A new species of Tripartiella (Ciliophora: Trichodinidae) from Aequidens tetramerus (Perciformes: Cichlidae) in north Brazil

A new species of Tripartiella is described from the gills of the wild saddle cichlid Aequidens tetramerus in north Brazil. discussed.


Introduction
Trichodinids (Trichodinidae Claus, 1874) are a widely distributed group of ciliated ectoparasites of mollusks, fishes and amphibians (Mitra et al., 2013).Representatives of the genus Tripartiella Lom 1959, however, are only found on the gills of marine and freshwater fish (Tang et al., 2013).Up to now, there is only one Tripartiella species reported in Brazil, which is Tripartiella pseudoplatystomae Pinto, Garcia, Figueiredo, Rodrigues and Martins 2009, parasite of the pintado Pseudoplatystoma corruscans in the state of Mato Grosso do Sul, Central-Western Brazil.However, considering the wide variety of fish species in Brazil and the great abundance of fish trichodinids, it is reasonable to accept that much more species are yet to be reported.
The saddle cichlid Aequidens tetramerus (Heckel 1840) (Cichlidae) is endemic to South America and is commonly used as ornamental fish, sport fishing and also as food for the Amazon riverine populations (Tavares-Dias et al., 2014).In course of a parasitological survey of the protozoan parasites of this cichlid in north Brazil, a new Tripartiella species was found.
This study characterizes morphologically Tripartiella tetramerii n.sp.parasite of A. tetramerus from north Brazil.Taxonomic and morphometric data for the new species are discussed.

Material and Methods
Sixty-three specimens of A. tetramerus were collected by net in November 2011 in the municipality of Macapá (00° 02' N, 51° 03' W), Amapá State, Brazil.
Wet smears of fish skin and gills of collected fish were air-dried and impregnated with Klein's dry silver method for observation of the adhesive disc as suggested by Lom (1958).The span of the denticle was measured from the tip of blade to the tip of ray as described by Arthur and Lom (1984).The body diameter is the dimension of the adhesive disc plus the border membrane.Wet mounts from the specimens preserved in 5% formalin solution were studied for the observation of adoral ciliature.All measurements are in micrometers and follow the recommendations of Lom (1958) and Van As and Basson (1989).Mean ± standard deviation is followed, in parentheses, by the minimum and maximum values and number of specimens or structures measured.

Results
A total of 65% of examined fish were parasitized by the new Tripartiella species (mean intensity of infection: 2,379 ± 1,344 (1,233-3,567)).Morphologically, it is characterized as a small-sized trichodinid, disc shaped.Blade of denticle elongated and straight, narrowing at distal end (Figure 1).Blade greater than ray.Tangent point rounded, lower than distal blade margin.Blade touching Y+1 and Y axes.Anterior blade projection broad, prominent and wide, fitting into indentation of next denticle.Section connecting anterior projection and central part constricted.Central part of the denticle with a remarkable rounded spine directed backwards.Ray slender, lower than blade, straight, rounded in its distal extremity and directed towards the center of the adhesive disc.Central part extends Y+1, Y and Y-1 axes (Figure 2).Adoral ciliature spiral 381°.Morphometrical data is presented in Table 1.
Reference material: Holotype and paratype slides are deposited in the National Institute of Amazonian Research (INPA 006, 007), Manaus, AM, Brazil.Denticles of both Tripartiella and Trichodinella species are wedged together both by central parts and anterior blade projection (Lom and Haldar, 1977).However, whereas in the former genus it bears developed straight rays, the latter possesses short ray curved along the delicate central part.
Concerning to Tripartiella, the type species Tripartiella copiosa Lom, 1959 has been regularly reported on the gills of Cyprinidae and Cobitidae fish throughout the European and Asian continents (Lom and Haldar, 1977;Mitra et al., 2012;Mohilal and Hemananda, 2012).Morphologically, its ray resembles those of T. tetramerii n.sp.(both the species have thin rays, terminating in a rounded point); however, the shape of the blade of T. copiosa (broad, directed backwards) differs completely from the present studied specimens (narrow and straight), besides almost all biometrical data (Table 1).