Helicometrina nimia Linton, 1910 (Digenea: Opecoelidae) in dusky grouper Epinephelus marginatus (Lowe, 1834) (Teleostei: Serranidae) from southeastern Brazil.

Helicometrina nimia (Opecoelidae) is a digenean with wide distribution. Fish families most commonly used as hosts for H. nimia are Serranidae, Pomodasydae, Scorpaenidae and Clinidae. In the present study, a new host and a new host locality are presented for the species. A description of the studied specimens, besides comments concerning its taxonomic status and biometrically compared tables of H. nimia reports are given. The taxonomic status of members of Helicometrina has been questionable. The greatest controversy for the genus seems to be related to the validity of diagnostic features, especially in regard to the number of testes. In the present study, all studied specimens presented a permanent and steady number of testes (n=9) and therefore its use as a diagnostic character is supported by the present authors. Epinephelus marginatus is considered a new host for Helicometrina nimia, and São Paulo state, southeastern Brazil, a new locality for the species.


Discussion
Helicometrina nimia Linton currently distributed in almost the entire American continent    Mittal and Pande. The authors also presented a key to the species of genus based on the number of testes.
described H. qatarensis (not included in the valid list species proposed by Mittal and and differentiated this species from H. nimia mainly in the position of the genital pore and the larger eggs. The authors did not recognise the synonimisation of H. nimia and H. orientalis proposed by since these species present a different arrangement of the vitellaria distribution, according to the former authors.
The taxonomic status of members of Helicometrina has been questionable. The greatest controversy for the genus seems to be related to the validity of diagnostic features, especially in regard to the number of testes.
studied 28 specimens of Helicometrina varying number of testes. Except for this characteristic, the author did not report any other difference among specimens and concluded that the number of testes should not form a character to distinguish species. Later, Gibson et al. recognized the logic of the comments of the later author, but supported a distinction on the number of testes. In the present study, all studied specimens presented a its use as a diagnostic characteristic is supported by the present authors. Moreover, the arrangement of testes also remained the same in all analysed specimens, distributed specimens previous reports for H. nimia presented an Oliva and Muñoz, 1985León, 1992Bunkley-Williams et al., 1996Moravec et al., 1997 testes in the present studied specimens (4 testes in the right compared to previous reports for the species, the authors do not consider that this difference might support a distinct species of H. nimia.
observed that in the and appeared disintegrating. attributed it to the presence of testes not as compact as in the mature ones, giving the impression mentioned by both authors. Measurements of the present studied specimens agree H. nimia such as those provided by , , Luque and (Table 1 Other features pointed out by are, in fact, highly variable and should not be used for species distinction. The extent of the cirrus sac seems to be specimens presented larger cirrus sac than the younger decrease in its length.
reported paddle-shaped expansions in the extremity of each caeca of H. nimia. Differently from the later, in the present study such a remarks of observed a great variability both in shape and number of ovary's lobes, being noticed, as the only pattern, the For all anteriorly mentioned, the authors believe that the number of testes, the position of the genital pore, the egg size, vitellaria arrangement and extension, the position are good indicators for Helicometrina species distinction.
In the present study, Epinephelus marginatus is Helicometrina nimia, and São locality for the species.