Typhlotanais guca, 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 : 33-38

Typhlotanais guca sp. nov.

Figs 20–22

Material. 1Ƥ, Holotype ( BMNH.2010.416), Station Ki 561, Kidd mud-volcano, 35º25.602’N 06º44.099’W, 526 m depth, mud, Boxcorer, 08.08.2004; 1 female, paratype, dissected (fragments) ( BMNH.2010.417), Station Fiu 566, Fiúza mud-volcano, 35º15.510’N 06º41.702’W, 414 m depth, mud-breccia, TV-grab, 09.08.2004; coll. MRC.

Other records. 3 specimens, Station Ki 560, Kidd mud-volcano, 35º25.306’N 06º43.976’W, 498 m depth, mud-breccia, Boxcorer, 08.08.2004; 2 females, Station JB391, Jesus Baraza mud-volcano, 35º35.439’N 07º12.264’W, 1105 m depth, carbonate clay and mud-breccia, TV-grab, 09.07.2002; 1 further female, Station Fiu 566, Fiúza mud-volcano, 35º15.510’N 06º41.702’W, 414 m depth, mud-breccia, TV-grab, 09.08.2004; 1 specimen, Station Mer 575, Mercator mud-volcano, 35º17.903’N 06º38.715’W, 355 m depth, mud breccia, Boxcorer, 26.07.2005; all coll. MRC.

Description. Body ( Fig. 20 A, B) slender, holotype 3.0 mm long, 6.6 times as long as wide. Cephalothorax subrectangular, lateral margins convex, 1.4 times as long as wide, as long as pereonites 2 and 3 together, naked, eyes absent, with triangular rostrum. Pereonite 1 shortest, one-third as long as pereonite 2, ventrally with anteriorlydirected hook-like hyposphenium; pereonites 2 and 3 subequal, half as long as cephalothorax; pereonite 4 longest, 1.13 times as long as pereonite 2; pereonites 5 and 6 subequal, just shorter than pereonite 2 (all pereonites respectively 4.5, 1.5, 1.5, 1.3, 1.6 and 1.6 times as wide as long). All pleonites bearing pleopods; each pleonite 5 times as wide as long, fifth pleonite slightly longer than preceding. Pleotelson semicircular, as long as last two pleonites, twice as wide as long, with one midlateral and one distal seta on each side.

Antennule ( Fig. 21 A) proximal article nearly 2.2 times as long as wide, as long as distal two articles together, with mesial and distal tufts of penicillate and one simple setae, and proximal penicillate seta; second article as long as wide, one-quarter as long as third article, with single distal simple and penicillate setae; third article tapering, with six distal setae.

Antenna ( Fig. 21 B, Bʹ) of six articles, proximal article compact, naked; second article longer than wide, with strong dorsodistal seta; third article 0.75 times as long as second article, with two dorsodistal and one ventrodistal fine setae; fourth article longest, six times as long as wide, 2.5 times as long as second article, distally with three simple and one penicillate setae; fifth article slender, tapering, 0.7 times as long as fourth, with single distal seta; sixth article small, 0.18 times as long as fifth, with five distal setae.

Labrum ( Fig. 21 C) rounded, distally finely setulose. Left mandible ( Fig. 21 E) with wide, denticulate lacinia mobilis, right mandible ( Fig. 21 D) without lacinia mobilis; pars molaris of both mandibles distally flattened, anteriorly with strong, rounded tooth-like protrusions, posteriorly with finer triangular denticulations. Labium not recovered. Maxillule ( Fig. 21 F) with eight slender distal spines, outer distal margin finely setulose, palp ( Fig. 21 Fʹ) with two distal setae. Maxilla ( Fig. 21 G) subtriangular, naked. Maxilliped ( Fig. 21 I) first palp article naked; second article with one fine outer seta, and one finely-setulose and two simple inner setae; third article with three finelysetulose and one shorter simple inner setae; fourth articles with five finely-setulose distal setae and one simple outer seta; basis with single, long seta reaching half length of endites; endites distally with inner rounded tubercle and outer stout spine, outer-distal corner finely setulose. Epignath ( Fig. 21 H) slender, linguiform, naked.

Cheliped ( Fig. 22 A) with slender basis, twice as long as wide, with single dorsodistal seta; merus subtriangular with single ventral seta; carpus with rounded extension, elongate, 2.9 times as long as wide, with two midventral setae and full dorsal marginal row of nine setae; propodus 2.3 times as long as wide, 1.6 times as long as chela; fixed finger with two ventral setae and three setae on cutting edge; dactylus naked.

Pereopod 1 ( Fig. 22 B) longer than others, coxa without apophysis; basis slender, arcuate, 4.2 times as long as wide, naked; ischium compact with one ventral seta; merus as long as carpus, and with one ventrodistal seta; carpus with three distal setae; propodus 1.15 times as long as carpus, with two subdistal setae and one fine ventral seta in distal half; dactylus with proximal seta longer than dactylus; unguis twice as long as dactylus, both together just shorter than propodus. Pereopod 2 ( Fig. 22 C), basis more compact than that of pereopod 1, 2.5 times as long as wide; merus subtriangular, 0.7 times as long as carpus, and ventrodistally with large spine 0.75 times as long as carpus and fine seta; carpus rectangular, 1.3 times as long as wide, with two fine ventrodistal spines and single dorsal and ventral distal setae; propodus as long as merus and carpus together, dorsodistally with one seta and one fine, small spine, ventral margin with microtrichia and short subdistal spine; dactylus with proximal seta nearly twice as long as dactylus, together with unguis 0.9 times as long as propodus. Pereopod 3 compact ( Fig. 22 D), similar to pereopod 2, basis with dorsal seta in proximal half; ventrodistal spine on merus 0.9 times as long as carpus.

Pereopod 4 ( Fig. 22 E) basis stout, 1.7 times as long as wide. with one mid-dorsal and two subdistal ventral penicillate setae; ischium with two ventral setae; merus just shorter than carpus, and with two ventral subdistal setae and microtrichia; carpus with dorsodistal seta, outer and inner mid-distal spines, and ventral prickly tubercle with adjacent microtrichia; propodus 0.8 times as long as carpus, with mid-dorsal penicillate seta, ventral microtrichia, two ventrodistal spines and dorsodistal seta more than half as long as dactylus; dactylus three times as long as unguis, with ventral microtrichia, together with unguis 1.2 times as long as propodus. Pereopod 5 ( Fig. 22 F) as pereopod 4, but basis naked, propodus as long as carpus. Pereopod 6 missing on both specimens.

Pleopods ( Fig. 22 G) all alike, rami subequal, all setae plumose; basis naked; endopod with two subdistal inner setae, 12 outer setae in distal two-thirds, separated proximal outer seta; exopod without setae on inner margin, outer margin with 22 marginal setae and separated proximal outer seta.

Uropod ( Fig. 22 H) biramous; endopod of two segments, proximal segment 1.6 times as long as distal segment, and with one simple and two penicillate distal setae, distal segment with one subdistal and four distal simple setae; exopod of one segment, just shorter than proximal endopod segment, and with one mesial and two extremely unequal distal setae.

Male unknown.

Etymology. “ guca ” derives from the first two letters of “Gulf” and “Cadiz”, the Gulf of Cadiz being the typelocality.

Remarks. in the presence of a large ventrodistal spine on the merus of pereopods 2 and 3, Typhlotanais guca sp. nov. is very similar (only) to T. proctagon Tattersall, 1905 , described from the west of Ireland at 364–586 m depth; however, the spine in T. proctagon appears proportionately shorter. Clearer distinctions between these two species include the dorsodistal propodal spine on pereopods 2 and 3 (fine and small in T. guca , stout and curved in T. proctagon ), the length of pereonite 1 (one-third as long as pereonite 2 in T. guca , more than half as long in T. proctagon ), the length of the cephalothorax (1.4 times as long as wide in T. guca , as long as wide in T. proctagon ), and the proportions of the merus:carpus:propodus of pereopods 2 and 3 (carpus 1.3 times as long as wide in T. guca , 1.7 to 1.8 times as long as wide in T. proctagon ; propodus also apparently longer). The proximal dactylus seta on pereopods 1 to 3 may also be a distinction, but a redescription of T. proctagon is required to confirm such details. T. proctagon is a larger animal, Tattersall (1906), commenting on his 6 mm type, stating it to be “... one of the largest Tanaids, ...” (albeit incorrectly).

With the presence of the merus spine and their broad similarity, these two species form an effective morphogroup within Typhlotanais sensu lato, but as T. proctagon is being studied elsewhere, we refrain from considering a separate genus. The anteriorly-directed hyposphenium ventrally on pereonite 1 is not a useful taxonomic feature, as is found across a number of typhlotanaid genera, occurring also in Peraeospinosus kerguelensis ( Beddard, 1886) , Pulcherella spiniventris ( Dollfus, 1897) , Typhlotanais ( sensu lato) longimanus Dollfus, 1897 and “ Typhlotanais ” richardi Dollfus, 1897, inter alia.

The new species was collected from the Fiúza, Kidd and Mercator mud-volcanoes in the El Arraiche field on the Moroccan margin, at 355 to 526 m depth, and from the Jesus Baraza mud-volcano (type-locality) in the western Moroccan field at 1105 m, on muddy-substrata.

Figures

FIGURE 21. Typhlotanais guca sp. nov., Ƥ, A, antennule; B, antenna; Bˏ, tip of antenna; C, labrum; D, right mandible; E, left mandible; F, maxillule; Fˏ, maxillule palp; G, maxilla; H, epignath; I, maxilliped. cale lines: A – B = 0.1 mm; C – I = 0.01 mm.

FIGURE 22. Typhlotanais guca sp. nov., A, cheliped; B pereopod 1; C, pereopod 2; D, pereopod 3; E, pereopod 4; F, pereopod 5; G, pleopod; H, uropod. Scale lines = 0.1 mm.