Digenea , Nematoda , Cestoda , and Acanthocephala , parasites in Potamotrygonidae ( Chondrichthyes ) from the upper Paraná River floodplain , states of Paraná and Mato Grosso do Sul , Brazil

The present paper represents the first study on the endoparasitic fauna of Potamotrygon falkneri and P. motoro in the upper Paraná River floodplain. Fishes were collected by fishing rod and gillnetting in different stations of the floodplain, from March, 2005 to September, 2006. Parasites were sampled, fixed and preserved according to specialized literature. About half of the analyzed fish were parasitized by at least one of the following species of endoparasites: Clinostomum complanatum, Genarchella sp. and Tylodelphys sp. (metacercaria) (Digenea); Acanthobothrium regoi, Rhinebothrium paratrygoni, Paroncomegas araya and Potamotrygonocestus travassosi (Cestoidea); Brevimulticaecum sp. (larva), Cucullanus sp., Echinocephalus sp. and Spinitectus sp. (Nematoda); and Quadrigyrus machadoi (Acanthocephala). Some species were already registered in Chondrichthyes and others were previously recorded in Osteichthyes from the study area. The study listed ten new records of parasites in the host P. falkneri, one new record in the host P. motoro and five new records in the locality upper Paraná River. Introduction Stingrays of the family Potamotrygonidae are the only elasmobranches permanently adapted to the freshwater environment, inhabiting rivers of South America that discharge into the Atlantic Ocean and Caribbean Sea (Compagno and Cook 1995). According to Lovejoy et al. (2006), this group appears to have entered South America since the isolation of the continent by the Cretaceous opening of the Atlantic. Such taxa display a diversity of biogeographic and phylogenetic patterns, having members of endemic Neotropical freshwater radiations with distributions that encompass multiple river basins. Potamotrygonidae is formed by three genera: Paratrygon Duméril, 1865, Plesiotrygon Rosa, Castello & Thorson, 1987, and Potamotrygon Garman, 1877. The two formers are monospecific, while Potamotrygon has approximately 26 valid species (Carvalho et al. 2003). Fifteen of these species have parasitological records, including the species of the present study, considering several regions: Salobra River (Paraguay River Basin, state of Mato Grosso, Brazil) (Rego 1979); vicinity of Corumbá (state of Mato Grosso do Sul, Brazil) (Brooks and Amato 1992); Amazonas River (Amazonas River Basin, Brazil) (Campbell et al. 1999); Orinoco River delta (Orinoco River Basin, Venezuela) (Marques and Brooks 2003); upper Madre de Dios River (Manu River Basin, Peru) (Reyda and Olson 2003). In general, the species of potamotrygonids exhibit distribution restricted to a single basin or fluvial system — P. falkneri is restricted to ParanáParaguay Basin (Carvalho et al. 2003) and P. motoro is present in Amazonas River, Orinoco River and La Plata system (Araújo et al. 2004). In the study area, only two species of Potamotrygonidae are registered: Potamotrygon falkneri Castex & Maciel, 1963 and P. motoro (Müller & Henle, 1841). These two species moved upstream from the middle to the upper Paraná River when the reservoir of Itaipu Hydroelectric Power Plant flooded Sete Quedas Falls, which was a physical barrier for fishes (Agostinho et al. 2004). Pavanelli et al. (2004) summarized data concerning more than 80 identified species of parasites from 57 species of fishes in the region, disclosing great biodiversity. However, detailed Check List 4(2): 115–122, 2008.


Introduction
Stingrays of the family Potamotrygonidae are the only elasmobranches permanently adapted to the freshwater environment, inhabiting rivers of South America that discharge into the Atlantic Ocean and Caribbean Sea (Compagno and Cook 1995).According to Lovejoy et al. (2006), this group appears to have entered South America since the isolation of the continent by the Cretaceous opening of the Atlantic.Such taxa display a diversity of biogeographic and phylogenetic patterns, having members of endemic Neotropical freshwater radiations with distributions that encompass multiple river basins.
In general, the species of potamotrygonids exhibit distribution restricted to a single basin or fluvial system -P.falkneri is restricted to Paraná-Paraguay Basin (Carvalho et al. 2003) and P. motoro is present in Amazonas River, Orinoco River and La Plata system (Araújo et al. 2004).In the study area, only two species of Potamotrygonidae are registered: Potamotrygon falkneri Castex &Maciel, 1963 andP. motoro (Müller &Henle, 1841).These two species moved upstream from the middle to the upper Paraná River when the reservoir of Itaipu Hydroelectric Power Plant flooded Sete Quedas Falls, which was a physical barrier for fishes (Agostinho et al. 2004).Pavanelli et al. (2004) summarized data concerning more than 80 identified species of parasites from 57 species of fishes in the region, disclosing great biodiversity.However, detailed studies on the parasitic fauna of potamotrygonids were never performed in the study area.The identification of new hosts and new localities for parasites contribute to the knowledge of local biodiversity as well as for the understanding of the evolution of parasites and their hosts.The present study aimed to perform a survey of the endoparasites of potamotrygonids from the upper Paraná River floodplain, and constitutes the register of new occurrences.
The study area is part of the upper Paraná River floodplain, Paraná River Basin, limit between the states of Paraná and Mato Grosso do Sul, near the city of Porto Rico (state of Paraná, 22°43' S, 53°10' W).The region is characterized as a fluvial floodplain, with periodic floods that result in the flooding of the marginal areas in the state of Mato Grosso do Sul.The area was characterized in details by Thomaz et al. (2004) (Figure 1).Sampling, fixation and preservation of parasites were according to Eiras et al. (2006).Identification of the parasites followed Szidat (1969), Rego andDias (1976), Brooks et al. (1981), Fábio (1983), Moravec (1998), Campbell et al. (1999), Gibson et al. (2002), and Marques et al. (2003).The taxonomic classification follows Moravec (1998) for nematodes, Bush et al. (2001) for cestodes, and Gibson et al. (2002) for digeneans and acanthocephalans.Voucher specimens were deposited at Coleção Helmintológica do Instituto Oswaldo Cruz, numbers 36969 to 36982.

Results and Discussion
Among the 47 specimens of P. falkneri collected, 22 presented at least one species of endoparasites (46.8 %) and of the 19 especimens analyzed of P. motoro, 11 were parasitized (57.9 %).One hundred and seventy five endoparasites were collected in P. falkneri, including adults and larvae.In P. motoro, 22 adult endoparasites were collected.Taxa, sites of infection, and levels of parasitism are shown in Table 1.In total, three species of digeneans, five species of cestodes, four species of nematodes and one species of acanthocephalan were recorded (Table 1).

Site of infection
Superfamily  (Castelnau, 1855) in the Amazonas River (Maicuru, state of Pará, Brazil).Brooks et al. (1981) recorded the parasite in the delta of Orinoco River (Venezuela).Marques et al. (2003) in their redescription of the species also recorded Paratrygon ayereba (Müller & Henle, 1841), Potamotrygon constellata (Vaillant, 1880) and Potamotrygon motoro as new hosts, and the lower Amazonas River (state of Pará, Brazil) and Paraná Januacá (state of Amazonas, Brazil) as new localities.The present study registered P. travassosi for the first time parasitizing P. falkneri and it is the first record of the parasite in the upper Paraná River.
Family Phyllobothriidae Braun, 1900 Genus Rhinebothrium Linton, 1890 Rhinebothrium paratrygoni Rego & Dias, 1976 Rhinebothrium paratrygoni was described parasitizing the spiral valvae of the intestine of P. ayereba in the region of Salobra (upper Paraguay River Basin, Brazil).Later it was found in Potamotrygon hystrix and Potamotrygon reticulatus (Günther, 1880) in the delta of the Orinoco River (Venezuela), in P. falkneri in Paraná River Basin (near Hohenau, Paraguay) (Brooks et al. 1981) and in P. motoro in Corumbá (state of Mato Grosso do Sul, Brazil).In the present study, R. paratrygoni was found in P. falkneri and P. motoro, being this the first register for those species in the studied region.
Order Trypanorhyncha Diesing, 1863 Family Eutetrarhynchidae Guiart, 1927 Genus Paroncomegas Campbell, Marques & Ivanov, 1999 Paroncomegas araya (Woodland, 1934) Paroncomegas araya corresponds to the cestode originally described as Tentacularia araya in P. motoro from Amazonas River (Brazil), and to Eutetrarhynchus araya described in P. motoro (Salobra River).In their work, Campbell et al. (1999) also registered as additional hosts Potamotrygon reticulatus (Garman, 1980) and P. falkneri , and they added the delta of Orinoco River (Venezuela), Paraná River (Paraguay) and Puerto Reconquista (Santa Fé, Argentina), respectively, as new occurrence localities.In the present study, P. araya was only found in P. falkneri, also the first register for the upper Paraná River floodplain.Besides the four species of adult cestodes, one larva was found in one specimen of P. falkneri, with 38.8 long by 12.2 width.The specimen could not be identified because of its early stage of development.(Moravec 1998).Still according to Moravec (1998), the genus parasitizes the digestive tract of marine and freshwater fishes and also amphibians.Due to the low number of specimens, the identification at species level was not possible.However, the genus could be identified by presenting cuticle with numerous transversal rings and by having a row of spines (Moravec 1998) (Pavanelli et al. 2004).This is the first register of this species in potamotrygonids from upper Paraná.According to Brooks (1992), the majority of the known parasites of Potamotrygonidae are restricted to this family of fish.However, four of eleven new records of parasites for Potamotrygonidae in the present study had already been registered in fishes of other families in the study region.

-Table 1 .
Parasites taxa, deposit numbers in CHIOC (Coleção Helmintológica do Instituto Oswaldo Cruz), infection sites (ES = external wall of stomach, S = stomach and SV = spiral valvae), number of parasitized fish (PF) and range of the number of parasites in infected hosts (R) in Potamotrygon falkneri and P. motoro collected in the upper Paraná River floodplain from March 2005 to September 2006 (P.falkneri) and from April 2005 to December 2006 (P.motoro).