Paratyphlotanais colouros, 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 : 175-179

Paratyphlotanais colouros sp. nov.

Figures 117–119

Material examined. 1 (J58551), holotype, 3 (J58552), paratypes, Eastern Bass Strait , 82 km ENE of North Point, Flinders Island, Stn BSS36 , 39º27.7'S 148º51.4'E, 293 m depth, coarse sand, 28 March 1979; coll. G.C.B. Poore ; 1 (J58553), paratype, Eastern Bass Strait , 67 km ENE of North Point, Flinders Island, Stn BSS38 , 39º22.4'S 148º38.7'E, 73 m depth, coarse sand, 29 March 1979; coll. G.C.B. Poore ; 2 (J58554), paratypes, Central Bass Strait , 44 km NE of Cape Wickham , King Island, Stn BSS203 , 39º22.0'S 144º18.3'E, 60 m depth, coarse sand, 23 November 1981 ; coll. R.S. Wilson .

Description of female. Body ( Fig. 117A, B) relatively slender, holotype 1.6 mm long, 6.4 times as long as wide. Cephalothorax subrectangular, tapering towards anterior with slight triangular rostrum, 1.5 times as long as wide, naked, eyes absent. Pereonites wider than long, ventrally with anteriorly-pointed hyposphenia on pereonites 1 to 3; pereonite 1 shortest, 0.12 times as long as cephalothorax; pereonite 2 parallel-sided, 2.4 times as long as pereonite 1; pereonite 3 with convex margins, 1.3 times as long as pereonite 2; pereonites 4 and 5 subequal, twice as long as pereonite 2; pereonite 6 as long as pereonite 3 (all pereonites respectively 5.8, 2.5, 1.9, 1.3, 1.3 and 1.7 times as wide as long). Pleon with five free subequal pleonites bearing pleopods; each pleonite four times as wide as long. Pleotelson pentangular, as long as last two pleonites together and 1.6 times as wide as long, with four small distal setae.

Antennule ( Fig. 118A) stout, proximal article 1.7 times as long as wide, 1.2 times as long as distal two articles together, with four simple setae along inner margin, outer margin with one simple seta at mid-length and two penicillate and one simple setae distally; second article shorter than wide, one-quarter as long as first article, with one outer simple seta and single inner penicillate and longer simple distal setae; third article tapering, 2.5 times as long as second article, with five simple and one penicillate subdistal setae adjacent to apical spur sensu Bird (2004) .

Antenna ( Fig. 118B) of six articles, proximal article compact, naked; second article as long as wide, with dorsodistal seta; third article shorter than wide, 0.6 times as long as second article, with dorsodistal seta; fourth article longest, four times as long as third article and four times as long as wide, curved, with three simple and one penicillate distal setae; fifth article half as long as fourth article with one distal seta; sixth article minute with four distal setae.

Labrum ( Fig. 118C) rounded, hood-shaped, marginally setose. Left mandible ( Fig. 118D) with bilobed, crenulate pars incisiva and wide, crenulate lacinia mobilis, right mandible ( Fig. 118E) similar but without lacinia mobilis; pars molaris of both mandibles with strong, rounded marginal tubercles. Labium ( Fig. 118H) simple, finely setose on outer and inner-distal margins. Maxillule ( Fig. 118F) with eight distal spines, palp not recovered. Maxilla not recovered. Maxilliped palp ( Fig. 118G) first article naked, second article with one outer and three inner setae; third article with four inner setae in distal half of article; fourth article with five inner to distal setae and one outer subdistal seta; basis with single, long seta reaching past distal margin of endites; endites distally with one seta and slight tubercle, outer distal margin denticulate. Epignath ( Fig. 118I) elongate, linguiform, naked.

Cheliped ( Fig. 119A) basis not reaching back to anterior of pereonite 1 ventrally, 1.7 times as long as wide, with single dorsodistal seta; merus subtriangular with three ventral setae; carpus 2.2 times as long as wide, with two longer and one shorter mid-ventral setae, one mid-dorsal and one dorsodistal setae; propodus slender, palm 1.25 times as long as wide, fixed finger as long as palm, with two ventral setae, three setae on cutting edge; dactylus with fine proximal seta.

Pereopod 1 ( Fig. 119B) longer than others, coxa without apophysis, with seta; basis straight, slender, 4.5 times as long as wide, with two dorsal and one ventral simple setae in proximal third; ischium compact, with ventral seta; merus 0.3 times as long as basis, with two ventral and one dorsal simple distal setae; carpus 1.5 times as long as merus with distal crown of six simple setae; propodus 1.4 times as long as carpus, with two dorsal subdistal setae, shorter ventral subdistal seta; slender dactylus with proximal seta exceeding tip of dactylus, slender unguis 1.6 times as long as dactylus, both together as long as propodus. Pereopod 2 ( Fig. 119C) similar to pereopod 1, basis 4.8 times as long as wide, with three dorsal but no ventral setae; ischium with seta; merus with single dorsal and ventral distal simple setae, and ventrodistal spine; carpus 1.1 times as long as merus, with dorsodistal and mesiodistal simple setae, and two unequal ventrodistal spines, longer spine denticulate; propodus with one dorsal subdistal seta; dactylus and unguis together 0.9 times as long as propodus. Pereopod 3 ( Fig. 119D) similar to pereopod 2, basis with two dorsal and one ventral setae; carpus with dorsodistal spine half as long as carpus.

Pereopod 4 ( Fig. 119E) basis stouter than that of anterior pereopods, three times as long as wide; ischium with two ventrodistal setae; merus as long as carpus, with one denticulate slender ventrodistal spine and one seta; carpus with one dorsodistal setae and four ventrodistal denticulate spines; propodus 1.3 times as long as carpus, with one dorsodistal and two ventral subdistal denticulate spines; dactylus twice as long as curved unguis, both together 0.6 times as long as propodus. Pereopod 5 (not figured) as pereopod 4, but basis with ventral penicillate seta. Pereopod 6 ( Fig. 119F) basis stout, 2.4 times as long as wide; ischium with two ventrodistal setae; merus 0.9 times as long as carpus, with two denticulate slender ventrodistal spines; carpus with one dorsodistal setae and apparently three ventrodistal slender denticulate spines; propodus as long as carpus, with three dorsodistal setae and two ventral subdistal slender spines; dactylus slender, with ventral microtrichia, twice as long as curved unguis, both together 0.7 times as long as propodus.

Pleopods ( Fig. 119G) all alike, with naked basis, exopod shorter than endopod; endopod with subdistal inner seta, exopod without setae on inner margin, outer margins with respectively 10 and 15 plumose setae, proximal seta on both rami separated from others.

Uropod ( Fig. 119H) biramous, basis naked; exopod of one segment, less than half as long as proximal endopod segment, with one shorter and one longer distal setae; endopod of two segments, distal segment 0.6 times as long as proximal segment; proximal segment with one simple and two penicillate distal setae, distal segment with one subdistal and three distal simple setae.

Male. Unknown.

Etymology. From the Greek kolouros – “bobtailed”, alluding to the characterizing short uropod exopod of this species.

Remarks. The present species, with its pereopod spination, elongate and tapering cephalothorax, hyposphenia (sternal spurs) on the anterior pereonites and apical spur on the antennule, accords comfortably with the genus Paratyphlotanais , as most recently competently analyzed by Bird (2004), since when only one further species, P. alveolus Błażewicz-Paszkowycz, 2007 , has been described. P. colouros sp. nov. has a unique conformation for the genus being without coxal apophyses (spurs) and with a narrow pereonite 1 (less than half the length of pereonite 2). Of the nine species previously attributed to this genus (see Błażewicz-Paszkowycz, 2007) only P. gracilipes (Hansen 1913) from the Northeast Atlantic south of Iceland, P. pectinatus Bird, 2004 , from the Northeast Atlantic Margin and P. armatus ( Vanhöffen, 1914) from the Antarctic share the short pereonite 1, but the first two have coxal spurs, while the last has a cephalothorax shorter than pereonites 1 to 3 together.

Furthermore, none of those species has such a short uropod exopod in proportion to the endopod, being much longer than half the length of the proximal segment of the endopod compared with 0.4 times that length in P. colouros (note that the endopod of P. pectinatus is only known from the proximal segment, but the exopod is much longer than that segment and two-segmented: see Bird, 2004, fig.7f).

P. colouros was collected from the Central and Eastern Bass Strait at 60 to 293 m in coarse sand.