Paratyphlotanais alveolus Błażewicz-Paszkowycz 2007, n. sp.

Paratyphlotanais alveolus n. sp. (Figs 8–10)

Material examined: Holotype: one female, (K 41390), ANT XXII-3, PS 67/74-6-E, 71°18.35’– 71°18.28’S, 13°57.71’– 13°57.31’W, depth 1030–1040 m, 20 Feb 2005; Paratypes: two females (one dissected on slides), (K 41387), ANT XXII-3, PS67/133-2-S, 62°46.49’– 62°46.38’S, 53°3.50’– 53°3.98’W, depth 1584– 1579 m, 16 Mar 2005; eight females, (K 41389), ANT XXII-3, PS 67/133-2-Epi, the same locality; one female, (K 41 391), ANT XXII-3, PS 67/80-9-Epi, 70°39.07’– 70°39.22’S, 14°43.36’– 14° 43.39’W, depth 3102– 3102 m, 23 Feb 2005; one female, (K 41449), ANT XXII-3, PS 67/80-9-S, the same locality; three mancae, (K 41388), ANT XXII-3, PS 67/74-6-S, 71°18.35’– 71°18.28’S, 13°57.71’– 13°57.31’W, depth 1030–1040 m, 20 Feb 2005.

Diagnosis (neuter/female): Paratyphlotanais with complex pereon outline; pereonite-1 depressed dorsally, with large hyposphaenium; pereonites 2 and 3 with hyposphaenium prominent; pereonites 4 and 5 with small hyposphaenium. Pereopods 1–2 coxa with large spur. Chelipeds gracile with one ventral carpal seta exceeding carpal width and with only two setae dorsally; meral and carpal spiniform setae of pereopods 1–3 only weakly serrate. Uropod endopod up to ten times as long as broad.

Etymology: Alveolus [Lat.] = cavity, tray, river-bed. The name alludes to the dorso-ventrally depressed form of pereonite-1.

Description: Non-ovigerous female body length 2.8 mm (Fig. 8A,B). Cephalothorax 15% of total length, 1.5 times as long as basal width; rostrum pointed, overlapping base of antennules. Pereonites 1–3 narrower caudally; pereonites 4 and 5 rounded; pereonite-6 narrowest rostrally; pereonite-1 four times wider than long, depressed at middle; pereonites width: length ratios: 3.5, 1.5, 1.2, 1.2, 1.0, 1.4 respectively; large sternal hyposphaenium on pereonite-1, prominent hook on each of pereonites 2 and 3, and small hook on each of pereonites 4 and 5. Pleon 22% of body length, little longer than carapace. Pleotelson (Fig. 10H) rectangular, just longer than two preceding pleonites, with modest apex.

Antennule (Fig. 9A): Almost 0.6 times length of cephalothorax; article-1 twice as long as wide, 1.4 times as long as articles 2 and 3 combined, with four setae along margin and one long (longer than article-2) simple seta and two pinnate setae distally; article-2 half as long as article-3, with one long (just as article-3) distal seta; article-3 with terminal spur and four simple setae distally.

Antenna (Fig. 9B): Article-2 three times as long as article-3, with dorsal seta; article-3 naked; article-4 with two long, one short and one pinnate setae distally, 4.5 times as long as wide; article-5 with one terminal seta; article-6 with four setae.

Mouth parts: Labrum (Fig. 9C) with rounded, setose distal margin. Mandible (Fig. 9D,E) molar broad with crenulated margin, and crenulated incisor; left mandible with broad lacinia mobilis. Maxillule endite (Fig. 9F) with eight distal setae; palp (Fig. 9 F’) with two terminal setae. Maxilla (Fig. 9G) oval. Labium (Fig. 9H) with inner lobe setose distally and with minute setae along margin on outer lobe. Maxilliped (Fig. 9I) basis 1.5 times as long as wide, with long seta reaching over endites distally; endites with one tubercle and one seta on distal margin; palp four-articled: article-1 naked; article-2 wedge-shaped, with three setae on inner margin and one relatively long seta on outer margin; article-3 with three long and one short setae on inner margin; article-4 shorter than article-3 with four long and two short setae distally.

Cheliped (Fig. 10A): Basis over twice as long as wide; merus triangular with long ventral seta; carpus three times as long as broad, with two small setae dorsally and two subequal, long setae and one minute seta ventrally; propodus and fixed finger slender, about three times as long as broad; dactylus about 0.7 times as long as propodus, with one seta near insertion of dactylus; fixed finger with three setae on strongly calcified inner margin and two setae on ventral margin; dactylus little shorter than fixed finger, with small setae in proximal part of dorsal margin.

Pereopod-1 (Fig. 10B): Coxa with one seta on spur; basis slender 6.5 times as long as broad, a little longer than merus and carpus combined, with proximal seta ventrally; ischium with small seta; merus about twice as long as broad, with spiniform ventral seta and simple dorsal seta; carpus little longer than merus, 2.3 times as long as broad, with spiniform dorsal seta and four minute setae distally; propodus about five times as long as broad, with one short serrate and one simple seta distally; dactylus and unguis about as long as propodus, unguis longer than dactylus.

Pereopod-2 (Fig. 10C): Coxa with one seta; basis slender, about six times as long as broad, with proximal and distal seta dorsally; ischium with small seta; merus about twice as long as broad, with ventral spine and two setae distally; carpus as long as merus, with two spiniform and five minute setae distally; propodus about 1.5 times as long as carpus, with one disto-dorsal spiniform seta and one minute seta ventrally; dactylus and unguis together as long as propodus.

Pereopod-3 (Fig. 10D): Similar to pereopod-2, but coxa without prominent spur, basis with one seta ventrally.

Pereopod-4 (Fig. 10E): More robust than pereopods 1–3; basis three times as long as wide, as long as merus, carpus and propodus combined, naked; ischium with one seta; merus, with two spiniform ventral serrate setae; carpus almost as long as merus, three times as long as broad, with four spiniform setae (one longer than the others); propodus little longer than carpus, with two spiniform setae on ventral margin and one spiniform seta distally; unguis 0.3 times dactylus length, combined 0.6 times propodus length.

Pereopod-5: similar to pereopod-4.

Pereopod-6 (Fig. 10F): Basis about three times as long as wide and almost as long as merus, carpus and propodus combined, with one pinnate seta ventrally; ischium with one seta; merus with two spiniform serrated setae ventrally; carpus almost as long as merus, twice as long as broad, with four spiniform setae and two short simple setae distally; propodus longer than carpus, with one spiniform seta subdistally on ventral margin and three spiniform setae distally reaching half of dactylus; unguis and dactylus 0.3 times as long as of propodus; unguis 0.3 times as long as dactylus.

Pleopods (Fig. 10G): Both rami subovate, with proximal seta separated from the others; endopod with ten plumose setae, exopod with twenty plumose setae.

Uropods (Fig. 10H): Very slender, nearly twice as long as pleotelson; endopod two-articled, proximal article 0.7 times length of ramus, ten times as long as broad; exopod one-articled almost as long as proximal article of endopod; setation as figured.

Distribution: Antarctic: Eastern Weddell Sea and line between tip of Antarctic Peninsula and Southern Orkney Island, at depths of 1030–3102 m.

Remarks: Paratyphlotanais alveolus n. sp. has a transverse depression on first pereonites. This unique character allows immediate recognition of the species; equally it is the only species with a coxal spur present only on the first pereopod.