Bascestus melmackenziae, 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 : 222-226

Bascestus melmackenziae sp. nov.

Figures 149–151

Material. 1 (J23600), holotype, Eastern Bass Strait, 3.2 km S of Cape Conran, Stn MSL-EG 55, 37º50.38'S 148º43.28'E, 49 m depth, sand and shell, 28 September 1990, coll. Marine Science Laboratories, Smith-McIntyre Grab. 2 (J56380) , paratypes, Eastern Bass Strait, 13.3 km E of eastern edge of Lake Tyers, Stn MSL-EG 68, 37º51.42'S 148º14.36'E, 37 m depth, 04 June 1991, coll. N. Coleman, Smith-McIntyre Grab. 1 (J28484) , allotype, Eastern Bass Strait, 13.3 km E of eastern edge of Lake Tyers, Stn MSL-EG 69, 37º51.42'S 148º14.36'E, 37 m depth, 04 June 1991, coll. N. Coleman, Smith-McIntyre Grab .

Description of female. Body ( Fig. 149C) slender, 12 times as long as wide, holotype 2 mm long. Cephalothorax parallel-sided in posterior half, narrowing anteriorly, 1.8times as long as wide, with slight rounded rostrum; eyelobes and eyes absent. Pereonites all rectangular, pereonite1 half as long as cephalothorax, as long as wide; pereonites 2 to 5 subequal in length, 1.4 times as long as pereonite 1, longer than wide; pereonite 6 shortest, 0.9 times as long as pereonite 1 (all pereonites respectively 1.0, 0.7, 0.8, 0.8, 0.7 and 1.1 times as wide as long). Pleon over three as long as pereonite 6; pleonites subequal in length, 2.8 times as wide as long, all bearing pleopods and single mid-lateral setae; pleotelson subpentangular, longer than two preceding pleonites, as wide as long, with single midlateral setae and two pairs of distal setae.

Antennule ( Fig. 150A) shorter than cephalothorax, fourarticled; article 1 nearly three times as long as wide, 0.9 times as long as articles 2 to 4 combined, with subdistal outer pair of penicillate setae, and single outer simple distal seta; article 2 slightly overlapping proximal part of article 3, twice as long as wide, less than half as long as article 1, with single inner and outer simple subdistal setae and tuft of five dorsodistal setae; article 3 slightly overlapping proximal part of article 4, 1.7 times as long as wide, 0.6 times as long as article 2, with single inner and outer simple subdistal setae; article 4 as long as article 2, five times as long as wide, with three simple and two penicillate subdistal setae and two longer simple distal setae.

Antenna ( Fig. 150C), six–articled, article 1 short and annular, naked; article 2 about as long as wide, distally with single shorter dorsal and longer lateral setae; article 3 just shorter than article 2, with dorsodistal seta; article 4 twice as long as articles 2 and 3 combined, 4.5 times as long as wide, curved, distally with two simple and three penicillate setae; article 5 one-third as long as article 4, with long distal seta; article 6 very small, with five distal setae.

Labrum ( Fig. 150D) rounded, hood-shaped, distally setose. Mandibles stout; left mandible ( Fig. 150E) with distally-crenulate incisor and narrow, simple lacinia mobilis, molar proximally stout, tapering, tip with six or seven slender spine-like teeth; right mandible ( Fig. 150F) incisor distally concave with few stout teeth; molar as on left mandible. Labium ( Fig. 150H) simple, each side with single subdistal spinule. Maxillule ( Fig. 150G) endite slightly sigmoid, with one distal seta and five terminal and two subterminal spines; palp and maxilla not recovered. Maxilliped ( Fig. 150I) bases rounded, fused, naked; palp article 1 naked, article 2 with two inner distal setae and one outer distal seta; article 3 with three stout inner setae; article 4 with five distal and one outer subdistal setae; endites not fused, distally with rounded tubercle and inner seta. Epignath not recovered.

Cheliped ( Fig. 149D, 151A) basis in situ proximally wellanterior of anterior margin of pereonite 1 ventrally, attached by distally rectangular sclerite; basis narrower posterior to this attachment, with rounded posterior free margin, twice as long as wide, with small dorso-subdistal seta; merus subtriangular, with ventral seta; carpus twice as long as wide, with three dorsoproximal and two mid-ventral setae, ventrodistally with slight expansion of margins into which chela can reflect; propodus longer than wide, with two ventral setae and comb-row of four simple setae, dorsal margin and mid-lateral face with rows of rounded nodules in distal half, and with inner ventral submarginal crenulate ridge; fixed finger cutting edge with three proximal denticulations and three adjacent setae; dactylus with several dorsal nodules and one small proximal seta.

Pereopod 1 ( Fig. 151B) basis relatively stout, 2.5 times as long as wide, with one mid-dorsal simple seta; ischium with one seta about half as long as merus; merus distally expanded, 0.4 times as long as basis, 1.4 times as long as distal width, ventrodistally with one shorter seta and one compound spine almost as long as carpus; carpus 1.1 times as long as merus, rectangular, with two short ventrodistal spinules and inner and outer compound distal spines; propodus 1.5 times as long as carpus, with one compound ventrodistal spine, one distal seta as long as dactylus, and dorsodistal spinulation; dactylus half as long as unguis, both together as long as propodus. Pereopod 2 as pereopod 3. Pereopod 3 ( Fig. 151C) similar to pereopod 1, but basis with mid-dorsal penicillate seta, carpus with single ventral, inner and outer compound distal spines.

Pereopod 4 ( Fig. 151D) basis 2.4 times as long as wide; ischium with two setae; merus 0.3 times as long as basis, with two ventrodistal compound spines; carpus 1.3 times as long as merus, with with single ventral, inner and outer compound distal spines and simple dorsodistal seta; propodus 1.1 times as long as carpus, with one dorsodistal seta and two ventrodistal compound spines; dactylus semicircular in cross-section, ventral edges finely denticulate; unguis half as long as dactylus, ventrally finely denticulate, dactylus and unguis together 1.2 times as long as propodus. Pereopod 5 ( Fig. 151E) similar to pereopod 4, propodus with microtrichia. Pereopod 6 ( Fig. 151F) similar to pereopods 4 and 5 but basis with dorsal undulation, propodus with two dorsodistal setae.

Pleopods all similar ( Fig. 151G), basal article naked; endopod and exopod rami rounded, all setae plumose; endopod with eight outer to distal setae and one inner subdistal seta, proximal outer margin naked; exopod with eight outer to distal setae and separated outer proximal seta.

Uropod ( Fig. 151H) slender, nearly twice as long as pleotelson; basal article twice as long as wide, naked, without distal apophyses; exopod two-segmented, shorter than proximal article of endopod, segments subequal in length, with one distal seta on proximal segment, two unequal distal setae on distal segment; endopod two–segmented, proximal segment shorter and with one penicillate distal seta, distal article with one subdistal and two distal simple setae and two distal penicillate setae.

Distinctions of male. Body ( Fig. 149A, B) smaller and less elongate than that of female, length 0.9 mm, 10 times as long as wide. Cephalothorax similar to that of female, 1.7 times as long as wide, tapering anteriorly. Pereonites more or less rectangular; pereonite 1 half as long as cephalothorax; pereonites 2 to 5 subequal in length although progressively shorter, about 1.2 times as long as pereonite 1, not longer than wide; pereonite 6 shortest, 0.9 times as long as pereonite 1; pereonites respectively 1.3, 1.0, 1.1, 1.0, 1.1 and 1.4 times as wide as long. Pleon as long as pereonites 4 to 6 inclusive, pleonites 2.8 times as wide as long.

Antennule ( Fig. 150B) five–articled, shorter than cephalothorax; peduncle article 1 stout, three times as long as wide, naked; peduncle article 2 compact, 0.4 times as long as article 1, 1.3 times as long as wide, with three penicillate and one simple ventrodistal setae; article 3 as long as wide, 0.6 times as long as article 2, with two dorsodistal simple setae; flagellum of two segments, proximal segment just longer than wide, 0.75 times as long as peduncle article 3, naked; second segment twice as long as wide, as long as peduncle article 3, with four simple and one penicillate subdistal setae and two simple distal setae.

Mouthparts, chelipeds, pereopods, pleopods and uropods similar to those of female.

Etymology. Named after Melanie Mackenzie of the Museum Victoria in gratitude for her diligent and uncomplaining assistance with the material and data of the collections.

Remarks. The characters of this species are discussed above under the generic remarks. The rugose tuberculation of the cheliped may be a specific rather than generic character as it is known to show intrageneric variation in other paratanaoid taxa (see discusison under Araphura ). Bascestus melmackenziae sp. nov. was taken from depths of 37 to 49 m in the Eastern Bass Strait.