Primitive decapods from the deep sea : fi rst record of blind lobsters ( Crustacea : Decapoda : Polychelidae ) in northeastern Brazil

We report herein the occurrence of the infraorder Polychelida in Potiguar Basin, northeastern Brazil. Specimens were collected by the project “Avaliação da Biota Bentônica e Planctônica na porção off shore das Bacias Potiguar e Ceará”, developed by the Brazilian Oil Company (PETROBRAS). Th ree species were recorded for the fi rst time in this region: Pentacheles validus A. Milne-Edwards, 1880, Polycheles typhlops Heller, 1862, and Stereomastis sculpta (Smith, 1880) at 2000 m, 400 m and 2057 m depth, respectively. Th e Brazilian deep-sea fl oor remains poorly known, but progress has been made as a result of collections obtained by oceanographic expeditions and research projects developed by PETROBRAS in Campos Basin (Rio de Janeiro) and Potiguar Basin (Rio Grande do Norte), expanding the knowledge of the distribution area of Polychelidae in Brazilian deep sea waters.


introduction
Deep-sea blind lobsters belong to the infraorder Polychelida Scholtz and Richter, 1995.Th ese uncommon crustaceans are characterized by the presence of chelate pereiopods 1-4 (sometimes also pereiopod 5) and fi xed and rudimentary eye-stalk in extant species (Galil, 2000).Th ese decapods can be found from less than 100 m in the lower slope and in abyssal depths down to 5000 m (Galil, 2000;2013).
Th e polychelids are members of the deep sea biota and are considered very rare and little known.Th e knowledge about this group derives from a small number of specimens collected by deep sea cruises and scattered in distant museums (Galil, 2000).In Brazil, in a general way, deep sea fauna remains poorly known, but progress has been made as a result of collections obtained by oceanographic expeditions and research projects developed by PETROBRAS in Campos Basin (Rio de Janeiro) and Potiguar Basin (Rio Grande do Norte), raising the number of crustaceans species known from Brazilian waters.

Materials and Methods
The material was collected on board the RV Seward Johnson on the upper part of the continental slope (150 m depth) off the Potiguar Basin, in cruises carried out in May 2009 and April 2011.The samples were collected under the framework of the project "Avaliação da Biota Bentônica e Planctônica na porção offshore das Bacias Potiguar e Ceará", developed by the Brazilian Oil Company (PETROBRAS).All samples were obtained using a box-corer (50 cm 3 ) or van Veen grab (70 l).
The specimens were identified following Ahyong andBrown (2002), andDall'Occo andTavares (2004).The classification adopted in the present contribution followed De Grave et al. (2009) proposed scheme to genus level.Terminology used followed Galil (2000) and abbreviations used include: (CL) carapace length (the distance from tip of rostrum to the middle of the posterior border of the carapace); (st.) station of collection.A restricted synonymy was provided for all species.
Diagnosis: Epipod of third maxilliped rudimentary; basal antennular segment proximally rounded.One rostral spine; posterior margin of carapace armed with three or more pairs of spines.

discussion
The present contribution reveals the occurrence of three polychelid species on the Brazilian northeastern coast, filling a gap of distribution of approximately 23º, between the north and south Brazil (Fig. 4).Pentacheles validus was first reported to Brazil by Dall'Occo and Tavares (2004), who examined material collected by the RV Marion Dufresne off the southeastern coast of Brazil.The present report is the second one from Brazil, as well as the northernmost occurrence of this species in Brazilian waters.
Polycheles typhlops is worldwide distributed and the most abundant species in Brazilian waters, once 33 specimens were reported by Dall'Occo and Tavares (2004) from the southeastern Brazil and one specimen recorded from Pará State, northern Brazil (Silva et al., 2003).This study brought an additional record of this species for Brazil, being the first record for northeastern coast.
Finally, Stereomastis sculpta was previously identified as Polycheles sculptus (Galil, 2000;Ahyong and Chan, 2004;Dall'Occo and Tavares, 2004;Ahyong and Galil, 2006) because Galil (2000) synonymised the genus Stereomastis with Polycheles.However, after a phylogenetic analysis, Ahyong (2009) concluded that both genera were monophyletic and morphologically distinct, placing then P. sculptus in the genus Stereomastis.Stereomastis sculpta is also worldwide distributed and previously reported to Brazil from two specimens from Pará (Ramos-Porto et al., 2000), and seven specimens recorded from southeastern and southern Brazil (Dall' Occo and Tavares, 2004).This present record extends the range of occurrence of S. sculpta in Brazil, consisting in the first record for northeastern coast.
In conclusion, this contribution extends the known Brazilian distribution of Polychelida species.We suggest that these species could be more frequent in deep sea Brazilian floor.Taking into account that this is an understudied group, more sampling is needed to describe the diversity of these deep sea crustaceans, and even biological aspects such as reproductive period and fecundity.

acknowledgMents
Thanks to Petróleo do Brasil S/A (PETROBRAS) for making available the studied samples.Special thanks to Arthur Anker for the help with the photographs.
42. Wallis and Futuna Islands, New Caledonia, Australian Bight, New Zealand and Tasmania; Eastern Atlantic: Bay of Biscay, Azores, Canary Islands, West Africa and South Africa; Western Atlantic: United States, Bahamas Islands, Gulf of Mexico, Caribbean Sea Diagnosis: Epipod of third maxilliped longer than ischium; basal antennular segment proximally quadrate, lamellar.Lateral margins of carapace posterior to postcervical incision with more than 25 spines.Distribution: Worldwide -Eastern Pacific: Chile; Indo-Pacific: East Indian Ridge, Vanuatu,