Ergasilus trygonophilus sp . nov . ( Copepoda : Ergasilidae ) a branchial parasite of freshwater stingrays ( Potamotrygonidae ) from state of Pará , Brazil

Ergasilus trygonophilus sp. nov. is described from freshwater stingrays (Potamotrygon spp. and Plesiotrygon iwamae Rosa, Castello & Thorson, 1987) from the state of Pará, Brazil. The new species differs from all known species of Ergasilus Nordman, 1832 from Brazilian waters by possessing: (1) an elongate bullet-shaped cephalosome; (2) antennule setal formula 1: 10: 4: 4: 2 + 1 ae: 6 + 1 ae; (3) maxillule bearing two distal setae; and (4) terminal endopodal segment of leg 1 with rosette-like array of blunt spinules. This is the first species of a freshwater stingray Ergasilus reported from Brazil.


MATERIAL AND METHODS
Potamotrygonids were captured with throw nets and long lines in the Igarapé do Urubu, municipality of Cachoeira do Arari (1º00'16.22"S,48º57'28.8"W)and Marajo Bay, municipality of Colares (0º55'47.22"S,48º17'30.68"W),state of Pará, Brazil.Copepod parasites were removed from the gill filaments with dissecting needles and fixed in 70% alcohol.They were transported to a laboratory of the Universidade Federal do Paraná, Curitiba, PR, where permanent slide preparations were made using the phenol-balsam method explained in THATCHER (2006).Drawings were prepared with the help of an Olympus BX 50 microscope with DIC optics and a camera lucida.Measurements were made utilizing a measuring ocular and are expressed in micrometers (µm).Basins and subbasin nomenclature following the Agência Nacional de Águas, Ministério do Meio Ambiente, Brasil (http://hidroweb.ana.gov.br).Type specimens and vouchers were deposited in the Crustacean Collection of the Instituto de Pesquisas da Amazônia (INPA), Manaus, AM, Brazil.Hosts have been deposited at the Museu de Zoologia, Universidade de São Paulo, São Paulo, SP, Brazil (MZUSP).

Figs 1-8
Diagnosis.Based on 10 females studied and measured; measurements in tables I and II.Cephalosome elongate, round anteriorly, longer than wide (bullet-shaped); antennules and antenna visible in dorsal view.Four free pedigers decreasing in width posteriorly; fifth pediger reduced (Fig. 1).Genital complex as wide as long, with a row of spinules on posteroventral margin (Fig. 5).Three free abdominal somites naked (Fig. 5), with a row of spinules on posteriorventral margin; anal somite with posteriorventral row of spinules, slightly indented medially.Caudal rami longer than wide, without ornamentation, each ramus with one long, one medium, and two short setae; principal seta plumose.
Antenna (Fig. 3) long, slender 4-segmented, comprising a short coxobasis, 3-segmented endopod and slightly recurved claw.Coxobasis without ornamentation; articulation membrane not inflated.Proximal endopodal segment slightly curved, longer than medial and distal endopodal segments combined, armed with short seta near mid-point on projection of inner margin.Medial endopodal segment with short seta near proximal portion on projection of inner margin and one short seta in distal portion of inner margin.Distal endopodal segment incomplete, vestigial, with one proximal seta on anterior surface.
Mandible (Fig. 4) with three blades: anterior delicate with bristles on anterior margin; median blade robust with large teeth on posterior margin; posterior blade falciform with teeth on posterior margin; Maxillule trapezoid, lobate, bearing two outer setae.Maxilla consisting of large syncoxa, with proximal projection, unarmed, tapering distally; and distal projection (small basis), armed distally with sharp teeth.
Legs .Legs 1-4 biramous, with rami 3-segmented, except for the first endopod and the fourth exopod, which are 2-segmented.Legs 1-4 with outer margins of both rami ornamented with rows of spinules of variable length outer margin of first and second endopodal segments of leg 4 pilose; inner margin of first exopodal segment of legs 1-4 pilose.Basis of legs 1-3 bearing outer naked setae on posterior surface, near the exopod (Figs 6-7); basis of leg 4 with plumose seta (Fig. 8).Interpodal plates of legs 1-3 with two rows of spinules.Leg 1 (Fig. 6) with first exopodal segment bearing a single spine on outer distal margin; second exopodal segment with a single, median, inner plumose seta; first seta of third exopodal segment falciform, semipinnate, four plumose setae on inner margin, two short plumose setae on outer margin, apical spine serrated on outer margin, plumose on inner margin; first endopodal segment elongate with long plumose seta near dis-tal portion; terminal endopodal segment with a rosette-like array of blunt spinules, first and second setae falciform, semipinnate, five plumose setae on inner margin.Legs 2 and 3 (Fig. 7) similar, first exopodal segment with distal spine on outer margin; second exopodial segment with inner medial plumose seta; third exopodial segment with outer small plumose seta, six plumose setae; first endopodal segment with inner plumose seta near distal portion; second endopodal segment with two inner plumose setae; third endopodal segment with apical spine serrated on outer margin only, four plumose setae.Leg 4 (Fig. 8) without seta or spine on first exopodal segment; terminal exopodal segment with outer short plumose seta, five plumose

Table I .
Measurements in micrometers (µm) of 10 adult females of E. trygonophilus sp.nov.collected from potamotrygonids in the state of Pará, Brazil.