Freshwater snails, Stenomelania denisoniensis (Brot) from Tinaroo Dam, North Queensland, Australia were found to be infected with a heterophyid cercaria identified as Procerovum sp. The tail of the cercaria has finfolds which are bilateral anteriorly and dorso-ventral posteriorly, features which separate it from other genera in the Haplorchis-group. This group is differentiated from the cercariae of all the other heterophyid genera by the presence of the penetration glands that extend to the posterior end of the body lateral to the excretory bladder. This paper presents a full description of the cercaria, together with comparisons with other known species of Procerovum.
A new sanguinicolid blood fluke, Parasanguinicola vastispina, is described from sea bass Lates calcarifer cultured in Malaysia. It is distinguished by its massive armature and widely spaced genital pores, the female pore being pre-ovarian. P. vastispina inhabits the branchial arteries, dorsal aorta, mesenteric venules and renal artery of its host. No pathological effect was observed in infected fish.
The diversity of monogeneans from Southeast Asia was examined using information from the literature to show their diversity at different taxonomic (subclass, family, genera, species) levels. Knowledge of monogeneans is still incomplete in Southeast Asia and the present numbers of monogeneans are likely an underestimate of what is present on/in aquatic organisms in the region, since so few hosts have been examined. An estimate of the possible numbers of monogeneans that could be present on/in fishes and turtles in Peninsular Malaysia indicates that only 8% of the monogeneans are presently known. Analysis of the available data on monogenean diversity (or species richness) at different taxonomic levels will provide useful information on their distribution patterns. There is an uneven distribution of investigations on this topic and Malayan fauna is considered to be representative of the Southeast Asian fauna. Southeast Asian (Sundaland) monogeneans are related (at the generic level) to the monogenean fauna of South China, India and Africa.
Ectoparasites cause serious problems during the aquaculture production of food fishes. In this study, we set out to develop and test protocols for maintenance and sampling European catfish (Silurus glanis L., 1758) stocks infected with a gill monogenean, Thaparocleidus vistulensis (Siwak 1932) Lim 1996. When we compared the feasibility of two cohabitation-based parasite culture systems (i.e., static vs. flow-through), we found that the life cycle of T. vistulensis was completed in both habitats. In our experience, static tank systems with regular water exchange allowed better daily quality control of the parasite culture than continuous flow-through systems. We investigated the microhabitat preference of T. vistulensis on the gills of infected European catfish. A balanced distribution on the two lateral gill sets and a decreasing trend in parasite numbers from anterior gill holobranches towards the posterior ones was observed. Using these results, we developed a minimally invasive sampling protocol to estimate the parasite load of individuals. The biopsy aimed at four sectors (#6, #7, #10, and #11) situated within the distal and middle zones of the first holobranch on the left side, encompassing both rows of filaments. Biopsy-based estimates of parasite loads were validated by comparing them to full parasite counts of the same individuals and showed statistically significant correlations. Our biopsy-based method is designed to identify experimental animals with similar parasite loads and create groups of hosts with comparable burdens. This setup is expected to generate reduced between-group differences for expensive experiments (e.g., high throughput transcriptomic or epigenetic studies). We propose that the biopsy-based pre-sorting procedure should be considered in similar experiments with other cultured fish species and their gill monogeneans following a thorough fine-tuning of the experimental conditions.