Redescription of Dracunculus globocephalus Mackin, 1927 (Nematoda: Dracunculidae), a parasite of the snapping turtle, Chelydra serpentina

Abstract

Abstract. Dracunculus globocephalus Mackin, 1927 (Nematoda: Dracunculoidea) is redescribed from specimens collected from the mesentery of the snapping turtle, Chelydra serpentina (L.), in Louisiana, USA. The use of scanning electron microscopy, applied for the first time in this species, made it possible to study details in the structure of the cephalic end and the arrangement of male caudal papillae that are difficult to observe under the light microscope. This species markedly differs from all other species of Dracunculus in having the spicules greatly unequal in size and shape, in the absence of a gubernaculum, and in the disposition of male caudal papillae. The validity of D. globocephalus is confirmed, but the above mentioned morphological differences are not sufficient for listing it in a separate genus. This is the first record of D. globocephalus in Louisiana.

DifferentiatingDracunculusmedinensisfromD.insignis, by the sequence analysis of the 18S rRNA gene

“…Even in the study of the dracunculid parasites that are never found in humans or other mammals, the molecular approach used in the present study may still be useful, negating the need for more complex and more labourintensive morphology based on light or electron microscopy (Moravec and Little, 2004). A nematode from the Ugandan DEP, recently received at the CDC, could not be identified as D. medinensis by light microscopy, and sequence analysis of the extracted and amplified DNA confirmed that the specimen was not Dracunculus (unpubl.…”

Dracunculus mulbus n. sp. (Nematoda: Spirurida) from the water python Liasis fuscus (Serpentes: Boidae) in northern Australia

“…Mirza (1957) subsequently suggested, from studies showing variations in morphology within a single species, that all specimens described from reptiles belonged to the same species. However, a redescription of D. globocephalus by Moravec and Little (2004) showed this species to be clearly different from D. ophidensis. The close similarity between species, including between those infecting mammals and those infecting reptiles, has been commented upon frequently (Yorke & Maplestone, 1926;Desportes, 1938;Moorthy, 1937;Muller, 1971;Moravec & Little, 2004).…”

“…However, a redescription of D. globocephalus by Moravec and Little (2004) showed this species to be clearly different from D. ophidensis. The close similarity between species, including between those infecting mammals and those infecting reptiles, has been commented upon frequently (Yorke & Maplestone, 1926;Desportes, 1938;Moorthy, 1937;Muller, 1971;Moravec & Little, 2004). Recently, ribosomal RNA analysis (Wijová , Moravec, Horá k, Modrý , & Lukeš, 2005) demonstrated conclusively that D. oesophageus from colubrid snakes and the morphologically similar D. medinensis (Linnaeus, 1758) from humans are distinct species.…”

“…At least 10 further species have since been described from reptiles, mainly snakes (Colubridae, Boidae, Pythonidae and Elapidae), from Varanus sp. in India and from the turtle Chelydra serpentina in North America (Moravec & Little, 2004).…”

Phylogenetic position of Dracunculus medinensis and some related nematodes inferred from 18S rRNA

“…from non-human hosts may well concern D. medinensis. Moreover, the validity of the other 11 nominal species of the genus Dracunculus, all histozoic parasites of mammals and reptiles, is frequently questioned because of their inadequate descriptions and/or morphological similarity (Mirza 1957;Muller 1971;Moravec and Little 2004). However, the 18S rRNA sequences presented herein show beyond any doubt that the dracunculid Fig.…”