Araphura yarra, 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 : 135-139

Araphura yarra sp. nov.

Figures 90–92

Material examined. 1 (J58836), holotype, Stn BSS 155 , Central Bass Strait, 38 km SW of Cape Paterson, 38º55.5'S 145º17.00'E, 70 m depth, fine sand, 12 November 1981 ; coll. R.S. Wilson; 1 (J58845) , paratype, Stn VC 31 C1, Central Bass Strait, 38º02.52'S 146º10.47'E, 40 m depth, 14 May 1999; coll. N. Coleman ; 1 (J56681), paratype, Stn VC 18 C2, Central Bass Strait, 38º30.2'S 144º15.00'E, 40 m depth, 13 May 1998; coll. N. Coleman. 1 (J28487), paratype, Stn MSL-EG 118, Eastern Bass Strait, 10.8 km E of eastern edge of Lake Tyers, 37º50.92'S 148º12.83'E, 25 September 1990, coll. N. Coleman (depth not available) . 1 (J58837), paratype, Stn BSS 197 , Western Bass Strait, 4 km SSW of Currie, King Island, 40º00.7'S 143º49.9'E, 46 m, 21 November 1981 , coll. R. S. Wilson,Smith-McIntyre Grab .

Description of female. Body ( Fig. 90A, B) slender, holotype 1.9 mm long, 8.8 times as long as wide. Cephalothorax subrectangular, narrowing anteriorly with slight rounded rostrum, 1.6 times as long as wide, 2.5 times as long as pereonite 1, naked, eyes absent. Pereonites all naked and rectangular; pereonites 1 and 6 subequal in length; pereonites 2 to 5 subequal, 1.5 times as long as pereonite 1 (all pereonites respectively 1.6, 1.0, 1.2, 1.0, 0.9 and 1.3 times as wide as long). Pleon of five free subequal pleonites bearing pleopods, plus pleotelson; each pleonite 3.6 times as wide as long. Pleotelson subrectangular, as long as last three pleonites together, 1.2 times as wide as long, without mid-distal process, but with disto-marginal tubercle adjacent to attachment of each uropod ( Fig. 90D).

Antennule ( Fig. 91A) of four articles, proximal article 2.8 times as long as wide, longer than distal three articles together, with single outer distal simple and penicillate setae; second article longer than wide, 0.35 times as long as first article, outer distal margin with one penicillate and one longer simple setae, latter longer than article; third article as long as wide, 0.6 times as long as second article, with two simple mesial setae; fourth article tapering, 1.3 times as long as third, with five simple distal setae.

Antenna ( Fig. 91B) of six articles, proximal article compact, fused to cephalothorax; second article 1.3 times as long as wide, with two dorsodistal setae; third article as long as wide, just shorter than second article, with single simple dorsodistal seta; fourth article longest, 3.6 times as long as wide, nearly three times as long as third article, with single distal simple and penicillate seta setae; fifth article as long as second, with one distal simple seta; sixth article minute with five distal setae.

Labrum ( Fig. 91C) rounded, hood-shaped, naked. Left mandible ( Fig. 91D) with bilobed pars incisiva and tridentate linguiform lacinia mobilis, right mandible ( Fig. 91E) with tridentate pars incisiva and without lacinia mobilis; pars molaris of both mandibles stout, with fine distal denticulations, ventralmost longest. Labium ( Fig. 91H) simple, outer distal corner slightly setose. Maxillule ( Fig. 91F) with eight finely-denticulate distal spines, palp with two relatively short distal setae. Maxilla not recovered. Maxilliped ( Fig. 91G) palp first article naked, second article with one outer and three distal inner setae, third article with two longer mesial and two shorter distal inner setae, fourth article with four distal setae and one small subdistal outer seta, ventral microtrichia; basis naked; endites distally with single inner setae but no tubercles. Epignath ( Fig. 91I) ribbon-like, naked.

Cheliped ( Fig. 92A) sclerite with triangular insertion into basis; rounded, naked basis 2.2 times as long as wide, with conspicuous proximal extension but not reaching to pereonite 1 ventrally ( Fig. 90C); merus subtriangular with single ventral seta shorter than width of merus, and covering about one-third of ventral margin of carpus; carpus nearly twice as long as wide, dorsal margin convoluted, with one longer and one shorter midventral setae, one dorsodistal seta and one dorsoproximal seta; propodus 1.2 times as long as wide, with two ventral setae, outer face with two submarginal tooth-like tubercles, inner comb-row of three setae; fixed finger with three setae below cutting edge, cutting edge with rounded crenulations; dactylus with dorsal rounded tubercles.

Pereopod 1 ( Fig. 92B) not longer than others, coxa without apophysis, with seta; basis 3.4 times as long as wide, naked; ischium compact, without seta; merus 1.4 times as long as carpus, ventrodistally with distally-denticulate spine exceeding half length of carpus; carpus distally with single distally-denticulate spines dorsally, mesially and ventrally; propodus 1.4 times as long as carpus, with subdistal seta, ventrodistal spine, distal microtrichia and dorsodistal spinous apophysis; dactylus naked, unguis 1.8 times as long as dactylus, both together as long as propodus. Pereopod 2 ( Fig. 92C) similar to pereopod 1, basis 3.8 times as long as wide; ischium with seta; merus 1.2 times as long as carpus; propodus 1.5 times as long as carpus and with ventral fields of microtrichia; dactylus and unguis together 0.9 times as long as propodus. Pereopod 3 (not figured) similar to pereopod 2.

Pereopod 4 ( Fig. 92D) coxa naked, basis 3.6 times as long as wide with midventral penicillate seta; ischium with ventral seta; merus as long as carpus, with two ventrodistal distally-denticulate spines; carpus with three distal distally-denticulate spines; propodus 1.3 times as long as carpus, with ventral fields of microtrichia, three distal distally-denticulate spines, distal microtrichia and dorsodistal spinous apophysis; dactylus 0.8 times as long as unguis, dactylus and unguis not fused into a claw, the two together 1.2 times as long as propodus. Pereopod 5 ( Fig. 92E) as pereopod 4, but basis somewhat stouter, propodus only just longer than carpus. Pereopod 6 ( Fig. 92F) as pereopod 5, but basis without penicillate seta, propodus with two ventral and three dorsal distal spines.

Pleopods ( Fig. 92G) all alike, with naked basis, endopod and exopod without setae on inner margin, outer-distal margins with respectively 7 and 9 plumose setae, exopod with additional separated proximal plumose seta.

Uropod ( Fig. 92H) basis naked, exopod process half as long as proximal endopod segment, with three distal setae; endopod of two segments, distal segment half as long as proximal segment, setose as figured.

Male.Unknown.

Etymology. Named after the Yarra River which runs through Melbourne (noun in apposition).

Remarks. Like Araphura pygmothymos (se above), Araphura yarra sp. nov. keys out to A. brevimanus in the key presented by Larsen et al. (2009), but is distinguished from that species for similar reasons, such as the tuberculate dorsal margin of the cheliped dactylus, the more compact antennule peduncle articles, the lack of a line of pseudoarticulation on the fourth article of the antenna, and the stronger distal spines on the merus and carpus of the pereopods. The present species is distinguished from the New Zealand species A. whakarakaia by its different tuberculation of the cheliped, and distinct spinulation of the pereopods (as in A. pygmothymos ). It is distinguished from A. pygmothymos by the shorter pereonites, the more slender cephalothorax, the absence of outer rows of tubercles on the cheliped propodus, the absence of a seta on the ischium of pereopod 1, in having only three (rather than four) spines on the carpi of pereopods 4 to 6, and in the setation of the uropodal exopod process, inter alia.

Araphura yarra was found in the Central Bass Strait at depths of 40 to 70 m on fine sand.