Digenean trematode infections in the endangered fish species Apricaphanius iberus

The Spanish toothcarp (Apricaphanius iberus), an endangered fish on the Iberian Peninsula, faces challenges like trematode parasitism and environmental fluctuations. In La Pletera, a protected area, fish gills showed metacercariae infestations, potentially impacting respiration and osmoregulation. The study aims to assess parasite descriptors, identify digenean species, detect larval stages in potential intermediate hosts (Hydrobia snails), estimate cercariae emerging from snails, and explore links between lagoon conditions and infection rates. Analysis found 21,256 digenean metacercariae in A. iberus, with host specificity in G. holbrooki. Histological studies revealed metacercariae in various fish tissues but no larval stages in snails