Labraxeudes heliodiscus, Błażewicz-Paszkowycz & Bamber, 2007

Błażewicz-Paszkowycz, M. & Bamber, R. N., 2007, New apseudomorph tanaidaceans (Crustacea: Peracarida: Tanaidacea) from eastern Australia: Apseudidae, Whiteleggiidae, Metapseudidae and Pagurapseudidae, Memoirs of Museum Victoria 64, pp. 107-148 : 136-141

Labraxeudes heliodiscus sp. nov.

Figures 17–19

Material. Brooding female, holotype ( NVM J47127 ), Australia, Victoria, Red Rock , Phillip I. (38°28'S, 145°14'E), 29/09/1974, W.F. Seed, B .

Leonard, B and R. Lennie; 2 females, paratypes ( NVM J55750 ) , 1 dissected on slides ( NVM J55940 ) same sample as holotype .

Description of female. Body compact, holotype 2.9 mm long (tip of rostrum to posterior of pleotelson), 3.8 times as long as wide, narrower posteriorly. Cephalothorax subrectangular, as long as wide including rostrum (1.3 times as wide as long without rostrum), anterior margin with conspicuous subcircular, flattened rostrum with finely denticulate anterior margin. Eyes present on robust eyelobes; paired lateral setae behind eyelobes and on laterally swollen branchial chambers. 6 free pereonites, all with lateral margins uniformly convex, appearing as posterolateral rounded apophyses on pereonites 3 to 6, each with 3 or 4 conspicuous simple setae; pereonite 1 about one-third as long as cephalothorax; pereonite 2 shortest, 0.9 times as long as pereonite 1; pereonites 3 and 4 subequal (4th longest), 1.3 times as long as pereonite 1; pereonites 5 and 6 subequal, as long as pereonite 1 (all pereonites respectively 3.4, 3.8, 2.6, 2.4, 2.9 and 2.7 times as wide as long). Pleon 2.6 times as long as pereonite 1, of 5 free subequal pleonites bearing pleopods plus pleotelson; pleonites dorsally convex, more than 3 times as wide as long, with paired mid-dorsal setae, laterally expanded by spiniform apophyses each bearing 3 simple setae distally. Pleotelson distally rounded, one-quarter as long as whole pleon, expanded laterally into rounded apophyses bearing long simple setae, thus 2.5 times as wide as long, long paired dorsal simple setae in posterior half, distal margin with 3 long simple setae on each side.

Antennule peduncle article 1 arcuate, compact, 2.7 times as long as wide, inner margin with triangular subdistal apophysis bearing 2 simple setae, outer margin with proximal penicillate seta, fine denticulations in distal 3rd with row of 4 adjacent simple setae; article 2 one-third as long as article 1, with outer distal pair of plumose setae, dorsodistal simple seta and inner subdistal pair of shorter simple setae; article 3 half length of article 2, with outer distal plumose seta and inner subdistal pair of shorter simple setae; article 4 0.7 times as long as article 3, with inner distal seta. Main flagellum of 4 segments, segment 3 bearing single aesthetasc; accessory flagellum of 2 segments, each with 2 distal setae.

Antenna peduncle article 1 with inner denticulate apophysis and rounded denticulate outer margin; article 2 1.4 times as long as article 1, inner margin bearing pair of simple setae and subdistal spinous apophysis, outer margin with penicillate seta and distal squama with 5 simple marginal setae; peduncle article 3 shorter than wide, one-quarter the length of article 2, with 1 inner seta; article 4 twice as long as article 3, with paired inner penicillate setae; article 5 slightly longer than article 1, with inner and outer penicillate setae and paired inner simple setae. Flagellum of 4 segments.

Mouth parts. Labrum not seen. Left mandible bearing strong, crenulated pars incisiva, lacinia mobilis robust with 5 strong denticulations, setiferous lobe with 1 compound, 3 bifurcate and 1 simple setae, pars molaris robust, blunt, margin with row of finely denticulate teeth; mandibular palp of 3 articles, article 1 just longer than wide with 4 setae on inner rounded apophysis, article 2 1.75 times as long as article 1 with 3 longer and 7 shorter finely denticulate setae in distal half; article 3 two-thirds length of article 2 with 8 inner finely denticulate setae in distal half and 1 outer subdistal seta. Right mandible as left. Maxillule inner endite with 5 finely setulate distal setae; outer endite with 8 distal spines and 2 subdistal setae, outer and inner margins finely setose; palp lost in dissection. Maxilla with fine setae on outer margin; outer lobe of moveable endite with 3 simple subdistal setae (1 mesially setulose) and 3 simple distal setae; inner lobe of moveable endite with 6 simple and 3 setulose setae; outer lobe of inner endite with 4 outer simple setae, 3 stout trifurcate spines, and 1 inner and 2 subdistal setulose setae; inner lobe of fixed endite with rostral row of 14 setae guarding 2 longer setae. Labium with smooth outer margin, palp with fine lateral setules and 3 simple distal spines. Maxilliped basis naked; palp article 1 with single distal seta on outer margin and long simple inner seta longer than article 2; palp article 2 longer than wide, with rows of numerous short setae and 6 longer simple setae along inner margin, outer margin denticulate and with single distal seta; palp article 3 as long as wide, with 8 simple setae along inner margin; palp article 4 with 7 distal setae and 1 subdistal seta. Endite with flagellate inner caudodistal seta and stout distal spines along setulose margin and three coupling hooks. Epignath not seen.

Cheliped robust, basis 1.8 times as long as wide, dorsally naked, ventrally with midventral spine and 2 plumose distal setae; exopodite present, 3-articled, article 2 naked, article 3 with 4 plumose setae. Merus subrectangular, with paired ventrodistal simple setae. Carpus 1.25 times as long as wide, with 3 simple setae along ventral margin. Chela fingers shorter than palm, ventral margin of fixed finger with 6 setae; 1 seta near articulation of fixed finger; cutting edge with row of 6 setae but no apophyses, distal claw stout; dactylus naked with central and proximal apophyses on cutting edge, distal claw pointed.

Pereopod 1 with rounded spine-like apophysis on coxa bearing row of fine setules and 3 distal plumose setae. Basis stout, 2.3 times as long as wide, dorsal margin with 6 plumose setae but no apophyses, ventral margin with 6 plumose setae, 2 subdistal simple setae and ventrodistal spine; exopodite present, 3-articled, article 2 naked, article 3 with 6 distal plumose setae. Ischium with 1 shorter and 2 longer simple ventrodistal setae. Merus just over half as long as basis, expanded distally, with 3 ventral simple setae, ventrodistal spine and adjacent simple seta and curved dorsodistal spine and 2 adjacent simple setae. Carpus half as long as merus, with 2 ventral spines and intervening simple seta, dorsal margin with numerous simple setae and single dorsodistal spine. Propodus as long as merus, with 4 ventral spines alternating with simple setae, 5 simple dorsal setae and 2 dorsodistal spines. Dactylus stout, more than half as long as propodus, with mid-dorsal fine seta; unguis short.

Pereopod 2 more slender. Coxa with 2 plumose setae. Basis 2.6 times as long as wide with 2 dorsal and 3 ventral plumose setae, and 2 simple ventrodistal setae. Merus 1.6 times as long as carpus, with elongate dorsodistal plumose seta, 2 ventral simple setae and ventrodistal spine. Carpus elongate, with 2 ventral spines and ventrodistal seta, 3 dorsal simple setae and dorsodistal spine. Propodus just longer than merus, with 4 ventral and 2 dorsodistal spines with interspersed setae. Dactylus curved, with fine mid-dorsal seta, unguis slender.

Pereopod 3 similar to pereopod 2, but basis with longer mesial plumose seta, merus with 3 ventrodistal spines, carpus with 2 dorsodistal spines, propodus with 3 dorsodistal spines.

Pereopod 4 similar to pereopod 3 but with no mesial seta on basis, longer anterior and posterior distal spines on carpus, propodus with mid-dorsal plumose sensory seta, dorsodistal tuft of 4 shorter and 2 longer finely denticulate setae; dactylus with fine ventrodistal seta.

Pereopod 5 similar to pereopod 4, basis with proximal penicillate setae and 4 dorsal plumose setae longer than basis width, 5 ventral plumose setae; ischium with 2 ventrodistal setae, longer of which exceeds distal edge of merus; merus shorter than carpus, with plumose dorsal seta longer than carpus, 3 shorter ventral plumose setae and 2 ventrodistal spines; carpus with ventral spines and distal crown of plumose setae; propodus with 2 plumose distal setae.

Pereopod 6 basis with 4 dorsal and 8 ventral plumose setae; merus with 3 dorsal plumose setae and 1 plumose and 2 simple ventral setae; carpus with 4 ventral and 3 dorsal plumose setae and dorsodistal spine; propodus with 2 ventral spines and crown of 10 shorter and 1 longer distal setae.

Pleopods all similar, all setae plumose; basis with 1 ventral seta, outer ramus with 2 articles, proximal article with single outer seta, distal article with 3 outer and 3 distal setae, inner ramus with 8 setae around entire margin.

Uropod biramous, exopod just longer than proximal segment of endopod, of 2 segments, distally with 2 setae exceeding tip of endopod; endopod of 3 segments.

Etymology. From the Greek: helios – the sun, and discos – a flat circular plate or disc, with reference to the shape of the rostrum; noun in apposition.

Remarks. See the generic remarks above. The holotype has 8 eggs in its brood pouch.