Strigeid parasites of Circus buffoni from Argentina, with the description of a new species of Parastrigea Szidat, 1928

Studying the Helminthological Collection of Museo de La Plata (MLP-He), several specimens of digeneans, recovered parasitizing a long-winged harrier, Circus buffoni (Accipitridae) from Buenos Aires Argentina, were analysed. The morphological and morphometric analysis of these specimens revealed the presence of two strigeid species, one of them new for science. Parastrigea buffoni n. sp. is characterised by a forebody differentiated in a retractile cephalic region with a large opening and a balloon-shaped collar region or collerette, suckers located in cephalic region, holdfast organ with well development dorsal and ventral lips that can emerge through opening, a claviform hindbody, a large copulatory bursa with muscular ring (Ringnapf) and a genital cone well delimited, crossed by a sinuous hermaphroditic duct with internal rugae. The euryxenous parasite, Strigea falconis brasiliana, is briefly described, parasitizing a new host. This is the first record of helminths parasitizing long-winged harrier.


Introduction
Circus buffoni (Gmelin) (Accipitridae) commonly known as long-winged harrier is a bird of prey found in open fields, marshes, grasslands and savannas of the Neotropical region, from SW Colombia to the Guianas, Trinidad and Tobago, NE Brazil, E Bolivia and N and central region of Argentina and Chile (Thiollay 1994).The long-winged harrier is considered to be a least concern species (BirdLife International 2017).The knowledge about the helminth parasites is very important for the conservation of wildlife with implications in host population biology (Youssefi et al. 2014).Until now, the helminth fauna of long-winged harriers has been unknown.Other two species of Circus Lacépède inhabit the Neotropical region, Circus cinereus Vieillot and Circus cyaneus (Linnaeus).In South America, the helminth fauna of these species is poorly known, only Ophiosoma microcephalum Szidat, 1928 (Digenea, Strigeidae) was reported parasitizing C. cyaneus (as Falco cyaneus) from Brazil (Szidat 1928).
The aim of this study is to know the diversity of helminths in long-winged harriers from natural environments.

Materials and methods
A total of 69 digenean specimens stored in the Helminthological Collection of Museo de La Plata (MLP-He), La Plata, Argentina, were examined.They were recovered from a single specimen of Circus buffoni collected in Puán (37°33′ S; 62°46′ W), Buenos Aires, Argentina, on April 1996.The specimens were stained with hydrochloric carmine, dehydrated and mounted in Canada balsam (Langeron 1942).Some specimens were removed from the slide and mounted between cover glasses in order to facilitate handling and observation.The terminal genitalia were studied in two specimens cleared in creosote.The measurements below are given in micrometres (μm) unless otherwise stated, as the range followed by mean in parentheses.Drawings were made with the aid of a drawing tube.The terms cephalic region and collerette of the forebody are used according to Dubois (1968).Cephalic region is the anterior region of the forebody containing the aperture and the collerette the posterior region containing the lateral expansions.Additionally, four of these specimens were deposited in the Collection of the Natural History Museum (NHM) in London, UK.

Results
The morphological and morphometric analysis of the studied specimens revealed the presence of two strigeid species, one of them new for science: Parastrigea buffoni n. sp.(22 specimens) and Strigea falconis brasiliana (47 specimens), a euryxenous parasite.
Parastrigea caballeroi has been reported parasitizing ciconiid birds, Jabiru mycteria (Lichtenstein) and Mycteria americana Linnaeus from Venezuela (Fernandes et al. 2015).This species mainly differs from P. buffoni n. sp. by having a forebody not divided and by the location of the ventral sucker, near the intersegmental constriction.It also differs in most metrical characters (Table 1).
Parastrigea diovadena was recovered parasitizing threskiornithid birds, Eudocimus ruber (Linnaeus) from Colombia (Dubois 1978).It is also reported in Central and North America parasitizing E. albus from Cuba, the USA and Mexico (Dubois and Macko 1972;Bush and Forrester 1976;Ortega-Olivares et al. 2011).This species mainly differs from P. buffoni n. sp. by having a forebody not divided, a copulatory bursa scarcely delimited and a large bilobed proteolytic gland.It also differs in most metrical characters (Table 1).
Parastrigea macrobursa was described parasitizing Buteogallus urubitinga (Gmelin) (Accipitridae) from Argentina (Drago and Lunaschi 2011b).This species differs from P. buffoni n. sp. by having a forebody not divided, with lateral expansions lesser-developed, a copulatory bursa without muscular ring (Ringnapf), a proteolytic gland located at the base of the forebody and testes not lobed.It also differs in most metrical characters (Table 1).
Parastrigea robusta was reported parasitizing Jacana jacana jacana (Jacanidae) from Brazil (Fernandes et al. 2015).It was also recovered in Tachybaptus ruficollis (Pallas) (Podicipedidae) from North America (Storer 2000) and in anatid and falconid birds from Eurasia (Dubois 1968).This species mainly differs from the new species by having a forebody with a small opening, a copulatory bursa poorly delimited, suckers situated in the collerette and an ovary located near the intersegmental constriction.It also differs in most metrical characters (Table 1).
Parastrigea mexicana has been reported parasitizing recurvirostrid birds, Himantopus mexicanus (Müller) from Cuba, Mexico and the USA and Recurvirostra americana Gmelin from Mexico, the USA and Canada (Coil 1957;Coil 1969;Dubois and Macko 1972;García and Canaris 1987;Hinojos and Canaris 1988;Edwards and Bush 1989).This species can be easily differentiated from P. buffoni n. sp. by having a forebody not divided with a small opening, an ovoid hindbody, a much shorter pre-ovarian region (occupying 14-18% of the hindbody length vs. 25-41%), and a genital cone and a copulatory bursa weakly developed (Dubois and Macko 1972).
Parastrigea plataleae has been reported parasitizing P. ajaja (Threskiornithidae) from Mexico (Hernández-Mena et al. 2014).This species mainly differs from P. buffoni n. sp. by having a forebody with moderate lateral expansions, a cephalic region not retractile and poorly differentiated, a proteolytic gland situated near the intersegmental constriction and a campaniform copulatory bursa wider than longer.Parastrigea tulipoides, reported Buteo lineatus (Gmelin) and Buteo jamaicensis (Gmelin) (Accipitridae) from the USA (Dubois 1968;Gibson et al. 2005), can be easily differentiated from the new species by having a forebody with lateral expansions poorly developed, a proteolytic gland situated near the intersegmental constriction, a long pre-ovarian region, occupying more than 50% of the hindbody and a shorter genital cone (200-240 × 150-210 vs. 532-783 × 367-435).

Discussion
Helminths of wild birds have been less studied than other vertebrates, mainly because the birds are one of the most charismatic and protected groups.Then, it is difficult to obtain a sufficient number of these hosts because many are protected by national and international laws (Perez Ponce de León et al. 2011).Much of the information available on parasites in wild birds comes from studies carried out in birds that died accidentally or by nature causes.In these cases, the hosts or their viscera are often fixed in formalin or frozen; thus, the parasites can contract or some structures are lost making taxonomic identification difficult.Therefore, the majority of parasites of wild birds have yet to be described taxonomically (Wobeser 2008).Other important sources of information for taxonomic studies on helminths of birds are the helminthological collections, which preserve information on spatial and temporal biodiversity.Collections also can provide about the habits and diet of birds.
The higher intensity of S. f. brasiliana can be associated with the preferred preys of the host (birds), while the moderate intensity of P. buffoni n. sp.can be related with the occasional consumption of amphibians.