Uroptychus macquariae, Schnabel & Burghardt & Ahyong, 2017

Schnabel, Kareen E., Burghardt, Ingo & Ahyong, Shane T., 2017, Southern high latitude squat lobsters II: description of Uroptychus macquariae sp. nov. from Macquarie Ridge, Zootaxa 4353 (2), pp. 327-338 : 330-334

Uroptychus macquariae n.sp.

( Figs. 4 , 5 , 6 )

Uroptychus insignis .— Ahyong et al. 2015: 111 , figs. 1, 2, 5A (part).

Holotype. AM P 100957 (ex NIWA 40904), 1 ov. female (cl 15.9, pcl 10.5 mm), Hjort Seamount, 56°14.78– 14.49'S, 158°30.34–30.9'E, 676–750 m, 16 April 2008, TAN0803/98.

Paratypes. NIWA 40904, 1 female (cl 8.7, pcl 5.5 mm), 2 males (cl 18.1, 12.0, pcl 11.8, 7.4 mm), collected with holotype .

Other material. NIWA 40664, 1 male (pcl 13.1 mm), 1 unknown (pcl 11.6 mm), Seamount 8, 55°13.75– 13.75'S 158°15.49–15.89'E, 501–775 m, 15 April 2008, TAN0803/88 (specimens lost at sea; studied from images).

Diagnosis. Carapace excluding rostrum wider than long; dorsum smooth, sparsely setose, with transverse row of strong epigastric spines in large specimens (in large specimens the epigastric spines are as large as adjacent branchial marginal spines); lateral margins divergent, spinose; anterolateral spine overreaching outer orbital spine; anterior branchial spine separated from remaining branchial spines by wide unarmed margin (occasionally with 1 or 2 small spines). Rostrum sharply triangular, margins unarmed or with few minute denticles. Sternite 3 anterior margin with deep, V-shaped median emargination. Basal antennal article with small outer spine; ultimate and penultimate articles each with distal spine. Antennal scale falling short of apex of ultimate peduncle article. Ocular peduncle 1.8–2.0 × as long as wide. Crista dentata uniformly and minutely dentate. P2–4 similar; merus with small spines on extensor margin; propodus flexor margin broadened distally and lined with movable spines; dactylus flexor margin lined with strong, obliquely directed, corneous teeth.

Description of type material. Carapace: Wider than long (length 0.8–[0.9] × width); greatest width 1.8–[1.9] × distance between anterolateral spines. Dorsal surface moderately convex from anterior to posterior, large specimens with feeble depression between gastric and anterior branchial regions; with sparse short setae; bearing transverse field of 4–8 [6] small spines across epigastric region. Lateral margins broadly convex, divergent posteriorly, with row of distinct spines: first (anterolateral spine) well developed, directed straight forward, overreaching lateral orbital spine, followed by 2 small spines on hepatic margin; fourth spine situated on anterior end of anterior branchial margin, nearly as large as anterolateral spine, flanked by spine mesially (2 spines in largest specimen); 1 or 2 extra small spines between fourth and fifth; fifth strong, distantly posterior to preceding spine, situated on anterior end of posterior branchial margin, followed by 4–[6] posteriorly diminishing spines; last spine followed by low ridge along lateral margin. Rostrum elongate triangular, horizontal and directed straight forward; dorsal surface flattish basally, becoming rounded in cross-section distally; lateral margin straight, with up to 3 minute spines distally; length [1.8]–1.9 × width, [0.5]–0.6 × pcl, width about half (small specimens) or less than half (large specimens) carapace width at posterior carapace margin. Outer orbital spine very small, moderately remote from and slightly anterior to base of anterolateral spine of carapace. Pterygostomian flap anteriorly angular, produced to small spine, surface somewhat granular or with several small spines on anterior portion.

Sternum: Excavated sternum with anterior margin convex between bases of maxilliped 1, surface without distinct ridge in midline. Sternal plastron length 0.7–0.8 × width, lateral extremities divergent posteriorly. Sternite 3 distinctly depressed, anterolateral angle blunt or rarely sharply produced; anterior margin with deep V-shaped median emargination, without median spines. Sternite 4 with bluntly or obsolescently denticulate anterolateral margin, anteriorly blunt angular or rounded, posterolateral margin 0.5–0.6 length of anterolateral margin. Sternite 5 slightly broader than sternite 4, anterolateral margins strongly convex anteriorly, 1.3–1.4 × length of posterolateral margin of sternite 4. Widest at sternite 7.

Abdomen: Tergite 1 gently convex from anterior to posterior. Tergite 2 [2.3]–3.0 × wider than long; pleural lateral margins weakly concave and weakly divergent posteriorly, posterolaterally angular. Pleuron 3 with angular lateral margin. Telson about half as long as wide; posterior plate 1.0–2.0 [1.4] × longer than anterior plate (longer in small specimens), posterior margin distinctly emarginate.

Eye: Relatively short (length [1.8]–2.0 × width), somewhat narrowed distally, reaching anteriorly at most to proximal one-third of rostrum. Cornea not dilated, half the length of remaining eyestalk in large specimens, less in small animals.

Antennule: Distal article of antennular peduncle relatively slender, 3.0–4.4 [3.9] × longer than high (proportionally longer in large specimens).

Antenna: Antennal peduncle extending far beyond cornea, overreaching midlength of rostrum. Article 2 with small distolateral spine. Antennal scale tapering, 1.1–[1.7] × wider than article 5, slightly falling short of article 5. Articles 4 and 5 each with small distomesial spine. Article 5 about twice as long as article 4, width [0.6]–0.8 × height of distal article of antennule. Flagellum of 12 segments, overreaching distal end of P1 merus.

Maxillipeds: Maxilliped 1 with bases broadly separated. Maxilliped 3 basis with mesial ridge proximally lobelike, with a few minute obsolescent denticles; ischium distally not rounded on flexor margin, crista dentata with numerous tiny denticles, similar in size across entire length; merus wide relative to length, about twice length of ischium, flattish on mesial face, distolateral spine distinct, flexor margin ridged along distal half, with 4–6 small spines distal to midlength; distolateral spine of carpus distinct.

Pereopod 1 (cheliped): Sparsely setose, length 3.2–4.1 × pcl (males), 3.0–[3.6] × pcl (females) (greater in larger specimens). Ischium with well-developed dorsal spine, ventromesial margin with strong subterminal spine proximally followed by small spines. Merus, carpus and palm with sparse denticles on dorsal surface (fewer on palm). Ischiomerus 0.9–1.1 [1.0] × pcl (longer in large specimens). Merus distally and mesially spinose (a few mesial spines strong), ventrally with small spines along mesial margin. Carpus 0.8–[1.0] × length of ischiomerus, distally spinose. Palm length 2.1–2.4 (males), 2.2–[2.6] (females) × width, [1.1]–1.3 × carpus length. Fingers (dactylus and pollex) inclined somewhat laterally in large specimens, straight in small specimens, not gaping, distally crossing. Dactylus length [0.6]–0.8 × palm length, occlusal margin with low median process proximal to position of opposite eminence on pollex.

Pereopods 2–4 (walking legs): Sparsely setose. Meri successively shorter posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.8 × length of P3 merus), P2–3 meri subequally broad, P4 merus slightly narrower than P3 merus; length-breadth ratio, 3.1–3.7 [3.5] on P2, 2.8–[3.5] on P3, 2.6–[2.9] on P4 (relatively narrow in large specimens); dorsal margin with several small spines including terminal spine, ventrolateral margin with terminal spine only. P2 merus length 0.6–[0.7] × pcl, slightly shorter than P2 propodus; P3 merus length [0.9]–1.0 × length of P3 propodus; P4 merus length 0.7–[0.8] × length of P4 propodus. Carpi successively slightly shorter posteriorly; carpus-propodus length ratio, 0.6–0.8 [0.7] on P2, 0.5–0.7 [0.6] on P3, 0.5–[0.6] on P4; extensor margin with small proximal spine. Propodi subequal on P2–4 or successively slightly shorter posteriorly; flexor margin distally convex (strongly in large specimens, feebly so in small specimens), ending in pair of spines preceded by 4–9, 4–8, 4–7 spines (fewer in small specimens) on P2, 3 and 4 respectively. Dactyli 0.4–0.5 × as long as propodi; dactyluscarpus length ratio, 0.6–0.8 [0.7] on P2, [0.6]–0.9 on P3, 0.8–1.0 [0.9] on P4; flexor margin slightly curving, with 8–10 [9 or 10] acute, proximally diminishing, somewhat inclined spines.

Eggs: Holotype with three remaining eggs under abdomen; 1.2–1.4 mm diameter.

Etymology. Named after the region encompassing Macquarie Island and Macquarie Ridge, used as a noun in the genitive singular.

Coloration. Vibrant orange and red ( Fig. 6 ).

Remarks. Uroptychus macquariae n.sp. only differs very subtly from U. insignis ( Henderson, 1885) , as remarked by Ahyong et al. (2015); it is comparably less setose, especially on the chelipeds and carapace, and large specimens bear more pronounced epigastric spines on the carapace. While the development of the epigastric spines varies allometrically in both species, fortunately, the series comprises both a small and large male and female each, allowing comparisons with similarly-sized specimens. In size-matched specimens, the spines of the U. macquariae n.sp. specimens are comparatively larger, except in the smallest specimens in which the epigastric armature is yet to appear. Ahyong et al. (2015) notes that the difference in epigastric armature to be most noticeable in the largest specimens in which the largest epigastric spines in Macquarie Ridge specimens are as large as, instead of smaller than, the adjacent branchial marginal spines. Further examinations suggest that in U. macquariae , the ocular peduncle may be more slender (length 1.8–2.0 × width versus 1.4–1.5 in U. insignis ) and the antennal scale might be more slender (1.1–1.7 × wider than antennal article 5 versus 1.8–2.1 in U. insignis ). The antennal scale also never reaches the end of the peduncle in the new species, while it can reach and overreach the peduncle in U. insignis . These characters can vary considerably in some other species of Uroptychus and more material is needed to ascertain whether these differences are constant.

Faunal associations between chirostylids and a variety of macro-invertebrates, most commonly corals, sea pens and sponges have been noted extensively in the literature (see review by Baeza 2011). Henderson (1888) points to a likely association between Uroptychus insignis and corals in his account of HMS Challenger samples from off Prince Edward Island. Unfortunately, no record remains on whether the specimens of U. macquariae n.sp. from Macquarie Ridge seamounts ‘Seamount 8’ and Hjort (stations TAN0803/88 and 98, respectively) were directly associated with coral. However, based on physical collections and camera tows on those two seamounts (7 and 6 sled and DTIS stations on SMT 8 and Hjort, respectively), it is apparent that live corals (bubblegum corals, gorgonian fans, bottlebrush corals, and stylasterids) and sponges dominated the habitat on both sites ( Rowden 2008). Figure 2 presents two examples of the habitat each for the two seamounts as encountered during the TAN0803 MacRidge 2 voyage. It is highly likely that U. macquariae n.sp. is living in association with these large habitat-forming organisms.

Distribution. Seamounts on the Macquarie Ridge; 501– 775 m.

Figures

FIGURE 2. Seamount habitat on Macquarie Ridge seamounts. Top panel: Seamount 8 (station TAN0803/92). Bottom panel: Hjort Seamount (station TAN0803/99). Credit:Deep-Towed Imaging System (DTIS)/ NIWA MacRidge 2 voyage.

FIGURE 4. Uroptychus macquariae n. sp., Holotype, female ov., pcl 10.5 mm, Hjort Seamount, Macquarie Ridge (AM P100957, ex. NIWA 40904). A, dorsal habitus. B, carapace, right lateral. C, right antenna, ventral view. D, right maxilliped 3, lateral. E, right crista dentata. F, right P1 ischiomerus, ventral. G, sternal plastron. H, telson.Scale: A, B, F = 2.5 mm; C, D, G, H = 1.25 mm; E = 0.5 mm. (Modified after Ahyong et al.2015)

FIGURE 5. Top row: Uroptychus macquariae n.sp., carapace, Hjort Seamount, Macquarie Ridge (NIWA 40904). A, female pcl 5.5 mm.B,male pcl 7.4 mm.C, male pcl 11.8mm.Bottom row: Uroptychus insignis (Henderson, 1885). D. female pcl 4.4 mm, Kerguelen Islands (MNHN IU-2010-5432), E. paralectotype, male pcl 4.5 mm, Prince Edward Islands (BMNH 1902.10.2.9–14), F. female pcl 7.2 mm, Kerguelen Islands (AM P97999), G. paralectotype, male pcl 10.7 mm, Prince Edward Islands (BMNH 1902.10.2.9–14), H. lectotype, ov. female, pcl 10.6 mm, Prince Edward Islands (BMNH 1902.10.2.9–14). Scale = 5 mm.(Modified after Ahyong et al. 2015).

FIGURE6. Colour in life.A, Uroptychus macquariae n.sp., male pcl 11.8mm, Hjort Seamount, Macquarie Ridge, TAN0803/ 98 (NIWA 40904); B, male pcl 13.1 mm, Seamount 8, Macquarie Ridge, TAN0803/88 (NIWA 40664, lost at sea). Scale = 10 mm.