A new species of Microtetrameres ( Nematoda , Tetrameridae ) parasitizing Buteogallus urubitinga ( Aves , Accipitridae ) from northeastern Argentina

A new tetramerid nematode, Microtetrameres urubitinga n. sp., is described from specimens recovered from the proventriculus of the great black-hawk, Buteogallus urubitinga (Aves: Accipitridae), from Formosa Province, Argentina. The males of the new species are characterized by having spicules unequal (length ratio of spicules 1:3.8–5.9) and dissimilar in shape (right spicule with a simple tip, left spicule with a symmetrical bifurcated tip), caudal papillae arranged asymmetrically (two pairs precloacal and two pairs postcloacal) and cloacal lips highly protruded forming a tube. The gravid females are permanently coiled clockwise or counterclockwise in a spiral and having a tail tapering gradually to a sharp point, with a cuticular fold. This is the first nominal species of Microtetrameres (Travassos, 1915) described parasitizing birds from Argentina. The relationship between the diet of B. urubitinga and the low prevalence of M. urubitinga n. sp. is discussed.

The members of Microhadjelia are found in the digestive tract of passeriform birds.They are filiform worms, the females are totally coiled, while the males only have the posterior end coiled (Quentin and Wertheim 1975).The members of Tetrameres and Microtetrameres are parasites of the proventriculus of birds.The females are typically embedded in the gastric glands, with the tails directed towards the lumen of the proventriculus.The filiform males are generally found on the mucosa, in the lumen of the proventriculus, or in the crypts (associated or not with females).The evidence suggests that males move about freely, to reach and fertilize the stationary females (Anderson 2000).The taxonomic status of genus Tetrameres is closely related to that of the genus Microtetrameres.These nematodes originally were grouped by Diesing (1835) under the name Tropidurus, including species from Brazilian birds.Creplin (1846) renamed the genus as Tetrameres, because the name Tropidurus was preoccupied.Travassos (1915) separated the genus into two subgenera, Tetrameres and Microtetrameres.Cram (1927) raises to generic category both subgenera based on female body form; globular or spindleshaped in Tetrameres and with its longitudinal axis spirally coiled in Microtetrameres.
The aim of this paper is to describe a new species of Microtetrameres obtained from the proventriculus of the great black-hawks, B. urubitinga, from northeastern Argentina.

MATERIALS AND METHODS
Six specimens of B. urubitinga were collected between 2004 and 2012 at La Marcela farm (26°17'35"S, 59°08'38"W), Pirané, Formosa Province, Argentina, with authorization of Ministerio de la Producción y Ambiente, Dirección de Fauna y Parques of Formosa Province.The birds were captured with a shotgun and dissected in the field, the viscera preserved in 10% formalin and transported to the laboratory for examination.Nematodes were removed from the proventriculus and preserved in 70% alcohol.For examination, the males were cleared by immersion in glycerinealcohol and the females in Amman's lactophenol.Measurements 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 helminths were deposited in the Helminthological Collection of the Museo de La Plata (MLP-He) and the hosts in the Ornithological Collection of the Museo de La Plata (MLP-Or), La Plata, Argentina.Additionally, one  II).
Site of infection: Proventriculus.Females within the glands, males free in the lumen.
Female (based on 8 specimens): Red.Gravid specimens permanently coiled clockwise or counterclockwise in a spiral.Cuticle with fine transverse striations.Body without longitudinal  paratypes MLP-He 7449; voucher specimens: MLP-He 7450.
Etymology: The new species is named after the specific name of the host.
Microtetrameres cruzi can be differentiated from M. urubitinga n. sp. by having shorter males, shorter right spicule, higher spicule length ratio, different distribution of caudal papillae (1 pair precloacal and 3 pairs postcloacal arranged symmetrically) and females with shorter tail without cuticular fold (Tables I, II).
Microtetrameres minima can be distinguished from the new species by having shorter males, shorter right spicule, and higher ratio between spicules.Females differ from those of M. urubitinga n. sp. by being smaller and by having shorter tail and smaller eggs (Tables I, II).
Microtetrameres pusilla can be differentiated from M. urubitinga n. sp. by having longer males with longer left spicule, shorter right spicule, higher spicular ratio and different distribution of caudal papillae (two pairs precloacal, 1 pair adcloacal and 2 pairs postcloacal), and wider females with longitudinal furrows (Tables I, II).
Males of M. cerci can be mainly distinguished from those of M. urubitinga n. sp. by having an undivided tip of left spicule and a higher spicular ratio (10.4-16 vs. 4-6).The females are unknown (Mawson 1977).
Males of M. cloacitectus described by Barus (1966) mainly differ from those of M. urubitinga n. sp. by the number of caudal papillae (five pairs vs. four pairs), the morphology of left spicule (tip leaf-shaped vs. symmetrically bifurcated) and the presence of a tongue-shaped prominence close to cloaca.Also, females have shorter and wider eggs (42-46 x 26-29 vs. 48-52 x 24).
Males of M. creplini can be mainly distinguished from those of M. urubitinga n. sp. by having a higher spicular ratio (19 vs. 4-6) and by the number and distribution of caudal papillae (two symmetrical pairs and one unpaired precloacal papillae and two pairs of postcloacal papillae, the first symmetrically, and the second asymmetric arranged).The females are unknown.Based on all these morphological and morphometrical differences, a new species Microtetrameres urubitinga n. sp. is proposed.This is the first nominal species of Microtetrameres described from Argentina.

DISCUSSION
The known life cycle of Microtetrameres spp.involve grasshoppers and cockroaches, as experimental intermediate hosts and birds as natural definitive hosts (Anderson 2000).
Cram (1934) described the experimental life cycle of Microtetrameres helix Cram, 1927 from North America.This author gave embryonated eggs of this species, to earthworms, isopods, grasshoppers [Melanoplus bivittatus (Say) and Melanoplus femurrubrum (De Geer)] and a cockroach [Blattella germanica (Linnaeus)].She obtained several infective third-stage larvae in the grasshoppers and only a single larva in the cockroach; while infections in annelids and isopods were negative.Ellis (1969) studied the life cycle of Microtetrameres centuri Barus, 1966 in USA.He obtained infective third-stage larvae in grasshopper nymphs (Melanoplus spp.) feed with embryonated eggs obtained from natural hosts, Sturnella neglecta Audubon and Sturnella magna (Linnaeus).Bethel (1973) described the experimental life cycle of Microtetrameres corax Schell, 1953 in USA.He obtained infective third-stage larvae in grasshoppers (Melanoplus spp.) fed with embryonated eggs found in the natural host, Pica hudsonia (Sabine).However, the examination of grasshopper from natural environments revealed no infections with this nematode.Quentin et al. (1986) studied the life cycle of M. inermis from Togo, Africa.They obtained infective third-stage larvae in orthopterans [Metaxymecus patagiatus (Karsch) and Locusta migratoria Linnaeus] fed with embryonated eggs found in the natural host, Ploceus aurantius (Vieillot).
The diet of the great black-hawks consists mainly of vertebrates (reptiles, amphibians, birds and mammals), and in lesser extent large insects (Carvalho Filho et al. 2006).The low prevalence of M. urubitinga (16.7%) in B. urubitinga would indicate the occasional ingestion of insects, which act as intermediate hosts.
Pathogenicity of Microtetrameres spp. is mainly related to mechanical effects caused by the location of the females in the proventricular glands.The poor physical appearance and loss of weight in the experimentally infected birds may have been due to their inability to compete for food and/or digest it (Bethel 1973) The pathological effects of a few species of Microtetrameres are known, among them M. centuri and Microtetrameres nestoris Black and Rutherford, 1979(Ellis 1970, Bethel 1973, Clark et al. 1979).These authors detected glandular atrophy in the proventriculus but no marked inflammatory response, despite finding females with red blood cells in the intestine.

Figure 3 -
Figure 3 -Female of Microtetrameres urubitinga n. sp.(a) Entire worm showing spiral coiling.(b) Gravid female.Scale bars: 300 μm.eggs were drawn without scale.Unfortunately, these specimens cannot be reviewed because no specimens were deposited at the appropriate time.The specimens of Microtetrameres sp. from S. vulgaris reported by Valente et al. (2014) were not described or drawn.The material deposited