Austinixa cuestai Theil & Felder 2020, sp. nov.
Creators: name: Theil, Emma Palacios
name: Felder, Darryl L.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Pinnotheridae
Austinixa
Austinixa cuestai

description: Austinixa cuestai sp. nov.
(Figs 6, 7, 12 G–J)
urn:lsid:zoobank.org:act: B7E3625F-9307-44B4-B56D-3F7489E32CCF
Austinixa sp. 1.— Palacios Theil et al. 2009: 461 (table 1), 464 (fig. 1), 465, 468; Palacios Theil et al. 2016: 4 (table 2), 9 (fig. 1), 10 (fig. 2), 11; present paper: Figs. 1–3, Tables 1, 2.
Material examined. Holotype: USNM 1558324, adult male, cw 7.4 cl 3.6 mm, intertidal zone, Estero Nagualapa, Nicaragua, rocky beach, with Upogebia, yabby pump, 20 Nov 2001, coll. José A. Cuesta, Rafael Robles, I. Teresa Rodríguez.
Paratypes: USNM 1558325, 4 adult males, cw 6.2–8.7 cl 2.9–3.9 mm, 2 ovigerous females, cw 7.8 and 8.4 cl 3.6 and 3.5 mm, adult female, cw 5.8 cl 3.1 mm, collection data same as holotype; ULLZ 5566, 13 adult males, cw 4.3–7.9 cl 2.1–3.5 mm, two of them DNA vouchers, 8 ovigerous females, cw 6.7–8.4 cl 3.1–3.6 mm, 3 of them DNA vouchers, 8 adult females, cw 5.2–8.9 cl 2.5–3.5 mm, one of them DNA voucher, collection data same as holotype; USNM 1552956, 3 males, cw 7.7–11.1 cl 3.4–4.8 mm, Punta Culebra, Panama, yabby pump, burrow in soft sediment, polychaete present in sample, 16 Apr 2018, coll. J. Scioli, photo voucher; USNM 1552957, 2 ovigerous females, cw 10.6 and 10.2 cl 4.3 and 4.6 mm, one female, cw 8.5 cl 3.7 mm, collection data same as previous, except no polychaete with this sample, photo voucher; USNM 1552958, 2 males, cw 9.5 and 6.9 cl 4.1 and 3.3 mm, 2 ovigerous females, cw 10.7 and 9.3 cl 4.8 and 4.5 mm, female, cw 10.2 cl 4.7 mm, Veracruz, Panama, yabby pump, burrow in soft sediment, 17 Apr 2018, coll. J. Scioli, photo voucher.
Additional material: UF 18899, male, cw 9.7 cl 3.9 mm, DNA voucher; UF 18900, 3 females, cw 9.0–9.6 cl 4.1–4.2 mm; UF 18911, male, cw 8.4 cl 3.4 mm, DNA voucher; UF 48329, 2 males, cw 8.7 and 10.0 cl 3.9 and 4.2 mm. All from Playa Venao, Panama, sand flat, in burrows, yabby pump, 6 Dec 2006, coll. A. Anker et al.
Comparative material. Austinixa aidae (Righi, 1967): ULLZ 5538 (12 males, 16 females) and ULLZ 9607 (one male) from Brazil, ULLZ 4684 (one male, one female) and ULLZ 14080 (one male, one female) from Venezuela, and ULLZ 13459 (one female) and ULLZ 13734 (one male) from Panama. [Type locality for A. aidae is Enseada de Caraguatatuba, São Paulo, Brazil].
Size: Males cw 4.3–11.1 mm (n = 28), ovigerous females cw 6.7–10.7 mm (n = 13), females cw 5.2–10.7 mm (n = 12).
Distribution. Known thus far from Estero Nagualapa (Nicaragua) and Playa Venao, Punta Culebra, and Veracruz (Panama).
Diagnosis. Carapace without branchial ridges; male carapace with setal patch on posterior third, anterior to cardiac ridge, connecting with setal patches on lateral regions; female carapace with setose lateral and anterolateral regions; P4 propodus opposable margin bicarinate; male pleon with subtriangular telson.
Description. Carapace smooth, regions defined, 1.9–2.5 times wider than long, with sharp cardiac crest extending entirely across cardiac region, above posterior margin; no branchial ridges; anterolateral margins tuberculate; setose lateral regions, male carapace with additional patch of short dark setae on posterior third, just anterior to cardiac crest. Antennae with nine segments, third longest (Fig. 6A, B). Third maxilliped ischiomerus indistinguishably fused, elongate; 3-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 clearly beyond end of propodus. Exopod with angle on non-opposable margin (Fig. 6C). Chelipeds of male and female similar, chela strong, palm swollen, smooth, with line of setae on inferior (ventral) margin, extending to fixed finger; fixed finger shortened, not deflexed, about one third to half as long as palm, cutting edge serrated; dactylus curved to meet fixed finger, smooth, with serrated tooth at about mid-length, gape setose (Figs 6D, E, 7D, E). P2–P5 long and slender, relative lengths P4> P3> P2> P5, posterior margins setose, dactyli slender, P3 dactylus longest, P2–P4 dactyli slightly curved, P5 dactylus straight, P4 and P5 dactyli with anterior and posterior ridges; P4 propodus posterior margin bicarinate (Fig. 6A, F–I). Male pleon with 6 somites plus telson, somites 1 and 6 subtrapezoidal, somites 2–5 subrectangular, somites 2–4 of similar width, somites 5 and 6 slightly decreasing in width, telson subtriangular, wider than long, telson longer than other somites, somites 1 and 2 shortest (Fig. 7A). Female pleon subcircular, with 6 somites plus telson, none fused, somites 4 and 5 widest, somites 3–5 about same length, somites 1 and 2 about half length of subsequent somites (Fig. 7F). Male first gonopod as illustrated (Fig. 7B, C), apex beak-shaped, with dense line of short setae forming brush on superior tip surface.
Etymology. The species name honors Jose A. Cuesta, a valued friend, previous collaborator, and inspiring colleague who collected these specimens and recognized them to likely represent a new species. His encouragement of this work and reviews of early versions were essential to its completion.
Remarks. Austinixa cuestai sp. nov., an eastern Pacific species, shows remarkable similarities to the western Atlantic A. aidae. Unlike other congeners, they lack branchial ridges on the carapace and males also have a patch of short dark setae on the posterior carapace region, just anterior to the cardiac crest. Austinixa cuestai sp. nov. differs from A. aidae in the shape of the male pleon. Whereas the telson of the male pleon is subtriangular in A. cuestai sp. nov., it is semicircular in the Atlantic species. In addition, the setae on the posterior region of the male carapace are proportionally longer and more densely distributed in A. cuestai sp. nov. In the examined males of A. aidae, the setae are frequently so sparse that they can be overlooked. They occupy a region clearly separated from the setae on the lateral regions. In males of A. cuestai sp. nov., however, the lateral regions are more setose and the setae extend into a major portion of the carapace, where they occupy the entire lateral areas, including the anterolateral regions, and connect with the setal patch on the posterior carapace region. Females of A. cuestai sp. nov. are also more setose, with longer and more setae on the pereopods and the lateral regions of the carapace. In A. aidae, on the other hand, the setae on the female carapace are confined to the most lateral areas and rarely reach into the anterolateral regions, as is the case for A. cuestai sp. nov.
A further difference between females of A. cuestai sp. nov. and A. aidae is the morphology of their gonopore tubercles, a character that has not been reported previously for Austinixa. In these two species, the gonopore forms a structure that projects from the sternite into the pleonal depression. In the examined specimens of A. aidae the gonopore tubercle shows a sharp triangular elevation that bends posteriorly. In A. cuestai sp. nov. the gonopore opening also bends posteriorly, but the tubercle appears to be broader than and not as sharp as in A. aidae. Ideally, further examinations, especially of the holotype, the paratypes, and topotypes of A. aidae should be undertaken to confirm this character state, though some specimens of A. aidae that we examined were collected from a beach only 50 km north of the type locality.
Austinixa cuestai sp. nov. can also be distinguished from its sympatric congener, A. felipensis, by the shape of the male telson, which is oblate-semiellipsoid in A. felipensis, more than twice as wide as long. Additionally, the right and left chelipeds are similar in A. cuestai sp. nov., whereas in available specimens of A. felipensis they are normally unequal, with one cheliped clearly larger than the other. The cheliped fixed finger is also much shorter relative to the palm in A. felipensis than in A. cuestai sp. nov. Consequently, the cheliped dactylus in A. cuestai sp. nov. does not curve as strongly to meet the fixed finger as it does in A. felipensis. Austinixa cuestai sp. nov. also has a generally more setose appearance than A. felipensis.
description: Published as part of Theil, Emma Palacios & Felder, Darryl L., 2020, Phylogeny of the genus Austinixa Heard & Manning, 1997, inferred from mitochondrial and nuclear molecular markers, with descriptions of three new species and redescription of Austinixa felipensis (Glassell, 1935) (Decapoda: Brachyura: Pinnotheridae), pp. 101-134 in Zootaxa 4778 (1) on pages 119-122, DOI: 10.11646/zootaxa.4778.1.4, http://zenodo.org/record/3823672