Veterinary Biosciences - Research Publications
Permanent URI for this collection
Search Results
1 - 9 of 9
-
ItemPhylogenetic Relationships of the Strongyloid Nematodes of Australasian Marsupials Based on Mitochondrial Protein Sequences(MDPI, 2022-11)Australasian marsupials harbour a diverse group of gastrointestinal strongyloid nematodes. These nematodes are currently grouped into two subfamilies, namely the Cloacininae and Phascolostrongylinae. Based on morphological criteria, the Cloacininae and Phascolostrongylinae were defined as monophyletic and placed in the family Cloacinidae, but this has not been supported by molecular data and they are currently placed in the Chabertiidae. Although molecular data (internal transcribed spacers of the nuclear ribosomal RNA genes or mitochondrial protein-coding genes) have been used to verify morphological classifications within the Cloacininae and Phascolostrongylinae, the phylogenetic relationships between the subfamilies have not been rigorously tested. This study determined the phylogenetic relationships of the subfamilies Cloacininae and Phascolostrongylinae using amino acid sequences conceptually translated from the twelve concatenated mitochondrial protein-coding genes. The findings demonstrated that the Cloacininae and Phascolostrongylinae formed a well-supported monophyletic assemblage, consistent with their morphological classification as an independent family, Cloacinidae. Unexpectedly, however, the subfamily Phascolostrongylinae was split into two groups comprising the genera from macropodid hosts (kangaroos and wallabies) and those from vombatid hosts (wombats). Genera of the Cloacininae and Phascolostrongylinae occurring in macropodid hosts were more closely related compared to genera of the Phascolostrongylinae occurring in wombats that formed a sister relationship with the remaining genera from macropods. These findings provide molecular evidence supporting the monophyly of the family Cloacinidae and an alternative hypothesis for the origin of marsupial strongyloid nematodes in vombatid hosts that requires further exploration using molecular approaches and additional samples.
-
ItemSpeciation in the genus Cloacina (Nematoda: Strongylida): species flocks and intra-host speciation(CAMBRIDGE UNIV PRESS, 2017-11)Sequences 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.
-
ItemPhylogenetic relationships of the nematode subfamily Phascolostrongylinae from macropodid and vombatid marsupials inferred using mitochondrial protein sequence data(BMC, 2021-10-09)BACKGROUND: The subfamily Phascolostrongylinae (Superfamily Strongyloidea) comprises nematodes that are parasitic in the gastrointestinal tracts of macropodid (Family Macropodidae) and vombatid (Family Vombatidae) marsupials. Currently, nine genera and 20 species have been attributed to the subfamily Phascolostrongylinae. Previous studies using sequence data sets for the internal transcribed spacers (ITS) of nuclear ribosomal DNA showed conflicting topologies between the Phascolostrongylinae and related subfamilies. Therefore, the aim of this study was to validate the phylogenetic relationships within the Phascolostrongylinae and its relationship with the families Chabertiidae and Strongylidae using mitochondrial amino acid sequences. METHODS: The sequences of all 12 mitochondrial protein-coding genes were obtained by next-generation sequencing of individual adult nematodes (n = 8) representing members of the Phascolostrongylinae. These sequences were conceptually translated and the phylogenetic relationships within the Phascolostrongylinae and its relationship with the families Chabertiidae and Strongylidae were inferred from aligned, concatenated amino acid sequence data sets. RESULTS: Within the Phascolostrongylinae, the wombat-specific genera grouped separately from the genera occurring in macropods. Two of the phascolostrongyline tribes were monophyletic, including Phascolostrongylinea and Hypodontinea, whereas the tribe Macropostrongyloidinea was paraphyletic. The tribe Phascolostrongylinea occurring in wombats was closely related to Oesophagostomum spp., also from the family Chabertiidae, which formed a sister relationship with the Phascolostrongylinae. CONCLUSION: The current phylogenetic relationship within the subfamily Phascolostrongylinae supports findings from a previous study based on ITS sequence data. This study contributes also to the understanding of the phylogenetic position of the subfamily Phascolostrongylinae within the Chabertiidae. Future studies investigating the relationships between the Phascolostrongylinae and Cloacininae from macropodid marsupials may advance our knowledge of the phylogeny of strongyloid nematodes in marsupials.
-
ItemMolecular detection of Strongyloides sp. in Australian Thoroughbred foals(BMC, 2021-09-03)BACKGROUND: Strongyloides westeri is found in the small intestine of young horses, mainly in foals up to about 16 weeks of age. The main source of infection for foals is through transmammary transmission, and foals can develop acute diarrhoea, weakness, dermatitis and respiratory signs. The epidemiology of S. westeri in Australia is largely unknown. Further, molecular techniques have never been employed for detection of S. westeri in horses. This pilot study aimed to assess the utility of a molecular phylogenetic method for the detection of S. westeri in the faeces of foals. METHODS: Faecal samples were collected from a foal of less than 2 months of age, and eggs of Strongyloides sp. were detected using the modified McMaster technique. DNA was extracted from purified eggs, and a partial fragment of the small subunit of the nuclear ribosomal DNA (18S) was characterised using polymerase chain reaction, DNA sequencing and phylogenetic methods. RESULTS: Microscopic examination of faeces revealed small ellipsoidal eggs typical of Strongyloides sp. The 18S sequence generated by PCR in this study revealed 98.4% identity with that of a reference sequence of S. westeri available from GenBank. Phylogenetic analyses revealed a polyphyletic clustering of S. westeri sequences. CONCLUSION: This is the first study reporting the detection of DNA of Strongyloides sp. in faeces of a foal using a molecular phylogenetic approach targeting the variable region of 18S rDNA. It is anticipated that this study will allow future molecular epidemiological studies on S. westeri in horses.
-
ItemPhylogenetic Analysis of Mitogenomic Data Sets Resolves the Relationship of Seven Macropostrongyloides Species from Australian Macropodid and Vombatid Marsupials(MDPI, 2020-12)Nematodes of the genus Macropostrongyloides inhabit the large intestines or stomachs of macropodid (kangaroos and wallabies) and vombatid (wombats) marsupials. This study established the relationships of seven species of Macropostrongyloides using mitochondrial (mt) protein amino acid sequence data sets. Phylogenetic analyses revealed that species of Macropostrongyloides (M. lasiorhini, M. baylisi, M. yamagutii, M. spearei, M. mawsonae and M. woodi) from the large intestines of their hosts formed a monophyletic assemblage with strong nodal support to the exclusion of M. dissimilis from the stomach of the swamp wallaby. Furthermore, the mitochondrial protein-coding genes provided greater insights into the diversity and phylogeny of the genus Macropostrongyloides; such data sets could potentially be used to elucidate the relationships among other parasitic nematodes of Australian marsupials.
-
ItemPhylogenetic analysis of the Australasian paralysis ticks and their relatives (Ixodidae: Ixodes: Sternalixodes)(BMC, 2017-03-02)BACKGROUND: The Australasian paralysis ticks and their relatives, Ixodes Latrielle, subgenus Sternalixodes Schulze, are some of the most important ticks in the region. However, very little is known about their phylogenetic relationships. The aim of this study was to elucidate the evolutionary relationships of members of the subgenus Sternalixodes by undertaking phylogenetic analyses of morphological and molecular datasets. METHODS: Adult females (n = 64) of Sternalixodes, including Ixodes anatis Chilton, 1904, Ixodes confusus Roberts, 1960, Ixodes cornuatus Roberts, 1960, Ixodes cordifer Neumann, 1908, Ixodes dendrolagi Wilson, 1967, Ixodes hirsti Hassall, 1931, Ixodes holocyclus Neumann, 1899, Ixodes myrmecobii Roberts, 1962 and Ixodes trichosuri Roberts, 1960, were examined morphologically. Subsequently, these Ixodes spp. were genetically characterised using cytochrome c oxidase subunit 1 (cox1) gene and the internal transcribed spacer 2 (ITS-2) of the rRNA. Both morphological and molecular datasets were analysed using various phylogenetic methods to assess the evolutionary relationship of various members of the subgenus Sternalixodes. RESULTS: Phylogenetic analyses of the cox1 sequences and morphological characters datasets revealed that the Australian and Papuan Sternalixodes formed a distinct clade with the New Zealand member of the group I. anatis positioned basally, in a separate clade. Ixodes holocyclus, I. cornuatus and I. myrmecobii formed a distinctive clade in both the cox1 and morphological phylogenies. However, based on phylogenetic analysis of the ITS-2 data, I. holocyclus formed a separate clade whereas I. cornuatus and I. myrmecobii grouped in a different clade. CONCLUSIONS: The cox1 and morphological data suggest that the subgenus Sternalixodes is paraphyletic, and I. anatis is not a sternalixodid tick; hence, it should not be included in the subgenus. Based on the phylogenetic analyses of cox1 and ITS-2 sequences, it appears that I. myrmecobii and I. cornuatus are not subspecies of I. holocyclus. Although this study provided better insights into the taxonomic status of the subgenus Sternalixodes, a complete morphological and molecular (using multiple markers) phylogenetic analysis including all members of the subgenus would be required to more accurately elucidate the evolutionary relationships within the subgenus.
-
ItemA morphological and molecular phylogenetic analysis of relationships between genera of the nematode sub-family Cloacininae (Stossich) (Strongyloidea: Chabertiidae) parasitic in kangaroos, wallabies and rat-kangaroos (Marsupialia: Macropodoidea)(Magnolia Press, 2020)A phylogenetic analysis of the genera of the strongyloid sub-family Cloacininae from macropodoid marsupials in Australasia was undertaken based on morphological characteristics and analysis of concatenated sequences (ITS+) of the first (ITS-1) and second (ITS-2) internal transcribed spacers of nuclear ribosomal DNA. Neither approach provided a robust phylogeny, but similarities between the two methods in terms of generic groupings suggested that substantial revision is needed of the current phenetic classification, with some of the key morphological characteristics currently used to define genera and tribes proving to be homoplasious.
-
ItemNew species and new records of species of Cloacina von Linstow, 1898 (Nematoda: Strongylida) parasitic in the western scrub wallaby, Notamacropus irma (Jourdan) (Marsupialia: Macropodidae) from Western Australia(SPRINGER, 2019-07)The helminth parasites of the western scrub wallaby or black-glove wallaby, Notamacropus irma (Jourdan) which occurs in Western Australia are relatively poorly documented. Six new species of the strongyloid genus Cloacina von Linstow, 1898 (Strongylida: Chabertiidae) are described namely C. asymmetrica n. sp., C. brazellei n. sp., C. harriganae n. sp., C. hobbsi n. sp., C. middletoni n. sp. and C. woodi n. sp. A redescription of C. laius Beveridge, 1999 from the same host species is included. Molecular sequence data (ITS1 and ITS2 ribosomal DNA) were obtained for C. asymmetrica, C. brazellei, C. hobbsi, C. middletoni and from the previously described species C. themis Beveridge, 1998 occurring in the same host species. Phylogenetically, C. asymmetrica, C. hobbsi and C. middletoni formed a distinct clade, suggesting the possibility of within-host speciation. Cloacina themis clustered with a group of morphologically distinctive species in a separate clade and C. brazellei clustered in a third clade but with poor support. This pattern of congeners in a single host species occurring in multiple clades mirrors the situation in other kangaroos and wallabies. Species of Cloacina from N. irma reported thus far therefore consist of a series of species found only in this host, with two species (C. brazellei and C. laius) shared with the sympatric macropodid Setonix brachyurus (Quoy & Gaimard).
-
ItemDescription of Cloacina atthis sp. nov. from the stomach of the euro (Macropus robustus) (Marsupialia: Macropodidae) from Western Australia based on morphological and molecular criteria(SPRINGER, 2014-09)A new species of strongyloid nematode from the genus Cloacina (Chabertiidae: Cloacininae) is described from the stomach of the hill kangaroo or euro (Macropus robustus) (Marsupialia: Macropodidae) from Western Australia. Cloacina atthis sp. nov. was found only in euros from the Pilbara region in the northwest of Western Australia, in spite of extensive collecting of the same host species from around the Australian continent. C. atthis is most closely related to Cloacina clymene, a species found in the same host species but only in the eastern half of the continent; the two species differ in minor morphological features (the shape of the wall of the buccal capsule, spicule lengths, the degree of sclerotisation of the gubernaculum and the shape of the vagina) as well as in differences in the internal transcribed spacers of ribosomal DNA. This study highlights the importance of using molecular methods when investigating the apparently disjunct distributions of strongyloid nematodes.