versión On-line ISSN 2007-8706
Rev. Mex. Biodiv. vol.83 no.2 México jun. 2012
Metacercariae of Renifer heterocoelium (Trematoda: Reniferidae) in tadpoles of Rhinella schneideri (Anura: Bufonidae) in Brazil
Metacercarias de Renifer heterocoelium (Trematoda: Reniferidae) en renacuajos de Rhinella schneideri (Anura: Bufonidae) en Brasil
Hudson Alves Pinto and Alan Lane de Melo*
Laboratorio de Taxonomia e Biologia de Invertebrados, Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 30123970, Belo Horizonte, 486 Minas Gerais, Brasil. *firstname.lastname@example.org.
Recibido: 27 julio 2011
Aceptado: 03 febrero 2012
Renifer heterocoelium is a parasite of the oral cavity of Neotropical snakes for which larval stages and the life cycle are still unknown. During studies of parasites of Rhinella schneideri, tadpoles collected in a lake from the municipality of Santa Luzia, Minas Gerais, Brazil, yielded specimens with metacercariae adhered to the external intestinal wall. After morphological characterization, the metacercariae were identified as R. heterocoelium. This is the first record and morphological characterization of metacercariae of R. heterocoelium for Brazil.
Key words: Rhinella schneideri, Amphibia, Bufonidae, Renifer heterocoelium, Digenea.
Renifer heterocoelium es un parásito de la cavidad bucal de las serpientes neotropicales cuyas formas larvales y ciclo de vida son todavía desconocidos. En un estudio de los parásitos de renacuajos de Rhinella schneideri recogidos en un estanque ubicado en el municipio de Santa Luzia, Minas Gerais, Brasil, se encontraron ejemplares con metacercarias en la pared intestinal. Después de caracterizarlos morfológicamente, los quistes fueron identificados como R. heterocoelium. Este es el primer registro y caracterización morfológica de las metacercarias de esta especie en Brasil.
Palabras clave: Rhinella schneideri, Amphibia, Bufonidae, Renifer heterocoelium, Digenea.
Recently, studies on associations between larval digeneans and tadpoles have become more important, considering that, for example, Ribeiroia Travassos, 1939, may be involved in malformation and possibly mortality among some species of amphibians in some localities in the United States (Johnson et al., 1999, 2004; Skelly et al., 2007).
In South America, few studies have reported tadpoles of different species of anurans as second intermediate hosts of digenetic trematodes, among them Clinostomum heluans Braun, 1899, Episthmium suspensum (Braun, 1901), Paryphostomum segregatum Dietz, 1909 (Lutz, 1935; Lie and Basch, 1967; Ostrowski de Nuñez, 1974). Recently, in Argentina, tadpoles of different species of amphibians were found infected with metacercariae of several species of digeneans, and some of the parasites found (Opisthogonimus Lühe, 1900, Styphlodora Looss, 1899, Travtrema Pereira, 1929) have snakes as the definitive hosts (Kehr and Hamann, 2003; Hamann and González, 2009).
In the present study, metacercariae of Renifer Pratt, 1902 (= Ochetosoma Braun, 1901, Pseudorenifer Price, 1935, Neorenifer Byrd and Denton, 1938, Neochetosoma Caballero, 1949) are reported in tadpoles of Rhinella schneideri (Werner, 1894) from Brazil.
Renifer is a trematode parasite of the upper digestive tract of snakes from Neotropical and Nearctic regions. Nine species are currently considered valid, among more than 30 nominal species that have been described (Byrd and Denton, 1938; Leão, 1945; Kagan, 1947; Dubois and Mahon, 1959; Tkack, 2008).
Aspects of the life cycle of these parasites have been elucidated with regard to some species in the United States. The life cycle involves gastropod molluscs (Physa Draparnaud, 1801, and Physella Haldeman, 1842), in which larvae of the xiphidiocercariae group are formed. These emerge and encyst in a second intermediate host, mainly amphibian tadpoles. Metacercarial excystment occurs after ingestion of the infected amphibians by snakes, and the adult parasites develop in the oral cavity and esophagus of these reptilian hosts (Byrd, 1935; Byrd and Scofield, 1952; SogandaresBernal and Grenier, 1971). Metacercariae of Renifer have been reported in different species of amphibians and fish in North America (PulidoFlores, 1994; SánchezNava et al., 2004; Muzzall, 2005; AguilarAguilar and SalgadoMaldonado, 2006; PérezPonce de León et al., 2007; McKenzie, 2007; LiraGuerrero et al., 2008).
Tadpoles of R. schneideri at different stages of development, ranging from level 25 to level 30 according to Gosner (1960), were collected between 1993 and 1994 during malacological surveys conducted in bodies of water from the rural area of the municipality of Santa Luzia (19°46'11" S, 43°51'05" W), state of Minas Gerais, Brazil. The specimens were captured with the aid of a metal scoop, and were packed and transported to the laboratory, where they were identified. The tadpoles were then necropsied in Petri dishes containing physiological saline solution and examined under a stereomicroscope for the presence of parasites. The metacercariae were found in the body cavity of the larval amphibians and were fixed in 10% formalin at 70 °C, stained with aceticalum carmine, dehydrated in increasing alcohol series, cleared in Beechwood creosote, and mounted in Canada balsam. The parasites were examined under a light microscope, and measurements (in µm) were made on 20 specimens using an eyepiece graduated in millimeters. Data are presented as means followed by standard deviation, and amplitude between parentheses. Drawings were made with the aid of a camera lucida attached to a microscope. Specific identification was performed by comparison with the morphology of adult parasites (Travassos, 1921; Dubois and Mahon, 1959; Travassos et al., 1969; Bray et al., 2008), and the association between the morphology of metacercariae and adult worms, in accordance with Byrd (1935). The slides studied were deposited in the collection of the Department of Parasitology, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brasil, under accession number 6152 av.
The metacercariae (Fig. 1) found adhered to the external intestinal wall are characterized below:
Encysted metacercariae (n = 20): oval, 551 ± 92 (375751) long by 247 ± 23 (218294) wide; cystic membrane transparent, 3 ± 1 (25) in thickness. Larvae with spinous tegument. Oral sucker subterminal, 125 ± 13 (106158) by 124 ± 9 (103137). Ventral sucker equatorial, 92 ± 17 (65115) by 110 ± 14 (86128). Suckers ratio 1:1.4 ± 0.2 (1.01.8). Prepharynx short; pharynx oval, 42 ± 4 (3451) by 35 ± 4 (2943); esophagus short, 43 ± 9 (2656) in length, bifurcated in preacetabular region; intestinal caeca sacciform, reaching level of ventral sucker. In some specimens (n= 8) 2 groups of 9 cephalic glands arranged in fields lateral to the pharynx and esophagus are visible, with tiny ducts directed to the oral sucker. Genital primordium formed by 3 spherical masses located in postacetabular region. Testes round, symmetrical, postovarian; right testis 17 ± 3 (1226) by 24 ± 6 (1534); left testis 18 ± 4 (1226) by 20 ± 5 (1226). Ovary rounded, submedian, located anterior to left testis, 18 ± 4 (1226) by 22 ± 5 (1734). Cirrus pouch primordium elongate, oblique, preacetabular, 97 ± 12 (77120) by 23 ± 3 (1726), in some specimens showing the posterior portion overlapping the anterior margin of the ventral sucker. Uterine primordium transverse to ventral sucker with the distal portion parallel to the cirrus pouch, opening into genital pore. Genital pore lateral, on the right side of the body at level of intestinal caeca. Excretory vesicle Y shaped.
The morphological features of the metacercariae found were compatible with digeneans of the genus Renifer; the extent of the intestinal caeca and the biometric relationship enabled the identification of our specimens as Renifer heterocoelium (Travassos, 1921) Tkach, 2008. The finding of adult parasites of this species in Wagler's snake, Xenodon merremii (Wagler, 1854), from the same region (Pinto et al., 2012), suggests that these adults are conspecific with the metacercariae found in the tadpoles. In fact, a correlation between the morphology of the metacercariae and adult parasites of Renifer aniarium (Leidy, 1890) from experimentally infected tadpoles and Natrix spp. was verified by Byrd (1935). Moreover, the general morphology of metacercariae reported in R. schneideri in the present study is similar to that of the young specimen of R. heterocoelium reported in snake by Lenis et al. (2009), although the latter is larger and has more developed vitellaria and uterus.
Renifer heterocoelium was described parasitizing Neuwied's lancehead, Bothrops neuwiedii (Wagler, 1824), from the state of São Paulo and was subsequently recorded in 21 other snake species from several Brazilian localities (Travassos, 1921; Travassos et al., 1969; Corrêa, 1980; Corrêa et al., 1990; Thatcher, 1993; Silva et al., 1999; Pinto et al., 2012). It has also been reported in Venezuela (Thatcher, 1993), and redescribed as Ochetosoma heterocoelium (Travassos, 1921) from adult specimens obtained from snakes in Colombia (Lenis et al., 2009).
New studies relating to the participation of amphibians in the life cycle of Neotropical trematodes are needed. This is the first report and morphometric characterization of metacercariae of R. heterocoelium, as well as the first report on the participation of amphibians in the biological cycle of this parasite in Brazil.
AguilarAguilar, R. and G. SalgadoMaldonado. 2006. Diversidad de helmintos parásitos de peces dulceacuícolas en dos cuencas hidrológicas de México: los helmintos y la hipótesis del México betadiverso. Interciência 31:484490. [ Links ]
Bray, R. A., D. I. Gibson and A. Jones. (eds.). 2008. Keys to the Trematoda, Volume 3. CAB International and Natural History Museum, London. 824 p. [ Links ]
Byrd, E. E. 1935. Life history studies of Reniferinae (Trematoda: Digenea) parasitic in Reptilia of the New Orleans area. Transactions of the American Microscopical Society 54:196225. [ Links ]
Byrd, E. E. and J. F. Denton. 1938. New trematodes of the subfamily Reniferinae, with a discussion of the systematics of the genera and species assigned to the subfamily group. Journal of Parasitology 24:379399. [ Links ]
Byrd, E. E. and G. F. Scofield. 1952. Developmental stages in the Digenea. I. Observations on the hatchability and infectivity of ochetosomatid eggs in physid snails. Journal of Parasitology 38:532539. [ Links ]
Corrêa, A. A. S. 1980. Fauna de trematóides parasitos de ofídios da área geográfica brasileira. Unpublished Ph.D. Thesis, Universidade de São Paulo, São Paulo, Brasil. 187 p. [ Links ]
Corrêa, F. M. A., R. C. Paulino, M. A. Buononato and P. A. Federsoni Jr. 1990. Ochetosoma heterocoelium (Travassos, 1921) (Trematoda: Digenea: Ochetosomatidae) em novo hospedeiro. Memórias do Instituto Butantan 52:116. [ Links ]
Dubois, G. and J. Mahon. 1959. Étude de quelques trématodes NordAmericains (avec note sur la position systematique de Parorchis Nicoll 1907) suivie d'une revision des genres Galactosomum Looss 1899 et Ochetosoma Braun 1901. Bulletin de la Societe des Sciences Naturelles de Neuchatel 82:191229. [ Links ]
Gosner, K. L. 1960. A simplified table for staging anuran embryos and larvae with notes on identification. Herpetologica 16:183190. [ Links ]
Hamann, M. I. and C. E. González. 2009. Larval digenetic trematodes in tadpoles of six amphibian species from Northeastern Argentina. Journal of Parasitology 95:623628. [ Links ]
Johnson, P. T. J., K. B. Lunde, E. G. Ritchie and A. E. Launer. 1999. The effect of trematode infection on amphibian limb development and survivorship. Science 284:802804. [ Links ]
Johnson, P. T. J., D. R. Sutherland, J. M. Kinsella and K. B. Lunde. 2004. Review of the trematode genus Ribeiroia (Psilostomidae): ecology, life history and pathogenesis with special emphasis on the amphibian malformation problem. Advances in Parasitology 57:191253. [ Links ]
Kagan, I. G. 1947. A new species of Renifer (Trematoda) from the kingsnake, Lampropeltis getulus, with an emendation of the genus Renifer Pratt, 1903. Journal of Parasitology 33:427432. [ Links ]
Kehr, A. I. and M. I. Hamann. 2003. Ecological aspects of parasitism in the tadpole of Pseudis paradoxa from Argentina. Herpetological Review 34:336341. [ Links ]
Leão, A. T. 1945. Discussão em tôrno dos gêneros Ochetosoma Braun, 1901, e Renifer Pratt, 1902 (Trematoda). Memórias do Instituto Butantan 18:6773. [ Links ]
Lenis, C., J. C. Arredondo and J. I. Calle. 2009. Ochetosoma heterocoelium (Digenea: Plagiorchiidae) in snakes from Colombia. Revista Mexicana de Biodiversidad 80:603609. [ Links ]
Lie, K. J. and P. F. Basch. 1967. The life cycle of Paryphostomum segregatum Dietz, 1909. Journal of Parasitology 53:280286. [ Links ]
LiraGuerrero, G., L. GarcíaPrieto and G. PérezPonce de León. 2008. Helminth parasites of atherinopsid freshwater fishes (Osteichthyes: Atheroniformis) from central Mexico. Revista Mexicana de Biodiversidad 79:325331. [ Links ]
Lutz, A. 1935. Evolution du Clinostomum heluans. Comptes Rendus de la Société de Biologie, Paris, 118:289290. [ Links ]
McKenzie, V. J. 2007. Human land use and patterns of parasitism in tropical amphibian hosts. Biological Conservation 137:102116. [ Links ]
Muzzall, P. M. 2005. Parasites of amphibians and reptiles from Michigan: a review of the literature 19162003. Michigan Department of Natural Resources, Fisheries Research Report 2077:130. [ Links ]
Ostrowski de Núñez, M. 1974. Sobre el ciclo biológico de Episthmium suspensum (Braun, 1901) Travassos, 1922. Revista del Museo Argentino de Ciencias Naturales Bernardino Rivadavia, Parasitología 1:153164. [ Links ]
PérezPonce de León, G., L. GarcíaPrieto and B. MendozaGarfias. 2007. Trematode parasites (Platyhelminthes) of wildlife vertebrates in Mexico. Zootaxa 1543:1247. [ Links ]
Pinto, H. A., V. L. T. Mati and A. L. Melo. 2012. New hosts and localities for trematodes of snakes (Reptilia: Squamata) from Minas Gerais State, Southeastern Brazil. Comparative Parasitology 79:238246. [ Links ]
PulidoFlores, G. 1994. Helmintos de Rana dunni, especie endémica del Lago de Pátzcuaro, Michoacán, México. Anales del Instituto de Biología, Universidad Nacional Autónoma de México, Serie Zoología 65:205207. [ Links ]
SánchezNava, P., G. SalgadoMaldonado, E. SotoGalera and B. J. Cruz. 2004. Helminth parasites of Girardinichthys multiradiatus (Pisces: Goodeidae) in the upper Lerma River subbasin, Mexico. Parasitology Research 93:396402. [ Links ]
Silva, R. J., R. R. Rodrigues, M. F. B. Stein, G. P. M. Sipoli, R. Pinhão and C. A. M. Lopes. 1999. The detection of Ochetosoma heterocoelium (Travassos, 1921) (Trematoda: Digenea: Ochetosomatidae) in Chironius exoletus (Linnaeus, 1758) (Serpentes: Colubridae). Journal of Venomous Animals and Toxins 5:8590. [ Links ]
Skelly, D. K., S. R. Bolden, L. K. Freidenburg, N. A. Friendefelds and R. Levey. 2007. Ribeiroia infection is not responsible for Vermont amphibian deformities. EcoHealth 4:156163. [ Links ]
SogandaresBernal, F. and H. Grenier, 1971. Life cycles and hostspecificity of the plagiorchiid trematodes Ochetosoma kansensis (Crow, 1913) and O. laterotrema (Byrd and Denton, 1938). Journal of Parasitology 57:297. [ Links ]
Thatcher, V. E. 1993. Trematódeos Neotropicais. Instituto Nacional de Pesquisas da Amazônia, Manaus. 553 p. [ Links ]
Tkach, V. V. 2008. Family Reniferidae Pratt, 1902. In Keys to the Trematoda, Volume 3, R. A. Bray, D. I. Gibson and A. Jones (eds.). CAB International and Natural History Museum London. p. 411419. [ Links ]
Travassos, L. 1921. Contribuições para o conhecimento da fauna helmintológica brasileira. XII. Sôbre as espécies brasileiras da subfamília Brachycoelinae. Archivos da Escola Superior de Agricultura e Medicina Veterinária 5:5967. [ Links ]
Travassos, L., J. F. T. Freitas and A. Kohn. 1969. Trematódeos do Brasil. Memórias do Instituto Oswaldo Cruz 67:1886. [ Links ]