Cyclopoida , Ergasilidae ) : a gill parasite of Serrasalmus hollandi Jégu , 2003 ( Characiformes , Serrasalmidae ) from the Paragua River , Bolivia

A new parasitic copepod species, Ergasilus turkayi n. sp., found on the gills of the Holland’s piranha, Serrasalmus hollandi Jégu, 2003, in the Paragua River, Bolivia, is described based on 10 adult females. Th e new species presents a triangular-shaped cephalothorax, spinules on interpodal plates and aesthetascs on antennule two aesthetascs on the sixth, and one aesthetasc plus two setae on the fi ft h segment. Additionally, the second abdominal somite of E. turkayi n. sp. bears an anal pseudoperculum, a dorsal and elongate projection which is usually absent or vestigial in poecilostome families within the Cyclopoida but that was never reported in species of Ergasilidae.


IntroductIon
Ergasilidae von Nordmann, 1832 is one of the major families of Poecilostomatoida (Cyclopoida) and comprehends 27 genera of parasitic copepods found in marine, brackish, and freshwater environments worldwide.The majority of the ergasilids parasitizes the gill filaments, gill rackers, nasal cavities and body surface of fish species (Boxshall and Defaye, 2007).Species of Ergasilidae share a unique life cycle: only fertilized females are parasitic, being the phase most widely used for the description and determination of most species (Boxshall and Defaye, 2007).Species of Ergasilidae feed on host tissue and are considered a pest in aquaculture (Kabata, 1970).
Copepods were cleared in lactic acid and mounted in Hoyer's mounting medium (prepared according to Humason, 1979).Whenever necessary, specimens were dissected with the help of acupuncture needles.Illustrations were made with the aid of an Olympus BX51 microscope with DIC illumination and camera lucida.All measurements are in micrometres; measurements are presented by the range followed by the mean and the number of measurements in parentheses).Type specimens are deposited in the Helminthological Collection of the Instituto Oswaldo Cruz, Brazil.
Six specimens used for scanning electron microscopy were dehydrated in an increasing ethanol series.The specimens were critical-point dried with CO 2 and sputter-coated with gold.The images were made with a TESCAN VEGA3 LMU scanning electron microscope at an accelerating voltage of 15.0 kV.All procedures were performed at the "Centro de Microscopia Eletrônica, Universidade Federal do Paraná (CME-UFPR)." Site on host.Gill filaments.
Etymology.The specific name is in honor of the late Dr. Michael Türkay (Research Institute and Natural History Museum Senckenberg (Frankfurt am Main, Germany) for his extensive contributions to the study of Crustacea.
Antenna (Fig. 1B) comprising coxobasis, threesegmented endopod, and terminal claw.Coxobasis short, presenting tiny distal seta at inner distal corner; membrane between coxa and first segment of endopod not inflated.First endopodal segment with length/width ratio approximately 3; sensillum near mid length.Second segment curved, as long as first segment, presenting proximal sensillum and small distal sensillum.Third endopodal segment with single seta.Claw evenly curved, with small pit (fossa) distally on concave margin.
Mouthparts (Fig. 1D) comprising mandible, maxilla and maxillule; maxilliped absent.Mandible with median and posterior blades; anterior blade absent; median blade completely toothed.Basis of maxilla partially toothed, with a sensillum on proximal region, spinulated setae on maxilla absent.Two setal elements on maxillule present.
Interpodal plates (Fig. 1E) of all legs ornamented with spinules ventrally, variable in number and distribution among plates.Swimming legs 1-4 biramous and with separate coxa and basis.Armature of legs (setae, Arabic numerals; spines, Roman numerals) as in Tab. 1.
Leg 1 (Fig. 1G).Coxa with smooth margins, lacking spinules; basis with smooth margins, lacking spinules, with proximal outer seta.Exopod with 3 segments; first segment pilose on inner margin, with spinules distally on outer margin, lacking inner seta, distal spine on outer margin present; second segment with spinules on entire outer margin, with one seta, distal spine absent; third segment with spinules distally on outer margin, with one pectinate seta and four pilose setae, two distal spines spinulated.Endopod with 2 segments; first segment not pilose, with spinules on entire outer margin, with one seta; second segment with spinules on entire outer margin, with five setae and two straight spines, only outer spine spinulated.
Legs 2 and 3 similar (Fig. 1H).Coxa ornamented with spinules; basis lacking spinules, with proximal seta.Exopod presenting 3 segments; first segment twice as long than wide, pilose on inner and outer sides, with spinules on all outer margin with non-spinulated distal spine, lacking seta; second segment with spinules on entire outer margin, with one seta, distal spine absent; third segment with spinules on entire outer margin, with six setae and one non-spinulated spine.Endopod with 3 segments; first segment pilose on outer side, with spinules on entire outer margin, with one seta; second segment not pilose, with spinules on entire outer margin, with two setae, distal spine absent; third segment with spinules on entire outer margin, with four setae and one non-spinulated distal spine.
Leg 4 (Fig 1I).Coxa ornamented with spinules; basis presenting single small proximal seta.Exopod with 2 segments; first segment pilose on inner margin, lacking spinules, lacking seta, with one non-spinulated distal spine; second segment lacking spinules, with four setae and one non-spinulated distal spine.Endopod with 2 segments; first segment pilose on outer side, with spinules on entire outer margin and one seta; second segment with spinules on entire outer margin, with five setae and one non-spinulated distal spine.
Ergasilus turkayi n. sp.presents a pinnate (falciform) seta on the third exopodal segment of the first pair of legs accompanied by four pilose setae, which is a trait shared with other Neotropical species of Ergasilus.

Figure 2 .
Figure 2. Scanning electron microscopy of Ergasilus turkayi n. sp., adult female.A, Dorsal view, arrow pointing the U-shaped dorsal pseudoperculum in the anal somite; B, closer dorsal view of the pseudoperculum; C, multiple small sensilla distributed along the entire body.Scale bars: A, 200 µm; B, 20 µm; C, 5 µm.