Helminthic parasites of invasive alien fish hosts in Marikina River system, Philippines: Revealing new parasite hosts and species records

Abstract

Purpose. The spread of invasive and endemic parasites in the Philippines, along with the co-introduction of invasive alien fish species (IAFS), could threaten the country’s local fauna, as well as pose socio-economic and public health concerns. However, due to the scarcity of knowledge about fish parasites in the country, this incidence remains poorly understood. Thus, this study aims to explore the parasitic diversity of the common IAFS within the Marikina River system. Methods. Isolated helminthic endo-parasites from IAFS samples were processed for morphological identification and were characterized using parasite and host fish population descriptors. Results. A total of 187 IAFS were collected from the Marikina River. From these, four parasite species and genera were identified, namely: Bovenia serialis (Cestoda: Lytocestidae), Contracaecum sp. larva (Nematoda: Anisakidae), Camallanus sonaiensis (Nematoda: Camallanidae), and Masenia cf. bangweulensis (Digenea: Cephalogonimidae). The former two represents a new host record in Clarias gariepinus. While the latter two represents its first account in the Philippines, adding to the list of the country’s current parasite species. Quantitative descriptors of parasite population showed that B. serialis infecting Clarias batrachus have the highest parasite burden in terms of their mean intensity and mean abundance. While, both B. serialis and M. cf. bangweulensis were the most prevalent parasites. Conclusion. This study revealed new parasite genera, species, and host records in the country, providing vital baseline information for future biological, ecological, conservation, and management studies on the Marikina River, with potential environmental, socio-economic, and public health implications.