Triaina makridonte, Just, Jean, 2009

Just, Jean, 2009, Triaina, a new genus in the Janirellidae Menzies, 1956 (Crustacea: Isopoda: Asellota), with two new species from south-eastern Australia, and a new diagnosis for the family, Zootaxa 1980, pp. 1-15 : 9

Triaina makridonte sp. nov.

Figs 5–7

Type fixation. Holotype, male, here designated. Australian Museum, AM P76938.

Type locality. Eastern Australia, New South Wales.

Material examined. Holotype, juvenile male (pleopods I and II not fully developed; left side of pereonite 3 damaged; antennae and all pereopods except pereopod I broken off), 6.8 mm (tip of pseudorostrum to apex of pleotelson), east of Port Jackson, New South Wales, Australia, 33°52'S 151°23'E, 80 m, mud, 2.5m sledge dredge, 11 December 1980, FRV Kapala , stn K 80-20-11, Australian Museum, AM P76938.

Description. Head approximately 2.5 times wider than long, frontal margin nearly straight; pseudorostrum with middle prong 3 times longer and much broader than side prongs, middle prong reaching just beyond article 1 of antennulae; dorsal surface of head with single low, broad, rounded hump in proximal half; lateral margins straight, with forward pointing triangular projection.

Pereonites 1–3 of equal width, 4–7 successively slightly less wide; 1–2 of equal length, slightly longer that subequal length 3–7; pereonites 1–3 with single anterior transverse groove, 4 with 2 grooves, 5 with single posterior transverse groove and two oblique grooves more anteriorly, 6 with single, 7 with 2 grooves, 1–5 with single low dorsolateral hump each side; lateral margins 1–4 flattened, truncate, entire; pereonite 5 lateral margins entire, obliquely truncate; pereonites 6–7 rectangular; pereonite 7 with mid-ventral pointed spine.

Pleotelson nearly as wide as pereonite 7, as long as pereonites 1 and 2 combined; lateral margins straight, slightly tapering towards sharply acute corners; entire lateral margins and projections finely serrate; posterior projection short, truncate, margin smooth, reaching as far as lateral corners.

Antennula of 9 articles, reaching just beyond article 4 of antenna, article 7–9 with single aestetasc.

Maxilliped, epipod tapering distally, reaching 2/3 length of palp article 4, partly covered with cuticular ridging, distal half of medial margin and apex with fine setules; apex of endite concave with row of 5 slender fan-shaped setae surrounded by assortment of simple and plumose setae; palp article 2 without cover of fine setules on ventrolateral surface.

Pereopod I basis length 3.5 width; ischium expanded distally, 0.54 length of basis; merus 0.47 length of ischium, with short anterodistal triangular projection; carpus length 3.0 width, slightly tapering distally, posterior margin with row of 10 robust setae; propodus 0.42 length of carpus, with 5 robust setae along posterior margin; dactylus 0.9 length of propodus, main claw 0.4 length of dactylar body.

Male (juvenile) pleopod I length 3.3 proximal width, lateral margins straight, slightly tapering, apical lobes evenly rounded without corners, with fringe of simple setae. Pleopod II protopod acutely pointed with apical simple setae. Pleopods III–V as in type species.

Uropods reaching well beyond apex of pleotelson posterior projection, ramus subequal in length to protopod, with apical tuft of simple and penicillate setae and 1 long simple seta.

Distribution. South-eastern Australia, 80 m.

Remarks. For comparison with Triaina isodonte sp. nov. see that species, above. Triaina makridonte sp. nov. represents the shallowest record of the family.

Etymology. The species name is composed of the Greek μακρɩς (makris) meaning long, and δόντɩ (donte) meaning tooth, alluding to the middle pseudorostral prong being much longer than the two lateral ones.

Figures

FIGURE 5. Triaina makridonte sp. nov. Holotype, male. cd, dorsal view of head; p 1, pereopod I; pt, ventral view of pleotelson; up, left uropod. Scale bar: 1 mm.

FIGURE 6. Triaina makridonte sp. nov. Holotype, juvenile male. ll, lower lip; md, mandible; r, right; l, left; mx 1 – 2, maxilla 1 and 2; mxp, maxilliped. Asterisk: some setae omitted.

FIGURE 7. Triaina makridonte sp. nov. Holotype, juvenile male. 1 - 5, pleopods I – V.