Macrolabrum haikung, 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 : 83-88

Macrolabrum haikung sp. nov.

Figures 55–57

Material examined. 1 brooding (J57787), holotype, Stn CRUST 23 , “The Whaleback”, Bommie , 0.5 km S of Point Hicks, Victoria, 37º48.30'S 149º16.48'E, 13 m depth, 08 April 1989, SCUBA, coll. G.C.B. Poore; 14 (J56374), paratypes, same sample as Holotype; 1

(27697), paratype, Stn BSS175 , Eastern Bass Strait, 40 km north of Deal Island , Tasmania, 39º05.8'S 147º26.2'E, 59 m depth, 18 November 1981, medium sand, coll. R. S. Wilson .

Description of female. Body ( Fig. 55A) typical of a pagurapseudid, pleon skewed to the right and curved under pereon; small, holotype about 2.4 mm long. Cephalothorax slightly longer than wide, rostrum rounded, finely denticulate ( Fig. 55B). Eyelobes distinguished with anterior pointed apophysis, eyes present as group of black-pigmented ocelli. Epistome not conspicuous. Pereonites 1, 2 and 3, 4 subequal, 0.3 times as long as cephalothorax; pereonites 4 and 5 subequal, 1.4 times as long as pereonite 1; pereonite 6 longest, 1.7 times as long as pereonite 1. Pleon of five free subequal pleonites, each pleonite about 0.7 times as long as pereonite 6; pleonites 1 and 2 only bearing pleopods. Pleotelson ( Fig. 57I) subrectangular, about as long as last pleonite, 1.4 times as wide as long, with single plumose lateral seta on each side, and paired simple posterior setae.

Antennule ( Fig. 56A) compact, proximal peduncle article 2.2 times as long as wide, without apophyses, inner margin sparsely setose, inner margin with three penicillate and one simple setae distally; second peduncle article 0.4 times as long as first with simple distal setae; third article 0.7 times as long as second, with simple distal setae; fourth article half length of second, with two simple and one penicillate distal setae. Main flagellum of two segments, with simple setae and single aesthetasc on each segment; accessory flagellum of one segment, distally exceeding distal edge of first segment of main flagellum.

Antenna ( Fig. 56B) with two basal articles fused into wide proximal peduncle article bearing inner denticulation and plumose seta, outer margin expanded into a flange with two simple setae; third article shorter than wide, one-fifth length of combined proximal articles, with simple inner seta; fourth peduncle article 1.7 times as long as third, with inner penicillate seta; fifth article three-times as long as third, with penicillate and simple distal setae. Flagellum of two minute segments, proximal segment with penicillate seta, distal segment with two distal setae.

Labrum (not figured) bilobed, rounded, sparsely setose. Right mandible ( Fig. 56C) with tricuspid pars incisiva, setiferous lobe with three trifid setae, pars molaris slender, round, blunt, simple; palp of three articles, proximal article with long, plumose inner seta, second article longest, twice as long as first article, naked; third article as long as first, with four progressively longer distal setae and one outer subdistal seta, each seta finely denticulate. Left mandible (not figured) as right but with narrow, bicuspid lacinia mobilis. Labium typically marginally setose, palp ( Fig. 56F) with setulose margins and two distal setae. Maxillule ( Fig. 56D) inner endite with four finely serrate distal setae, margins naked, no outer apophysis; outer endite with 9 serrate distal spines, outer margin setose; palp of two articles, distally with outer setules and three simple setae. Maxilla ( Fig. 56E) outer margin naked, outer lobe of moveable endite with two subdistal and four distal simple setae, inner lobe with six simple setae; fixed endite outer lobe with three simple, three trifurcate and one bilaterally denticulate distal spines, inner lobe with one longer distally denticulate seta and rostral row of 10 setae. Maxilliped ( Fig. 56G) basis with two inner plumose setae, outer margin denticulate and with one short plumose seta; proximal palp article with two denticulations and one plumose seta on inner and outer margins; second article with denticulate inner and outer margins, outer margin with two plumose setae, inner margin with four plumose and two simple setae; third article with three inner marginal simple setae; distal article with seven finely-denticulate and one simple distal setae, paired outer subdistal setae each with setules at mid-length and finely-denticulate distal half; endite ( Fig. 56 G') with naked outer margin, five bifurcate distal spines, and two coupling-hooks. Epignath ( Fig. 56H) narrow, inner lobes conspicuous, distal spine with short marginal setules in distal half.

Chelipeds showing slight dimorphism. Right cheliped ( Fig. 57A) with compact basis 1.1 times as long as wide, with mid-ventral spine, two simple setae proximal to this, and two plumose setae and one spine ventrodistally; stout proximal spine dorsally; exopodite absent. Merus subtriangular, with complex, denticulate triangular distal apophysis, two mid-ventral, two inner-proximal and three outer-proximal plumose setae. Carpus elongate, 1.65 times as long as wide, widening distally, with six teeth in ventrodistal denticulation, four ventral and four dorsal simple setae. Propodus 1.3 times as long as wide, single dorsodistal seta, ventrally with two simple setae and expanded into thin flange; fixed finger with three ventral, one distal and five dorsal marginal setae, crenulate cutting edge; moveable finger stout, curved, naked. Left cheliped ( Fig. 57B) similar, ventral denticulations on carpus limited to three on distal apophysis, chela slightly more slender (propodus 1.2 times as long as wide), with fewer setae and denticulation restricted to distal half of cutting edge of fixed finger.

Pereopod 1 ( Fig. 57C) longest pereopod, with stout basis twice as long as wide, dorsal margin bearing seven plumose setae interspersed amongst triangular tooth-like apophyses, and three rounded paddle-like apophyses proximally; ventral margin with simple proximal seta and distal plumose seta; exopodite present ( Fig. 57 C'), large, second article naked, distal article with thirteen plumose setae. Ischium 0.3 times as long as basis, with single ventral plumose seta. Merus relatively compact for the genus, twice as long as wide, 0.75 times as long as basis, with two denticulate dorsodistal setae, ventral margin with five longer plumose setae and four shorter denticulate spines. Carpus shorter than merus, with denticulate spine and simple seta dorsodistally and ventrodistally. Propodus as long as merus, with dorsodistal group of one simple seta, one penicillate seta and one curved spine, ventrodistally with two simple setae and one denticulate spine. Dactylus almost straight, just longer then propodus, with single dorsal but no ventral setae, unguis slender, curved, blunt, half as long as dactylus.

Pereopods 2 to 6 similar to each other, each about one-half to one-third as long as pereopod 1. Pereopod 2 ( Fig. 57D) basis stout, 1.7 times as long as wide, naked; ischium with one shorter and one longer ventrodistal setae. Merus, carpus and propodus bearing “sucker-like” spines, generally in three ventral rows, and sparse plumose setae as figured. Merus longer carpus; propodus 0.6 times as long as carpus, both with stout, finely denticulate distal spine; dactylus and unguis not fused, with minute inner seta. Pereopod 3 ( Fig. 57E) with very short basis, shorter than wide, ischium with three ventrodistal plumose setae, merus with fewer sucker-like spines, merus and carpus subequal in length, carpus and propodus both with stout, finely denticulate distal spine. Pereopod 4 as pereopod 5. Pereopod 5 ( Fig. 57F) with one dorsal and one ventrodistal setae on basis, one longer and one shorter ventrodistal setae on ischium, merus without setae, shorter than carpus; stout, finely denticulate distal spine on propodus only. Pereopod 6 ( Fig. 57G) basis with two plumose dorsal setae, mid-ventrally with plumose seta and penicillate seta; ischium with one ventrodistal seta; merus with only one sucker-like spine; unguis mounted subdistally on dactylus.

Pleopods ( Fig. 57H) only present on pleonites 1 and 2, biramous, reduced; basis with two ventral plumose setae; exopod with three distal plumose setae, endopod almost circular with seven marginal plumose setae. Uropod ( Fig. 57I) biramous, basis with one simple and one plumose distal setae; endopod longer thanbasis,ofthreesegments,firstandsecondsegmentssubequal, distally naked, third segment longer than first two together, with three stout distal setae and one penicillate seta; exopod of two segments, together subequal in length to proximal two endopod segments together, with two distal setae.

Male. Unknown.

Etymology. The FRV Hai Kung was one of the vessels used on the Bass Strait Survey between 1979 and 1984 (noun in apposition).

Remarks. The only other species of Macrolabrum with three and two segments in the uropod endopod and exopod respectively, and two and one segments in the antennular main and accessory flagellum respectively is M. distonyx , from New Caledonia (see Bamber, 2007), which also has a proximal spine on the cheliped basis like M. haikung sp. nov. and an epistome not exceeding the anterior margin of the carapace, but that species has a far more elongate antennule with denticulation on the proximal peduncle article, a triangular, denticulate rostrum, four spines on the mandible palp second article, more slender pereopod bases, and a huge chela on the right cheliped, inter alia.

Indeed, the present species is unique in its extremely compact pereopod bases, the relatively short articles of pereopod 1 with their sparse setation, the lack of ventral setae on the dactylus of pereopod 1, the subdistal attachment of the unguis on pereopod 6, the serration of the distal spines on the maxillule outer endite, and in particular the inner flange on the antenna proximal article and the ventral flange on the cheliped propodus.

Macrolabrum haikung was taken from the Eastern Bass Strait at 13 to 59 m depth on medium sand.