Tirana vallis, García-Herrero & Esquete & Cunha, 2021

García-Herrero, Álvaro, Esquete, Patricia & Cunha, Marina R., 2021, Two new tanaidaceans (Crustacea: Peracarida) from Portuguese submarine canyons (NE Atlantic, West Iberian Margin), European Journal of Taxonomy 740, pp. 55-76 : 67-72

Tirana vallis gen. et sp. nov.

urn:lsid:zoobank.org:act:83F4E8E6-F501-43C1-89B7-5040180FE8C6

Figs 6–8

Etymology

The species name, ‘ vallis ’ (Latin for valley), refers to the type location of the species in the marine canyons, since there is no a literal translation of ‘canyon’ in the Latin language.

Material examined

Holotype PORTUGAL • ♀; West Iberian Margin , Cascais Canyon ; 38°17.97′ N, 9°46.89′ W, depth 3214 m; 27 Apr. 2006; stn CD179_21-2; MNCN 20.04/12540 .

Paratypes PORTUGAL • 1 manca, 1 juv., 1 ♀ (dissected); same collection data as for holotype; DBUA0002211.02 .

Description of holotype

BODY ( Fig. 6A–B ). 8.9 times as long as wide (3.7 mm length, 0.5 mm width). Cephalothorax without eyes or eyelobes, elongate (1.3 times as long as wide) and subhexagonal, 0.15 of body length, narrower than pereon. Rostrum rounded. Pereon 0.63 of body length, pereonites 2–5 subhexagonal. Pereonites 1–6: 0.7, 0.9, 1.1, 0.9, 1.2 and 0.8 times as long as wide respectively. Coxal setae visible in dorsal view. Pleonites altogether shorter than last two pereonites together, 0.14 of body length. Pleonite 5 slightly longer than rest of them. All pleonites with a mediodorsal seta. Pleotelson 0.09 of body length, widest in its medial part, with posterior protuberance carrying four setae on distal margin.

ANTENNULE ( Fig. 6C ). Five-articled. Article 1 longest and widest, 3.4 times as long as wide, with three outer penicillate setae in medial and distal position, respectively, three penicillate setae on subdistal outer margin, and one seta on subdistal inner margin. Article 2, 1.7 times as along as wide, with one seta on inner margin and three setae on outer margin (two of them penicillate), all subdistal. Article 3, as long as wide, with one long distal seta on outer margin and two on inner margin. Article 4, 4.4 times as long as wide, with one distal seta on inner margin. Article 5 minute, with five terminal setae and one aesthetasc (not figured).

ANTENNA ( Fig. 6D , ventral view). Six-articled. Article 1 short and naked. Article 2, 2.1 times as long as wide, with one outer seta in medial margin and a dorsodistal spine. Article 3, 1.5 times as long as wide, with dorsodistal spine. Article 4 longest, 9.9 times as long as wide, with four subterminal setae, two penicillate. Article 5, 5.0 times as long as wide, with one long terminal seta. Article 6 minute, carrying five terminal setae, two of them longer.

MOUTHPARTS (described from paratype DBUA0002211.02). Labrum ( Fig. 7A , ventral view) rounded, posteriorly setulated. Left mandible ( Fig. 7B–C ) incisor process naked, slightly concave; lacinia mobilis long and wide; molar process with rounded tip, wide on its basis, with several distal spiniform processes. Right mandible (not figured) as left but without lacinia mobilis. Labium composed of two lobes, quadrangular, naked (not figured). Maxillule ( Fig. 7D ) endite with row of spines on outer margin, distally with microtrichia, seven rounded-tip spines. Maxilla ovoid, naked (not figured). Maxilliped ( Fig. 7E ) basis narrower posteriorly, partially fused, with seta near palp insertion. Endites not fused, bearing one pair of slender gustatory cusps, and one pair of simple setae posteriorly to them. Palp 4-articled. Article 1 naked. Article 2 subtriangular with three inner setae. Article 3 longest, with three inner pinnate setae and one simple seta. Terminal article long with five terminal and one subterminal pinnate setae.

CHELIPED ( Fig. 6G–H ). Attached ventrally via large sclerite. Basis naked, 1.4 times as long as wide, posteriorly rounded. Merus naked, 1.3 times as long as wide with one medioventral seta. Carpus 1.8 times as long as wide, with two medioventral seta. Propodus robust, 1.8 times as long as wide, with inner row of seven setae. Ventral margin of fixed finger with two pinnate setae near dactylus insertion and cutting edge crenulated with three setae. Dactylus robust, 2.1 times as long as wide, not fused with unguis. Dactylus and unguis together not reaching end of propodus and claw.

PEREOPOD 1 ( Fig. 8A –A’). Coxa with seta. Basis 4.5 times as long as wide, with two mediodorsal setae. Ischium wider than long, with ventral seta. Merus 2.4 times as long as wide, with subdistal ventral seta and distoventral pinnate spine. Carpus 4.3 times as long as wide, with two ventrodistal pinnate spines and one distodorsal pinnate spine. Propodus 5.5 times as long as wide, ventral margin serrates with two dorsodistal spines, one of the setulose and the other simple, and one ventrodistal simple spine. Dactylus as long as unguis, naked, together as long as propodus.

PEREOPOD 2 ( Fig. 8B –B’). Coxa with seta. Basis 4.5 times as long as wide, with three mediodorsal setae. Ischium wider than long, with ventral seta. Merus 2.5 times as long as wide, with long ventrodistal seta and pinnate spine. Carpus 3.5 times as long as wide, bearing one dorsodistal long pinnate spine and one short simple spine, and one ventrodistal long pinnate spine and one short simple spine. Propodus 6.1 times as long as wide, ventral margin serrated, with one one subdistal long seta, one subdistal short seta and one subdistal pinnate spine in dorsal margin and one pinnate spine in ventral margin. Dactylus and unguis naked, together about as long as propodus.

PEREOPOD 3 ( Fig. 8C ). Similar to pereopod 2, except for: seta from coxa not illustrated. Basis 4.1 times as long as wide, with one mediodorsal seta. Merus 2.8 times as long as wide. Carpus 3.6 times as long as wide. Propodus 5.6 times as long as wide.

PEREOPOD 4 ( Fig. 8D ). Coxa with seta. Basis 3 times as long as wide, with mediodorsal penicillate seta. Ischium wider than long, with two ventral setae. Merus 2.7 times as long as wide, with two ventrodistal pinnate spines. Carpus 2.3 times as long as wide, one dorsodistal, two in mediodistal and one ventrodistal pinnate spines. Propodus 6.2 times as long as wide, ventral margin serrated, with two dorsodistal and one ventrodistal pinnate spines. Dactylus and unguis naked, together 0.8 times as long as propodus.

PEREOPOD 5 ( Fig. 8E –E’). As pereopod 4, except for: basis 5.0 times as long as wide. Merus 3.8 times as long as wide. Carpus 2.8 times as long as wide, with dorsodistal seta, and simple spine, and one dorsodistal and two ventrodistal pinnate spines. Propodus 6.0 times as long as wide with a mediodorsal penicillate seta, (not figured in Fig. 8 E’) one dorsodistal simple spine and two ramified ventral-subdistal spines. Dactylus and unguis naked, together 0.7 times as long as propodus.

PEREOPOD 6 ( Fig. 8F –F’). As pereopod 4, except for: basis 4.7 times as long as wide. Merus 2.3 times as long as wide. Carpus 2.9 times as long as wide Propodus 6.0 times as long as wide with a mediodorsal penicillate seta (not figured in Fig. 8 E’) three dorsodistal distal simple and two and two ramified ventralsubdistal spines. Dactylus and unguis naked, together 0.7 times as long as propodus.

PLEOPODS ( Fig. 6F ). Present in all pleonites, all with same chaetotaxy. Protopod naked. Endopod long and narrow, 5.1 times as long as broad, with eight terminal long plumose setae and one subdistal seta on inner margin. Exopod long and narrow, 6.1 times as long as broad bearing seven long plumose setae.

UROPODS ( Fig. 6E ). Biramous. Protopod naked, 1.5 times as long as broad. Endopod 2-articled, 2.3 times as long as protopod. Article 1 with two subdistal setae, one penicillate. Article 2, 1.2 times as long as article 1, with five setae, two of them broken in holotype. Exopod 1.7 times as long as protopod. Article 1 with distal seta. Article 2, 1.8 times as long as article 1, with two distal setae, one of them broken in holotype.

Distribution and ecology

Tirana vallis gen. et sp. nov. was found in the middle reaches of Cascais Canyon (North-east Atlantic, West Iberian Margin), between 3214 and 3219 m depth (see Billet et al. 2006 and Cunha et al. 2011 for more information). It was found sympatric with other tanaidacean species: Agathotanais ingolfi Hansen, 1913 , Paragathotanais sp., Paranarthrura intermedia Kudinova-Pasternak, 1982 , Anarthrura sp., Araphuroides cf. parabreviremis Sieg, 1986, Cristatotanais contoura Błażewicz-Paszkowycz, Bamber & Cunha, 2011, and Typhlotanais cf. spinicauda Hansen, 1913 .

Figures

Fig. 6. Tirana vallis gen. et sp. nov. Holotype, adult, ♀ (MNCN 20.04/12540). A. Habitus dorsal view. B. Habitus lateral view. C. Left antennule, dorsal view. D. Right antenna, lateral view. E. Left uropod. F. Pleopod 3 (all setae are plumose). G. Left cheliped, outer view. H. Left cheliped, inner view. Scale bars: A–B = 1 mm; C–D, F–H = 100 μm; E = 50 μm..

Fig. 7. Tirana vallis gen. et sp. nov. Paratype, adult, ♀ (DBUA0002211.02). A. Labrum. B–C. Left mandible. D. Maxillule. E. Maxilliped. Scale bar = 100 μm.

Fig. 8. Tirana vallis gen. et sp. nov. Holotype, adult, ♀ (MNCN 20.04/12540). A–F. Pereopods 1–6. A’–F’. Detail in dactylus and unguis pereopods 1–3, 5 and 6. Scale bars = 100 μm.