Zootaxa 3861 (1): 086–090 www.mapress.com /zootaxa / Copyright © 2014 Magnolia Press
Article
ISSN 1175-5326 (print edition)
ZOOTAXA
ISSN 1175-5334 (online edition)
http://dx.doi.org/10.11646/zootaxa.3861.1.5 http://zoobank.org/urn:lsid:zoobank.org:pub:BBDD80D8-59DA-40BD-B50E-431A8648C0BC
A new species of Naxia Latreille, 1825 (Brachyura: Majidae) from deep water off Brazil MARCOS TAVARES1,3 & GARY C. B. POORE2 1
Museu de Zoologia, Universidade de São Paulo, Av. Nazareth 481, Ipiranga 04263-000, São Paulo, SP, Brazil. E-mail:
[email protected]
2
Museum Victoria, GPO Box 666, Melbourne, Vic. 3001 Australia. E-mail:
[email protected] Corresponding author
3
Abstract A new species of spider crab, Naxia atlantica n. sp., is described and illustrated from deep waters off São Paulo (southeastern Brazil). The new species can be separated from its congeners by a suite of characters including shapes of the propodi of the walking legs, rostrum and basal antennal article. This is the first record of the genus outside southern Australia and New Zealand. Key words: Crustacea, new species, spider crab, Brazil, Australia, New Zealand
Introduction The REVIZEE (Recursos Vivos na Zona Econômica Exclusiva) Program, among the major efforts to broaden the knowledge of Brazilian deep-water benthic fauna, was conducted from 1996 through 2003 at depths of about 2100 m (Anonymous, 2006; Tavares, 1999). The REVIZEE collections yielded a wealth of decapod crustacean material, some of which remains under study. Here we report a new species of spider crab, Naxia atlantica n. sp. The following abbreviations are used: MZUSP (Museu Zoologia, Universidade de São Paulo); USNM (National Museum of Natural History, Smithsonian Institution, Washington, D.C.); cl, carapace length (rostrum not included); cw, carapace maximum width; pereopods 2–5, walking legs.
Superfamily Majoidea Samouelle, 1819 Family Majidae Samouelle, 1819 Naxia Latreille, 1825 Remarks. Species of Naxia Latreille, 1825, are immediately distinguished from most other majids by having the propodi of walking legs ventrally expanded near the distal margin. The carapace is bare or with a few small hairs between groups of strong curled hairs. A prehepatic spine is present. Griffin & Tranter (1986) and Poore (2004) diagnosed the genus and provided keys to the four species known previously. The possession of laterally flattened and ventrally broadened propodi of pereopods 2–5 (walking legs) in Naxia is paralleled in Trichoplatus huttoni A. Milne-Edwards, 1876, type species of the monotypic genus Trichoplatus and a member of Inachidae (Griffin 1966: fig. 8). Richardson (1949: 63), based in part on the subchelate condition of the walking legs, transferred Trichoplatus huttoni to Naxia, a position that was followed by Dell (1960). Griffin (1966) argued against the synonymy of Trichoplatus with Naxia. Griffin & Tranter (1986: 61), however, followed Bennett (1964: 33) and resurrected Trichoplatus after concluding that T. huttoni is not related to Naxia from which it differs in the morphologies of the male first gonopod, orbits, third maxillipeds and male abdomen.
86 Accepted by P. Castro: 8 Aug. 2014; published: 11 Sept. 2014
Included species. The genera of the original combination are indicated within brackets. Naxia aries (H. Milne Edwards, 1834) [Halimus]; N. aurita (Latreille, 1825) [Pisa] (type species by monotypy); N. spinosa (Hess, 1865) [Halimus]; N. tumida (Dana, 1851) [Halimus]; Naxia atlantica n. sp. Distribution. The species of Naxia are restricted to the Southern Hemisphere between 24°S and 42°S. Three of the five species only occur in southern Australia, one in southeastern Australia and at Kermadec Island north of New Zealand (Poore 2004) and the fifth in Brazil. The Australia and New Zealand records are from the low intertidal to about 108 m, where the sea-surface temperature can get as low as 11.5°C. Naxia atlantica n. sp. occurs in southeastern Brazil at depths greater than in Australia and New Zealand, with bottom temperatures ranging from 6°C to 18°C (Esteves et al. 1988; Stramma 1999).
FIGURE 1. Naxia atlantica n. sp., holotype male, cl 23.2 mm (MZUSP 32370). Habitus, dorsal view (appendages from the right side omitted). Abdominal somites 1–6 and telson (1–6, T). Left margin of male sterno-abdominal cavity on sternites 4–6 (S4–S6). Right maxilliped 3, dorsal view (Mxp3). Left cheliped, lateral view (P1). Left dactyli and propodi of pereopods 2–5 (P2–P5). Profile of the dorsal surface of rostrum and carapace, lateral view.
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FIGURE 2. A–C, habitus, dorsal view. D, E, dactyli and propodi of right pereopod 5, lateral view. A, Naxia aries (H. Milne Edwards, 1834): male cl 31 mm (MZUSP 32366). B, Naxia atlantica n. sp., holotype male, cl 23.2 mm (MZUSP 32370). C, D, Naxia aurita (Latreille, 1825): female cl 47 mm (USNM 76543). E, Naxia tumida (Dana, 1851): male cl 30 mm (USNM 64728). Scale bars: D, 13 mm. E, 4mm.
Naxia atlantica n. sp. (Figs 1, 2B) Type Material. Holotype. Off the coast of São Paulo, Brazil, REVIZEE SUL, stn 6670, 11 Nov. 1998, 503 m: male cl 23.2 mm, cw 13.0 mm (MZUSP 32370). Comparative material. Naxia aries (H. Milne Edwards, 1834): Australia, Bass Strait, 40°06.2'S, 148°25.0'E, coarse shell, 22 m: 1 male cl 31 mm (MZUSP 32366). Naxia aurita (Latreille, 1825): Australia, Victoria, Port Phillip, off Swan Island, dredged in less than 1.8 m: 1 female cl 47 mm (USNM 76543). Victoria: 1 male cl 45 mm (MZUSP 32369). Naxia spinosa (Hess, 1865): Australia, Victoria, Hamers Haven: male cl 36 mm (MZUSP 32367). Naxia tumida (Dana, 1851): Australia, New South Wales, Little Bay near Port Jackson, among seaweed in rock pools between tide marks: 1 male cl 30 mm (USNM 64728). Victoria, Port Phillip Heads: 1 male cl 26 mm and 1 ovigerous female cl 17 mm (MZUSP 32368).
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Diagnosis. Length:width ratios of pereopods 2–5 propodi 3.5, 3.1, 2.8 and 2.4 respectively. Anterolateral spine of the basal antennal article with an accessory spinule. Prehepatic spine well separated from supraorbital eave. Description. Carapace pyriform, postrostral carapace length 1.5 times width. Rostral spines (measured obliquely) 0.2 times as long as cl, separated basally by right-angled curve, unarmed, cylindrical, outwardly directed, ending in upturned acute spine, densely covered dorsally with hooked setae. Orbital margin with supraorbital eave produced anteriorly into rounded boss; eave armed posteriorly with strong, sharp spine separated from anterior boss by U-shaped notch. Hepatic region with 2 spines, anterior spine outwardly directed, large, sharp; posterior spine laterally directed, shorter than anterior spine; with small subhepatic spine. Dorsal surface with regions weakly defined by shallow grooves, with widely-spaced obsolete tubercles, bosses, each with few simple or hooked setae: 2 frontal bosses; protogastric regions with 3 tubercles each; 5 mesogastric; 4 metagastric; 2 urogastric; 1 low cardiac; 1 medial intestinal, 1 erect intestinal spine on mid-posterior margin of carapace. Branchial regions inflated laterally, greatest width 1.3 times width at branchial-hepatic juncture; epibranchial with 3 tubercles each; 3 mesobranchial stout, sharp spines, first largest, anteriorly directed, second smaller, third smallest, both laterally directed; metabranchial region naked. Epistome concave, smooth; anterolateral margin of buccal cavity carinate, paired. Antennular articles unarmed; first short; second cylindrical; third gently compressed laterally, distally broadened. Antennal articles 2+3 ventrally flat, with prominent triangular distolateral spine (with microscopic subdistal lateral tooth), short ventral spine at base of article 3; remaining articles cylindrical. Eyestalk with 3 club setae, 3 longer stiff setae on small tubercle on disto-anterior margin. Cornea unpigmented; ommatidia very small, clearly recognizable. Maxilliped 3 ischium 2.4 times as long as wide, with 20 blunt teeth along mesial margin, strongly excavated distolaterally to accommodate merus, distal margin with small, incurved spine; merus with strong mesial triangular projection, exceeding mesial margin of ischium, with semicircular distolateral lobe, small distal spine. Male sterno-abdominal cavity limited laterally by small, spherical tubercle at level of thoracic sternite 7, large boss at level of sternite 8. Complementary parts of abdominal locking system present, functional; thoracic sternal button adjacent to sternal suture 5/6; abdominal socket well excavated. Cheliped smooth; palm 10 times as long as greatest depth, tapering; fingers 0.2 times upper length of palm, each with about 15 small teeth along margins. Pereopod 2 as long as cl, others decreasing in length posteriorly to 0.9 cl (pereopod 5); merus, carpus of all walking legs cylindrical. Propodi of pereopods 4, 5 about 0.8 length of pereopods 2, 3; all propodi with strong, flat distal rounded lobe on flexor margin, more pronounced on posterior legs; 2–5 pereopod propodi length:width ratios 3.5, 3.1, 2.8, 2.4 respectively; oblique distal palms of propodi with dense, multiple rows of stout acute setae; dactyli curved, with small thorns along flexor face. Male abdomen with 6 somites, telson; somites 1–2, 4, 6 with median tubercle; widest at somite 3, tapering to semicircular telson. Gonopod 1 strongly convergent at midline of thoracic sternum, gently curved outwards distally. Gonopod 2 straight, short (one fifth length of gonopod 1). Etymology. The epithet atlantica, Latin feminine adjective, refers to the Atlantic Ocean where the species was collected. Distribution. Southwestern Atlantic; known only from the type locality off São Paulo, Brazil, at a depth of 503 m. Remarks. Naxia atlantica n. sp. superficially resembles N. aries, N. spinosa and N. tumida in having pereopods 2–5 propodi strongly flattened laterally and ventrally expanded, a character that separates them from N. aurita, in which the propodi of the walking legs are only slightly expanded ventrally (cf. Figs 1, 2D). Naxia atlantica n. sp. and N. tumida are unique in the genus in having the anterolateral spine of the basal antennal article with an accessory spinule. The new species can nevertheless be readily distinguished from N. tumida by a prehepatic spine that is well separated from the supraorbital eave (prehepatic spine fused to the postorbital spine or separated from it by a narrow notch in N. tumida) (cf. Figs 1, 2B, 3A). Naxia atlantica n. sp. can also be quickly distinguished from N. aries by the propodi of the walking legs being more expanded ventrally than in N. aries (cf. Figs 1, 2A) and from N. aries and N. spinosa in having a rather straight rostrum that is outwardly directed and distinctly upturned at its tip (rostrum strongly curved outwards and slightly turned downward at the tip in N. aries and straight and directed outward and downward in N. spinosa) (cf. Figs 2A, B, 3B).
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FIGURE 3. A–B, habitus, dorsal view. A, Naxia tumida (Dana, 1851): male cl 30 mm, (USNM 64728). B, Naxia spinosa (Hess, 1865): male cl 36 mm (MZUSP 32367).
Acknowledgements MT thanks Rafael Lemaitre (USNM) for providing working space and access to the collections, Karen Reed (USNM) for helping with the collections and bibliographic references, Museum Victoria for the donation of specimens of Naxia to MZUSP, and Joana d'Arc and Manoel Pedraza (both from MZUSP) for helping with photographs and plates. MT also thanks CNPq (301806/2010-1) and PETROBRAS (4600224970) for supporting studies on the systematics of decapod crustaceans.
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