Metacestodes of Glossocercus auritus ( Cyclophyllidea , Gryporhynchidae ) in Poecilia reticulata ( Pisces , Poeciliidae ) from Brazil Metacestoides de Glossocercus auritus ( Cyclophyllidea , Gryporhynchidae ) em Poecilia reticulata ( Pisces , Poeciliidae ) no Brasil

Studies on fish parasites in Pampulha dam, Belo Horizonte, Minas Gerais, Brazil, found specimens of Poecilia reticulata Peters, 1859 harboring natural infection by larval stages of tapeworms. A total of 250 specimens of P. reticulata were collected and analyzed between February and August 2010, of which 23 were found infected (prevalence 9.2%) with one metacestode each (mean intensity 1, mean abundance 0.09). The analyses of the parasites, particularly the morphology of rostellar hooks, made it possible to identify Glossocercus auritus (Rudolphi, 1818). This is the first report of G. auritus metacestode in South America and P. reticulata is a newly known host for this parasite.


Introduction
The Gryporhynchidae (Cestoda: Cyclophyllidea) are intestinal tapeworms parasites of fish-eating birds, and their larval forms (metacestodes) are found infecting over a hundred freshwater fish species, mainly in the Palearctic region (reviewed by SCHOLZ et al., 2004).Although several species of these cestodes have been reported, studies relating to species composition and distribution of these parasites are scarce, and for a significant percentage of gryporhynchid species, their metacestodes and life cycle remain unknown.In South America, and specifically in Brazil, the only species for which metacestodes are known is Valipora campylancristrota (Wedl, 1855), found in Prochilodus lineatus (Valenciennes, 1836), Pimelodus maculatus Lacépède, 1803, and Hoplosternum littorale (Hancock, 1828) in the State of Paraná, Southern Brazil (REGO et al., 1999;TAKEMOTO et al., 2009).Recently, Valipora sp. and another unidentified metacestodes were found in Prochilodus argenteus Spix & Agassiz, 1829 in the State of Minas Gerais (MONTEIRO et al., 2009).
In the present study, metacestodes of Glossocercus auritus (Rudolphi, 1818) are reported for the first time in Poecilia reticulata Peters, 1859 in Brazil.

Material and Methods
The fish specimens were collected with the aid of a scoop net during monthly sampling conducted in Pampulha dam (19° 51' 77" S and 43° 58' 54" W), an artificial eutrophic waterbody located in the northern region of the city of Belo Horizonte, from February to August 2010.The specimens collected were placed in plastic containers with water and transported alive to the laboratory.Then they were measured with a caliper, killed by decapitation in accordance with the recommendations from the local animal experimentation ethics committee (CETEA/UFMG), dissected and examined for parasites under a stereomicroscope.
When the cysts obtained were removed intact, they were measured.The larvae were then mechanically excysted and transferred to Petri dishes containing saline solution (0.85% NaCl).They were then flattened under soft pressure between glass slides and fixed in Railliet-Henry solution at 70 °C.The parasites were stained with acetic alum carmine, dehydrated in an alcohol series, cleared in beechwood creosote and mounted as permanent preparations in Canada balsam.
Additionally, scolices of some specimens were squashed and the hooks obtained were mounted in non-permanent preparations after addition of lactophenol.A morphological analysis was conducted using a light microscope, and specimens were measured through an eyepiece graduated in millimeters.Drawings of the rostellar hooks were made with aid of a camera lucida and photographic documentation was obtained using a digital camera coupled to the microscope.Some larvae obtained were also used to experimentally infect mice (Mus musculus Linnaeus, 1758), young chicken (Gallus gallus domesticus (Linnaeus, 1758)), and young and adult pigeons (Columba livia Gmelin, 1789).Metacestodes were force-fed to these hosts and, fifteen days after infection, the hosts were killed by cervical dislocation and examined for parasites.
Ecological terms were used as proposed by Bush et al. (1997).The specimens studied were deposited in the collection of the Laboratory of Taxonomy and Biology of Invertebrates, at the Department of Parasitology, Universidade Federal de Minas Gerais (UFMG) (accession number 6157 a-j).
In the present study, attempts to recovery adult parasites from vertebrate host were unsuccessful after experimental infection, and their absence in the hosts evaluated could be attributable to a potential host specificity of this cestode for ardeids.In fact, there are no records of experimental or natural infection in mammals and non-ardeid birds.
The diversity and life cycle of gryporhynchid parasites of Brazilian fishes need further studies to improve the knowledge about these biological interactions.This is the first report on metacestodes of G. auritus in Brazil and South America, and P. reticulata is a new intermediary host recorded for this parasite.

Table 1 .
Morphometric comparison between rostellar hook measurements of metacestodes of Glossocercus spp.obtained in the present study and those reported by other authors (in micrometers).