Araleptochelia macrostonyx, 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 : 113-119

Araleptochelia macrostonyx sp. nov.

Figures 75–78

Material examined. 1 brooding (J58470), holotype, 11 (J56622), paratypes, Stn 81-HK-1 134, 40º56.0'S 146º05.40'E, 68 m depth, mud, 4 February 1981, coll. MF Gamon et al., FRV Hai Kung, pipe-dredge. 3 (J56629), paratypes, Stn 80-Sa-1 113, 40º23.8'S 146º32'E, 65 m depth, muddy sand, 3 November 1980, coll. MF Gamon et al., FRV Sarda . 14 (J56630), paratypes, Stn 83-SG-1 209, 38º18.0' S 147º37.0'E, 55 m depth, muddy fine shell, 31 July 1983, coll. MF Gamon et al., FV Silver Gull.

13, 2 (J56636), 5, 1 juvenile (J56635), paratypes, Stn 81-T- 1 158, 39º49.5'S 146º18.5'E, 82 m depth, sand-silt-mud, 13 November 1981. 1 (J56634), paratype, Stn 81-HK-1 189, 38º42.8'S 142º35.6'E, 69 m depth, coarse sand, 20 November 1981. 1 (J56626), paratype, Stn 81-HK-1 201, 39º08.3'S 144º43.9'E, 66 m depth, coarse sand, 23 November 1981. 9, 1 (J56627), 1 preparatory (J56639), 8 preparatory (J56640), paratypes, Stn 81-HK-1 159, 39º43.5'S 146º18.8'E, 80 m depth, muddy shell, 13 November 1981. 1 (J56631), 1 (J56633), 1 preparatory (J56638), paratypes, Stn 81-HK-1 161, 39º48.3'S 147º19.2'E, 60 m depth, muddy sand, 14 November 1981. 1 (J56624), paratype, Stn 81-HK-1 173, 39º26.3'S 147º48.7'E, 49 m depth, medium sand, 17 November 1981. 2 (J56628), paratypes, Stn 81-T-1 169, 39º02.4'S 148º30.6'E, 120 m depth, muddy sand, 15 November 1981. All coll. R. S. Wilson, RV Tangaroa .

1 preparatory (J56637), paratype, Stn 83-SG-1 209, 38º18.0'S 147º37.0'E, 55 m depth, muddy fine shell, 31 July 1983, coll. M.F. Gomon & R. S. Wilson, FV Silver Gull .

Description of female. Body ( Fig. 75A, B) slender, holotype 2.3 mm long, 7.4 times as long as wide. Cephalothorax subrectangular, 1.3 times as long as wide, as long as pereonites 1 and 2 together, with slight rostrum, eyelobes and black eyes present, single setae at posterior of eyelobes, midlaterally and posterolaterally. Pereonites 1 and 2 subequal, shortest; pereonites 3 and 6 subequal, slightly longer than pereonite 1; pereonites 4 and 5 subequal, longest and almost twice as long as pereonite 1 (all pereonites respectively 1.5, 1.6, 1.5, 0.9, 0.9 and 1.4 times as wide as long). Pleon with five free subequal pleonites bearing pleopods, each pleonite about 6 times as wide as long, with paired lateral setae. Pleotelson semicircular, longer than last two pleonites together, 1.7 times as wide as long, on each side bearing one posterolateral seta and a pair of one simple and one penicillate setae posterior to uropod attachment, and two distal setae.

Antennule ( Fig. 76A) of four tapering articles, as long as cephalothorax, proximal article 3.1 times as long as wide; second article almost twice as long as wide, one-quarter as long as first article, longest distal outer only just longer than article; third article 1.3 times as long as second; fourth article minute, eccentric, with four distal setae and one aesthetasc.

Antenna ( Fig. 76B) of six articles, proximal three articles subequal in length; proximal article naked; second article with single dorsodistal slender spine; third article as long as wide, with slender dorsodistal spine; fourth article longest, 2.7 times as long as third article and nearly 5 times as long as wide; fifth article 0.75 times as long as fourth; sixth article minute.

Labrum ( Fig. 76C) hood-shaped, setose, typical of genus. Left mandible ( Fig. 35E, E') with crenulate lacinia mobilis narrower than distal end of mandible, proximal crenulation on pars incisiva, pars molaris ( Fig. 76E) robust; right mandible ( Fig. 76D) similar but without lacinia mobilis. Labium ( Fig. 76H) wide, bilobed, distally finely setose, without palp. Maxillule ( Fig. 76F) with ten distal spines and setose margins, setules on inner distal face paired. Maxilla ( Fig. 76G) simple, linguiform, naked. Maxilliped ( Fig. 76I) palp first article naked, second article with one outer and three inner setae in distal half, distal-most inner seta only half as long as third palp article; third and fourth articles with filtering rows of six and five setae respectively, fourth article with outer seta; basis with four long setae extending to half length of second palp article; endites distally with single seta and three slender spatulate spines.

Cheliped ( Fig. 77A) basis nearly twice as long as wide; merus subtriangular with two ventral setae; carpus 2.8 times as long as wide, with three ventral setae in distal half, one proximal and one distal dorsal setae; propodus elongate for the genus, palm 1.8 times as long as wide, fixed finger 0.45 times as long as palm with two ventral and three inner setae alongside cutting edge, cutting edge crenulate, comb-row at base of dactylus of four setae with adjacent microtrichia; dactylus with outer proximal seta.

Pereopod 1 ( Fig. 77B) longer than other pereopods, coxa with seta; basis slender, five times as long as wide; ischium compact with one ventral seta; merus 0.6 times as long as carpus, with single distal seta; merus-carpus articulation strongly oblique; carpus with one dorsal and three ventral distal setae, longest of which is less than one-third as long as propodus; propodus twice as long as carpus, with three setae on subdistal dorsal mound and one subdistal ventral seta; dactylus slender, with proximal seta, extending into slightly longer slender unguis, the two together 1.5 times as long as propodus. Pereopod 2 ( Fig. 77C) more compact than pereopod 1; basis 3.3 times as long as wide; ischium with 2 setae; merus as long as carpus, with slender ventrodistal spine more than half as long as carpus; carpus with dorsodistal seta and short ventrodistal spine; propodus 1.75 times as long as carpus, with two dorsodistal and one ventrodistal setae, and dorsodistal sharp apophysis; curved dactylus and slightly longer unguis together 0.7 times as long as propodus. Pereopod 3 ( Fig. 77D) similar to pereopod 2, but dactylus and unguis subequal.

Pereopod 4 ( Fig. 77E) basis stouter than those of anterior pereopods, twice as long as wide; ischium with two seta; merus and carpus subequal, merus with two short, ventrodistal spines and microtrichia, carpus with one outer, one ventral and one inner distal spines each with serrate ventral margin, single inner and outer simple dorsodistal setae and ventral microtrichia; propodus 1.2 times as long as carpus, with ventral microtrichia, two ventrodistal serrate spines, and three dorsodistal finely-denticulate setae almost as long as dactylus; dactylus and short unguis distinct, curved, together two-thirds as long as propodus. Pereopod 5 as pereopod 4. Pereopod 6 ( Fig. 77F) similar to but stouter than pereopod 4, but distal carpal spines larger, propodus with two pectinate and three finely-denticulate distal setae.

Pleopods ( Fig. 77G) all alike, with no inner plumose seta on endopod; proximal outer seta separated from others on both rami.

Uropod ( Fig. 77H) biramous, basis naked; exopod of one slender segment as long as proximal endopod segment, outer distal seta longer than inner distal seta; endopod of five elongate segments.

Description of male. Typical primary male, smaller than female (allotype length 1.6 mm), body ( Fig. 75C) more compact, cephalon as long as pereonites 1 to 3, with large eyelobes bearing large black eyes; pereonite 5 longest, other pereonites subequal in length. Five free pleonites, subequal in length and about as long as pereonite 1, pleotelson nearly twice as long as pleonite 5. Sexual dimorphism as follows.

Antennule ( Fig. 78A) elongate, first peduncle article curved, 2.8 times as long as wide with one dorsodistal seta; second article compact, 0.25 times as long as first with long outer distal seta; third article compact with dorsodistal spine and ventrodistal penicillate and simple setae; flagellum of 19 segments, first 18 each bearing distal row of aesthetascs, proximal flagellum article with extraordinarily-long dorsodistal spine extending almost full length of flagellum; distal article short and with four simple setae. Antenna ( Fig. 78B) with slender distal setae rather than spines on articles 2 and 3, articles 4 and 5 apparently fused. Mouthparts atrophied.

Cheliped ( Fig. 78C) very slender, three-quarters as long as body; basis arcuate, about 3 times as long as wide; carpus slender and sinuous, about 5 times as long as wide with two ventral setae in proximal half; palm of propodus twice as long as wide, fingers of chela 0.8 times length of palm; fixed finger longer than palm, with two ventral and three inner setae alongside cutting edge, cutting edge with sharp denticulations but no large tooth-like apophyses, distal spine rugose; dactylus with sharp tooth-like denticulations along cutting edge, unguis rugose.

Pereopods ( Fig. 78D to G) more elongate than those of female; unguis of pereopod 1 shorter than dactylus; on pereopods 4 to 6 carpal spines more slender, distal articles without dense fields of microtrichia, unguis longer and more slender, together with dactylus>0.8 times as long as propodus.

Preparatory male. As female, but antennule with four longer articles as well as minute distal article, from division of third peduncle article of neuter.

Etymology. From the Greek macro – long and stonyx – a sharp point, in reference to both the extremely long dactylus and unguis on pereopod 1, the ventrodistal spine on the merus of pereopods 2 and 3, and the spine on the fourth antennal article of the male, all characterizing features of this species.

Remarks. The numerous distinctions of this species from those most similar, i.e. species of Leptochelia , are described under the remarks for the genus. Araleptochelia macrostonyx sp. nov. contributes further to the great diversity of the Leptocheliidae in Australian waters and is readily distinguished from other species without dissection owing to its unique cheliped morphology and the extremely long dactylus plus unguis on pereopod 1. The antennular morphology of four longer segments in the subadult male was demonstrated for the related Leptochelia savignyi (Krøyer, 1842) by Bamber (2010).

A. macrostonyx was found on muddy to coarse sand substrata at depths from 49 to 120 m right across the northern half of the Bass Strait.