A New Acanthocephalan Species (archiacanthocephala: Oligacanthorhynchidae) from Cerdocyon Thous, a Crab-eating Fox in the Brazilian Pantanal Wetlands

A new species ?1 of Oligacanthorhynchidae (Acanthocephala) Prosthenorchis cerdocyonis n. sp. is described from 17 specimens collected from the small intestine of the crab-eating fox Cerdocyon thous Linnaeus, 1766 (Canidae: Carnivora) found in the Brazilian Pantanal wetlands. ?2 Specimens were studied using light and scanning electron microscopy. Characteristic features distinguishing the new species from others already described are presented, such as size of the body, the position of lemnisci, size of the eggs, host, and geographical distribution. Details of the body surface obtained by scanning electron microscopy, such as the presence of 2 lateral papillae in the proximal region of the proboscis, the presence of barbs in hooks, and a robust and festooned collar, helped to identify the species. Until now, specimens belonging to Prosthenorchis reported from Cerdocyon thous were not identified to species. Furthermore, the new species is the first to be recorded in C. thous found in the Pantanal wetlands. The family Oligacanthorhynchidae Southwell and Macfie, 1925, includes 12 genera (Amin, 1985, 2013) and includes Prosthenorchis Travassos, 1915. Species of Prosthenorchis have been reported as follows: in South America as Prosthenorchis elegans (Diesing, 1851) Travassos (1915) from primates; in Africa as Prosthenorchis lemuri Machado (1950) from lemurs in Madagascar, Prosthenorchis pardalis Southwell and Macfie (1925) from Felis pardus in Sierra Leone, and Prosthenorchis fraterna (Baer, 1959) Schmidt, 1972, from felid Panthera pardus in Congo; and in Asia as Prosthenorchis sinicus Hu-Jiand, 1990, from a dog in China (Schmidt, 1972; Amin et al., 2008; Amin, 2013). The crab-eating fox, Cerdocyon thous, is a wild canid that inhabits savannas and woodlands in South America (Silveira, 1999; Courtenay and Maffei, 2004). Cerdocyon thous (Linnaeus, 1766) has been the subject of a research program conducted by Embrapa/Pantanal and the Institute Oswaldo Cruz Foundation (FIOCRUZ-RJ) that studies the ecology and health of wild carnivores in the Brazilian Pantanal wetlands. This research program also includes the study of helminth parasites, and specimens of helminths were made available to parasitologists at Fiocruz by Embrapa/Pantanal researchers. Although specimens of acanthocephalans have been reported from C. thous in Brazil (Griese, 2007; Ruas et al., 2008; Vieira et al., 2008; Lima, 2009), species of the genus Prosthenorchis had not been previously identified. In this report, we describe a new species of the genus Prosthenorchis collected from the wall of the small intestine of crab-eating foxes (C. thous) from the Pantanal wetlands, Mato Grosso do Sul State, Brazil. MATERIALS AND METHODS Two adult crab-eating female foxes (C. thous) were found dead in 2007 on Nhumirim Ranch (18859S, 56839W), located in the Nhecolândia subregion of the Pantanal in Brazil. The animals were necropsied, and acanthocephalans were collected from the small intestine of each fox for taxonomic study. The study area is characterized by sandy soil with mosaic vegetation of semi-deciduous forest with open grassy areas (Rodela, 2006). Animal procedures were approved by the Brazilian Federal Environmental Agency (IBAMA, first license #183/2005, CGFAU/LIC; last license #11772-2). Acanthocephalans were collected, washed in physiological saline (0.95% NaCl), and stored in 70% alcohol. At the laboratory, only adult specimens of both sexes were cleared in 90% phenol to study the hooks of the proboscides. To describe the internal structures, the specimens were stained with acid carmine, destained in acid (HCl) alcohol, dehydrated in a graded alcohol series, cleared in methyl salicylate, and whole-mounted in Canada balsam (modified from Amato, 1985). Identification of the genus followed the key of Schmidt (1972). The description of Prosthenorchis sp. was based on 17 specimens (7 males and 10 females). Measurements are in millimeters unless otherwise stated. The range is followed by the mean in parentheses. Specimens of Prosthenorchis sp. (CHIOC 17840 a–f, 10123; Lima, 2009) and Prosthenorchis elegans (CHIOC 417, 418, 419, 421, 441, 442, 998, 7661, 8864, 10122, 16147; Machado Filho, 1950) deposited in the Helminth Collection of the Oswaldo Cruz Institute (CHIOC) were used for comparison. Ultrastructural surface morphology was described for adult female and male specimens using scanning electron microscopy (SEM). Specimens were fixed for 1 hr at room temperature with 2.5% glutaraldehyde in 0.1 M Na-cacodylate buffer. After being washed in the same buffer, specimens were post-fixed for 3 hr at room temperature in 1% osmium tetroxide in 0.1 M Na-cacodylate buffer. The material was then dehydrated in an ascending acetone series, dried by the critical point method with CO2, mounted with silver cellotape on aluminum stubs, and sputter-coated with a 20-nm-thick layer of gold. Samples were examined using a Jeol JSM6390 LV microscope at an accelerating voltage of 15 kV at the Electron Microscopy Platform of the Oswaldo Cruz Institute.