Conference Agenda

Bali, an Indonesian island located at the centre of the Coral triangle, is considered a marine biodiversity hotspot; however, the diversity and taxonomy of many parasitic groups in fishes remain poorly understood. Myxosporeans a taxonomically diverse group, are obligate, spore-forming parasitic cnidarians. Their true diversity is likely much higher than currently described, due to cryptic species and limited number of studies in region. To date, no myxosporean species have been formally described from Bali. This study aims to identify myxozoan infections in marine fishes from Bali. Gall bladder and muscle samples from 18 host families, including commercially significant families Carangidae, Siganidae, Lutjanidae and Scombridae, were obtained from the Queensland Museum research collection. Morphological traits of myxospores were described using light microscopy following the guidelines of Lom & Arthur (1989). DNA was extracted from spore preparations, and ribosomal DNA regions (18S-28S) were amplified using universal and myxosporean-specific primers. PCR amplicons were prepared for long-read sequencing (Oxford Nanopore PromethION), and the resulting sequences were analysed using Geneious Prime. Based on morphological and molecular approaches, these samples are provisionally assigned to the genera Kudoa spp. and Ceratomyxa spp., pending formal description. This dataset will provide the first comprehensive baseline for myxosporean in Bali.

Myxosporean parasites are obligate spore-forming, microscopic, parasitic cnidarians. The genera Unicapsula and Kudoa are increasingly recognised as contributors to post-harvest myoliquefaction (“jellymeat”) in commercially important marine fishes. Despite the economic and social impact, these parasites remain understudied, particularly in Australian waters. Molecular data remains limited, with most studies relying on partial 18S and 28S ribosomal DNA (rDNA) sequences. This study focuses on the genetic characterisation of myxosporean parasites infecting wild-caught Yellowtail Kingfish (Seriola lalandi) and Mahi Mahi (Coryphaena hippurus), and the identification of infections in previously unreported species, including Australasian Snapper (Pagrus auratus) and Australian Bonito (Sarda australis). Long-range amplification of the complete rDNA operon (18S-ITS1-5.8S-ITS2-28S) was performed using LongAMP Taq DNA polymerase followed by Oxford Nanopore long-read sequencing. This resulted in the generation of high-coverage, near-complete rDNA operons without the need for multiple overlapping PCRs, addressing a key limitation in current myxosporean molecular studies. These findings expand the known host range of myxosporean parasites in Australian fisheries and provide genomic resources for future diagnostics and ecological studies. This work also highlights the need for improved molecular surveillance of myxosporean parasites in Australian waters using long-read sequencing approaches.

The Opecoelidae is the richest family of the Trematoda, with sexual adults in a broad range of marine and freshwater fishes. Opecoelids are usually recognisable for a combination of generalised characters and the lack of specialised features; the most conspicuously absent feature is tegument spines. We present a new opecoelid, representing a new genus, with tegument spines, justified as belonging to the family on the basis of morphological and phylogenetic study. The new species was found in the northern pearl perch Glaucosoma buergeri (Glaucosomatidae) from Ningaloo Reef, Western Australia. It is the first trematode known from any pearl perch, which is a small but commercially important family comprising four species, three of which are endemic to Australian waters. The most intriguing question raised by this discovery is determining whether the spines in this opecoelid can be considered homologous with those found in many other trematode families – we will present a case that the spines are indeed homologous.

Knowledge of the parasitic infections of freshwater fish in Australia is sporadic but is concentrated on reports of infection in larger specimens. The dynamics of infection with parasites in larval and juvenile freshwater fish is unknown. Thus, this study utilised fish specimens previously collected for a river health monitoring program to determine levels of parasitic infection: the native Macullochella peelii, Retropinna semoni, Hypseleotris spp., Phylipnodon grandiceps, Macquaria ambigua, and the introduced Cyprinus carpio. Dissections of fish found six different morphotypes: the monogenean Dactylogyrus extensus, the adult nematode Procamallanus (Spirocamallanus) sp., the mite Hydrozetes sp., and the unidentified larval cysts, larval nematodes and adult nematodes. Histological examination determined infections with the protozoans Trichodina sp. and Chilodonella sp. The smallest fish found to be infected with a parasite was a 6mm C. carpio.