Hexapleomera wombat Bamber, 2012, sp. nov.
Creators: name: Bamber, Roger N.
Publisher: name: Zenodo
Year: 2012
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Tanaidacea
Tanaididae
Hexapleomera
Hexapleomera wombat

description: Hexapleomera wombat sp. nov.
(Figs 1–5)
Diagnosis: Adult uropod with five segments; pleopod endopod with one subdistal inner marginal seta, pleopod 3 basis without inner seta; coxa of pereopod 1 without apophysis; maxillule palp with five distal setae; maxilliped basis with one distal seta, coxa with three setae, endite without distal spines; cheliped fixed finger of female with four ventral setae; dactylus of male cheliped with spinulation along cutting edge; fixed finger with no proximal tooth-like apophysis on cutting edge.
Type material: brooding Ƥ, holotype (BMNH 2012.625), 2Ƥ (1 brooding, 1 with oostegites), paratypes (BMNH 2012.626-627), 1 brooding Ƥ, dissected, from hull of Wombat, 28 January 2010. 1 adult 3, allotype (BMNH 2012.628), 1Ƥ, 1 juvenile, paratypes (BMNH 2012.629-630), 2 brooding Ƥ, paratypes (BMNH 2012.631-632), from hull of Piper of Hornet, 30 October 2009. 1 sub-adult 3, 1Ƥ, 4 juveniles, paratypes (BMNH 2012.633-638), from hull of Black Pig, 30 September 2009. 1Ƥ (dissected), from hull of Delphi, 0 5 October 2009. 1 brooding Ƥ, paratype (BMNH 2012.639), from hull of Anodyne, 21 January 2010. 3Ƥ (1 with oostegites), 3 juveniles, paratypes (BMNH 2012.640-645), from hull of Senor Torro, 0 5 February 2010. 7Ƥ, paratypes (BMNH 2012.646-652), from hull of Frivolity, 22 February 2010. 1Ƥ with oostegites, paratype (BMNH 2012.653), from hull of Nibo, 23 February 2010. All collected from yacht hulls in Queen Anne’s Battery Marina at Plymouth, UK (ca 50°22ʹN 004°08ʹW), by John Bishop.
Other material: 1Ƥ with oostegites, Château Marina, Brest, 48°22.88ʹN 4°29.68ʹW, Panel 31, 23 August 2012. 1Ƥ with oostegites, Trébeurden Marina, Brittany, 48°46.22ʹN 3°34.02ʹW, Panel 57, 27 March 2012. 1Ƥ with oostegites, 2 mancae, Trébeurden Marina, Brittany, 48°46.22ʹN 3°34.02ʹW, Panel 20 (outer) 3 August 2012. 233, 1Ƥ with oostegites, Perros Guirec Marina, Brittany, 48°48.85ʹN 3°26.53ʹW, panel 44, 21 March 2012. 333, 14Ƥ (5 brooding, 4 with oostegites), 22 juveniles, 15 mancae, Perros Guirec Marina, Brittany, 48°48.85ʹN 3°26.53ʹW, panels 1 (inner), 2 (inner) and 8 (outer), 1 August 2012. All collected from fouling panels by John Bishop.
Description of female: body (Fig. 1 A) 4.6 times as long as wide, dorsally with black mottling on cephalon, all pereonites and whole pleon; length of holotype 2.6 mm. Cephalothorax stout, pear-shaped, tapering towards anterior, as wide as long, with slight rounded frons but no distinct rostrum, eyes present, pigmented. Cephalothorax as long as pereonites 1–3 together. Pereonites 1 to 3 together 0.9 times as long as wide, rounded laterally, pereonites 1 and 2 equal in length and 0.3 times as long as cephalothorax, and each 3.7 times as wide as long; pereonite 3 longer, 1.5 times as long as pereonite 2 and 2.3 times as long as wide; pereonite 1 apparently naked, pereonites 2 with paired dorsolateral setae, pereonite 3 with single dorsolateral setae and mid-dorsal seta towards frontal edge. Pereonites 4 and 5 wider posteriorly, with concave anterolateral margins, twice as long as pereonite 2 and 1.7 times as wide as long, each with single dorsolateral and paired mid-dorsal setae; pereonite 6 as long as pereonite 3 and 1.9 times as wide as long, with single dorsolateral setae. Pleon of five free pleonites, pleonites 1 to 3 with sparse tufts of plumose lateral setae; pleonite 1 longest, trapezoid, as long as pereonite 1 and three times as wide as long; pleonite 2 trapezoid, three-quarters as long as pleonite 1 and nearly four times as wide as long; pleonite 3 half as long as pleonite 1; pleonites 4 and 5 subequal, with paired mid-lateral setae, half as long as pleonite 2 and five times as wide as long, without pleopods. Pleotelson (Fig. 1 B) semicircular, 1.5 times as wide as long, with paired lateral and three laterodistal setae on each side and one longer and one shorter pair of distal setae.
Antennule (Fig. 1 C) proximal article about 1.5 times as long as distal articles together, 2.5 times as long as wide, both inner and outer margins with penicillate setae in proximal half and simple distal setae; second article one-third as long as first with inner and outer distal tufts of simple setae; third article as long as second with inner and outer distal tufts of one penicillate and one simple setae; distal article (flagellum) very small, with six distal setae and four aesthetascs.
Antenna (Fig. 1 D) first article naked, 0.6 times length of second; second article with paired ventral simple setae and paired dorsodistal simple setae; third article as long as first article, naked; fourth article longest, 1.5 times as long as third article and 2.6 times as long as wide, with three simple distal setae; fifth article just shorter than fourth, with three simple distal setae; sixth article half as long as third article, with 12 distal setae.
Labrum (Fig. 1 E) rounded, setose. Left mandible (Fig. 1 G) with wide, robust, distally denticulate lacinia mobilis with adjacent seta, pars incisiva stout, smooth; right mandible (Fig. 1 F) with narrower, distally crenulate lacinia mobilis, pars incisiva more pointed; pars molaris of each mandible robust, rugose. Labium (Fig. 1 I) wide, all lobes finely setose distally; labial palp present, as long as wide. Maxillule (Fig. 1 H) with eight distal spines, each spine denticulate in distal half, endite with distal tuft of setules on outer margin, palp with five distal setae. Maxilla ovoid, simple. Maxilliped (Fig. 1 J) generally typical of genus; coxa with three inner setae; basis with single distal seta reaching distal margin of palp article 1; proximal palp article with curved outer-distal spine, second palp article with outer-distal spine, and ten simple inner setae of varied lengths; third article with fourteen inner setae in two rows; fourth article with eight distal and one outer subdistal simple setae. Maxilliped endites (Fig. 1 K) with setose distal margins, two longer coarsely-plumose setae, but no spines. Epignath (Fig. 1 L) typical of genus, elongate with distal spine and finely setose margins.
Cheliped (Fig. 2 A) comparatively stout, rounded, basis 1.4 times as long as wide with single dorso-subdistal and ventrodistal setae; merus ventrally with two subdistal seta and single seta towards dorsal margin; carpus 1.5 times as long as wide, with single proximo-dorsal, four dorsodistal, and three midventral setae; propodus shorter than wide with one inner seta and four outer setae distally near dactylus insertion; fixed finger 0.75 times as long as propodus, with four ventral setae, three outer distal setae, and five setae along cutting edge, cutting edge distally expanded into rounded lamella; dactylus with eight fine spinules along cutting edge.
Pereopod 1 (Fig. 2 B) longer than others; coxa without apophysis; ischio-basis slender, five times as long as wide, dorso-proximally with one simple and one penicillate setae, one ventrodistal seta; merus 0.3 times length of ischio-basis with one ventrodistal seta; carpus one-third longer than merus with single dorsodistal and ventrodistal setae; propodus 1.6 times as long as carpus, with subdistal dorsal seta, one dorsodistal and three ventrodistal simple setae; dactylus with distinct, slender, longer claw, both together 0.7 times as long as propodus. Pereopod 2 (Fig. 2 C) ischio-basis three times as long as wide, dorso-proximally with one simple and two penicillate setae, one ventrodistal seta; merus half length of ischio-basis with two ventrodistal setae and short tooth-like spine, and one dorsodistal seta; carpus compact, shorter than merus, with dorsal seta, three posterodistal and one anterodistal short tooth-like spines; propodus 1.5 times as long as carpus; dactylus plus claw just shorter than carpus. Pereopod 3 (Fig. 2 D) similar to pereopod 2 but merus apparently without dorsodistal seta.
Pereopod 4 (Fig. 2 E) ischio-basis 2.6 times as long as wide, with two ventrodistal setae; merus 0.4 times as long as ischio-basis, with paired subdistal ventral short spines; carpus 0.8 times as long as merus, with crown of three posterodistal and two anterodistal short tooth-like spines; propodus 1.6 times as long as carpus with middorsal penicillate seta; dactylus and unguis fused into a claw, curved, with lateral comb of six or seven spinules. Pereopod 5 (Fig. 2 F) as pereopod 4 but without penicillate seta on propodus. Pereopod 6 (Fig. 2 G) as pereopod 5, but propodus with distal row of five leaf-like spines, claw with eight or nine lateral spinules.
Pleopod 1 basis with one inner and five outer plumose setae, pleopod 2 (Fig. 1 M) basis with one inner and four outer plumose setae, pleopod 3 basis with no inner and 3 outer plumose setae; exopods with about 25 plumose setae along outer edge; endopods with one inner and about thirteen outer plumose setae, distally with shorter, stout seta.
Uropod (Fig. 2 H) of four segments plus basis, segments 1.5–2 times as long as wide, subequal in length.
Juvenile: Body lengths between 1.2 and 2 mm; similar overall to mature female, but with only four (in total) uropod segments; specimens <1.3 mm in body length with only two aesthetascs on antennule; specimens> 1.3 mm with three aesthetascs.
Adult male (Fig. 3): body (Fig. 4 B) 4.4 times as long as wide, dorsally with dark mottling as in female (in preserved material); length of allotype 2.8 mm. Cephalothorax onion-shaped, tapering towards anterior, as wide as long, parallel-sided anterior part 0.4 times as wide as posterior width; with slight rounded rostrum, eyes present, pigmented. Cephalothorax 1.2 times as long as pereonites 1–3 together, and one-quarter of total body-length. Pereonites rounded laterally; pereonites 1 to 3 together nearly as long as wide; pereonites 1 and 2 subequal in length, 3.5 times as wide as long; pereonite 3 about 1.2 times as long as pereonite 2 and 2.6 times as wide as long; pereonites 4 and 5 longest, 1.7 times as long as pereonite 2 and twice as wide as long; pereonite 6 as long as pereonite 3. Pleon comprising some 22% of total body length.
Appendages similar to those of female except for antennules, antennae and chelipeds.
Antennule (Fig. 4 C) longer than cephalothorax, elongate, proximal peduncle article 0.83 times as long as cephalothorax, 6.9 times as long as wide, with proximal fields of microtrichia and distal tufts of simple and penicillate setae; second article one-third as long as first, with distal crown of simple setae; third article 0.8 times as long as second, with two simple distal setae; distal article (flagellum) very short, with one penicillate and twelve simple setae and six aesthetascs.
Antenna (Fig. 4 D) more elongate than that of female, proximal article compact, naked; second article four times as long as first and three times as long as wide, with two simple distal setae; third article twice as long as first, naked; fourth article longest, 1.3 times as long as second article, with five distal setae of varying lengths, the longest longer than fifth article; fifth article 0.8 times as long as second article, distally with two simple and four penicillate setae; sixth article one-third as long as fifth article, with one short penicillate seta and eleven longer simple setae.
Cheliped (Fig. 4 E) much stouter than that of female, in life reaching well-forward of rostrum (Fig.3); basis compact, about 1.2 times as long as wide, with one ventrodistal seta and one outer submarginal dorsodistal seta; merus triangular, with outer mesial seta and two ventral setae; carpus 1.2 times as long as wide, 1.4 times as long as basis, ventral margin very short, with three dorsodistal and three mid-ventral setae. Propodus wider than long, with two inner setae (comb-row) adjacent to dactylus attachment, and five setae distally between fingers; fixed finger longer than palm, with five ventral setae, two inner-distal setae and row of eight setae alongside cutting edge; dactylus arcuate, with proximal apophysis bearing five spinules, inner seta in distal half, and row of eleven toothlike spinules along cutting edge, becoming more densely-grouped around distal rounded apophysis.
Subadult male (Fig. 4 A): Morphology somewhat intermediate between those of female and adult male. Cephalothorax as long as wide, tapering towards rostrum, but anterior margins not laterally concave; antennule as long as cephalothorax; cheliped similar to that of female but more robust.
Etymology: Named after the yacht from which the holotype was collected (noun in apposition), derived from the Australian Sydney aboriginal word “wambad”.
Remarks: With the distal uropod segment of “normal” proportion, the compact anterior pereonites, and the sexual dimorphism of the chelipeds and antennulae, Hexapleomera wombat sp. nov. accords with the generic diagnosis. With a five-segmented uropod, no tooth-like apophysis on fixed finger of the male cheliped, and the presence of only one distal seta on the maxilliped basis, the present species is only similar to H. moverleyi.
There are a number of subtle differences from the male of H. moverleyi, such as the proportions of the antennule and the cheliped articles, the presence of six (rather than five) aesthetascs on the antennule, and the setation of the maxilliped, but the clearest distinctions are in the lack of an apophysis on the coxa of pereopod one (present in H. moverleyi), the lack of an inner seta on the basis of the third pleopod (one seta present in H. moverleyi), the presence of three setae on the coxa of the maxilliped (two in H. moverleyi), and the presence of spinulation along the cutting edge of the cheliped dactylus (absent in H. moverleyi).
The size distribution of the type-series is shown in Fig. 5. All specimens below 2 mm body-length were juveniles, while adults (both preparatory and mature males and females) overlapped over a range between 2 and 3.25 mm body-length. That there were three females with oostegites either at the top end of the adult size range or exceeding it suggests that these females have moulted and grown after breeding, and that the species is iteroparous. The species was present on 21 of 63 boats inspected at Queen Anne’s Battery Marina, Plymouth. A few of the specimens were found in silty tubes, although most, taken in hull scrapings, were loose in the samples. The Brittany samples from Perros Guirec and Trébeurden also included specimens of Zeuxo holdichi Bamber, 1990. ‘Inner’ and ‘Outer’ refer to sets of settlement panels far from and near to the marina entrance, perhaps reflecting the amount of water movement, although the distinction is sometimes somewhat arbitrary. Panels from two further marinas in northern France, at Moulin Blanc Marina, Brest, and Aber Wrac’h, Brittany, had collected a few Z. holdichi but no Hexapleomera.
description: Published as part of Bamber, Roger N., 2012, A re-assessment of Hexapleomera Dudich, 1931 (Crustacea: Tanaidacea: Tanaidae), with designation of three new species, pp. 51-70 in Zootaxa 3583 on pages 56-62, DOI: 10.5281/zenodo.283096