Paratanais hamulus, Bird & Bamber, 2013

BIRD, GRAHAM J. & BAMBER, ROGER N., 2013, New littoral, shelf, and bathyal Paratanaidae (Crustacea: Peracarida: Tanaidacea) from New Zealand, with descriptions of three new genera, Zootaxa 3676 (1), pp. 1-71 : 32-38

Paratanais hamulus sp. nov.

Figures 17 – 20, 36E, N, Y–Z

Material examined. Holotype: non-ovigerous ♀, CR.23496, Stn AW / 42-5, Otago Shelf, 25% bryozoan cover, 80 m, 45.8268°S, 170.8802°E, 21 September 2007, Polaris 2.

Allotype; prep. male, CR.23497, Stn AW /27L5, Otago Shelf, 25% bryozoan cover, 82 m, 45.8252°S, 170.8843°E, 12 September 2007, Polaris 2.

Paratypes: one non-ov. ♀, CR.23498, Stn AW /2L5, Otago Shelf, 40% bryozoan cover, 83 m, 45.8316°S, 170.8828°E, 7 September 2007 , Polaris 2; one non-ov. ♀, CR.23499, partly dissected on microslides CR.23499/ 1,2,3, Stn AW /3-5, Otago Shelf, 70% bryozoan cover, 83 m, 45.8224°S, 170.8881°E, 7 September 2007 , Polaris 2; prep. male, PML 2390, Stn AW /6L5, Otago Shelf, 30% bryozoan cover, 84 m, 45.8327°S, 170.8798°E, 7 September 2007 , Polaris 2; one ♀, PML 2391, Stn AW /19L, Otago Shelf, 85% bryozoan cover, 81 m, 45.8221°S, 170.8854°E, 11 September 2007 , Polaris 2; one non-ov. ♀, PML 2392, Stn AW /37A5, Otago Shelf, 50% bryozoan cover, 82 m, 45.8334°S, 170.8756°E, 21 September 2007 , Polaris 2; one non-ovigerous ♀, partly dissected on microslide NIWA 13617 , Stn D. 1, Veryan Bank, Chatham Rise, 141 m, 44.3000°S, 176.16670°E, 12 April 1963 , cruise 7007; one non-ov. ♀, NIWA 27325 , Stn Z. 6052, Pitt Island , Chatham Islands, 55 m, 44.3583°S, 176.2167°W, 1 February 1954, coll. G.A. Knox.

Other material: one female in silt-sand nest with mancae, Stn AW /3L5, Otago Shelf, 70% bryozoan cover, 83 m, 45.8224°S, 170.8881°E, 7 September 2007 .

Diagnosis. Female: with carapace entire. Pleon shorter than broad, shorter than pereonites 5–6 combined. Antennule with cap-like segment. Antenna article-2 with sub-distal inferior thorn-like apophysis and seta, superodistal seta as long as article-3; article-3 superodistal spine acute. Mandible lacinia mobilis with crenulate distal margin. Maxilliped basis seta not reaching endite margin; endite tubercles large, ovoid; palp article-2 with one medial seta robust but minutely serrate on oral margin. Cheliped palm with sinuate spine. Pereopod-1 basis with superoproximal seta. Pereopods 2–3 basis with inferior seta only. Pereopods 2–6 spines finely serrate; pereopods 2–3 basis with inferior seta only. Pereopods 4–6 merus with seta. Pleopod endopod medial edge not setulate. Uropod rami two-segmented, longer than peduncle, exopod one-segmented.

Etymology. Latin noun hamulus , ‘a hook’, diminutive, referring to the antennal article-2 spine.

Description. Female: Habitus ( Fig. 17A,E ) fairly slender, about six times ltb; length 2.67–5.44 mm [nonovigerous], 3.88 to> 5 mm [ovigerous]. Cephalothorax, slightly longer than pereonites 1–2 combined, 0.9 times as long as broad. Pereon compact, straight-sided, pereonite-1 shortest, 0.3 times as long as broad, pereonites 2–3 subequal, 0.5 times as long as broad (pereonite-2); pereonites 4–5 slightly longer than pereonites 2–3, pereonite-5 longest, 0.6 times as long as broad. Pleon 14% of total length. Pleotelson ( Fig. 17F ) as long as pleonites 3–5 combined, half as long as wide, with rounded apex extended and deflexed.

Antennule ( Fig. 17B,C ) just shorter than cephalothorax; article-1 half total length; article-4 longer than articles 2–3 combined [large pre-moult female with hint of articulation proximally]; cap-like segment present, with three setae and one aesthetasc. Antenna ( Figs 17D,G , 36N,U ) article-2 with setulate superior margin, with lateral seta, inferior margin strongly convex; article-3 with few small setules; article-4 three times ltb; article-6 with four setae.

Mouthparts: Mandibles ( Fig. 18A–B ) typical. Labium ( Fig. 18C ) typical, both lobes sparsely setulate. Maxillule ( Fig. 18D ) typical, endite with ten spines, and with several distal combs. Maxilliped ( Fig. 18E–G ) bases unfused distally; palp article-2 with long medial seta minutely serrulate, one shorter weakly serrulate seta and strong serrate seta ( Fig. 18G ). Epignath ( Fig. 18H ) typical, apex with cluster of setules.

Cheliped (Fig. 19A–B) typical; basis 1.4 times ltb, posterior lobe large; merus typical; carpus twice as long as broad; chela as long as carpus, propodus 2.5 times ltb, palm medial comb with up to four spines; fixed finger 0.4 times length of palm, distal tooth rounded.

Pereopod-1 (Figs 20A, 21A) basis four times ltb; ischium with small seta; merus 3.0–3.6 times ltb, with superodistal seta and two small inferodistal setae; carpus about half length of merus, 1.8 times ltb with two superior setae (one more robust than other) and two small inferodistal setae [and possibly with small spine or apophysis]; propodus as long as or longer than merus, five times ltb, with two or three superodistal setae; dactylus-unguis combined as long as propodus, dactylus with accessory seta. Pereopod-2 (Figs 20B, 36Y) 0.7 times length of propodus as long as merus-carpus combined, with one superodistal seta; dactylus-unguis combined as long as propodus; dactylus with accessory seta. Pereopod-3 (Fig. 20C) similar to pereopod-2 but slightly shorter.

Pereopod-4 (Fig. 20D) basis stout, twice as long as broad, inferior margin with simple seta and two PSS, superior margin with two simple setae; ischium with two setae; merus about twice as long as broad; carpus as long as merus, spines relatively small; propodus as long as carpus, superodistal spine half length of dactylus; dactylusunguis combined half length of propodus. Pereopod-5 (Figs 20E, 36E) similar to pereopod-4. Pereopod-6 (Figs 20F, 21B, 36Z) typical and similar to pereopods 4–5 but basis with superoproximal PSS and inferior margin with one PSS, merus with distal medial seta.

Pleopod (Fig. 19C) typical; endopod 2.5 times ltb, with distomedial seta and fringe of twenty plumose setae; exopod slightly narrower than endopod, 2.9 times ltb, with fringe of thirty setae; both rami without gaps in setal fringe.

Uropod (Fig. 19D) about as long as pleotelson; peduncle 1.3 times ltb; exopod as long as peduncle or segment- 1 of endopod; endopod 1.7 times length of peduncle, segment-2 shorter than segment-1.

Preparatory male (?): Habitus ( Fig. 21C ) generally similar to female, but pleon proportionately longer, 17% of body length and longer than broad; length 2.6–2.9 mm. Antennule ( Fig. 21D ) stouter than that of female.

Distribution and ecology. Bryozoan thickets, principally Cinctipora elegans Hutton , about 80 m depth on the Otago Shelf, off the Otago Peninsula. Only other two specimens have been recorded, from the Chatham Rise and shelf off Pitt Island (Chatham Islands), at 55– 141 m.

Remarks. The conformation of the antenna suggests that this species is close to P. tara but is also similar to that of Penteparatanais gen. nov. (see below). Apart from the more robust body shape, the superior spine of antennal article-3 of P. hamulus sp. nov. is longer and more acute than in P. tara , and the uropods are both stouter and relatively smaller (for example, compared to the pleotelson that often overhangs). The presence of inferior setae on the basis of pereopods 2–3 and the additional seta on the merus of pereopods 4–6 appear to distinguish this species from most others in the genus.

A preparatory male phase is provisionally identified here, although this has not been recorded or published in previous studies on Paratanais . It would be fairly unusual for there not to be such a stage although the variability in antennule shape among certain females is an obscuring factor.

It is a large species that constructs tubes or galleries of mineral and other particles within the bryozoan substrate. This habitat is quite extensive off the Otago coast ( Probert 2003) and provides shelter for other tanaidacean species (as yet undescribed apseudomorphans).

Figures

FIGURE 17. Paratanais hamulus sp. nov. Holotype female [CR.23496]: A habitus; B antennule; C antennule article-4with

FIGURE 18. Paratanais hamulus sp. nov. Paratype female [CR.23499]: A–B left and right mandibles respectively; C labium;

FIGURE 21. Paratanais hamulus sp. nov. Paratype female [NIWA 27325]: A pereopod-1; B pereopod-6. Paratype preparatory male (?) [CR.23497]: C habitus; D antennule, oblique, setae omitted for clarity. Scale bar: 1 mm for C, 0.25 mm for A–B, D.

FIGURE 36. A Metatanais sp. antennule, lateral; B Metatanais sp. uropod; C Xeplenois pleon-pleotelson, dorsal and lateral (pleopod & setae omitted), after Bamber 2005; D Penteparatanais pereopod-4 carpus; E Paratanais hamulus pereopod- 5carpus; F Acallocheirus pereopod-2 carpal spines; G P. incomptus pereopod-2 carpal spines; H Aparatanais timutimu maxilliped palp article-2 spine; J A. timutimu cheliped kukri spine: K A. timutimu uropod; L Paratanais caterae cheliped spine; M P. puia uropod; N P.hamulus antenna article-3. O Atemtanais antenna article-3, after Bird 2011; P Atemtanais pereopod-2 carpal spines, after Bird 2011; Q Paratanais caterae pereopod carpal spines; R P.caterae maxilliped palp article-2 spine; S P.