Bunakenia labanticheiros, 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 : 10-15

Bunakenia labanticheiros sp. nov.

Figures 6–9

Material examined. 1 brooding (J50813), holotype,Central Bass Strait Stn VC 31 C2, 39º02.52'S 146º10.47'E, 40 m depth, 14 May 1999, coll. N. Coleman; 1, 7, 2 juveniles (J50814), paratypes, Eastern Bass Strait Stn VC 31 C1, 38º18.3'S 147º15.25'E, 40 m depth, 10 May 1998, coll. N. Coleman ; 115 specimens (J23633), paratypes, East Gippsland Survey Stn MSL-EG 32, 37º54.07'S 148º12.09'E, 42 m depth, 25 September 1990 , sand with shell; 27 specimens (J23634), paratypes, East Gippsland Survey Stn MSL-EG 33, 37º53.42'S 148º11.87'E, 43 m depth, 25 September 1990 , sand with shell; 20, 5 (J23637), paratypes, East Gippsland Survey Stn MSL-EG55, 37º50.63'S 148º43.47'E, 49 m depth, 28 September 1990 , sand with shell; 3, 1 (J23639), paratypes, East Gippsland Survey Stn MSL-EG57, 37º51.29'S 148º43.73'E, 50 m depth, 28 September 1990 , sand with shell; 27 specimens (J29174), paratypes, East Gippsland Survey Stn MSL-EG71, 37º53.39'S 148º15.40'E, 43 m depth, 4 June 1991 , coarse sand; 45 specimens (J28619), paratypes, East Gippsland Survey Stn MSL-EG97, 37º53.39'S 148º15.40'E, 43 m depth, February 1991 , coarse sand.

Description of female. Body ( Fig. 6) dorsoventrally flattened, slender, holotype 2.4 mm long, 5.6 times as long as wide, tapering towards posterior, glabrous. Cephalothorax subrectangular, as long as wide, with uniform triangular rostrum; eyelobes and eyes present. Six free subequal pereonites, each glabrous and without lateral apophyses; pereonite 1 trapezoidal, wider anteriorly, just less than half as long as cephalothorax; pereonites 2 and 6 subequal, subrectangular, half as long as cephalothorax; pereonites 3 and 5 subequal, subrectangular, two-thirds as long as cephalothorax; pereonite 4 longest, 0.8 times as long as cephalothorax (all pereonites respectively 2.3, 2.0, 1.5, 1.25, 1.5 and 1.8 times as wide as long), lateral margins smooth, without apophyses. Pleon 2.4 times as long as pereonite 6, tapering posteriorly, of five free subequal pleonites bearing pleopods plus pleotelson; each pleonite about five times as wide as long, without dorsolateral rows of plumose setae. Pleotelson subrectangular, 0.7 times as long as all pleonites together, as long as wide.

Antennule ( Fig. 7A) proximal peduncle article 3.2 times as long as wide, outer margin with numerous penicillate setae and one subdistal and two distal simple setae, inner margin centrally rugose, one simple proximal seta and five plumose setae; second peduncle article 1.5 times as long as wide, 0.3 times as long as first, with penicillate outer seta and numerous simple inner setae; third article half length of second, 1.5 times as long as wide, distally with inner and outer setae, the former longer than article; fourth peduncle article about half length of third. Main flagellum of 9 segments, single aesthetascs present on fifth, eighth and ninth segments; accessory flagellum of three segments.

Antenna ( Fig. 7B), proximal peduncle article without apophysis. Second article with linguiform squama bearing 11 marginal setae, two setae next to base of squama. Third peduncle article twice as long as wide and two-thirds as long as second, fourth article as long as second, fifth article half length of fourth. Flagellum of five segments.

Labrum rounded, simple, distally setose. Right mandible ( Fig. 7C) with strong, crenulate pars incisiva, setiferous lobe with six forked setae, outer margin finely spinose. Left mandible ( Fig. 7D) similar but with crenulate lacinia mobilis. Pars molaris robust, with posterodistal denticulation; palp of three articles, proximal article with five simple setae, second article longest with two medial simple setae and, distal to these, three rows of two, three and four simple, third article with ten setae in a single row. Labium ( Fig. 7G) with denticulate outer margin, palp with fine lateral setules and three simple distal setae. Maxillule ( Fig. 7E) inner endite with outer apophysis, finely setose outer margin and five setulose distal setae, outer endite with eleven distal spines and two subdistal setae (not seen on figure), outer and inner margins finely setose, palp of two articles, distally with three setae. Maxilla ( Fig. 7F) typical of the genus, with a rostral row of 25 setae, compound setae on the fixed endite and serrate sickle-like setae on the moveable endite inside five compound outer setae on the outer lobe. Maxilliped ( Fig. 7H) basis with medial inner seta; first palp article with one very long inner setae and small, naked outer apophysis; second palp article just longer than wide, with one row of inner simple setae, parallel row of shorter setulose setae, and outer distal spine; third palp article wider than long with inner distal group of thirteen simple setae; fourth palp article mounted anaxially, with eight distal setae. Endites ( Fig. 7 H') with three coupling hooks, distally with four outer setae and numerous inner slender, blunt spines.

Cheliped ( Fig. 8A) slender, smaller than pereopod 1, basis twice as long as wide, ventrally with long proximal seta, central sharp spine and distal group of four simple setae; three-articled exopodite present, slender, distal article with three plumose setae. Merus subtriangular, twice as long as wide, ventral margin with eight setae; carpus 4.7 times as long as wide, with longer ventral marginal setae and shorter dorsal marginal setae. Chela slender, fixed finger just shorter than palm with dense distal setation; dactylus and claw slightly overreaching fixed finger, both fingers without apophyses on cutting edge.

Pereopod 1 ( Fig. 8B) with conspicuous sharp setose apophysis on coxa; stout basis less than twice as long as wide, dorsal margin bearing only simple setae in proximal half, single ventrodistal spine; exopodite large, three-articled, distal article with six plumose setae. Ischium with simple ventrodistal setae. Merus widening distally, with single dorsodistal and ventrodistal spines and associated simple setae. Carpus compact, wider than long, with fan of dorsodistal setae, one dorsodistal and two ventrodistal blunt spines. Propodus with two dorsodistal spines and four ventral blunt spines interspersed with single fine setae. Dactylus slender, with paired mid-dorsal and ventral fine setae; claw slender, finely denticulate.

Pereopods 2 and 3 ( Fig. 8C, D) basis 3.2 times as long as wide with sparse penicillate setae, one (pereopod 2) or two (pereopod 3) ventromedial setae and tuft of longer ventrodistal setae; ischium half as long as wide; merus as long as carpus, widening distally and with long ventral setae and single ventrodistal slender spine; carpus with slender ventrodistal spine I tuft of simple setae and crown of dorsodistal simple setae; propodus with two or three ventral and one dorsodistal slender spines; dactylus slender, claw not denticulate.

Pereopods 4 ( Fig. 8E) and 5 with slender basis with penicillate seta and fine ventrodistal simple setae; carpus slightly longer than merus; propodus of pereopod 4 with mid-dorsal penicillate seta; dactylus and claw less slender than those of anterior pereopods.

Pereopod 6 ( Fig. 8F) proportionately as pereopod 5, but basis with ventral marginal row of five simple and three plumose setae; merus shorter than carpus and with three dorsal plumose setae; carpus with four dorsal plumose setae; propodus with 20 small compound spines ventrally and distally on each side in tapering row; dactylus plus claw slender, simple.

Pleopods as those of male ( Fig. 9G) all alike, basis with two inner but no outer plumose setae, endopod and exopod subequal, slender, each with 11 plumose setae.

Uropod ( Fig. 9H) biramous, basis with three distal simple and two penicillate setae; exopod just less than three times as long as basis and of six segments; endopod elongate, filiform, multisegmented.

Description of male. generally similar to female. Antennule ( Fig. 9A) main flagellum of 11 segments with single aesthetascs on segments 3, 5, 7 and 9, accessory flagellum of 5 segments. Antenna ( Fig. 9B) flagellum of eight segments.

Conspicuous dimorphism of cheliped ( Fig. 9D): basis 1.5 times as long as wide, ventrally with central spine and paired distal plumose setae; three-articled exopodite present, stout, distal article with four plumose setae. Carpus stouter, widening distally, twice as long as wide. Chela robust, highly modified, fixed finger flexed back along distal margin of propodus (palm), distal tip truncate with rugose cutting edge, tooth-like apophysis in angle between fixed finger and palm; dactylus narrowing rapidly from base, distally truncate, with five spines but no apophysis on cutting edge. Chela of subadult male ( Fig. 9C) intermediate between that of mature male and that of female, carpus slender, fixed finger longer than palm, but not reflexed.

Pereopod 1 ( Fig. 9E) with stout basis twice as long as wide, dorsal margin bearing nine plumose setae in proximal half. Ischium dorsally wide. Merus dorsal margin with flattened, flange-like apophysis and dorsodistal spine. Pereopods 2 ( Fig. 9F) and 3, merus shorter than carpus.

Etymology. From the Greek – labe – something for grasping, and anticheiros – thumb, in reference to the extra tooth on the fixed finger of the chela of the male.

Remarks. Guţu (1996c) described two subgenera of Bunakenia . The nominate B. ( Bunakenia ), distinguished only by having rows of plumose setae on the basis of pereopod 1, includes three species, B. (B.) indonesiana Guţu, (1995a) from Sulawesi, at 4–5 m depth, B. (B.) tanzaniana Guţu, 1996 (d) from the Indian Ocean coast of Africa at 20 m depth, and B. (B.) salzella Bamber, 2005 from the littoral to 30 m depth in southwestern Australia. The subgenus B. (Extensibasella), without plumose setae on the basis of pereopod 1, includes B. (E.) sudvestatlantica Guţu, 1996 (c) from Brazil at 31 m depth, B. (E.) aspalieus Bamber, Bird and Angsupanich, 2003 , from Thailand in littoralinfralittoral seagrass beds, B. (E.) kadazan Bamber and Sheader, 2005 from Sabah in sand at 23–35 m depth, and B. (E.) anomala Guţu, 2006 from Moreton Bay, Australia (depth unspecified).

The present species has plumose setae on the basis of pereopod 1 in the male, but not in the female, and thus falls quite between the two subgenera; Bamber & Sheader (2005) questioned the validity of the subgenera, their species B. kadazan showing little affinity to B. (E.) sudvestatlantica , and the zoogeography of these two “groups” is inconsistent. We therefore choose to dispense with those subgenera.

In the conformation of the male chela, with extreme reflexion of the fixed finger, Bunakenia labanticheiros sp. nov. is similar only to the other Australian species, B. salzella , from which it can be distinguished by the presence of the tooth-like apophysis in the angle between the fixed finger and the palm of the male chela (absent in B. salzella ), the absence of plumose setae on the basis of pereopod 1 in the female (present in B. salzella ), the mid-ventral spine on the basis of the cheliped (a plumose seta in B. salzella ), fewer ventral spines on the propodus of pereopod 1, fewer plumose setae on the basis of pereopod 6, and details of the setation of the mouthparts and pleopods, inter alia.

Unlike the present species, B. kadazan has a thin, pointed rostrum; B. sudvestatlantica has a more elaborate cheliped basis in the male, and is without the tooth-like apophysis in angle between fixed finger and palm of the male chela, as also are B. tanzaniana and B. anomala ; B. aspalieus (male unknown) has posterolateral hook-like apophyses on the pereonites; all four have plumose setae on both margins of the pleopod; B. indonesiana has only one basis seta on the pleopod, but dense rows of plumose setae on the pereopod 1 basis of both genders, and a more pronounced rostrum. All of these species have an inner apophysis on the proximal peduncle article of the antenna, unlike Bunakenia labanticheiros .

All specimens were taken from sandy substrata at between 40 and 50 m depth in the Central and Eastern Bass Strait.