Metazoan endoparasites of Serrasalmus marginatus (Characiformes: Serrasalminae) in the Negro River, Pantanal, Brazil

In order to inventory the metazoan endoparasites of Serrasalmus marginatus, 91 specimens were examined. They were captured in the Negro River in Pantanal wetland, State of Mato Grosso do Sul, Central-Western Brazil, from October 2007 to August 2008. Parasites of six taxa were recovered: Procamallanus (Spirocamallanus) inopinatus, Contracaecum sp. (Nematoda), metacercarial type Diplostomulum (Digenea), Brevimulticaecum sp. (Nematoda) and Sebekia oxycephala, Subtriquetra sp. 1 and Subtriquetra sp. 2 (Pentastomida). The latter five species are reported for the first time in S. marginatus.

Studies on the parasitofauna of piranha Serrasalmus marginatus (Valenciennes, 1837) are scarce and mostly have focused on the taxonomy of some groups.The most remarkable reports on endoparasites in S. marginatus include that of Tanaka (2000) who reported Procamallanus (Spirocamallanus) inopinatus, specimens of Capilariidae, Railliet, 1915, andKritskyia sp. andthat of Böeger et al. (2001) who described Kritskyia annakohnae in ureters and urinary bladder, both studies in the Paraná River basin.The hydrographic network of the Pantanal, with a variety of species of teleost fishes, has few records on parasite faunas, including piranha (S. marginatus) that is widely distributed in the Paraguay River basin.
Thus, with the aim of registering species composition of metazoan endoparasites in S. marginatus, there were necropsied 91 specimens caught with hooks and cast nets from October 2007 to August 2008.Six collections were performed in the middle of the main channel of Negro River (19° 35' 20.04" S and 56° 11' 4.19" W), a tributary of Paraguay River, Pantanal, State of Mato Grosso do Sul, Central-Western Brazil.
The procedures of necropsy, specimen collection, preparation and conservation of endoparasites were performed according to Eiras et al. (2006).The recovered parasites were compared with deposited specimens from the Helminthological Collection of Oswaldo Cruz Institute (CHIOC).Representative specimens of parasites were deposited in the Zoological Collection of Reference at Universidade Federal do Mato Grosso do Sul, such as the host (ZUFMS-PIS No. 3086).Parasitological descriptors were calculated according to Bush et al. (1997).
The observed morphological characteristics in P. (S.) inopinatus are consistent with Moravec descriptions (MORAVEC et al., 1997), except for eight cephalic papillae arranged in two circles around the oral opening as the recovered specimens had only four cephalic papillae.Some individuals of P. (S.) inopinatus were compared with the voucher specimen CHIOC 31.324,host: Leporinus sp., Machado River, State of Rondônia, Brazil (GIESE et al., 2009).The specimen was visibly smaller, but with the same morphological structures of the one collected in the present study.This parasite is well documented in the literature and has been described in different fish species (PAVANELLI et al., 2004), including S. marginatus (TANAKA, 2000).
Pentastomids of genus Subtriquetra were divided into two morphospecies due to differences in body size, mouth, hooks and spines that are larger in Subtriquetra sp. 2. It was not possible to identify the species due to missing larvae descriptions of these pentastomids.Some individuals of both morphospecies were compared with larvae of S. subtriquetra (Diesing, 1836) CHIOC 17.697, reported in Hoplias malabaricus (Bloch, 1794) in the Salobra River, State of Mato Grosso do Sul, Brazil (TRAVASSOS;FREITAS, 1940), and with some larvae of Subtriquetra CHIOC 11.424, hots: P. nattereri, Salobra River, State of Mato Grosso do Sul (unpublished information).The specimens collected showed morphological similarities with both voucher specimens.
It is the first report of metacercarial type Diplostomulum and larvae of Brevimulticaecum sp., Sebekia oxycephala and Subtriquetra spp.parasitizing S. marginatus.