Pseudotanais (Pseudotanais) falcifer, Błażewicz-Paszkowycz, Magdalena & Bamber, Roger N., 2011

Błażewicz-Paszkowycz, Magdalena & Bamber, Roger N., 2011, Tanaidomorph Tanaidacea (Crustacea: Peracarida) from Mud-Volcano and Seep Sites on the Norwegian Margin, Zootaxa 3061, pp. 1-35 : 3-9

publication ID	https://doi.org/ 10.5281/zenodo.278931
DOI	https://doi.org/10.5281/zenodo.6186193
persistent identifier	https://treatment.plazi.org/id/03DF8762-FFCF-FFAD-FF0A-7D20FDC4C602
treatment provided by	Plazi
scientific name	Pseudotanais (Pseudotanais) falcifer
status	sp. nov.

Treatment

Pseudotanais (Pseudotanais) falcifer View in CoL sp. nov.

( Figs 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Material examined. Holotype, Ƥ (MNHN-IU- 2010-2806), Vicking, PL272-2, GCL 1, G11 Nyegga, 64°39.996ʹN 05°17.346ʹE, 736 m, 25/05/2006. Paratypes: 152 specimens (15 adult females, 15 subadult females, 29 juveniles, 63 manca-1, 26 manca-2, 4 males) (in ethanol, MNHN-IU- 2010-2807), 41 adult ƤƤ, 123 subadult ƤƤ (1 dissected), 4033 (1 dissected), 297 juveniles, 437 manca 1, 261 manca 2 (MNHN-MNHN-IU- 2010-2808), 1 subadult Ƥ (dissected ion three slides) (MNHN-IU- 2010-2809), Vicking, PL272-2, GCL 1, G11 Nyegga, 64°39.996ʹN 05°17.346ʹE, 736 m, 25/05/2006; 1Ƥ with oostegites (MNHN-IU-2010-2810), Vicking, PL272-2, ASPI 4, G11 Nyegga, 64°39.991ʹN 005°17.346ʹE, 733 m, 25/05/2006; 15ƤƤ (2 brooding, 7 with oostegites), 3 mancae (MNHN-IU- 2010-2811), Vicking, PL272-2, ASPI 5, G11 Nyegga, 64°39.998ʹN 005°17.347ʹE, 736 m, 25/05/2006; 1 specimen (MNHN-IU- 2010-2812), Vicking, PL272-2, ASPI 8, G11 Nyegga, 64°39.980ʹN 05°17.351ʹE, 733 m, 26/05/2006; 1 specimen (MNHN-IU- 2010-2813), Vicking, PL275-5, ASPI 6, Storegga NE, 64°45.271ʹN 04°58.870ʹE, 746 m, 01/06/2006; 1Ƥ with oostegites (MNHN-IU- 2010-2814), Vicking, PL275-5, GTB3, Storegga NE, 64°45.273ʹN 04°58.871ʹE, 745 m, 31/05/2006; 1Ƥ with oostegites, 1 juvenile (MNHN-IU- 2010-2815), Vicking, PL275-5, GTB2, Storegga NE, 64°45.276ʹN 05°04.149ʹE, 722 m, 01/06/2006; 2ƤƤ with oostegites, 1 juvenile (MNHN-IU- 2010-2816), Vicking, PL276-6, ASPI 6, HMMV, 72°00.187ʹN 14°43.901ʹE, 1258 m, 04/06/2006; 12ƤƤ (5 with oostegites), 11 juveniles, 1 manca (MNHN-IU- 2010-2817), Vicking, PL276-6, ASPI 7, HMMV, 72°00.183ʹN 14°43.908ʹE, 1258 m, 04/06/2006; 2ƤƤ, 23, 7 juveniles (MNHN-IU- 2010-2818), Vicking, PL276- 6, ASPI 8, HMMV, 72°00.184ʹN 14°43.908ʹE, 1258 m, 04/06/2006; 4 juveniles (MNHN-IU-2010-2820), Vicking, PL276-6, PBT3, HMMV, 72°00.166ʹN 14°43.922ʹE, 1258 m, 04/06/2006; 1 subadult Ƥ (MNHN-IU- 2010-2821), Vicking, PL277-7, ASPI 3, PP-V16 HMMV, 72°00.335ʹN 14°42.732ʹE, 1264 m, 06/06/2006; 1 specimen (MNHN- IU- 2010-2822), Vicking, PL277-7, ASPI 4, PP-V16 HMMV, 72°00.336ʹN 14°42.723ʹE, 1263 m, 06/06/2006; 1 specimen (MNHN-IU- 2010-2823), Vicking, PL277-7, ASPI 8, PP-V16 HMMV, 72°00.336ʹN 14°42.746ʹE, 1263 m, 06/06/2006; 2ƤƤ, 13 (MNHN-IU- 2010-2824), Vicking, PL277-7, CL7, PP-V16 HMMV, 72°00.335ʹN 14°42.758ʹE, 1261 m, 06/06/2006; 1Ƥ, 13 (MNHN-IU- 2010-2825), 1Ƥ (MNHN-IU- 2010-2826), 4 specimens (MNHN-IU- 2010-2827), Vicking, MTB-5, HMMV, 72°00.177ʹN 14°43.958ʹE, 1272 m, 07/06/2006; 998 specimens (MNHN-IU- 2010-2828), ARK 22-1, PL170-7, CL21, HMMV, 72°00.34ʹN 14°43.22ʹE, 1259 m, 03/07/2007; 277 specimens (MNHN-IU- 2010-2829), ARK 22-1, PL170-7, CL12, HMMV, 72°00.34ʹN 14°43.22ʹE, 1259 m, 03/ 07/2007; 501 specimens (MNHN-IU-2010-2830), ARK 22-1, PL170-7, CL22, HMMV, 72°00.34ʹN 14°43.22ʹE, 1259 m, 03/07/2007; 1 3 (1 slide, MNHN-IU- 2010-2831) Vicking, PL276-6, ASPI 7, HMMV, 72°00.183ʹN 14°43.908ʹE, 1258 m, 04/06/2006; 1 3 (MNHN-IU- 2010-2832), Vicking, PL277-7, CL7, PP-V16 HMMV, 72°00.335ʹN 14°42.758ʹE, 1261 m, 06/06/2006; 5 specimens (MNHN-IU- 2010-2833), Vicking, PL276-6, ASPI 7, HMMV, 72°00.183ʹN 14°43.908ʹE, 1258 m, 04/06/2006.

Description of female. Holotype length 2.4 mm, body ( Fig. 1 View FIGURE 1 A) five times as long as wide. Cephalothorax subtriangular, 1.1 times as wide as long, 1.3 times as long as first three pereonites, naked; eyes absent. Pereonites, mostly with convex lateral margins; pereonite 1 shortest, 0.15 times as long as cephalothorax; pereonite 2 1.5 times as long as pereonite 1, pereonite 3 about 1.6 times as long as pereonite 2, pereonite 4 longest, twice as long as pereonite 3; pereonite 5 with straight sides, 0.85 times as long as pereonite 4; pereonite 6 three times as long as pereonite 1 (all pereonites respectively 7.3, 5, 3, 1.4, 1.6 and 2.4 times as wide as long). Pleon of five free subequal pleonites bearing pleopods plus pleotelson; pleonites 5.7 times as wide as long. Pleotelson semicircular, short, 3 times as long as pleonite 5, 1.6 times as wide as long.

Antennule ( Fig. 2 View FIGURE 2 A) proximal article 4.5 times as long as wide, 1.5 times as long as distal two articles together, with outer medial and distal tufts of penicillate and simple setae, longest distal seta longer than second article; second article 0.3 times as long as first, with outer distal simple seta almost as long as article and single smaller inner simple and penicillate distal setae; third article just longer than second, with six simple distal setae and one aesthetasc; tips of some terminal antennular setae bifurcate ( Fig. 2 View FIGURE 2 Aʹ).

Antenna ( Fig. 2 View FIGURE 2 B) of six articles, proximal article compact, naked; second article with fine dorsodistal spine; third article 1.2 times as long as second with fine dorsodistal spine; fourth article curved, nearly three times as long as third, and five times as long as wide, with three simple and three penicillate distal setae; fifth article twice as long as third with distal seta; sixth article minute with four distal setae.

Labrum ( Fig. 2 View FIGURE 2 C) rounded, hood-shaped, naked. Left mandible ( Fig. 2 View FIGURE 2 D) with smooth cutting edge on pars incisiva, large, triangular, crenulate lacinia mobilis, pars molaris a very slender spike with simple point, curved proximally at right angles; right mandible ( Fig. 2 View FIGURE 2 E) pars incisiva distally serrated and with bifid tip. Labium ( Fig. 2 View FIGURE 2 H) bilobed, squared, naked. Maxillule ( Fig. 2 View FIGURE 2 F) endite with nine slender distal spines and one subdistal seta; palp ( Fig. 2 View FIGURE 2 F’) with two unequal distal setae. Maxilla ( Fig. 2 View FIGURE 2 G) subtriangular, naked. Maxilliped ( Fig. 2 View FIGURE 2 I) endites flared, distal third unfused, each with slight distal tubercles and small subdistal seta; palp first article naked, second article with slender outer distal spine, distally with one simple and one finely-denticulate inner setae; third article with three distally-finely-denticulate and one simple inner setae; fourth article with five distal finely-denticulate setae and one subdistal outer simple seta; basis with single short seta. Epignath not recovered.

Cheliped ( Fig. 3 View FIGURE 3 A) sclerite attachment well-developed, basis 1.6 times as long as wide, with dorsodistal outer seta; merus subtriangular, with single mid-ventral seta; carpus 1.6 times as long as wide, with one shorter and one longer mid-ventral setae, and dorsodistal and dorso-sub-proximal single setae; chela not forcipate, propodus palm as long as fixed finger, with ventral seta distal to fixed finger origin, small seta in axis of chela, comb-row of six spines; fixed finger slender, cutting edge with three distal setae; dactylus with fine dorsoproximal seta and two spinules distally on cutting edge.

Pereopod 1 ( Fig. 3 View FIGURE 3 B) slender; coxa simple with one seta; basis 5.8 times as long as wide; ischium with single small ventral seta; merus short, about half as long as carpus, naked; carpus with single inner distal and dorsodistal setae; propodus 1.8 times as long as carpus with ventroproximal seta and slight pointed dorsodistal apophysis; dactylus just over half as long as slender unguis, both together 1.1 times as long as propodus.

Pereopod 2 ( Fig. 3 View FIGURE 3 C) somewhat more compact, basis 5.4 times as long as wide with single dorsal penicillate seta; ischium with single small seta; merus and carpus subequal in length, merus with paired ventrodistal setae, carpus with single dorsodistal seta and large, blade-like, distally-denticulate ventrodistal spine; propodus 1.5 times as long as carpus, with distal spine longer than dactylus but not reaching half length of unguis, dactylus plus longer unguis 0.8 times as long as propodus. Pereopod 3 ( Fig. 3 View FIGURE 3 D) similar to pereopod 2, merus stouter, propodus 1.25 times as long as carpus.

Pereopod 4 ( Fig. 3 View FIGURE 3 E) basis 4.1 times as long as wide with single ventral penicillate seta; ischium with two setae; merus one-third as long as carpus, with two fine ventrodistal simple spines, carpus with two dorsodistal setae, inner–distal seta and blade-like, distally-denticulate ventrodistal spine (as that on pereopod 5, Fig. F’); propodus 1.1 times as long as carpus with one long dorsodistal seta 0.8 times as long as propodus and twice as long as dactylus plus unguis, paired ventrodistal setae, and dorsal penicillate seta; dactylus and unguis not fused into claw, dactylus with inner distal denticulation and outer distal spine-like apophysis ( Fig. 3 View FIGURE 3 E’), unguis 0.25 times as long as dactylus, both together 0.4 times as long as propodus. Pereopod 5 ( Fig. 3 View FIGURE 3 F, F’) similar to pereopod 4. Pereopod 6 ( Fig. 3 View FIGURE 3 G) as pereopod 4, but propodus with two simple distal setae, dactylus with distal crown of spinules ( Fig. 3 View FIGURE 3 G’).

Pleopods ( Fig. 3 View FIGURE 3 H) all alike, with naked basis, exopod larger than endopod, with six distal plumose setae; exopod with four distal plumose setae.

Uropod ( Fig. 3 View FIGURE 3 I) basis naked, endopod of two partially fused segments, proximal segment with one simple and one penicillate distal setae, distal segment with five simple and two penicillate setae; exopod of one segment, half as long as endopod, single outer subdistal seta and paired distal unequal setae.

Distinctions of juvenile female: body ( Fig. 1 View FIGURE 1 B) smaller and more compact than adult, 1.3 mm long, 3.8 times as long as wide. Cephalothorax tapering slightly less than that of adult female, 0.8 times as long as wide. Pereonites 4 and 5 subequal in length, twice as wide as long, pereonite 6 as long as pereonite 3.

Description of male: ( Fig. 1 View FIGURE 1 C) similar to (but smaller than) female, 0.8 mm long, 4.9 times as long as wide. Cephalothorax with indentations anterior to branchial chambers, eyes absent. Pereonites 4 and 5 subequal in length, pleon ovoid rather than parallel-sided.

Antennule ( Fig. 4 View FIGURE 4 A) peduncle more compact than that of female; first article 2.3 times as long as wide with three fine and one longer outer-distal setae; second article 0.6 times as long as first and with single inner-distal seta, outer-distal corner with long simple seta and three penicillate setae; third article 0.74 times as long as second, with single inner-distal seta; flagellum of four segments, first segment very short, much wider than long, with five or six ventral aesthetascs, second segment much longer than wide but shorter than third peduncle article with four ventrodistal aesthetascs, third segment with four aesthetascs, fourth article with three distal aesthetascs and four setae. Antenna similar to that of female.

Mouthparts highly reduced: maxillule ( Fig. 4 View FIGURE 4 D) without endite, palp with two distal setae; maxilliped ( Fig. 4 View FIGURE 4 C) bases and endites naked, palp with simple setae much longer and more slender than in female, articles 1 to 3 with as many setae as in female, article 4 with four distal setae; epignath slender, twisted, naked.

Cheliped ( Fig. 4 View FIGURE 4 B) somewhat more robust than that of female, propodus much larger than carpus with distal comb–row of 16 spines. Other appendages not noticeably different from those of female.

Etymology. From the Latin, falcifer , “scythe-carrying”, referring to the recurved pars molaris on the mandible (noun in apposition).

Remarks. The Pseudotanaidae of the North-East Atlantic and Mediterranean were reviewed comprehensively by Bird and Holdich (1989a), since when the only new species described from this region was Pseudotanais (P.) stiletto Bamber, 2009 (vide Bamber et al. 2009), from muddy substrata at 25–62 m depth off the Mediterranean coast of Israel.

With a blade-like distal spine on the carpus of pereopods 2 to 6, a non-forcipate chela, and a ventrodistal spine on the propodus of pereopods 2 and 3, which is much shorter than the dactylus and unguis combined, the present species is of the nominate subgenus, but not a member of the “ P. forcipatus -group” nor of the “ P. affinis -group” of Bird and Holdich (1989a). From their identification key, it keys out as, and indeed it is closest to, P. colonus Bird and Holdich 1989b , a species known only from recolonization experiments in the northern Bay of Biscay at 2150 m. Pseudotanais falcifer sp. nov. is distinguished from P. colonus by its much lower differentiation in habitus between the sexes (males of P. colonus having all pereonites subequal in length), by having more-attenuate articles in the antennule (proximal article in P. colonus being 3.3 times as long as wide compared with 4.5 times in P. falcifer ), slender (as opposed to stout, robust) spines on the second and third peduncle articles of the antenna, a downcurved (as opposed to straight) pars molaris on the mandibles, subdistal setae on the maxilliped endites (naked in P. c o l o n u s), and two setae on the ischium of the posterior pereonites (only one seta in P. colonus ), inter alia. P. falcifer is immediately distinguished from P. stiletto as the latter has a straight pars molaris on the mandible, and a two-segmented uropod exopod.

Pseudotanais falcifer differs from the other species of Pseudotanais recorded from the Norwegian-Arctic region, viz. P. m a c ro c h e l e s Sars, 1882, P. lilljeborgi Sars, 1882 and P. corollatus Bird & Holdich, 1989 , by onesegmented uropod exopod (these other three having two segments) and shorter uropod endopod distal article, a less elongate distal antennule article, a shorter merus on pereopod 1 (half as long as the carpus, compared with 0.7 to 0.8 times as long in the other three), the downcurved pars molaris on the mandibles, and additionally from P. m a c ro c h e l e s in having the chela fingers not longer than the palm.

Pseudotanais falcifer was taken over a depth range of 722 to 1263 m, at the HMMV, Storegga and Nyegga sites, including sympatrically with P. affinis .