Three new species of Monogenea (Platyhelminthes) parasites of fish in the Guandu river, southeastern Brazil

. Current essay describes three new Monogenean species, namely, Cosmetocleithrum striatuli sp. nov., Jainus leporini sp. nov. and Rhabdosynochus guanduensis sp. nov., parasites on the gills of Trachelyopterus striatulus (Steindachner, 1877), Leporinus copelandii Steindachner, 1875 and Centropomus undecimalis (Bloch, 1792), respectively. Fish were collected from the Guandu river, State of Rio de Janeiro, Brazil between August 2005 and November 2008. Cosmetocleithrum striatuli sp. nov. differs from all other congeneric species by the shape of an accessory piece (more robust and resembling a crustacean claw or chela) and by the shape of its ventral and dorsal bars (not V-shaped and with expanded lateral ends directed to the rear). Jainus leporini sp. nov. differs from all other Jainus species by the male copulation organ (MCO), with a 2-ring coil, by the absence of medial projection on ventral bar and by a plate-like sclerotized structure associated to the vagina. Rhabdosynochus guanduensis sp. nov. differs from all other congeneric species by the morphology of the copulation complex and by a shell-shaped vagina.


Introduction
Despite the efforts of taxonomists, the diversity of the Monogenea in neotropical waters is still largely unknown (BOEGER; VIANNA, 2006) and further efforts to carry out studies on their biodiversity are relevant.The Guandu river supplies water to 90% of the population of the city of Rio de Janeiro, Brazil.It has the greatest diversity of fish and the highest biomass within the Bay of Sepetiba Hydrographic Basin (BIZERRIL; PRIMO, 2001).To date, five taxonomic studies on monogenean species have been carried out on fishes from the Guandu river.Boeger and Popazoglo (1995) described a new species of Gyrodactylus, parasitic on Hoplias malabaricus (Bloch, 1794); Kritsky et al. (1995) studied the morphometric variability of the anchors and hooks of Scleroductus spp.; Abdallah et al. (2008) published a note on the morphology of Gussevia asota; Kritsky et al. (1986) on G. astronoti; Kritsky et al. (1986) collected Astronotus ocellatus (Agassiz, 1831); Carvalho et al. (2008) described a new species of Sciadicleithrum in Geophagus brasiliensis (Quoy and Gaimard, 1824), and more recently, Abdallah et al. (2009) described four new species of Ligophorus parasitizing the gills of Mugil liza Valenciennes, 1836.This paper provides the description of three new species of Monogenea from the Guandu river, or rather, Cosmetocleithrum striatuli sp.nov., Jainus leporini sp.nov.and Rhabdosynochus guanduensis sp.nov.parasitizing the gills of Trachelyopterus striatulus (Steindachner, 1877), Leporinus copelandii Steindachner, 1875 and Centropomus undecimalis (Bloch, 1792) respectively.

Material and methods
Sixty specimens of cumbaca (T.striatulus), 30 of piau (L.copelandii) and 31 of robalo (C.undecimalis) were collected between August 2005 and November 2008 from the Guandu river (22°48'32"S; 43º37'35"W), State of Rio de Janeiro, Brazil, to study the abovementioned monogenean species.The gills were removed and placed in vials with formalin 5% to fix ectoparasites.Some specimens were stained with Gomori trichrome and mounted in Canada balsam; other specimens were mounted in Gray and Wess medium (HUMASON, 1979) for study of sclerotized structures.Measurements are given in micrometers.Average measurements are followed by ranges and number of specimens measured (n) between parentheses.Unstained flattened specimens mounted in Gray and Wess medium were used to obtain measurements of the haptoral sclerites; all other measurements were obtained from non-flattened specimens stained in Gomori trichrome.Drawings were made with the aid of a drawing tube mounted on a Hund Wetzlar H-600 phase contrast microscope.Measurements were made using software Motic Images Plus™ 2.0.Type specimens were deposited at the Instituto Nacional de Pesquisas da Amazônia (INPA), Manaus, Amazonas State, Brazil.

Results and discussion
Dactylogyridae Bychowsky, 1933.Cosmetocleithrum striatuli sp.nov.(Figure 1, A-G Remarks: Species of Cosmetocleithrum are parasites on Neotropical siluriform fishes and are characterized by having gonads tandem, MCO J-shaped or coiled, non-articulated accessory piece and by having posterior projections on ribbon-like dorsal bar.According Boeger and Vianna (2006), seven Cosmetocleithrum species were described, six of them with known distribution restricted to the Amazon basin and described by Kritsky et al. (1986) and the other, C. longivaginatum, is from Paranean-Platean province, Argentina (SURIANO; INCORVAIA, 1995).
Cosmetocleithrum striatuli sp.n. differs from all other congeneric species by the shape of accessory piece (very robust and resembling a crustacean claw or chela) and by the shape of ventral and dorsal bars (not V-shaped and with expanded lateral ends directed to the rear).Based on the morphology of the copulation complex of the Cosmetocleithrum species, C. striatuli sp.n. is close to C. gussevi Kritsky et al. (1986)  Also, eyes and eye granules are present in the new species (absent in C. gussevi).Examination of paratype of C. gussevi shows that this species was adequately described by Kritsky et al. (1986) and confirmed the differences reported in this study.This is the first record of Cosmetocleithrum species in auchenipterid siluriform fishes.Remarks: Jainus Mizelle, Kritsky and Crane, 1968 included dactylogyrid species parasitic on characiform fish, characterized by having gonads tandem or overlapping, accessory piece articulated or non-articulated proximally, and ventral anchor robust with elongate superficial and deep roots.To date, five species of Jainus are known, four from Brazil, J. jainus Mizelle, Kritsky and Crane, 1968 on Chalceus macrolepidotus Cuvier, 1818, J. robustus Mizelle Mizelle, Kritsky and Crane, 1968 on Creatochanes affinis (Günther, 1864), J. amazonensis Kritsky, Thatcher andKayton, 1980 from Brycon melanopterus (Cope, 1872) and Jainus iocensins Cohen, Kohn and Boeger, 2012 from Salminus brasiliensis (Cuvier, 1817); and one from Costa Rica, J. hexops Kritsky and Leiby, 1972 on Astyanax fasciatus (Cuvier, 1819) (MIZELLE et al., 1968;KRITSKY;LEIBY, 1972;KRITSKY et al., 1980;BOEGER;VIANNA, 2006;COHEN et al., 2012).
Jainus leporini sp.nov.differs from all other congeneric species by male copulation organ (MCO) with a coil of 2 rings, by absence of medial projection in ventral bar and by a vagina associated to a plate-like sclerotized structure.Based on the shape of the accessory piece, J. leporini sp.nov. is close to J. amazonensis.The new species differs from J. amazonensis by accessory piece not flabellate distally (flabellate in J. amazonensis), by a vagina associated to plate-like sclerotized structure (simple in J. amazonensis) and by possessing a coiled male copulation organ comprising 2 rings (cirrus is a coil of one ring in J. amazonensis).Also, the new species does not have an elongate terminal extension on the superficial root of the ventral anchor (present in J. amazonensis) and a medial projection in ventral bar.Examination of paratypes of J. amazonensis showed that this species was adequately described by Kritsky et al. (1980) and confirmed the differences reported in current study.This is the first record of Jainus species in anostomid characiform fishes.
Etymology: The specific name refers to typelocality of the new species.Remarks: Rhabdosynochus Mizelle and Blatz, 1942 -included diplectanid species which parasitize centropomid fish and characterized by having or not scaled tegument; MCO tubular, coiled; accessory piece complex; vaginal sclerotized with medial vaginal aperture; accessory adhesive organ absent and superficial root of ventral anchor reduced.Currently, seven species of this genus are known as parasites of Centropomus species from Brazil and Mexico (DOMINGUES;BOEGER, 2008).
Rhabdosynochus guanduensis sp.nov.differs from all other congeneric species by the morphology of the copulation complex and by having a shell-shaped vagina.According to key provided by Kritsky et al. (2001), R. guanduensis sp.nov.appears to be close to R. hudsoni Kritsky, Boeger and Robaldo, 2001 by lacking bilateral membranous frills on peduncle and by shape of haptor.The new species differs from R. hudsoni by the morphology of the accessory piece and MCO; lacking tegumental scales; absence of the superficial bulbous blade arising from the inner surface of distal shaft of the dorsal anchor and by the morphology of the vagina.Examination of paratypes of R. hudsoni showed that this species was adequately described by Kritsky et al. (2001) and confirmed the differences observed in this study.

Conclusion
The description of the three new species of monogeneans parasitic on fish is an indicator of the biodiversity of Guandu River which supplies water to 90% of the population of the city of Rio de Janeiro, Brazil.
parasite of Oxydoras niger (Valenciennes, 1821) from Janauacá lake, Brazil.The new species differs from C. gussevi mainly by having robust accessory piece resembling a crustacean chela (accessory piece is slender and Y-shaped in C. gussevi); by well-defined anchors roots (C.gussevi has non well-defined anchor roots); by the dorsal bar shape (the new species lack a pointed posteromedial protuberance, present in C. gussevi); by the ventral bar shape (without posteromedial rounded keel, present in C. gussevi); and by presence of seven pairs of haptoral hooks (C.gussevi do not have hook pairs 5 and 6).