Perspectives on the biodiversity of parasitic protozoa in Australia

A fine-scale phylogenetic assessment of digenean trematodes in central Alberta reveals we have yet to uncover their total diversity

Despite over 100 years of digenean trematode parasite species descriptions, from a wide diversity of vertebrate and invertebrate host species, our ability to recognize the diversity of trematode species within a single lake remains an incredible challenge. The most challenging aspect is the identification of species from larval stages derived from intermediate hosts, due to the disjointed data of adult worm morphological descriptions, from which species are named, and links to corresponding molecular identifiers in depauperate databases. Cryptic species also play a significant role in the challenge of linking trematode larvae to adults, species identifications, and estimating diversity. Herein, we utilize a large, longitudinal dataset of snail first-intermediate host infection data from lakes in Alberta, Canada, to infer trematode larval diversity using molecular phylogenetics and snail host associations. From our assessments, we uncover a diversity of 79 larval trematode species among just five snail host species. Only 14 species were identified to a previously described species, while the other 65 species are either cryptic or otherwise unrepresented by mitochondrial genes in GenBank. This study currently represents the largest and most diverse singular molecular survey of trematode larval fauna composed of over one thousand mitochondrial sequences. Surprisingly, rarefaction analyses indicate we have yet to capture the complete diversity of trematodes from our sampling area.

Haematozoa of wild catfishes in northern Australia

Very little is known about the diversity, prevalence, or pathogenicity of haematozoa in Australian freshwater fishes. Blood smears from 189 native catfishes, of six different species, from northern Australia were examined for haematozoa. Haematozoan infections were observed only in fishes from Queensland, at an overall prevalence of 0.191 (95% CI = 0.134-0.265). Intraerythrocytic haemogregarines were present in Neoarius graeffei from the Brisbane River at a prevalence of 0.35 (0.181-0.567). Trypanosomes were present in Tandanus species from four rivers, at prevalences ranging from 0.111 (0.020-0.330) to 1 (0.635-1), and in N. graeffei from one river in Queensland, at a prevalence of 0.063 (0.003-0.305). The haematozoans observed appeared to have little impact on their hosts. Tandanus spp. were significantly more likely to be infected with trypanosomes, suggesting a high parasite-host specificity. This is the first widespread survey of wild Australian freshwater catfishes for haematozoa, resulting in the first report of haemogregarines from Australian freshwater fish, and the first report of trypanosomes from Neoarius graeffei and Tandanus tropicanus.

Using the Neptune project to benefit Australian aquatic animal health research

Diseases of aquatic animals have had, and continue to have, a significant impact on aquatic animal health. In Australia, where fisheries and aquaculture are important industries, aquatic species have been subject to serious disease outbreaks, including pilchard herpesvirus, the cause of one of the largest wild fish kills ever recorded. At the same time, there is a consensus that Australia's parasite fauna are largely unknown, and that aquatic animal health information is difficult to access. Managing aquatic animal diseases is challenging because they may be entirely new, their hosts may be new to aquaculture, and specialist expertise and basic diagnostic tools may be lacking or absent. The Neptune project was created in response to these challenges, and it aims to increase awareness of aquatic animal diseases, improve disease management, and promote communication between aquatic animal health professionals in Australia. The project consists of an online database, a digital microscopy platform containing a whole-slide image library, a community space, and online communications technology. The database contains aquatic animal health information from published papers, government reports, and other sources, while the library contains slides of key diseases both endemic and exotic to Australia. These assets make Neptune a powerful resource for researchers, students, and biosecurity officials.

Bivalvulidan (Myxozoa: Myxosporea) parasites of damselfishes with description of twelve novel species from Australia's Great Barrier Reef

Bivalvulidan parasites from the gall bladder of 31 species of damselfishes (family Pomacentridae) were examined for their taxonomic identity and their relatedness to other species of myxozoans. This paper describes 11 novel ceratomyxid species and a novel Myxidium sp. Each species is characterized morphologically and small subunit (SSU) rDNA sequences were used in molecular phylogenetic analyses. Five pomacentrid species were found to harbour multiple infections of bivalvulidan species. One species of Ceratomyxa and Myxidium were found to infect more than a single species of damselfish. Phylogenetic analyses revealed there has been no radiation of ceratomyxids that can be associated with the fish host taxon and that Myxidium queenslandicus n.sp. was more closely related to Zschokkella mugilis and Ellipsomyxa gobii than other members of the genus Myxidium.

Three new species of Eimeria from Bolivian marsupials

Faecal samples collected from 300 Bolivian marsupials (Didelphimorphia: Didelphidae) between 1984 and 1993 were examined for coccidian parasites. Sporulated oocysts were present in the faeces of 50 (17%) marsupials representing 11 genera and 22 species. Three new species of Eimeria are described and named from six host species. One species occurred in Marmosops dorothea, Monodelphis domestica and Thylamys venustus, another in Micoureus constantiae constantiae and Micoureus constantiae budini and a third in Marmosops dorothea. A discriminant analysis performed on five quantitative oocyst measurements revealed similarities between the first and third Eimeria species because of similar sizes and shapes of the oocysts, whereas the second Eimeria species was structurally discrete. The Eimeria that infects multiple hosts may be a common widespread species. Future surveys are advised for a thorough assessment of the coccidian biodiversity within Bolivian marsupials.