Life cycle and transmission paths of the apicomplexan Aggregata valdessensis parasitizing octopus tehuelchus on the Patagonian coast, SW Atlantic

Abstract

The species of the genus Aggregata are intracellular parasites that infect cephalopods. In this study, A. valdessensis descripton is expanded from cecum and intestine samples of Octopus tehuelchus by in vivo observations as well as scanning and transmission electron microscopy of gametogonic and sporogonic stages. Infection in O. tehuelchus is noticeable as white spherical cysts, visible to the naked eye. Additionally, merogony stages were found in field-collected Cyrtograpsus spp. crabs, and described from histological slides and TEM images. We established two transmission paths by coproparasitological analyses and experimental infections, confirming that the crustaceans acquire infection by feeding on octopus feces, but also by scavenging octopuses’ dead bodies. Genetic analyses using the 18S molecular marker from octopus and crab stages allowed us to to confirm that they are conspecific, establishing the complete life cycle of A. valdessensis. For the first time in the southern hemisphere, a life cycle for the genus Aggregata is elucidated, being the second worldwide