Parafilitanais vadosus, Błażewicz-Paszkowycz & Bamber, 2012

Błażewicz-Paszkowycz, M. & Bamber, R. N., 2012, The Shallow-water Tanaidacea (Arthropoda: Malacostraca: Peracarida) of the Bass Strait, Victoria, Australia (other than the Tanaidae), Memoirs of Museum Victoria 69, pp. 1-235 : 217-221

Parafilitanais vadosus sp. nov.

Figures 146–148 Material examined. 1 (J56378), holotype, Stn MSL-EG 41, Eastern Bass Strait, 11.7 km W of Pt Ricardo, 37º49.90'S 148º30.02'E, 29 m depth, 28 September 1990, coll. Marine Sciences Laboratory. Smith-McIntyre grab. 1 (J28486), paratype dissected, Stn MSL-EG 113, EasternBassStrait,2.9kmSE.ofCapeConran, 37º50.00'S 148º36.90'E, 29 m depth, coarse sand, February 1991, coll. N. Coleman, Smith-McIntyre grab. 1 (J56375), paratype, Stn MSL-EG 29, Eastern Bass Strait, 10.4 km ESE of eastern edge of Lake Tyers, 37º52.52'S 148º12.55'E, 38 m depth, 25 September 1990, coll. Marine Sciences Laboratory. Smith-McIntyre grab.

Description of female ( Fig. 146A, B). Body slender, holotype 1.45 mm long, nearly nine times as long as wide. Cephalothorax subrectangular, slightly narrower anteriorly with slight triangular rostrum, as long as wide, about as long as pereonites 1 and 2 together, naked, eyes absent. Pereonites 1 and 6 shortest, 0.43 times as long as cephalothorax; pereonites 2 to 5 subequal, pereonite 2 slightly longest, 1.4 times as long as cephalothorax, (all pereonites respectively 1.6, 1.2, 1.3, 1.3, 1.3 and 1.6 times as wide as long). Pleon with five free subequal cylindrical pleonites without pleopods; each pleonite 2.7 times as wide as long. Pleotelson pentangular, one-third length of pleon and as wide as long, with blunt distal apex.

Antennule ( Fig. 147A) of four articles, proximal article just over twice as long as wide, just shorter than distal three articles together, with simple distal seta; second article about 1.3 times as long as third article, with one simple and two penicillate outer distal setae; third article with two simple inner distal setae; fourth article 1.4 times as long as third, with five simple and two penicillate distal setae.

Antenna ( Fig. 147B) of six articles, proximal article compact, naked, fused to cephalothorax; second article stout, as long as wide, with dorsodistal seta; third longer than wide, with fine dorsodistal seta; fourth article longest, three times as long as third article, 5.4 times as long as wide, curved, with two simple and four penicillate distal setae; fifth article 0.3 times as long as fourth with one distal seta; sixth article minute with four distal setae.

Labrum not recovered. Left mandible ( Fig. 147C) with subtriangular, crenulate pars incisiva and linguiform, crenulate lacinia mobilis, right mandible ( Fig. 147D) without lacinia mobilis; pars molaris of both mandibles tapering abruptly with fine tooth-like protrusions around distal margin. Labium ( Fig. 147F) simple, distally slender, naked. Maxillule ( Fig. 147E) with nine finely-denticulate distal spines, palp not recovered. Maxilla not recovered. Maxilliped ( Fig. 147G) palp first and second articles with microtrichia on outer margin, second article with two shorter and one stout longer inner setae; third article with two inner setae in distal half of article; fourth with four inner to distal setae, and one outer subdistal seta; bases fused, naked; endites distally with outer microtrichia and inner rounded tubercle. Epignath not recovered.

Cheliped ( Fig. 147H) basis twice as long as wide, naked, posterior lobe small, sclerite large; merus with one ventral seta; carpus rounded, 1.2 times as long as wide, wider proximally, with one dorsodistal and two mid-ventral setae; propodus elongate, 1.4 times as long as wide, with two ventral setae, one inner and one outer mid-distal setae adjacent to dactylus articulation; fixed finger with three setae alongside cutting edge, distal spine with two adjacent tooth-like tubercles ( Fig. 147 H'); dactylus naked, shorter than fixed finger.

Pereopod 1 ( Fig. 148A) coxa with simple seta; basis four times as long as wide, naked; ischium compact with one ventral seta; merus, carpus and propodus subequal in length, merus with one slender ventrodistal spine, carpus with three fine distal setae, propodus with subdistal dorsal seta, dorsodistal spine-like apophysis, distal microtrichia and distal spine with denticulations in distal half; dactylus shorter than unguis, both together two-thirds as long as propodus. Pereopods 2 ( Fig. 148B) similar to pereopod 1, but basis with two dorsal penicillate setae, merus just longer than carpus; pereopod 3 ( Fig. 148C) similar to pereopod 2, basis with one penicillate seta.

Pereopod 4 ( Fig. 148D) coxa with seta, basis four times as long as wide with two penicillate setae; ischium with one ventral seta; merus just shorter than carpus, with two ventrodistal distally-denticulate spines; carpus with two fine dorsodistal setae, and one dorsodistal and two ventrodistal short, curved spines; propodus 1.3 times as long as carpus, with dorsodistal seta and spine-like apophysis, and two ventrodistal distally-denticulate spines; dactylus half as long as laterally-denticulate unguis, both together 1.2 times as long as propodus. Pereopod 5 ( Fig. 148E) as pereopod 4, but carpus with four distal spines and one dorsodistal seta; pereopod 6 ( Fig. 148F) as pereopod 5, but ischium with two setae, unguis as long as dactylus.

Pleopods absent.

Uropod ( Fig. 148H) uniramous, basis 1.5 times as long as wide, with one shorter and one longer outer distal (“exopodal”) setae, longer seta exceeding distal tip of endopod; proximal segment of endopod about twice as long as basis, 2.5 times as long as wide, with one simple and two penicillate distal setae; distal segment half as long as proximal segment, with one subdistal and five distal setae.

Male similar to female, but with pleopods: pleopod ( Fig. 148G) basis naked, endopod half as long as exopod, rami with four and seven distal setae respectively.

Etymology. From the Latin vadosus – shallow, this species being by far the shallowest recorded for the genus.

Remarks. The morphology of this species accords entirely with the diagnosis of the genus Parafilitanais as given by Larsen (2002), including the proportions of the cheliped and the pereopods, and the structure of the uropod, but excepting his statement that the fourth to sixth pereopod are without a coxa: coxae are present and unfused in this genus, as shown by the present specimen and by Larsen’s (loc. cit.) figures 1A and 1L.

Of the three previously-described species of the genus (see Larsen, 2005), Parafilitanais vadosus sp. nov. has a proportionately shorter pereonite 1 than does P. caudatus Kudinova-Pasternak, 1989 , a proportionately longer pleon than does P. similis Kudinova-Pasternak, 1990 , and is without the distally-flattened pleotelson and the extended cheliped dactylus of P. mexicana Larsen, 2002 . In addition, the present species is distinct from all of the other three in having the distal segment of the uropod endopod about half as long as the proximal segment (>0.7 times in the others), and in the proportionately shorter dactylus and unguis of the anterior pereopods.

Parafilitanais vadosus was taken at 29 to 38 m depth in the Eastern Bass Strait. The previous species were all recorded in deep waters, P. caudatus at 3660 m in the Indian Ocean, P. similis at 750 m in the Pacific Ocean, and P. mexicana at 625–2030 m in the Gulf of Mexico.