Histopathological insights into the parasitoid interaction between Sarcophaga sp. and Theba pisana

Abstract Theba pisana is becoming an urgent threat to agriculture and biodiversity owing to its ability to harm various plants, to be a competitor with other snail species over food resources, and to be an intermediate host for zoonotic parasites. Environmentally sustainable agents are needed to control the expansion of this species out of its original range of distribution. We report for the first time the development of the parasitoid fly Sarcophaga sp. within a population of T. pisana in Southern Italy and the associated histopathological lesions. Histological analyses of 60 samples revealed infection in 47 individuals, and two possible aspects: 33/47 individuals showed early larval degeneration and moderate immune response, whereas 14/47 individuals presented fully degenerated larvae and enhanced immune activation. Molecular analyses based on the cytochrome c oxidase subunit I marker indicated high affinity with the Sarcophaga genus; however, species-level identification remains uncertain. These findings provide the first histopathological description of T. pisana immune responses against Sarcophaga sp. and suggest a variable host–parasitoid interaction. The observed host mortality suggests potential use of this fly as a biological control agent; its effectiveness and possible ecological risks for non-target gastropods require careful evaluation through further studies.