(Amphipoda, Senticaudata, Corophiida) from the Continental Slope and Abyssal Plain of the Gulf of Mexico
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Bull Mar Sci. 92(2):243–255. 2016 new taxa paper http://dx.doi.org/10.5343/bms.2015.1068 Two new species (Amphipoda, Senticaudata, Corophiida) from the continental slope and abyssal plain of the Gulf of Mexico 1 * 1 Laboratorio de Crustáceos, Ignacio Winfield Facultad de Estudios Superiores Manuel Ortiz 1 Iztacala, Universidad Nacional 2 Autónoma de México, Avenida Pedro-Luis Ardisson de Los Barrios 1, Los Reyes Iztacala, Tlalnepantla, Estado de México, C.P. 54090, Mexico. ABSTRACT.—Two new species of deep-sea amphipods 2 Departamento de Recursos of the genera Podocerus and Ericthonius are described and del Mar, Cinvestav. Carretera illustrated. They were collected on soft bottoms of the Bay antigua a Progreso, km 6. Apdo. of Campeche, SW Gulf of Mexico, at depths of 1400 to 2383 Postal 73-Cordemex, 97310. m. The two new species increase the numbers of Ericthonius Mérida, Yucatán, Mexico. species recorded to 22, the Podocerus species to 58, and the * Corresponding author email: deep-sea amphipods from the Gulf of Mexico to 17 species. <[email protected]>. Ericthonius camposi sp. nov. is characterized by the cephalic lobes, gnathopod 1 basis; stridulating ridges on coxal plate of gnathopod 2 and epimera 2–3, and uropod 3 ramus. Males of Ericthonius camposi sp. nov., is most similar to males of Ericthonius brasiliensis (Dana, 1852), Ericthonius punctatus (Bate, 1857), and Ericthonius parabrasiliensis Just, 2009. Podocerus delacruzi sp. nov., is characterized by carinations on pereonites 2–4, pereonite 7 and pleonites 1–2 posterodorsally produced, uropod 2 peduncle, and telson. Males of Podocerus delacruzi sp. nov., are most similar to males of Podocerus kleidus Thomas and Barnard, 1992, Date Submitted: 8 October, 2015. Podocerus lazowasemi Baldinger and Gable, 1994, and Date Accepted: 21 January, 2016. Podocerus cristatus Thomson, 1879. Available Online: 9 March, 2016. Gammaridean amphipods represent a predominantly marine group of crustaceans that are numerous and dominant in benthic communities. They have colonized dif- ferent offshore habitats as herbivores, detritivores, micropredators, and scavengers (Marques-Junior and Senna 2013). In the deep-sea benthos, the amphipod suborders Gammaridea and Senticaudata are well represented from the continental slope to the abyssal plains (Cartes and Sorbe 1999). However, knowledge of biodiversity and geographic distribution of deep-sea amphipods remains limited in most oceanic ba- sins due to lack of adequate sampling, and the efficiency of the sampling gear used (Martínez-Arbizu and Brix 2008, Brökeland and George 2009, Dauvin et al. 2012). The study of benthic amphipods of the Gulf of Mexico (GoM) has focused mainly on coastal habitats, in addition to the continental shelf and the continental upper slope from 20 to 550 m depth (Myers 1981, Pequegnat et al. 1990, Ortiz 1991, LeCroy 1995, Lowry and Stoddart 1997, LeCroy et al. 2009). According to Escobar-Briones and Winfield (2003), the number of benthic amphipod species from the GoM ba- sin decreases from the inner continental shelf to shelf edge. Winfield et al. (2006) documented a total of 15 deep-sea amphipod species associated with soft bottom, of Bulletin of Marine Science 243 © 2016 Rosenstiel School of Marine & Atmospheric Science of the University of Miami 244 Bulletin of Marine Science. Vol 92, No 2. 2016 Figure 1. Map of the Gulf of Mexico showing the sampling locality at Bay of Campeche. Marks, square = station 65_41; circle = station 65_33. which 10 species inhabit the continental slope (200–2000 m depth), and five species the Sigsbee abyssal plain (>2000 m depth). The GoM is a semi-closed oceanic basin connected with the Caribbean Sea by the Yucatán Channel and the Atlantic Ocean throughout the Straits of Florida. The Bay of Campeche, positioned in the southwest GoM (Fig. 1), is a complex topographic region with canyons, submarine channels and knolls, and is documented as one of the most productive areas in the GoM (Salas de León et al. 2007). During an oceanographic cruise (2013-PEMEX-EPRM) along the Bay of Campeche, several peracarid crustaceans were collected from soft bottom samples of the conti- nental slope and the abyssal plain. Among this material, amphipods of the families Ischyroceridae and Podoceridae were recognized and represent two new species of the genera Ericthonius and Podocerus. The present study describes the two new spe- cies and updates the benthic amphipod species diversity of the GoM occurring from the continental slope to the abyssal plain. Methods Study Area.—The Bay of Campeche is located in the southwestern GoM, bound on three sides by the Mexican states of Campeche, Veracruz, and Tabasco. The area of the bay covers 9700 km2 with depths >200 m. At the shelf edge, the depth increases rapidly to 1000 m, reaching >3000 m at the central part of the bay (Expósito-Díaz et al. 2009). The continental slope includes canyons, submarine channels, escarpments, salt domes, and foldings that extend from the shelf edge to the upper limit of the con- tinental rise at depths of 2800 m in the north and west to 3600 m off the Campeche Escarpment (Bryant et al. 1991). The material examined in this study was collected during the Oceanographic Expedition 2013 – PEMEX Exploración y Producción Regiones Marinas (Bay of Campeche, SWW GoM, July 2013), aboard the RV Justo Sierra of the Universidad Winfield et al.: New amphipod species from the Gulf of Mexico 245 Nacional Autónoma de México (UNAM). Position coordinates for the sampling sta- tions were plotted using a SIMRAD-NSS12-EVO2, GPS navigation system. During the oceanographic cruise samples were obtained from 50 to 3260 m using a Hessler- Sandia MK II benthic box corer. Four samples were taken from each sampling sta- tion by using a PVC corer (diameter of 20 cm). Material was sieved with a 500-µm mesh and fixed with MgCl2 and 4% formalin. In the laboratory, organisms were sepa- rated, washed, and preserved in 70% alcohol. All material was examined, dissected, and illustrated in the Laboratory of Crustaceans (FESIztacala-UNAM) using Motic Microscopes SMZ168 and BA210, both equipped with a camera lucida. Illustrations were completed using the Corel Draw V-X7 program. Measurements of type material were made with the Motic Images Plus v2 program. The type material of amphipods is deposited in the Colección Nacional de Crustáceos (CNCR), Instituto de Biología, Universidad Nacional Autónoma de México. Results Order Amphipoda Latreille, 1816 Suborder Senticaudata Lowry and Myers, 2013 Infraorder Corophiida Leach, 1814 (sensu Lowry and Myers, 2013) Family Ischyroceridae Stebbing, 1899 Genus Ericthonius Milne-Edwards, 1830 Ericthonius camposi new species (Figs. 2–5) urn:lsid:zoobank.org:act:2E2E250E-52E8-4303-BBD0-7AD66D66BE17 Material Examined.—Holotype.—Adult male, 5.5 mm length (CNCR30085); col- lected from the type locality; station 65_33; July 30, 2013; coll., María Teresa Herrera- Dorantes. Paratype.—Incomplete juvenile (3.1 mm), same date as holotype. Type Locality.—The material was collected from soft bottom characterized by mud (silty-clay) sediments of terrigenous origin, at 1400 m in depth; 20°00´N and 94°00´W. Diagnosis.—Head elongate; rostrum short; lateral cephalic lobes projected, sub- acute with pointed tip; a large robust seta on cephalic anteroventral corner; gna- thopod 1 coxal plate small and rectangular, basis posterior margin with a large posteromedial protuberance; gnathopod 2 coxal plate subrectangular, posteroven- tral margin with stridulating ridge, five robust setae on anteroventral margin, carpus elongate and curved; coxal plate 5 deeper than wide, eleven ventral setae; coxal plate 6 small; coxal plate 7 convex; stridulating ridge on posteroventral margin of epimera 2–3; uropod 1 peduncle bearing seven short robust setae on outer margin; uropod 3 ramus with two proximal robust setae, tip with three acute protuberances, and a simple seta. Description.—Holotype: adult male (CNCR30085), 5.5 mm total length. Body (Fig. 2) head elongate, rostrum short, lateral cephalic lobes projected, subacute with pointed tip; eyes large; large robust seta on cephalic anteroventral corner. Antenna 246 Bulletin of Marine Science. Vol 92, No 2. 2016 Figure 2. Ericthonius camposi sp. nov., holotype: adult male 5.5 mm length, CNCR30085. Habitus. Scale bar: 1.0 mm. 1, peduncular article 1, 0.75× length head; posterior margin with four subdistal aes- thetascs and several simple setae; five facial simple setae; anterior margin with two tufts of simple setae. Antenna 2 peduncular articles 1–3, 0.5× length of head; several marginal simple setae. The rest of antennae 1 and 2 missing. Gnathopod 1 (Fig. 3A) smaller than 2, subchelate; coxal plate 1 subrectangular; basis wide, dorsal margin convex, a large posterodorsal protuberance, two postero- ventral robust setae subdistally; ischium the smallest; merus with two robust setae and an acute process; carpus subtriangular with ventral margin serrate; propodus triangular; palm with minute spines; dactylus elongate subequal in length to palm, posterior margin with many small indentations where simple setae are inserted. Gnathopod 2 (Fig. 3B) carpus and propodus elongate, 0.5× length of body, carpo- chelate; coxal plate 2 subrectangular, deeper than broad, stridulating ridge on pos- teroventral margin, five robust setae on anteroventral margin; basis elongate; carpus 1.5× length of head, with distinct free posterior expansion, margin extended into two carpal teeth; propodus shorter than carpus, subconical; dactylus slender, 0.75× length of propodus. Mouthparts: left mandible (Fig. 4A) incisor 7-dentate, lacinia mobilis 4-dentate (right mandible incisor 6-dentate, lacinia mobilis 3-dentate); mandibles with seven rakers each; molar strong, triturative; mandible palp large, 3-articulate, second ar- ticle longest, third lanceolate. Maxilla 1 (Fig. 4B) inner plate conical, apically acute; outer plate longer than wide, 15–16 distal setae; palp 2-articulate, second article lon- ger than outer plate, nine distal and five subdistal robust setae. Maxilla 2 (Fig. 4C) plates heavily setose; inner plate with a row of 12 robust facial setae.