Phylogenetic Relationships within the Nematode Subfamily Phascolostrongylinae (Nematoda: Strongyloidea) from Australian Macropodid and Vombatid Marsupials

Background: The strongyloid nematode subfamily Phascolostrongylinae are parasites of the large intestine and stomach of Australian macropods (Macropodidae) and wombats (Vombatidae). Based on morphological classifications, the Phascolostrongylinae is comprised of seven genera belonging to three tribes (Phascolostrongylinea, Macropostrongyloidinea, and Hypodontinea). The phylogenetic relationships among the genera of the Phascolostrongylinae were tested using the first and second internal transcribed spacer (ITS+) sequences of the ribosomal DNA. Results: Monophyly was encountered in the tribe Phascolostrongylinea comprising two genera, Phascolostrongylus and Oesophagostomoides, found exclusively in the large intestine of wombats. The tribe Hypodontinea, represented by the genera Hypodontus and Macropicola from the ileum and large intestine of macropods was also found to be monophyletic, but with low support. The tribe Macropostrongyloidinea comprising the genera Macropostrongyloides and Paramacropostrongylus was paraphyletic with the species occurring in the stomach grouping separately to those found in the large intestines of their hosts. Finally, Macropostrongyloides dissimilis from the stomach of the swamp wallaby and Paramacropostrongylus toraliformis from the large intestine of the eastern grey kangaroo were distinct from their respective congeners. Conclusion: The current study provided strong support for the generic composition of the tribe Phascolostrongylinea and low support for the tribe Hypodontinea. However, the relationships within the tribe Macropostrongyloidinea are more complex and its monophyly was not supported by the current ITS+ dataset. The unexpected finding of M. dissimilis and P. toraliformis being distantly related to their respective congeners suggests a requirement for future taxonomic revision which may warrant separation of these species at the generic level.

Speciation in the genus Cloacina (Nematoda: Strongylida): species flocks and intra-host speciation

SUMMARYSequences of the first and second internal transcribed spacers (ITS1 + ITS2) of nuclear ribosomal DNA were employed to determine whether the congeneric assemblages of species of the strongyloid nematode genus Cloacina, found in the forestomachs of individual species of kangaroos and wallabies (Marsupialia: Macropodidae), considered to represent species flocks, were monophyletic. Nematode assemblages examined in the black-striped wallaby, Macropus (Notamacropus) dorsalis, the wallaroos, Macropus (Osphranter) antilopinus/robustus, rock wallabies, Petrogale spp., the quokka, Setonix brachyurus, and the swamp wallaby, Wallabia bicolor, were not monophyletic and appeared to have arisen by host colonization. However, a number of instances of within-host speciation were detected, suggesting that a variety of methods of speciation have contributed to the evolution of the complex assemblages of species present in this genus.

Molecular identification of the strongyloid nematode Oesophagostomum aculeatum in the Asian wild elephant Elephas maximus

The transmission of zoonoses by wildlife, including elephants, is a growing global concern. In this study, we screened for helminth infections among Asian wild elephants (Elephas maximus) of the Salakpra Wildlife Sanctuary, Kanchanaburi, Thailand. Elephant faecal samples (45) were collected from the sanctuary grounds during January through November 2013 and assayed individually using the tetranucleotide microsatellite technique. Microscopic examination indicated a high prevalence of strongylids (93.0%) and low prevalences of trichurids (2.3%) and ascarids (2.3%). To identify the strongylid species, small subunit (SSU) rDNA sequences were amplified from copro-DNA and compared with sequences in GenBank. The generated SSU-rDNA sequences comprised five distinct haplotypes that were closely related to Oesophagostomum aculeatum. A phylogenetic analysis that incorporated related nematodes yielded a tree separated into two main clades, one containing our samples and human and domestic animal hookworms and the other consisting of Strongyloides. The present results indicate that O. aculeatum in local elephants is a potential source of helminthiasis in human and domestic animals in this wild-elephant irrupted area.

Taxonomic revision of the genus Cloacina von Linstow (Nematoda : Strongyloidea) from macropodid marsupials.

The strongyloid nematode genus Cloacina von Linstow,parasitic in the stomachs of macropodid marsupials, is revised andmorphological taxonomic characters are analysed. Ninety species arerecognised, including 48 which are new. A key to the species is provided.New species are as follows: C. aedon,C. antigone,C. antiope,C. ares,C. artemis, C. caenis,C. cloelia, C. clymene,C. cybele, C. dindymene,C. dirce,C. dis,C. dryope,C. echidne, C. eileithyia,C. enyo, C. eos,C. epona, C. feronia,C. hebe, C. hecuba,C. hera,C. herceus,C. hermes,C. hestia,C. hypsipyle,C. io, C. ips,C. ixion, C. leto,C. littoralis,C. lityerses,C. maia, C. metis,C. nike, C. niobe,C. papillatissima, C. petronius,C . phaeax, C. phaedra,C. phaethon, C. polyxena,C. polyxo, C. selene,C. themis, C. tyche,C. typhon and C. tyro.Cloacina clarkae Mawson is treated as a synonym ofC. similis Johnston & Mawson, whileC. vestibulata Johnston & Mawson becomes a synonymof C. obtusa Johnston & Mawson.C. dubia Johnston & Mawson,C. inflataJohnston & Mawson andC. typica (Johnston & Mawson) are treated asspeciesinquirendae. An annotated checklist of parasites and hosts is provided.

Population studies on the infective stage of some nematode parasites of sheep

Observations have been made on the distribution of faecal deposits on a number of small fields of varying size stocked with varying numbers of sheep. These studies were undertaken to examine certain hypotheses proposed in the construction of mathematical models for the distribution of strongyloid nematode infective larvae in pastures grazed by sheep.The negative binomial distribution was found to provide a reasonable empirical description of the distribution of faeces, although there was evidence of departure from the negative binomial on the largest field.Although, tentatively, the distributions were additive with respect to the number of sheep, there was evidence of departure from additivity in respect of field area and time. The implications of these findings for the model are discussed.Significant positive correlations were found between successive time intervals in the number of faecal deposits present in individual subplots of the majority of fields. It is suggested that these arise from the tendency of sheep to use the same portion of a field for resting and rumination when heavy concentrations of faeces are deposited. The effects of this and other possible patterns of grazing and faecal deposition are discussed in relation to the intake of strongyloid infective larvae.The average number of discrete deposits of faeces on pasture produced per sheep per day was greater in flocks producing faeces in pellet form than in flocks producing soft faecal masses. However, within faeces types, there was evidence that the expected number of deposits produced per sheep per day could reasonably be assumed constant.The greater part of this work was carried out while one of us (A.D.D.) was the holder of a C.S.I.R.O. Overseas Research Studentship. For his advice and constructive criticism I am much indebted to Dr H. D. Crofton, under whose supervision this study was undertaken. My thanks go also to Professor J. E. Harris, C.B.E., F.R.S., for the provision of facilities in the Department of Zoology, and to Professor T. K. Ewer and Mr M. R. McCrea for their willing co-operation in the provision and handling of pastures and sheep at the School of Veterinary Science, Langford.Mr David Culpin and Mrs Jean Williams, of the Division of Mathematical Statistics, were responsible for programming and organizing the calculations on the CDC 3200 Computer, and were consistently helpful in proposing and criticizing tests and procedures.

Population studies on the infective stage of some nematode parasites of sheep

Studies have been undertaken to examine the alternative hypotheses of a Poisson or a negative binomial distribution of the numbers of strongyloid nematode eggs in deposits of faeces produced by flocks of grazing sheep, which were proposed in certain mathematical models for the distribution of strongyloid infective larvae on pastures.Observations were made on the distribution of the weights of faecal deposits produced by flocks of ewes and lambs. In all cases the distribution was found to be significantly positively skewed. A possible fundamental basis for this skewness has been suggested.The distribution of strongyloid egg concentration in random samples of faecal deposits collected from pasture, and the distribution of egg concentration for the single species N. battus and N. filicollis in rectal samples of faeces collected from a lamb flock, have both shown highly significant departures from a Poisson distribution. This, coupled with the fact that the weights of individual deposits vary widely, provide strong empirical grounds for rejecting the Poisson distribution as a model for the distribution of egg numbers per deposit.An examination of the distribution of egg counts for N. battus and N. filicollis in samples of faeces collected from a lamb flock at weekly intervals through the spring and summer has suggested that the distribution tends to become more overdispersed with the passage of time and as the mean egg count is falling.Fundamental grounds for preferring a more general model, such as the negative binomial, to describe the distribution of strongyloid egg output in flocks of sheep have been discussed.These studies were carried out under the supervision of Dr H. D. Crofton, to whom I am deeply grateful for his stimulating encouragement and constructive criticism. My thanks go also to Professor J. E. Harris, C.B.E., F.R.S., for the provision of facilities in the Department of Zoology, and to Professor T. K. Ewer and Mr M. R. McCrea for the provision and handling of pastures and sheep at the School of Veterinary Science, Langford. This work was undertaken during tenure of a C.S.I.R.O. Overseas Research Studentship.