Cloacina johnstoni sp. nov. (Nematoda: Strongyloidea) is described from the sacculated forestomach of the wallaroo, Macropus robustus (Marsupialia: Macropodidae) from Australia. It resembles the synhospitalic species Cloacina macropodis but differs from it principally in the shape of the cephalic papillae. The two species are also distinguishable based on differences in the first and second internal transcribed spacers (ITS) of nuclear ribosomal DNA (rDNA). Cloacina johnstoni commonly co-occurs in the same individual host as C. macropodis but has a more restricted geographical distribution.
This study examined genetic variation within and among species of Cloacina found in the common wallaroo (Macropus robustus) collected at different localities from mainland Australia, and evaluated geographical distance as a potential driver for genetic variation. The first and second internal transcribed spacers (ITS-1 and ITS-2=ITS) of nuclear ribosomal DNA were used to characterize individuals of 17 morphospecies of Cloacina that parasitize Macropus robustus and its sub-species. Results revealed intraspecific variation in ITS within some morphospecies of Cloacina. Phylogenetic analyses showed little correlation between host speciation patterns and geographical location for the majority of the nematode species, although it did suggest geographical distance was a driver for speciation within Cloacina communis, C. phaethon and C. parva. Our results suggest that nucleotide variation within Cloacina species is complex, and is likely to be propagated by factors such as geographical distance and host sub-species. Further studies determining factors involved in speciation, such as host-parasite relationships, are needed to improve our understanding of the diversity of populations of species of Cloacina.
A new species of the 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. Cloacina atthis is most closely related to C. 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 sclerotization 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.
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