Austinixa artankeri Theil & Felder 2020, sp. nov.

Austinixa artankeri sp. nov.

(Figs 4, 5, 12 A–C)

urn:lsid:zoobank.org:act: FD0FA1AC-9D6E-4784-8763-9B7151ED1566

Austinixa cristata— Manning & Felder 1989: 16, 17, fig. 9a–l (in part, specimens from Barra del Tordo, Tamaulipas, Mexico

only). Not Austinixa cristata (Rathbun, 1900).

Austinixa sp. 2,— Palacios Theil et al. 2016: 4 (table 2), 9 (fig. 1), 10 (fig. 2); present paper: Figs 1–3, Tables 1, 2.

Material examined. Holotype: USNM 1558334, adult male, cw 7.6 cl 3.5 mm, playa Boca del Drago, Bocas del Toro, Panama, 09° 24.79’N 82° 19.92’W, intertidal zone, low energy sandy beach, patches of sea grass, yabby pump, 10 Aug 2011, coll. D.L.F., F. Mantelatto, E.P.T. et al.

Paratypes: USNM 1558331, ovigerous female, cw 9.0 cl 4.6 mm, collection data same as holotype; USNM 1558329, male, cw 6.7 cl 3.5 mm, ovigerous female, cw 7.7 cl 3.9 mm, Isla Grande, Panama, 2007, coll. A. Anker; ULLZ 4428, female, cw 7.3 cl 3.9 mm, Barú, Colombia, 11 Mar 1996, coll. D.L.F., R. Lemaitre et al .; ULLZ 9548, female, cw 5.3 cl 2.8 mm, Barú, Colombia, 9 Mar 1997, coll. D.L.F., R. Lemaitre; ULLZ 13332, male, cw 4.6 cl 2.4 mm, collection data same as holotype, photograph voucher; ULLZ 13334, female, 6 Aug 2011, other data same as holotype, photograph voucher; ULLZ 13336, ovigerous female, cw 6.8 cl 3.5 mm, 6 Aug 2011, other data same as holotype, DNA voucher, photograph voucher; ULLZ 13642, male, cw 5.5 cl 3.0 mm, collection data same as holotype, DNA voucher; ULLZ 13643, male, cw 5.0 cl 2.9 mm, 6 Aug 2011, other data same as holotype; ULLZ 13644, female, cw 5.8 cl 2.9 mm, collection data same as holotype; ULLZ 13731, male, cw 6.2 cl 3.0 mm, collection data same as holotype, DNA voucher; ULLZ 13732, 2 males, cw 5.5 and 8.5 cl 2.5 and 4.1 mm, collection data same as holotype; ULLZ 14081, male, cw 5.0 cl 2.7 mm, data collection same as USNM 1558329; ULLZ 14142, ovigerous female, cw 9.6 cl 5.0 mm; collection data same as USNM 1558329; ULLZ 14841, male, cw 4.9 cl 2.4 mm; 6 Aug 2011, other data same as holotype; ULLZ 14902, male, cw 4.5 cl 2.5 mm, collection data same as holotype; ULLZ 17481, male, cw 7.1 cl 3.1 mm, Cachamaure, Venezuela, Jun 1997, coll. D.L.F. et al ..

Additional material: UF 18691, male, cw 8.8 cl 4.1 mm, Isla Carenero, near Buccaneer Resort, Bocas del Toro, Panama, in burrow, 0.3–1 m, yabby pump, 5 Oct 2005, coll. A. Anker; UF 18895, male, cw 7.3 cl 4.1 mm, Bocas del Toro, Panama, at the Smithsonian Tropical Research Station, facing Carenero, sand flat, in burrow, 0.5–1 m, yabby pump, 18 Nov 2006, coll. A. Anker et al.; UF 18898, female, cw 6.6 cl 3.2 mm, collection data same as for UF 18691; UF 18907, ovigerous female, cw 8.6 cl 4.2 mm, Boca del Drago, Bocas del Toro, Panama, seagrass flat, in burrow, 0.5–1 m, yabby pump, 15 Nov 2006, coll. A. Anker, A. Baeza; UF 18914, male, cw 8.2 cl 3.7 mm, 14 Nov 2006, other data same as UF 18907; UF 18916, male, cw 7.3 cl 3.4 mm, collection data same as for UF 18895, DNA voucher; UF 18917, ovigerous female, cw 7.2 cl 3.8 mm, collection data same as for UF 18895; UF 18920, male, cw 6.4 cl 3.2 mm, Isla Grande, Panama, south shore, sand flat with firm sand, silt, some seagrass, in burrow, 0.5–1 m, yabby pump, 6 Oct 2005, coll. A. Anker; UF 18927, male, cw 8.3 cl 3.9 mm, 2 ovigerous females, cw 8.5 and 8.9 cl 4.3 and 4.5 mm, collection data same as for UF 18914; UF 18931, male, cw 6.7 cl 3.3 mm, ovigerous female, cw 7.4 cl 3.9 mm, 22 Apr 2006, other data same as for UF 18920; UF 18946, ovigerous female, cw 8.4 cl 4.3 mm, 25 Nov 2006, other data same as for UF 18907, DNA voucher; UF 18950, male, cw 8.9 cl 4.0 mm, ovigerous female, cw 8.8 cl 4.5 mm, collection data same as for UF 18907, male DNA voucher; UF 18954, male, cw 7.3 cl 3.7 mm, collection data same as for UF 18920; UF48327, ovigerous female, cw 8.3 cl 3.6 mm, Isla Grande, Panama, fine sand close to seagrass, 09° 37.68’N 79° 34.14’W, coll. A. Anker; USNM 11192239, male, C. de Colón, south of Cartagena, Colombia, with Neochallichirus, yabby pump, 31 Jul 1994, coll. R. Lemaitre, DNA voucher.

Size: Males cw 4.5–8.9 mm (n = 21), ovigerous females cw 6.8–9.6 mm (n = 12), females cw 5.3–7.3 mm (n = 4).

Distribution. Known from Bocas del Toro and Isla Grande (Panama), Barú and C. de Colón (Colombia), Cachamaure (Venezuela) and provisionally (see Remarks) from Barra del Tordo, Tamaulipas (México).

Diagnosis. Carapace with each branchial region traversed by diagonal ridge, ridge not extending to orbit, not bending at lateral end sharply towards posterior; carapace anterior margin with a depression on each side lateral to eyes, extending across frontal region; lateral regions setose, male carapace lacking patch of short setae on posterior third; P4 merus with sharp laminate anterior margin, P4 propodus opposable margin bicarinate; P5 dactylus not or barely reaching P4 merus distal end; male telson semi-ellipsoidal, width less than twice length.

Description. Carapace sparsely punctate, 1.7–2.3 times wider than long, regions defined, with sharp cardiac crest extending entirely across cardiac region above posterior margin; anterior margins with 2 depressions, one each laterally to eyes, at about one fourth of distance between eye and lateral edge, reaching toward branchial regions; each branchial region crossed by ridge, not extending to orbit, not turning at lateral end sharply toward posterior; lateral regions setose. Antennae with 9 articles, third longest (Fig. 4A, B). Third maxilliped ischiomerus indistinguishably fused, elongate; three-segmented palp, nearly as long as ischiomerus; carpus very short; dactylus and propodus elongate, margins with long setae, dactylus inserted near base of propodus, reaching beyond end of propodus. Exopod with angle on non-opposable margin (Fig. 4C). Chelipeds of male and female similar; chela strong, smooth, palm with line of setae at inferior margin, extending to fixed finger, gape setose; fixed finger slightly deflexed, shortened, about ¼ length of palm, cutting edge with strong median serrated tooth, smooth gap between tooth and serrated tip; dactylus curved to meet fixed finger, serrated cutting edge, without large teeth (Figs 4D, 5A, E, G). P2–P5 long slender, relative lengths P4> P3> P2> P5, margins setose, setae sparse for P2 and P3, denser relatively longer for P4 and P5, P4 merus proximal region setose, P4 merus posterior half swollen, building posterior surface covered by setae and delimited by 2 margins, dorsal margin blunt, ventral margin sharp and serrated, P4 merus anterior margin forms sharp laminate crest; P4 propodus posterior surface bicarinate; P2–P4 dactyli slightly curved, P5 dactylus straight, barely reaching P4 merus distal end (Fig. 4A, E–J). Male pleon with 6 somites plus telson, none fused, somites 1 and 6 subtrapezoidal, somites 2–5 subrectangular, somites decreasing in width after somite 4, somites 1 and 2 half length of third somite, somites 3–6 about same length, telson longer; telson prolate subellipsoidal, less than twice as wide as long (Fig. 5B). Female pleon subcircular, with 6 somites plus telson, none fused, somites 4 and 5 widest, first 2 somites each half length of somite 3, somites 3–6 and telson about same length, telson subtriangular, about five times wider than long (Fig. 5H). Male first gonopod as illustrated (Fig. 5C, D), apex beak-shaped, with small circular setal brush on superior tip surface.

Etymology. The species name honors Arthur Anker, a valued friend and colleague whose dedicated field work has yielded specimens and photographs of this and related species, all generously made available for our studies.

Remarks. Although genetically distinct (Figs 2, 3), Austinixa artankeri sp. nov. in morphology (Manning & Felder 1989: fig. 9a–l; Figs 4 A–J, 5A–H) very closely resembles A. cristata (Manning & Felder 1989: frontispiece [e, f]; figs 6, 7a–h, 8a–m). They both have a ridge on each branchial region that medially falls short of the orbits, and in both cases these branchial ridges do not bend laterally in a sharp angle towards posterior, as they do in A. chacei and A. behreae. Both species show a depression on each side of the frontal region, laterally to the eyes and the P4 propodus shows a bicarinate posterior (opposable) margin. Additionally, the males lack an obvious setal patch on the posterior third of the carapace, as seen for other congeners, and their male first gonopod morphologies are homologous. Nevertheless, A. artankeri sp. nov. and A. cristata can be distinguished by the morphology of the P4 merus, the length of P5 relative to the P4 merus, and characteristics of their carapaces. In A. artankeri sp. nov., the posterior part of the P4 merus is swollen to form a relative wide setose posterior (opposable) surface, whereas the anterior margin flattens into a sharp laminate crest. In A. cristata a ridge is present on the anterior margin, although it is rather less sharp. Additionally, the P4 merus and P5 are more slender in A. cristata, where the posterior surface is not as wide as in A. artankeri sp. nov., and with a P5 dactylus clearly reaching to and many times beyond the distal end of the P4 merus. In A. artankeri sp. nov. the P5 dactylus falls short of the distal end of the P4 merus. Further differences can be observed in the morphology of the carapace. In A. artankeri sp. nov., the carapace appears more sculpted, with the regions and depressions more defined, including in many cases a marked interorbital boss. Also, the frontal depressions lateral to the eyes are relatively shorter and narrower in A. cristata. Whereas in A. artankeri the lateral depressions reach up to the branchial regions and are delimited in part by the branchial ridges, in A. cristata those are mostly reduced to triangular indentations on the ventral region of the front. Additionally, the carapace is transversely elongated in A. cristata when compared to A. artankeri sp. nov. In A. cristata the cw: cl ratio ranges from 2.2–2.9, but it is smaller for A. artankeri sp. nov. (1.7–2.3). Males of A. artankeri sp. nov. and A. cristata can also be distinguished by the shape of the pleonal telson. In A. cristata the telson is semicircular in shape, with a width about twice its length, but in A. artankeri sp. nov. the telson has a prolate ellipsoid shape, with a width less than twice its length.

Manning & Felder (1989) assigned two specimens collected at Barra del Tordo, Mexico, to A. cristata, although they noticed some differences between those materials and specimens representing northern Gulf of Mexico and Atlantic populations. They mentioned as one of the differences a more pronounced interorbital boss, similar to that observed for many specimens of A. artankeri sp. nov. Additionally, the illustration of the male pleon of one of the specimens from Barra del Tordo (Manning and Felder 1989: fig. 9g) shows a telson that matches the shape of other males in A. artankeri sp. nov. (Fig. 2H). Only two specimens were available for comparison and unfortunately no mention is made of the merus of the fourth pereopod, wherein important characters are found to define A. artankeri sp. nov. The specimens from Mexico (USNM 221633) were also not suitable for sequence analyses, since they were fixed in formalin. However, morphological evidence suggests that these specimens should be assigned to the newly described species Austinixa artankeri sp. nov., thereby extending its distribution into the southern Gulf of Mexico.

Due to their close morphological resemblance and their distributions, A. cristata and A. patagoniensis have been historically considered north-south counterpart species (Manning & Felder 1989). Neither has been reported from the Caribbean Sea where A. artankeri sp. nov. was found. It appears that A. artankeri r eplaces both A. cristata and A. patagoniensis in intertidal waters of the southern Caribbean, perhaps ranging as far north as Tamaulipas in the southwestern Gulf of Mexico. However, the latter record remains provisional pending collection and molecular phylogenetic analysis of sequence-quality specimens from that region