Larval stages of the widely distributed digenean species Proctoeces maculatus (Looss, 1901) were reported 40 years ago from South Africa in the common octopus, Octopus vulgaris Cuvier (Octopodidae). However, the absence of adult specimens and molecular data from this region has hindered a comprehensive understanding of its distribution. In this study, we collected three species of intertidal and near-shore marine fishes [Clinus superciliosus (L.) (Clinidae), Diplodus capensis (Smith) (Sparidae) and Sparodon durbanensis (Castelnau) (Sparidae)] along the South African coast and discovered adult specimens of P. maculatus at five localities. By employing a combination of morphological and molecular techniques, including 28S rDNA, 18S rDNA and COI mtDNA analyses, the first report of adult P. maculatus from South Africa is presented. The findings encompass a comprehensive morphological description and molecular data, illuminating the true distribution of this species in the region.

It has increasingly been recognized that organisms can interfere with parasitic free-living stages, preventing them from infecting their specified host and thus reducing infection levels. This common phenomenon in freshwater and terrestrial systems has been termed the ‘dilution effect’ and, so far, is poorly studied in marine systems. Ten common intertidal organisms found in the Dutch Wadden Sea (North Sea) were tested to establish their effects on the free-living cercarial stages of the trematode parasite Himasthla elongata. Most species tested resulted in a significant reduction in cercariae over a 3 hr time period. The amphipod Gammarus marinus removed 100% of the cercariae, while other effective diluters were Crangon crangon (93%), Sargassum muticum (87%), Semibalanus balanoides (71%), Crassostrea gigas (67%), Hemigrapsus takanoi (>54%), Crassostrea gigas shells (44%) and Idotea balthica (24%). In contrast, mixed shells (Cerastoderma edule, Mytilus edulis, Ensis americanus and Littorina littorea) and Fucus versiculosus had no significant effect. These results suggest that dilution effects are widespread in the trematode of H. elongata, with potentially strong effects on its population dynamics.