Paratanais Dana

Larsen, Kim, Nagaoka, Ryoko & Froufe, Elsa, 2012, Tanaidacea (Crustacea) from Macaronesia III. The shallow-water Tanaidomorpha from the Cape Verde archipelago, Zootaxa 3498, pp. 24-44 : 34-38

Genus Paratanais Dana

Type species. Paratanais elongatus (Dana) .

Paratanais vicentetis n. sp. Larsen ( Figs. 7–8 )

Material examined. Holotype non-ovigerous female. Body length 3.5 mm. (Reg # MMF 42310), Mindelo marina, St. Vicente Island, 0.5 m depth, sandy bottom algae. Paratype (Reg # MMF 42311): one dissected non-ovigerous female, one manca III, same locality

Diagnosis. Antenna article 2 without setules or ventral process but with dorsal spiniform seta arising from a process; article 3 dorsal spiniform seta shorter half of article. Maxilliped palp article 2 without outer setae, with pronounced serrated spiniform inner seta; cheliped fixed finger with only one ventral seta (see remarks), propodus with broad leaf-shape setae at dactylus insertion, fixed finger with large blunt inner process with small medial depression; Pereopods 4–6 with three or four carpal spines. Pereopod 6 propodus with three pinnate dorsodistal setae. Uropods shorter than pleotelson; endopod pseudoarticulated.

Etymology. Named after the type locality, St. Vicente Island.

Description. Non-ovigerous female.

Body: ( Fig. 7 A,B) Stout, subcylindrical, less than seven times longer than broad. Cephalothorax: as long as pereonite 1 and 2 together. Pereonites wider than long. Pleon about 0.3 times as long as body. Pleonites 1–4 with setulated lateral setae on lateral shield; pleonite 5 with simple lateral seta. Pleotelson as wide as pleonites, marginally longer than last two pleonites combined.

Antennule ( Fig. 7 C): Length 0.8 times as long as cephalothorax. Article 1 shorter than combined length of articles 2–5, with one distal simple distal seta. Article 2 less than half as long as article 1, with one simple and three small setulated distal setae. Article 3 longer than half of article 2, with one simple distal seta. Article 4 longer than half of article 1 but only half as wide, with one simple distal seta. Article 5 minute, with four simple and one small setulated distal setae. No aesthetascs were observed, but this could be due to the rather poor condition of the material.

Antenna ( Fig. 7 D): 0.7 times as long as antennule. Article 1 narrower and shorter than article 2, naked. Article 2 marginally longer than article 3, with one simple ventrodistal and one dorso-subdistal setae arising from a process. Article 3 with large dorsal spiniform seta shorter than half of article. Article 4 longer than other articles, with one simple distal seta. Article 5 marginally shorter than article 3, with one simple distal seta. Article 6 length minute, with one short and four setae longer than half of antenna.

Mouthparts. Labrum ( Fig. 7 E) extending ventrally from clypeus, with scattered setules; clypeus with lateral setules and small spines. Mandibles molar process broad with heavily calcified denticles on apex. Left mandible ( Figs. 7 F,G) incisor as long as- but narrower than lacinia mobilis, of simple spine shape; lacinia mobilis trifurcate. Right mandible ( Fig. 7 H) incisor with four blunt crenulations on outer margin. Labium ( Fig. 7 I) with two lobes, lateral margins with small spines/setulation. Maxillule endite ( Fig. 7 J) outer margin with regularly spaced setules, with eight spiniform apical setae. Palp ( Fig. 7 K) biarticulate, first article twice as long as second, with two distal setae shorter than palp. Maxilla ( Fig. 7 L) tapering distally, naked. Maxilliped ( Fig. 7 M) basis with one inner distal seta. Palp article 1 naked. Article 2 without outer setae, with three bipinnate inner setae and robust serrated spiniform seta. Article 3 with four bipinnate setae. Article 4 with four pinnate inner setae and one outer subdistal simple seta. Endite ( Fig. 7 N) lateral and distal margin with regularly spaced spines, with one inner simple seta and two flat, rounded distal setae. Epignath not recovered.

Cheliped ( Fig. 8 A): basis divided by triangular sclerite, shorter than carpus, with one sub-dorsodistal simple seta. Merus triangular with one ventral seta. Carpus with two ventral and two dorsal setae. Propodus including fixed finger as long as basis, with one wide flat outer distal seta near dactylus insertion. Fixed finger with one ventral seta (see remarks) and three on inner margin; inner margin with large blunt inner process; unguis heavily calcified. Dactylus stout with one stout seta on dorsal margin and one on the ventral margin. Unguis with large denticle.

Pereopod 1 ( Fig. 8 B): length 1.5 times that of other pereopods. Coxa with one simple seta (not illustrated). Basis with one simple dorsoproximal seta. Ischium with one simple seta. Merus as long as carpus, naked. Carpus rectangular with two simple dorsodistal setae. Propodus longer than merus, with one ventro-subdistal simple seta and two dorso-subdistal setae of which one is bipinnate, and distal spine. Dactylus and unguis combined about as long as propodus. Dactylus shorter than unguis, with simple proximal seta.

Pereopod 2 ( Fig. 8 C): coxa with one simple seta (not illustrated). Basis with dorsoproximal seta. Merus with one spiniform and one simple ventrodistal setae. Carpus shorter than propodus, with two short ventrodistal and one longer dorsodistal spiniform setae, with one dorsodistal apparently simple seta. Propodus shorter than merus and carpus combined, with one ventro-subdistal simple seta and two dorso-subdistal setae, and distal spine. Dactylus and unguis combined shorter than propodus. Dactylus shorter than unguis, with simple proximal seta.

Pereopod 3 ( Fig. 8 D): similar to pereopod 2.

Pereopod 4 ( Fig. 8 E): basis twice as wide as on pereopod 1 to 3, with two dorsoproximal simple and three ventromedial setulose setae. Ischium with one seta. Merus longer than carpus, with two bifurcate ventrodistal spiniform setae and ventral scales. Carpus with four spiniform setae, either bifurcate or with subdistal ring of spinules, and one dorsal bone-shaped distal seta, and ventral scales. Propodus with one dorsomedial setulated, one dorsodistal rigid, and two ventrodistal spiniform setae. Dactylus and unguis combined shorter than propodus, shape as a claw but incompletely fused. Dactylus apparently naked, twice as long as unguis.

Pereopod 5 ( Fig. 8 F): similar to pereopod 4.

Pereopod 6 ( Fig. 8 G): similar to pereopod 5 except: basis naked. Carpus with only three spiniform setae (potentially an artefact), either bifurcate or with subdistal ring of spinules, one dorsal bone-shaped distal seta, and ventral scales. Propodus with three rigid bipinnate dorsodistal setae and two ventrodistal spiniform setae.

Pleopods ( Fig. 7 H): all five pairs similar. Basal square and naked. Exopod with 15 plumose outer setae, with gap between most proximal and other setae. Endopod with one inner and nine outer plumose setae of which the most distal have a modified curved tip with a seemingly unequally length bifurcate apex (unlike the one in Leptochelia ); large gap present between most proximal and other setae.

Uropods: ( Figs. 7 I): basal article naked. Endopod only as long as basal article, with partly fused articles; pseudoarticle 1 as long as exopod, with one simple setulose distal seta; pseudoarticle 2 with four long (longer than uropod) simple, and one shorter simple and one short setulated setae. Exopod uniarticulate with one medial simple seta, one simple distal seta, and one simple seta longer than endopod.

Remarks. This species is unique for the genus by the combination of a pronounced antenna article 2 dorsal process; the cheliped fixed finger with only one seta (see below); a maxilliped palp article 2 without outer setae, the serrated spiniform seta on same article is also remarkably large and robust; and the presence pleopodal endopod inner seta. The new species also differs from the two recently described species of Paratanais , from the Mid- Atlantic, P. martinsi Bamber & Costa and P. pseudomartinsi Larsen , by the much stouter and partly fused uropodal endopod as well as the lack of a ventral process on antenna article 2 (but with a small dorsal one instead).

This species is morphologically close to P. denticulatus Guţu & Ramos, P. s p i n a n o t a n d u s Sieg, and P. malignus Larsen but it differs from P. denticulatus and P. malignus by the pronounced dorsal process on antenna article 2, although the illustrations of P. denticulatus indicate a small gently curved process is present ( Guţu & Ramos 1995:41,fig.6C). The new species also differs by the presence on pereopod 6 of only three pinnate dorsodistal setae, although this could be an artefact. From P. spinanotandus the new species differs by the presence of only one seta on the ventral margin of the cheliped fixed finger and much shorter pereopod 1 merus. The former character would be considered an artefact by most specialists (the current authors among them). However, only a single seta was observed on both chelipeds of the holotype as well as both chelipeds of the paratype, making the ‘artefact’ explanation statistically unlikely. Paratanais paraoa Bird also has a small dorsal process on the antenna article 2 but differs in also having setules and an additional ventral process ( Bird 2011:36, fig.18F). From other species of the genus, the new species can be separated by the same characters as described for P. martinsi ( Bamber & Costa 2009:192)

Figures

FIGURE 7. Paratanais vicentetis n. sp., female. A – B holotype, scale bar 1.0 mm. C – N paratype, Scale bars 0.1 mm. A, dorsal view. B, lateral view. C, antennule. D, antenna. E, labrum. F, left mandible, incisor & lacinia mobilis. G, same, molar. H, right mandible. I, labium. J, maxillule, endite. K, same, palp. L, maxilla. M, maxilliped. N, same endite.

FIGURE 8. Paratanais vicentetis n. sp., paratype, female. A, cheliped. B, pereopod 1. C, pereopod 2. D, pereopod 3. E, Pereopod 4. F, pereopod 5. G, pereopod 6. H, pleopod. I, uropod. Scale bar 0.5 mm.