Co-infection with another species suppresses both cercarial quantity and quality in a trematode

Parasite co-infection is common in nature, yet the mechanisms and consequences of interactions among co-occurring species remain poorly understood, particularly for trematodes that compete intensely within their molluscan hosts.In the Philophthalmus attenuatus-Maritrema novaezealandense-Zeacumantus subcarinatus system, redial-forming P. attenuatus employs active interference strategies, whereas sporocyst-forming M. novaezealandense relies on passive resource acquisition, making their interactions a useful model for examining competitive asymmetry.Using naturally solo-infected and co-infected snails, we quantified how co-infection affects multiple M. novaezealandense cercarial traits, including total output, latency to first emergence, survival, and infectivity.Co-infection with P. attenuatus markedly reduced M. novaezealandense performance across all traits: sporocysts produced fewer cercariae, released them later, and generated cercariae with shorter longevity and lower infectivity.These results demonstrate that interference competition affects not only parasite output but also multiple qualitative traits directly linked to transmission success.Our findings show that competition within snail hosts affects not only parasite abundance but also multiple traits central to transmission success, highlighting the broader ecological and epidemiological consequences of co-infection for sporocyst-forming https://