) simple, rectangular, distal margin finely setose, without palp. Maxillule ( Fig. 8 E) endite distally in-curved with eight slender distal spines, palp not recovered. Maxilla not recovered. Maxilliped palp ( Fig. 8 H) first article naked, second article with one outer and two inner setae, third article with three longer and one shorter (left) or three shorter and one longer (right) inner setae, fourth article with four distal setae; basis fused, naked; endites distally rounded, naked. Epignath ( Fig. 8 G) linguiform, naked.

Cheliped ( Fig. 8 I) with rounded, compact basis bearing single dorsal seta, merus subtriangular with single ventral seta; carpus stout, twice as long as wide, with two unequal midventral, one dorsoproximal and one dorsodistal setae, distally gaping to accommodate flexed propodus; chela palm rugose, 1.5 times as long as wide, fixed finger half as long as palm with two inner mesial, one sub-ventral and one outer setae, two setae on cutting edge, one seta near dactylus insertion, and accessory denticulation on the unguis; dactylus with single seta.

Pereopod 1 ( Fig. 9 A) longer than others, coxa with seta; basis slender, 4.6 times as long as wide; ischium compact with one seta; merus 1.5 times as long as carpus, with two ventrodistal setae; carpus with three distal setae; propodus twice as long as carpus, with fine setule-rows on dorsal margin and one ventrodistal seta; dactylus with proximal seta, unguis 1.5 times as long as dactylus, both together 1.3 times as long as propodus. Pereopod 2 ( Fig. 9 B) similar to pereopod 1, basis 3.3 times as long as wide; merus just longer than carpus, propodus 1.7 times as long as carpus; dactylus with curved unguis 1.4 times as long as propodus. Pereopod 3 ( Fig. 9 C) similar to pereopod 2, but carpus 1.3 times as long as merus.

Pereopod 4 ( Fig. 9 D) coxa fused, basis stout, 1.8 times as long as wide; ischium with two ventrodistal setae; merus 1.2 times as long as carpus, with two stout (“cone-shaped” sensu Larsen 2003 ) ventrodistal spines, carpus with three stout distal spines and one dorsodistal fine seta; propodus just longer than carpus, with two stout distal spines and one dorsodistal fine seta; dactylus much longer than, but not fused with, unguis, both together as long as propodus. Pereopod 5 ( Fig. 9 E) as pereopod 4, but basis with two penicillate setae, propodus just shorter than carpus. Pereopod 6 ( Fig. 9 F) as pereopod 4, but propodus just shorter than carpus and with two dorsodistal setae.

Pleopods ( Fig. 9 G) all alike, with naked basis, endopod with one subdistal and six distal plumose setae, exopod with 10 outer-distal plumose setae restricted to the distal half of the exopod margin.

Uropod ( Fig. 9 H) uniramous, exopod represented by slight outer distal swelling of basis; endopod of two segments, proximal segment twice as long as wide and as long as distal segment; proximal segment distally with one simple and two penicillate setae, second segment with outer subdistal seta, distally with four simple and two penicillate setae.

Description of male: habitus ( Fig. 7 C), and most of morphology as female, pereonites slightly rounder in outline, pereonite 1 proportionately longer (1.7 times as wide as long, 0.4 times as long as cephalothorax), pereonites 2.3 times as wide as long. Antennule ( Fig. 8 C) of five articles, proximal article 1.6 times as long as wide with outer tuft of penicillate setae, article 2 half as long as article 1 with two simple distal setae, article 3 half as long as article 2 with simple inner-distal seta, article 4 just more than half as long as article 3, article 5 three times as long as article 4, distally with five setae and one aesthetasc. Pleopods with longer setae.

Etymology. from the Greek kontos – short, and oura (f.) – tail, alluding to the reduced uropod exopod.

Remarks. This is the third species to be described for the genus Cristatotanais ; notably, C. insolituchelia was recorded from a cold-seep, although the habitat for C. longicheles is not described. In order to interpret more reliably the relationships between these three taxa, the holotype of the generotype, C. longicheles , has been re-examined, and the surviving trunk appendages drawn ( Fig. 10 ). Notable differences found between the specimen and the figures of Kudinova-Pasternak (1990) are that pereopods 1 and 3 have additional distal setae on the propodus ( Fig. 10 A, C), these anterior propodi are in reality less slender than figured by Kudinova-Pasternak (1990), pereopods 4 and 5 have a penicillate seta on the basis ( Fig. 10 D, E), the pleopod basis is naked ( Fig. 10 G), and the uropod exopod does not articulate with the basis ( Fig. 10 H).

Cristatotanais contoura sp. nov. shares with C. insolituchelia (but not with C. longicheles ) the presence on the cheliped fixed finger of two mesial setae and two setae on the cutting edge. Cristatotanais contoura (as well as C. longicheles ) differs from C. insolituchelia in the less-clear separation of the cheliped fixed-finger from the palm, in having eight (not seven) distal spines on the maxillule endite, in the absence of a spine on the unguis of the cheliped dactylus, and in the complete fusion of the uropod exopod with the basis.

Cristatotanais contoura is distinct from both of the other species in the presence of a proximal seta on the dactylus of pereopods 1 to 3, and particularly in the almost complete reduction of the uropod exopod, the latter being distinct and half as long as the basis the other two; further, C. longicheles and C. insolituchelia have the proximal segment of the uropod endopod more slender, respectively 3 and 5 times as long as wide, and 1.5 times as long as the distal segment, while in C. contoura it is less than twice as long as wide and only as long as the distal segment. Finally, the plumose setae on the outer margin of the pleopod exopod do not extend into its proximal half in C. contoura , unlike the condition in both of the other two species.

The mandibles of the two previously described species were found to be almost completely reduced, having no more description than that (nor figure) for C. longicheles in Kudinova-Pasternak (1990), and merely represented as simple comma-shaped structures with no lacinia mobilis or molar process in C. insolituchelia ( Larsen, 2003) . Mandibles were not found in the present material: either they are so reduced in this species as to be indistinguishable as distinct structures, or they may be absent.

The present material allows the first description of the male of this genus, the material of the previous two species having been females or mancae. At least two of the species are associated with chemically-reduced deep-sea habitats, to which the genus may be endemic.

Cristatotanais contoura was collected from the Captain Arutyunov mud-volcano (type-locality) and the Aveiro mud-volcano, in the deep-water field within the Portuguese margin, at depths from 1320 to 1345 m and 1098 m respectively, from the Mercator mud-volcano in the El Arraiche field on the Moroccan margin, at 355 m depth, and from the Yuma mud-volcano in the western Moroccan field at 960 m, on muddy-substrata often with gas-hydrate or hydrogen sulphide present.

Figures

FIGURE 7. Cristatotanais contoura sp. nov., A, Ƥ holotype, lateral; B, Ƥ holotype, dorsal; C, 3, dorsal. Scale line = 0.1 mm.

FIGURE 8. Cristatotanais contoura sp. nov., Ƥ paratype. A, antennule of Ƥ; B, antenna; C, antennule of 3; D, labrum; E, maxillule; F, labium; G, epignath; H, maxilliped; I, cheliped (3). Scale line = 0.1 mm.

FIGURE 9. Cristatotanais contoura sp. nov., A to F, pereopods 1 to 6, respectively; G, pleopod; H, pleotelson and uropod. Scale line = 0.1 mm.

FIGURE 10. Cristatotanais longicheles Kudinova-Pasternak, holotype: A to F, pereopods 1 to 6; G, pleopod; H, uropod. Scale lines = 0.2 mm.