Spiroxys contortus ( Rudolphi , 1819 ) and Hedruris orestiae ( Moniez , 1889 ) in Argentine turtles

Knowledge of parasites in turtles is scarce, particularly with regard to freshwater turtles of South America. Here, we describe the association of Spiroxys contortus (Rudolphi, 1819) in Phrynops hilarii (Duméril & Bibron, 1835) and S. contortus and Hedruris orestiae (Moniez, 1889) in Hydromedusa tectifera (Cope, 1870). The presence of S. contortus in P. hilarii represents a new host record and also the southernmost geographic record for this species. More interestingly, the presence of H. orestiae in H. tectifera represents the first record of this helminth species from a reptilian host.

Knowledge of the parasite fauna in South American turtles is particularly scarce and fragmentary (Fernandes and Kohn 2014;Mascarenhas et al. 2016), especially with regard to the Argentine species, the southernmost species in the region (Brusa and Damborenea 2000;Alcalde et al. 2010).
Phrynops hilarii (Duméril & Bibron, 1835) inhabits a wide variety of aquatic environments in Uruguay, southern Brazil and Paraguay, and northeastern and central Argentina (Cabrera 1998).No natural populations of P. hilarii are known from the western Argentine provinces of Mendoza, San Juan and Tucumán (Prado et al. 2012).Excluding isolated populations, the westernmost occurrence of this species is in northwestern Cordoba province (Cabrera et al. 1986) and the southernmost records are from streams entering the Rio de La Plata shoreline, near Bahía Samborombón, Buenos Aires province, Argentina (Derocco et al. 2005;Williams and Kacoliris 2009).Although ecological studies of habitat usage and preferences are virtually lacking for this species, miscellaneous reports and observations indicate that P. hilarii is a swimming species that prefers deep, moderately vegetated waters; it is usually in association with large rivers such as the Paraná, Uruguay, Paraguay, and Río de la Plata rivers (Cabrera 1998).
Hydromedusa tectifera (Cope, 1870) is usually found in sympatry with P. hilarii, particularly in the southernmost part of its range.They occur in the same aquatic environments in Uruguay, southern Brazil, southeastern Paraguay, and northeastern and central Argentina.The southernmost occurrence of H. tectifera is in Río Sauce Grande (Sierra de la Ventana, Buenos Aires province), and the westernmost occurrence is in several mountain streams in Cordoba province, Argentina (Cabrera 1998;Di Pietro et al. 2012;Prado et al. 2012).
Reports on the diets of P. hilarii and H. tectifera indicate that these species ingest very similar food items, mainly adult and larvae of arthropods (Bonino et al. 2009;Alcalde et al. 2010), many of which have been reported as intermediate hosts for several parasite species (Moravec 1998).
Few species of nematodes have been reported parasitizing southern Brazilian populations of P. hilarii and H. tectifera.Spiroxys sp.(Gnathostomatidae) and Camallanus sp.(Camallanidae) were documented in P. hilarii (Bernardon et al. 2013).Spiroxys contortus (Rudolphi, 1819), Camallanus sp.(Mascarenhas et al. 2013) and Spirocamallanus sp.(Camallanidae) were reported in H. tectifera (Novelli et al. 2014).Knowledge of nematodes for Argentine populations of H. tectifera corresponds to the observations of Alcalde et al. (2010) who studied the diet of this turtle species and found nematodes in many of the stomach contents, but these helminthes remained unidentified until now.
Therefore, we present new geographical records of nematodes and new host-parasite associations for turtle populations from Argentina.This work highlights the fragmentary knowledge of the parasite fauna of the turtles in the region.

Gnathostomatidae Spiroxynae
Spiroxys contortus Rudolphi, 1819 (Figures 2 and 3; Table 1) Description based on 17 adult specimens.Slender, colorless, semitransparent worms; intestine distinctly brown or approaching black in some individuals.Oral opening surrounded by two trilobed lips with a rather thick cuticular lining that projects anteriorly in each median lobe to form a blunt tooth (Figure 2).Each lip bears one lateral and two submedian papillae.Small cervical papillae located posterior from the excretory pore.Tail rather short in both sexes, ending in an abrupt, sharp, conical tip.
Male: Four pre-anal and seven post-anal pairs of pa pillae.Seventh and eighth pairs from the posterior end are sessile and located immediately posterior and anterior, respectively, to the anus.Long, slender, cylindrical, and equal spicule, without keel, distinctly transverse striated, ending in a sharp point.Gubernaculum composed of dense cuticular material.(Rudolphi, 1819) and Hedruris orestiae (Moniez, 1889) in Argentine turtles Female: Two cuticular prominences guard the opening of the vulva, which is just posterior to the middle of the body.Vagina anteriorly directed, thick-walled, muscular, and annulated.No ovijectors.
Comments: Spiroxys species can be distinguished from one another by the number and distribution of male caudal papillae, the position of excretory pore and cervical papillae, presence or absence of gubernaculum and size of several features.
Female: Prodelphic, didelphic, vulva at back of the body.When gravid, egg-filled uteri occupy entire body cavity.Tail curved dorsally and formed into a sucker-like apparatus armed with a large sclerotized, barbed hook (Figure 6).Eggs nonmammillated and cylindrical.
Comments: Hedruris species can be distinguished from each other, including those reported in H. tectifera (i.e., Hedruris moniezi Ibanez & Córdova, 1976 and Hedruris basilichtensis [Mateo, 1971]) by their general body shape, body length, number and distribution of male caudal papillae, spicule length, size and shape of the eggs, and hosts (Mateo 1971;Ibanez and Córbova 1976) (Table 2).
Spiroxys contortus is widely distributed in Eurasia, North Africa, and America (Baker 1987).In South America, the species was previously recorded from H. tectifera in Brazil (Mascarenhas et al. 2013) and Trachemys dorbigni (Duméril & Bibron, 1835) (Emydidae) (Mascarenhas and Müller, 2015) (Figure 1).Our find of S. contortus in a population of P. hilarii from Argentina represents a new host and the southernmost geographic distribution record of this nematode.
Dragonfly naiads are an important prey of turtles (Alcalde et al. 2010), and interestingly, dragonflies have been recorded as intermediate hosts of S. contortus in other regions of the world (Hedrick 1935).
Most species of Hedruris (Habronematoidea, Hedruridae) were reported parasitizing fishes, amphibians, and reptiles (Anderson 2000).In turtles, an unidentified species of Hedruris was reported from Rhinoclemmys nasuta (Boulenger, 1902) in Mexico (Dyer and Carr 1990).Moravec (1998) suggested that some species of nematodes, whose definitive hosts are usually amphibians and reptiles, could be found in the stomachs of fishes that accidentally acquired parasites by feeding on intermediate hosts.Because Hedruris larvae present precocity in their development and reach immature adulthood in their intermediate host (isopods), fish can acquire the nematodes when feeding on infected isopods (Moravec 1998).Thus, the fish should be considered facultative hosts.Consequently, our record of Hedruris orestiae in Hydromedusa tectifera is the first from chelonians, which should be considered suitable definitive hosts of this species.Present study Present study *From anterior end.Palumbo et al. | Spiroxys contortus (Rudolphi, 1819) and Hedruris orestiae (Moniez, 1889) in Argentine turtles

ACKNOWLEDGEMENTS
We acknowledge CONICET and UNLP for continuous support.We especially thank Merlina Mancuso for helping in the English revision of the manuscript and Maria Laura Morote for editing the pictures.Fieldwork was carried out with permission of the Dirección de Flora y Fauna de la Provincia de Buenos Aires (Disposition No. 102/2014).The present paper represents the Scientific Contribution No. 987 of the Instituto de Limnología Dr. R.A. Ringuelet.
using the Quantitative Parasitology Program (QP 3.0, Reiczigel and Rózsa 2005).Voucher specimens are deposited in the Helminthological Collection of the Museo de La Plata (MLP He 7141-7143), La Plata, Buenos Aires, Argentina.

Table 1 .
Comparative features on males and females of Spiroxys contortus found in freshwater turtles.

Table 2 .
Selected characteristics of South America species of Hedruris with 18 cloacal papillae. H.