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Atypical infection of adult Macdonaldius seetae Khanna, 1933 (Nematoda: Filariata) in a Trans-Pecos rat snake, Bogertophis subocularis (Serpentes: Colubridae).

The genus Macdonaldius was established by Khanna (1933) for the type species Macdonaldius seetae Khanna 1933, which was collected from the portal vein of the colubrid snake, Coluber melanoleucus. Since it's description, eight more species have been described from Squamata hosts (four from snakes, four from lizards); and one from the order Testudines. Two of these species: Macdonaldius carinii Vaz & Pereira 1935, from snakes of Brazil; and Macdonaldius pflugfelderi Frank 1964, from Physignathus lesueurii of Australia, were transferred to the genus Oswaldofilaria Travassos, 1933 by Sonin & Barus (1968). The following are considered valid species by Sonin (1968): M. seetae Khanna, 1933; Macdonaldius andersoni, Chabaud & Frank 1961; Macdonaldius grassii (Caballero 1954) Chabaud & Frank 1961; Macdonaldius oschei, Chabaud & Frank 1961; Macdonaldius innisfailensis (Mackerras 1962) Frank 1964; Macdonaldius colimensis Telford, 1965; and additionally, Macdonaldius mackiewiczi Chattervati, 1985, which has subsequently been described.

The purpose of this note is to report adult M. seetae in the colubrid snake Bogertophis subocularis (syn. Elaphe subocularis) for the first time, and additionally, to report this helminth being located atypically within a host.

One Trans-Pecos rat snake, B. subocularis (Brown 1901), (Serpentes: Colubridae) was received from a herpetological dealer on 21 December 1994, which was reported to be wildcaught from southwestern North America. It had died shortly after its arrival at the dealer, was frozen and maintained at -20[degrees]C until examined for parasites, then deposited in the Carnegie Museum of Natural History (Section of Amphibians and Reptiles, Pittsburgh, Pennsylvania; Collection No. CM-147,466). The snakes internal organs did not appear to have undergone any obvious autolytic change.

Four adult specimens (one male, three females) of M. seetae (Filariata: Diplotriaenoidea) were collected from the surface of the hosts mesentery on 24 June 1997. No specimens were found in any of the large abdominal vessels. Helminths were placed in 10% buffered formalin, transferred to 70% ethyl alcohol and studied as wet mounts in glycerin. Voucher M. seetae were deposited in the United States National Parasite Collection (USDA, Beltsville, Maryland; USNPC No. 87587). Morphological comparisons were made to the original descriptions of all recognized species, and to the following voucher and paratype specimens from the USNPC: M. andersoni (No. 34786); M. colimensis (No. 82139); M. grassii (No. 85041); and M. seetae (No. 34786).

The specimens were very filariform, whitish in color, and their morphological characteristics consistent with those described for the genus by Khanna (1933). The male specimen measured 25.3 mm long by 0.21 mm wide at its greatest width. The posterior end was tightly coiled in four spiral turns, and possessed five pair papillae: two pair preanal, one of which is directly anterior to the anus; and three pair postanal. The postanal papillae are positioned accordingly: one pair proximal (nearly perianal), one pair mesal, and one pair distal. Two pair of amphids were located at the terminal end of the tail, one pair positioned slightly ventral and the other slightly dorsal. The right spicule was stout, and measured 0.11 mm long. The left spicule was long, slender, and possessed a filariform terminal end. No gubernaculum could be distinguished, nor could an exact measurement be determined for the left spicule. The female specimens measured 45.18-50.75 mm (mean 47.43) long by 0.27-0.37 mm (mean 0.31) wide at the greatest width. The undivided esophagus measured 0.758-0.808 mm (mean 0.775) long. The vulva possessed a single sphincter and was situated post-esophageal, 1.25-1.59 mm (mean 1.38) from the anterior end.

Macdonaldius is quite similar in its morphological characteristics between species and exhibits considerable intraspecific variation. Telford (1965) studied three endemic species from Colima, Mexico and considered the following characteristics taxonomically significant for species determination: total body length, arrangement of male caudal papillae, appearance of the distal tip of the left spicule, vulvar sphincter morphology, and comparative ratio's of esophageal length and distance of vulva from anterior end. Based on these taxonomic characteristics, the present specimens were identical to the M. seetae specimens described by Khanna (1933) with the exception of total length. However, this reduction in size may have resulted because of the specimens aberrancy within the host.

Hull & Camin (1959) redescribed this species as a result of numerous specimens being collected from two common bullsnakes, Pituophis catenifer sayi from Texas, which allowed a more thorough description of the species. The authors discussed a group of adanal papillae which they considered to be present in all male specimens of this species. They indicated that Khanna (1933) may have overlooked these papillae in the original description of M. seetae, since these are difficult to observe unless the specimen is properly oriented. Curiously, these papillae were not observed on the present male specimen either, even after numerous positioning attempts. The same positioning techniques, however, did allow this group of adanal papillae to be observed in the male M. seetae specimens loaned from the USNPC.

Of the Macdonaldius species which infect snakes (including M. seetae), all adults have been recovered from within the large abdominal vessels (renal, hepatic-portal, portal and post vena cava) and hepatic sinusoids (Khanna 1933; Hull & Camin 1959; Chabaud & Frank 1961; Telford 1965). Macdonaldius grassii and M. innisfailensis have been reported from the peritoneum of Sceloporus ferrariperezi (Iguanidae) and the subperitoneal tissues of Physignathus lesueurii (Agamidae) respectively (Caballero 1954; Mackerras 1962). Adult specimens of M. seetae have apparently never been reported from a host's mesentery.

The microfilaria of M. seetae have recently been reported from a wildcaught B. subocularis (as Elaphe subocularis) from El Paso County, Texas (Smith 1997). The collection of adult M. seetae from this host species supports Smith's (1997) determination that this onchocercid occurs in the Trans-Pecos rat snake.

ACKNOWLEDGMENTS

I am grateful to Ellen J. Censky (Carnegie Museum of Natural History, Pittsburgh, Pennsylvania) for confirming the identification of the snake.

LITERATURE CITED

Caballero, E. 1954. Nematodos de los reptiles de Mexico. XI. Neuvo genero y especie de filaria de iguanidos. Riv. Parassitol., Roma, 15(4):305-313.

Chabaud, A. G. & W. Frank. 1961a. Nouvelle filaire parasite des arteres de pythons: Macdonaldius oschei n. sp. (Nematodes, Onchocercidae). Zeitschr. f. Parasitenk., 20(5):434-439.

Chabaud, A. G. & W. Frank. 1961b. Nouvelle filaire parasite des arteres de l'Heloderma suspectum Cope: Macdonaldius andersoni n. sp. (Nematodes, Onchocercidae). Ann. Parasitol. hum. & comp., 36(1/2):127-133.

Chattervati, S. 1985. Macdonaldius mackiewiczi n. sp. (Filarioidea: Onchocercidae) from an Indian saw back turtle. Ind. J. Parasit., 9(2):271-273.

Frank, W. 1964. Neubeschreibung einer filarie, Macdonaldius pflugfelderi n. spec. (Nematodes, Filaroidea) aus der Muskulatur der Wasseragame, Physignathus lesueurii (Reptilia, Agamidae). Zeitschr. f. Parasitenk., 24(4):442-452.

Hull, R. W. & J. H. Camin. 1959. Macdonaldius seetae Khanna, 1933 in captive snakes. Trans. Amer. Microscop. Soc., 78(2):323-329.

Khanna, R. K. 1933. A new filarial worm from a North American snake. J. Helminthol., 11(2):105-108.

Mackerras, M. J. 1962. Filarial parasites (Nematoda: Filaroidea) of Australian animals. Austral. J. Zool., 10(3):400-457.

Smith, T. G. 1997. Macdonaldius seetae (Nematoda: Spirurida: Filaroidea) in a Trans-Pecos rat snake (Elaphe subocularis). Southwestern Naturalist, 42(3):329-332.

Sonin. M. D. 1968. Filariata of animals and man and diseases caused by them. Part 2. Diplotriaenoidea. In Osnovij Nematodologii, K. I. Skrjabin (ed.). Moscow: Izdatel'stro "Nauka", (In Russian, English Translation, 1977, Israel Program for Scientific Translations, cat. no. 610338), 21:xx + 411 pp.

Sonin, M. D. & V. Barus. 1968. Filariid nematodes in birds and reptiles of Cuba. Folia Parasitol., Praha. 15:55-65.

Telford, S. R. Jr. 1965. A study of filariasis in Mexican snakes. Japan. J. Exp. Med., 35(6):565-586.

Vaz, Z. & C. Pereira. 1935. Some new Brazilian nematodes. Trans. Amer. Microscop. Soc., 54(1):36-40.

David P. Bolette

University of Pittsburgh, Laboratory Animal Resources

S1040 Biomedical Science Tower, Pittsburgh, Pennsylvania 15261

DPB at: dbolette@vms.cis.pitt.edu
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Title Annotation:GENERAL NOTES
Author:Bolette, David P.
Publication:The Texas Journal of Science
Geographic Code:100NA
Date:Aug 1, 1998
Words:1292
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