Nota científica

 

First record of the genus Rhabdias (Nematoda: Rhabdiasidae), endoparasite from Scinax staufferi (Anura: Hylidae) in Mexico

 

Primer registro del género Rhabdias (Nematoda: Rhabdiasidae), endoparásito de Scinax staufferi (Anura: Hylidae) en México

 

Elizabeth Aurelia Martínez–Salazar*^,1, Gerardo Pérez–Ponce de León² and Gabriela Parra Olea³

 

¹ Biology Department (Box 19498), University of Texas at Arlington, 501 South Nedderman Drive, 337 Life Science Building, Arlington, Texas 76019–049, USA.

² Laboratorio de Helmintología Dr. Eduardo Caballero y Caballero, Instituto de Biología, Universidad Nacional Autónoma de México. Apartado postal 70–153, 04510 México, D. F., México.

³ Laboratorio de Herpetología, Universidad Nacional Autónoma de México. Instituto de Biología, Universidad Nacional Autónoma de México. Apartado Postal 70–153, 04510 México, D. F., México.

 

* Correspodent:
lizmart@uta.edu ; eamsmex@hotmail.com

 

Recibido: 12 enero 2009
Aceptado: 21 abril 2009

 

Abstract

A lungworm of the genus Rhabdias (Nematoda: Rhabdiasidae) was recovered from Scinax staufferi (Anura: Hylidae) collected in Guadalupe Victoria Mapastepec, Chiapas, Mexico (15°28'28"N, 92°53'26"W, 102 m). Morphology of the nematode is briefly described and compared with other species of the genus, and mainly with parasites of hylids in the Neotropical Realm. This study represents the first record of a species of Rhabdias species parasitizing S. staufferi, and also constitutes the first record of a nematode parasite of hylid frogs in Chiapas State, Mexico.

Key words: Rhabdias, Rhabdiasidae, Nematoda, parasite, lungworm, Scinax staufferi, Hylidae, Chiapas, Mexico.

 

Resumen

Un gusano pulmonar del género Rhabdias (Nematoda: Rhabdiasidae) fue recuperado de Scinax staufferi (Anura: Hylidae) recolectado en Guadalupe Victoria Mapastepec, Chiapas, México (15°28'28"N, 92°53'26"O, 102 m). La morfología del rhabdiásido se describe brevemente y se compara con otras especies del género y principalmente con aquellas parásitas de hílidos distribuidos en la región Neotropical. El presente estudio representa el primer registro de una especie de Rhabdias como parásito de S. staufferi, y también constituye el primer registro de un nematodo parásito en hílidos para el estado de Chiapas, México.

Palabras clave: Rhabdias, Rhabdiasidae, Nematoda, parásito, gusano pulmonar, Scinax staufferi, Hylidae, Chiapas, México.

 

Scinax staufferi Cope 1865 (Anura: Hylidae) is distributed in lowlands along the Gulf of Mexico and Caribbean of Mexico and Central America, from central Tamaulipas south through the Yucatan Peninsula and into Belize, Guatemala, Honduras and Nicaragua. On the Pacific slope, it is distributed from Guerrero, through the Isthmus of Tehuantepec south to northwestern Costa Rica (Lee, 1996; Cedeño–Vázquez et al., 2006; Amphibia Web, www.amphibiaweb.org, Sept, 2008). To the best of our knowledge, with the exception of the papers by Goldberg and Bursey (2008) and Brooks et al. (2006) on the helminth parasites of selected frogs from Costa Rica, no other report exists on the endoparasites of Scinax spp. Likewise, no reports on rhabdiasid nematodes have been published in species of this genus. In one study, S. elaeochrous Cope, 1875 was found to be parasitized by 3 nematodes, Cosmocerca podicipinus Baker and Vaucher, 1984, Oswaldocruzia costaricensis Bursey and Goldberg, 2005, both of which were found in the intestine, while a larva of Acuariidae gen. sp. was found encysted in the stomach wall (Goldberg and Bursey, 2008). Scinax boulengeri Cope, 1887 was found to be infected in the urinary blander with a monogenean, Polystoma naevius Caballero and Cerecero, 1941 (Brooks et al., 2006). The aim of the present work is to report for the first time the presence of a helminth parasite of S. staufferi.

On August 17^th 2007, 2 specimens of S. staufferi were collected in Guadalupe Victoria, Mapastepec, Chiapas, Mexico (15°28'28"N; 92°53'26"W; 102 m) (Figs. 1 and 2). Frogs were dissected after an overdose of sodium pentobarbital. All internal organs were examined for helminths using a stereoscope. A single nematode was collected and placed in saline solution (0.65%), and fixed by immersion in hot (steaming) 70% ethanol, and finally stored in 70% ethanol. The worm was cleared with a mixture of ethanol–glycerin (7:3) and the taxonomic determination was conducted by comparing morphological traits with descriptions from the literature and with reference to material deposited in the United States National Parasite Collection, Beltsville, Maryland (USNPC) and the Colección Nacional de Helmintos (CNHE), Instituto de Biología, Universidad Nacional Autónoma de México, Mexico City. For comparison, the following specimens were studied: Rhabdias alabialis Kuzmin, Tkach and Brooks, 2007 (USPNC 098144.00), R. americanus Baker, 1987 (USPNC 081011.00, 089802.00), R. bakeri Tkach, Kuzmin and Pulis, 2006 (USPNC 096379.00, 096381.00), R. elegans Gutierrez, 1945 (USPNC 084920.00, 087516.00), R. füelleborni Travassos, 1926 (USPNC 032536.00, 083796.00; CNHE 001975, 3771, 3776), R. hermaphrodita Kloss, 1971 (USPNC 08525.00), R. hylae Johnston and Simpson, 1942 (USPNC 091190.00), R. joaquinensis Ingles,1935 (USPNC 088047.02), R. kuzmini Martínez–Salazar and León–Règagnon, 2007 (CNHE 05807, 5808, 5809, 5810, 5811; USPNC 99550.00), R. manantlanensis Martínez–Salazar, 2008 (CNHE 5804, 5805, 5806), R. ranae Walton, 1930 (USPNC 0885986.00), R. savagei Bursey and Goldberg, 2005 (USPNC 094848.00; CNHE 5034), R. pseudosphaerocephala Kuzmin, Tkach and Brooks, 2007 (USPNC 098146.00). In addition, material originally assigned to R. cf. sphaerocephala Goodey, 1924 (CNHE 001986, 002057, 002227, 002284) was also analyzed.

Measurements of the specimen are given in micrometers (|jm) unless otherwise stated. Voucher specimens of host and parasite were deposited in the Colección Nacional de Herpetología, Instituto de Biología, UNAM (IBH22163–IBH22164), and in the CNHE (6768), respectively.

Only 1 nematode was found in the left lung (prevalence and intensity of infection: 1 of 2 host infected (50%), 1 specimen) (Fig. 3). This nematode was identified as an undetermined species of the genus Rhabdias Stiles and Hassall (Rhabdiasidae). This hermaphrodite nematode possesses a cylindrical body and is relatively small (5.483 mm body length x 286 width). The specimen is characterized by having a truncated anterior end, tapered posterior end, body cuticle slightly swollen in the anterior end, comparatively thin in mid–body and terminal end; capsule cup–like in lateral view (7 depth x 19 width), with 6 indistinct lips observed in lateral and dorsal view. The esophagus is almost cylindrical (esophagus length 352, 6.43% of body length), 33 width at anterior region of the body, 34 at muscular region, 54 at the glandular region, with indistinct posterior bulb, 62 wide. An inconspicuous cuticular nerve ring, 186 from the anterior region of the body (3.39% of body length) is present. Intestine wide and filled with brown and black contents, distinguished easily from the internal structures. Vulva near middle body, located 2.821 mm (51.45% of body length) from anterior end. Tail comparatively short, conical, 251 long (4.59% of body length), with sharp terminal point. Genital system amphidelphic, with limbs approximately equal in length. Ovaries straight, extending along intestine. Uteri filled with numerous, oval, thin–walled eggs (100 x 58) in different stages of development, some containing larvae.

Rhabdiasids are typical lung parasites of amphibians and reptiles; species of Rhabdias are host–specific and rarely are parasites of more than 1 host group (see Kuzmin et al., 2003, Martínez–Salazar, 2006, 2008; Tkach et al., 2006). There are 17 species described from the Neotropical Realm: R. alabialis, R. androgyna Kloss, 1974, R. anolis Bursey, Goldberg and Telford, 2003, R. elegans, R. füelleborni, R. hermafrodita, R. kuzmin, R. lamothei Martínez–Salazar and León–Règagnon, 2006, R. leonae Martínez–Salazar, 2006, R. manantlanensis, R. mucronata Schuurmans–Stekhoven, 1952 (species inquirenda, adults unknown), R. nicaraguensis Bursey, Goldberg and Vitt, 2007, R. pseudosphaerocephala, R. savagei, R. tobagoensis Moravec and Kaiser, 1995, R. truncata Schuurmans–Stekhoven, 1952 (species inquirenda, adults unknown), and R. vellardi Pereira, 1928. Nine species of this group of nematodes have been recorded in Mexico: R. füelleborni, R. kuzmini, R. lamothei, R. leonae, R. manantlanensis, R. savagei, Rhabdias sp. [=R. tobagoensis of Goldberg et al. (2002)], Rhabdias sp. [=R. cf. elegans of Goldberg et al. (2002)], and R. pseudosphaerocephala [=R. sphaerocephala of Bravo Hollis and Caballero (1940)] (see Martínez–Salazar and León–Règagnon, 2007 and Martínez–Salazar, 2008).

The material examined in the present study differs from R. savagei and R. leonae in that those species present a postequatorial vulva instead of equatorial as in our specimen; it can also be distinguished because the former species parasitize exclusively Ranidae (frogs) and Polychrotidae (lizards), respectively (Bursey et al., 2003; Martínez–Salazar, 2006). With respect to R. lamothei, it differs mainly in body shape (coiled in R. lamothei instead of cylindrical as in the specimen herein reported) and body size, smaller in R. lamothei. In addition, R. lamothei infects snakes and not anurans (Martínez–Salazar and León–Règagnon, 2006).

From R. elegans, R. füelleborni, R. kuzmini, and R. pseudosphaerocephala, the material collected from S. staufferi can be differentiated by body dimensions (larger in all those species) (see Martínez–Salazar and León–Règagnon, 2007), and by host preference (all the 4 species are typical parasites of Bufonidae while the specimen examined here is a parasite of Hylidae).

In addition to the present record, 2 other species of Rhabdias have been recorded in hylid frogs in Mexico: Rhabdias sp. (=R. tobagoensis) from Dendropsophus microcephalus Cope, 1886 (=Hyla microcephala) (Anura: Hylidae) in Veracruz State (Goldberg et al., 2002), andR. manantlanensis from Craugastor occidentalis Taylor, 1921 (=Eleutherodactylus occidentalis) (Anura: Craugastoridae) in Jalisco State (Martínez–Salazar, 2008) (Fig. 2). The original record of R. tobagoensis was made as a parasite of Pristimantis charlottevillensis Kaiser, Dwyer, Feichtinger, and Schmidt, 1995 (=Eleuthero dactylus charlottevillensis) (Anura: Strabomantidae) from Tobago Island, in the West Indies (Moravec and Kaiser, 1995).The Mexican record of R. tobagoensis is controversial; Martínez–Salazar (2008) suggested that this material could pertain to other species based on host preference. Unfortunately, these specimens are not available for re–examination (Goldberg et al., 2002).

Our material differs from the other 2 aforementioned Rhabdias species infecting hylid frogs from the Neotropical Realm by body and buccal capsule size, esophagus length (Table 1), as well as the shape of body cuticle (in R. tobagoensis the outer layers of body are infl ated along the body; in R. manantlanensis cuticle is slightly swollen, thin and smooth, and the specimen described here has body cuticle slightly swollen, being more evident in anterior and uniform at middle body and terminal ends).

Finally, these 3 species parasitize hosts of different families: R. manantlanensis and R. tobagoensis are typical parasites of Craugastoridae and Strabomantidaerespectively, whereas our specimen was found in Hylidae.

The conservative morphology of Rhabdias has resulted in the incorrect identification of some species; re–examination of these species with new taxonomical tools, e.g., molecular markers, scanning electron microscopy, etc., as well as considering host specificity and geographic distribution, has allowed to redefine the specific composition of the genus (see re–determinations in Kuzmin et al., 2003, Tkach et al., 2006; Kuzmin et al., 2007, Martínez–Salazar, 2008). Species richness of rhabdiasid nematodes had been under–estimated in Mexico; helminthological surveys on several species of the Mexican herpetofauna that have not been studied previously, revealed the existence of 4 new species and 2 more which description is currently in process.

Since only 1 specimen of nematode was collected from S. staufferi, it was not possible to establish the proper identification at species level, even though a comparison with species of Rhabdias parasitic in hylids and a comparison with congeners found as parasites of several species of amphibians in the Neotropical Realm were conducted. The morphology and host preference of the species of Rhabdias reported here suggest that it may represent an undescribed species. However the low prevalence and abundance values preclude a proper description, and more specimens will be required for both a morphological and a molecular study.

This note represents the first record of a nematode as a parasite of hylid frogs from Chiapas State in Mexico, and provides the first record of a member of the genus Rhabdias as parasite of Scinax staufferi from anywhere along its distribution. More studies on the parasite fauna of hylids and other host families of frogs are needed to obtain more information about the geographical distribution and host specificity of members of the genus Rhabdias in Mexico.

 

Acknowledgements

We thank Ernesto Recuero Gil and Guillermo Velo Antón for collecting the hosts. Guillermo Velo provided the host photography. We are also thankful with Eric P. Hoberg, USNPC, Beltsville, Maryland, and Luis García–Prieto, CNHE, Instituto de Biología, UNAM, for the loan of specimens. We also thank Luis García–Prieto also for his valuable comments on an earlier draft of the manuscript. This work was partially funded by grants from PAPIIT–UNAM No. IN211808 and SEP–CONACYT No. 50563 to GPO. EAMS thanks to CONACyT and DGEP–UNAM for their support in the form of scholarships, and also to CONACyT for providing her postdoctoral fellowship.

 

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