Ascaridoid nematodes of amphibians and reptiles: Ophidascaris Baylis, 1920

The genus Ophidascaris is revised and divided into five groups of species. A key for the species groups is provided. Group 1 (‘filaria’ group) occurs in pythons and a key is provided for differentiating eight species based on fresh and preserved specimens and on developmental patterns. O. papillifera (Linstow, 1898) is redescribed from the type-specimens and is considered to be close or identical to O. niuginiensis, for which Candoia carinatus is recorded as a new host. A key for the differentiation of species in Groups 2 to 5 is based on preserved specimens only. Group 2 (‘obconica’ group) contains (i) O. obconica and O. trichuriformis = caballeroi] in South American colubrids (further investigation will probably show that O. trichuriformis is a synonym of O. obconica); new host records are Xenodon severus, X. neuwiedii, X. colubrinus, Leptodeira annulata, Thamnodynastes pallidus, Leimadophis poecilogyrus and Boa constrictor; (ii) O. ashi n. sp. (new species name for ‘O. labiatopapillosa’) in North American colubrids, new host records are Nerodia valida, Heterodon nasicus and Storeria occipitomaculata; (iii) O. mombasica in African colubrids; new host records are Psammophis phillipsii and P. sibilans; (iv) O. solenopoion in Madagascan colubrids; (v) O. pyrrhus in Australian elapids; new host records are Cacophis squamulosus, Cryptophis nigrescens, Demansia atra, D. olivacea, Hemiaspis signata, Hoplocephalus bitorquatus, H. stephensi, H. bungaroides and Tropedechis carinatus, it is also recorded in Australia in the colubrid Styporhyncus mairii (new host record) and in Demansia papuensis papuensis and D. olivacea papuensis in Papua New Guinea; (vi) O. piscatori in Asian colubrids; (vii) O. excavata ? = schikhobalovi] in Agkistrodon spp. and possibly other aquatic snakes in Asia; new host record is Agkistrodon halys blomhoffi. Group 3 (‘radiosa’ group) in African viperids contains O. radiosa = intorta] in Bitis spp. Specimens from Atheris nitschei, Causus rhombeatus and the colubrid Boaedon lineatus were similar, but showed differences indicating possibility of other species in this group. Group 4 (‘najae’ group) in African elapids and Asian elapids and colubrids contains O. najae = daubaylisi]; new host records are Ophiophagus hannah, Boiga cyanea, Elaphe carinata. Group 5 (‘arndti’ group) in South American crotalids and colubrids contains O. arndti = travassosi and sprenti] in Crotalus spp. and Bothrops spp.; new host record is B. atrox in Panama. No morphological differentiation except size could be detected between O. arndti in crotalines and O. sicki in colubrids, but in view of difference in the feeding habits of their host, both species names were tentatively sustained; new host records for O. sicki are Xenodon neuwiedii, Leimadophis poecilogyrus, Pseudoboa cloelia, Philodryas patagoniensis and Micrurus frontalis; O. ochoteranai was regarded as a species inquirenda. The following species previously placed in Amplicaecum are placed in Ophidascaris; excavata Hsu & Hoeppli, 1931; schikhobalovi Mozgovoy, 1950; robertsi Sprent & Mines, 1960; longispiculum Oshmarin & Demshin, 1972; orientalis Wang, 1965. The position of Ophidascaris in relation to other ascaridoids is discussed: it is placed within the subfamily Ascaridinae sensu Sprent (1983) containing all other ascaridoids of terrestrial animals. It is concluded that Ophidascaris is in a relatively recent stage of evolution. The most likely centre of dispersal for the genus appears to have been Central Africa with spread in one direction to Asia and thence to the New World and in another direction to Madagascar and Australia.