Litomosoides silvai (Nematoda: Onchocercidae) parasitizing Akodon montensis (Rodentia: Cricetidae) in the southern region of Brazil Litomosoides silvai (Nematoda: Onchocercidae) parasitando Akodon montensis (Rodentia: Cricetidae) na região Sul do Brasil

In the present study, Litomosoides silvai parasitizing Akodon montensis in the southern region of Brazil is reported for the "rst time. New morphological information is provided for some structures of this nematode species, such as a #attened cephalic extremity, presence of two dorsal cephalic papillae, female tail with a constriction at its tip, “s” shaped vagina, spicules characteristic of the carinii species group and micro"laria tail constricted at the tip. $is nematode was found parasitizing the thoracic cavity with a prevalence of 10% (2/20), mean intensity of 4 (6/2), mean abundance of 0.4%(8/20) and range of infection of 2-6 specimens per host, in southern Brazil. $is occurrence of L. silvai in A. montensis is a new geographical record for southern Brazil, in the Upper Paraná Atlantic Forest ecoregion of the northwestern region of Rio Grande do Sul, which is part of the Atlantic Forest biome.


Introduction
Turvo State Park (Parque Estadual do Turvo, PST) is a natural reserve located in the northwest of the state of Rio Grande do Sul, southern Brazil, comprising an area of approximately 17,491 hectares. e park is covered almost entirely by subtropical broadleaf or broadleaf deciduous forest. e mammal fauna of the park consists of carnivores such as Galictis sp., Cerdocyon thous, Nasua nasua, Procyon cancrivorus, Eira barbara, wild cats, herbivorous like deer and tapirs, some species of lagomorphs, primates, didelphimorphia, and xenarthrans, many species of chiropterans and as well as numerous rodents (KASPER et al., 2007;MELO et al., 2011).
One of the genera of Cricetidae rodents that is well represented in Brazil is Akodon Meyen, 1833, with 10 species recorded in this country (SILVEIRA et al., 2013). Among these, Akodon montensis omas, 1913 is the only species of this genus found in this reserve (MELO et al., 2011). is species occurs in Paraguay, northern Argentina and southeastern to southern Brazil, including the states of Minas Gerais, Rio de Janeiro, São Paulo, Paraná, Santa Catarina, and Rio Grande do Sul (MUSSER & CARLETON, 2005).
Filarioids of the genus Litomosoides Chandler, 1931, are parasites of the abdominal and thoracic cavities of bats, marsupials and many rodents. Currently, this genus is represented by 43 known species (NOTARNICOLA et al., 2012;NOTARNICOLA & de la SANCHA, 2015;OVIEDO et al., 2016). In Brazil, species of Litomosoides have been found parasitizing marsupials (BAIN et al., 1980;MULLER, 1980), bats (LINS DE ALMEIDA, 1936apud NOTARNICOLA et al., 2010REGO, 1961;GUERRERO et al., 2002;BAIN et al., 2003) and rodents (TRAVASSOS, 1919apud PADILHA & FARIA, 1977PADILHA & FARIA, 1977;BAIN et al., 1989;SIMÕES et al., 2012). Two species, Litomosoides silvai (PADILHA & FARIA, 1977) and Litomosoides chagas lhoi  have been recorded in the rodent Akodon cursor Winge, 1887, in Itaguaí and Rio Bonito, in the Atlantic Forest region of the state of Rio de Janeiro (PADILHA & FARIA, 1977;MORAES-NETO et al., 1996SIMÕES et al., 2011SIMÕES et al., , 2012. e aim of the present study was to report on L. silvai parasitizing A. montensis in the Turvo State Park, state of Rio Grande do Sul, Brazil, which is in the Upper Paraná Atlantic Forest ecoregion, part of Atlantic Forest biome. Furthermore, this study provides new morphological data for some structures, such as the cephalic extremity, tail and vagina, spicules and micro lariae tail; and it presents parasitological indices (prevalence, mean intensity and mean abundance) and data on range and infection site.

Materials and Methods
During a survey carried out to study tick-borne diseases (KRAWCZAK, 2016), 164 specimens of small mammals were caught: 117 Akodon montensis, 13 Brucepattersonius iheringi, 1 Cryptonanus guahybae, 7 Didelphis aurita, 1 Euryoryzomys russatus, 9 Oligoryzomys nigripes, 7 Oxymycterus judex, 4 Sooretamys angouya and 5 aptomys nigrita. ey were caught in the Turvo State Park (latitude 27°00' S to 27°20' S; longitude 53°40' W to 54°10' W), in the northwest of the state of Rio Grande do Sul, Brazil, between June 2013 and January 2014. However, only some of the rodents, which died due to the procedures for anesthesia and blood collection, were used in the present study: 20 specimens of Akodon montensis omas, 1913; two Brucepattersonius iheringi omas, 1896; one Oxymycterus judex omas, 1909; and one Oligoryzomys nigripes Olfers, 1818. Some other rodents that died were preserved in absolute ethanol until arrival at the Parasitic Diseases Laboratory of the School of Veterinary Medicine and Animal Science, Universidade de São Paulo (USP). ese were then analyzed for tick presence and were identi ed in accordance with Bonvicino et al. (2008) and Melo et al. (2011). ese animals were deposited in the Rodent Collection of the "Luiz de Queiroz" Higher Agriculture School, USP, state of São Paulo, Brazil. e animals were caught using a total of 80 live traps (75 Sherman and ve Tomahawk) baited with bacon, banana, apple and peanut butter. ese were set up for four consecutive nights during each eld campaign. Additionally, three pitfall stationary traps each consisting of ve buckets of 42.5 cm in diameter and 60 cm in height, which were connected using a plastic fence (at least 30 m long and 50 cm high), were set up for the same period. e animals thus trapped were then anaesthetized using ketamine and xylazine.
Adult nematode specimens were recovered from the thoracic cavity of A. montensis, stored in Railliet & Henry liquid, and were sent to the Veterinary Parasitology Laboratory, Universidade Federal de Santa Maria, state of Rio Grande do Sul, Brazil, for identi cation. To study their morphological characteristics, they were then cleared in lactophenol, temporarily mounted, examined under a bright-eld microscope (Olympus BX-51) and photographed using a Zeiss Axiophot. Micro lariae from the uterus of one xed female were dissected and examined. Illustrations were made with the aid of a drawing tube. Measurements are given in micrometers unless otherwise stated. e parasite terms used are in accordance with Bush et al. (1997).
Nematode specimens were deposited in the Helminth Collection of the Museum of La Plata (MLP-he). Moreover, specimens of L. silvai parasitizing A. cursor, from Rio Bonito, state of Rio de Janeiro (MORAES-NETO et al., 1996)

Results
ree female larioid specimens, two anterior extremities and three posterior extremities were recovered from the thoracic cavity of two specimens of A. montensis. Morphometric data on the female and micro larial specimens are showed in Table 1. e species identi cation was aided through studying male and female specimens deposited in CHIOC (number 33518).

Litomosoides silvai parasitizing Akodon montensis, Brazil
Litomosoides silvai Padilha and Faria, 1977 (Figures 1-11) Diagnosis: Adult worms small, males four times smaller than females. Cephalic extremity attened. In apical view, 4 labial papillae distributed in a stretched dorsoventral rectangle; 2 dorsal cephalic papillae. Buccal capsule slender; anterior segment transparent and posterior chitinous portion with irregular external walls; buccal cavity with 2 short enlargements near the base. Female tail slender, with a constriction at tip of tail. Esophagus muscular, becoming slightly glandular in the posterior portion. Vulva posterior to the esophagus-intestine junction. Vagina "s" shaped; vagina perpendicular to the axis of the vulva with a attened lumen consisting of a simple "s" shaped tube surrounded by muscular walls. Male tail slender; left spicule with handle longer than blade; blade consisting of a membranous ala that converts into a lament; right spicule is a twisted conduit with a heel that is not strongly cuticularized. Micro lariae slender, with sheath closely applied to the body; nuclei not extending to the tip of tail; tail becomes constricted. Remarks e specimens found in A. montensis correspond to the species L. silvai and are in accordance with the morphology and morphometrical characteristics given by Padilha & Faria (1977) and Moraes-Neto et al. (1996). e identi cation was con rmed by the shape of the buccal capsule, attened anterior extremity, vulva located posteriorly to the esophagus-intestine junction, non-globular shape of the vulva, tail tip with a constriction, shape of the spicules corresponding to the carinii species group, and constricted tail tip of the micro lariae. In the present study, female specimens were compared with previous specimens deposited in CHIOC, which con rmed the identity of the species.

Discussion
Litomosoides silvai was originally described by Padilha & Faria (1977), as a parasite of A. cursor. Later on, Moraes-Neto et al. (1996) redescribed the species including new morphological data and scanning electron microphotographs. ese authors showed the distribution of the head papillae, the rugose area, the tip of the tail and the structure of the cuticle at the vulva. However, the position of the head papillae was not stated.
Here, four labial papillae distributed in a stretched dorsoventral rectangle and two dorsal cephalic papillae were observed; amphids were located ventrally in relation to the cephalic papillae. Additionally, the vulva was "s" shaped and di ered from the globular shape of other Litomosoides species (NOTARNICOLA et al., 2000;OVIEDO et al., 2016).
Recently, Simões et al. (2011Simões et al. ( , 2012 reported the presence of L. silvai parasitizing the sympatric rodents A. cursor and A. montensis in Teresópolis, state of Rio de Janeiro (RJ). All previous reports of L. silvai are from the Atlantic Forest ecoregion, in the state of Rio de Janeiro. erefore, in the present study, the occurrence of L. silvai in A. montensis in southern Brazil is a new geographical record, in the Upper Paraná Atlantic Forest ecoregion of the northwest of the state of Rio Grande do Sul, which is part of the Atlantic Forest biome.
e results from the present study show intermediate values that may be related to a di erent ecoregion or that may show that environmental factors are involved. Interestingly, in Rio Bonito A. cursor was also found to be parasitized with L. chagas lhoi, with a prevalence of 12%, and both species of larioids were Detail of anterior extremities of Litomosoides silvai. 8-9. Female and male specimens, respectively, of L. silvai parasitizing Akodon cursor, from Rio Bonito, state of Rio de Janeiro, CHIOC 33518. 10-11. Female specimen of L. silvai parasitizing A. montensis from Turvo State Park, state of Rio Grande do Sul. Scale bars: 8-9 = 25 µm; 10-11: 10 µm. concurrent in 4 out of the 58 hosts sampled .
It seems that L. silvai always is located in the thoracic cavity when it parasitizes A. cursor or A. montensis, while L. chagas lhoi is located in the abdominal cavity. Both species of larioid are present in Rio Bonito, while only L. silvai is present in the other localities (Teresópolis and Turvo State Park). us, L. silvai is present in both Akodon species, but because of the di erent southern distribution of their hosts, the larioid only follows A. montensis, which is the only species of this genus that has been trapped in the study area (MELO et al., 2011). It is interesting to note that among more than 236 specimens of A. montensis that were sampled by one of the present authors (JN, unpublished data) in di erent localities in Misiones province (Argentina), which is close to Turvo State Park, no larioid specimens were detected.