Conference Agenda

Sri Lanka is known for remarkable marine biodiversity, yet the parasite faunas of its fishes remain unexamined. For digenean trematodes, perhaps the richest of metazoan faunas parasitic in fishes, few species have been documented in Sri Lanka. Conversely, the broader South Asia region has been intensively studied, though comparative molecular data are almost entirely lacking, and the quality of taxonomic work has varied wildly such that the historical record poses a daunting mire of obscure records and complex synonyms. We are undertaking the first broad and intensive collection effort for marine fish digeneans in Sri Lanka. Utilising an integrated taxonomic approach that combines detailed morphological study with molecular genetic analyses, our research aims to identify the fauna, prospect for new taxa, and apply molecular analyses to compare the South Asia fauna with that of the broader Indo-West Pacific. The marine environments in Sri Lanka, and much of the developing tropical world, face significant and imminent threats; our opportunity to collect, document and understanding parasites faunas in these regions is diminishing, at an unknown rate. Our research will build taxonomic capacity in the region.

Polystomatid flatworms (Monogenea, Polystomatidae) are known from the Australian lungfish; all three orders of amphibians namely salamanders, frogs and caecilians; freshwater turtles; and from the eye of the common hippopotamus. Of the 30 currently known polystome genera, 19 are known from amphibians, nine from freshwater turtles, one from the lungfish and one from the hippopotamus. Parasite transmission can only occur in an aquatic environment, involving the oncomiracidium. As a result, the diversity of host species is limited to aquatic or semi-aquatic hosts. Polystomes co-evolved with their amphibious hosts and unique life cycles evolved in close synchronisation with that of the host.

Although polystomes are globally distributed, most genera are restricted to specific continents or host groups. If we include Australia in the area of interest we have Concinnocotyla from the Australian lungfish, Parapolystoma and Sundapolystoma from anuran hosts and Aussietrema, Fornixtrema, Pleurodirotrema and Uropolystomoides from chelonian hosts. No polystomes are known from New Zealand. Globally we find a direct correlation between polystome diversity and search effort. It could thus be a case that many more polystomes remain undiscovered in the Pacific.

Evaluating the host body condition index (BCI) based on relationships between host mass and length is a general and pervasive approach to assess the negative effects of parasites on host health. Although many researchers, especially fish biologists and fisheries managers, commonly utilize BCI, overall patterns among BCI – infection relationships remain unclear. Here, we systematically reviewed 973 fish BCI – infection relationships from 216 publications and investigated factors potentially affecting the relationships’ significance and direction. Trematodes (22%) were the most commonly studied parasites across all datasets, followed by Cestodes (15%), Nematodes (14%), and Copepods (9%). Surprisingly, most studies reported non-significant associations between BCI and infection (72%), while significant negative (20%) or positive (7%) relationships were rarely reported. Almost half of the studies used Fulton’s BCI (mass/length³). Simple generalized linear mixed models based on a subset of publications revealed that (1) studies using Fulton’s BCI were more likely to report significant associations compared to other BCI measures, and (2) studies focused on Acanthocephalans tended to report significant positive relationships. Our study suggests that the outcomes of fish BCI- infection relationships may vary depending on several factors such as BCI measure used and parasite taxonomic group.