Observations on an apicomplexan microparasite from the pericardic body of Ciona intestinalis L. (Protochordata)

Abstract

Summary Specimens of the ascidia Ciona intestinalis L. collected in the Gulf of Naples showed the occurrence within the pericardic body of a microorganism characterized by sporogonial plasmodia and complex sporulation stages. An ultrastructural study revealed several sporonts and plasmodia. The latter showed asynchronous merogonic stages, characterized by merozoites budding at their periphery. These stages were abundant and aggregated at the periphery of the pericardic body among haematic cells, cell debris and other host degenerative material. The merogonic plasmodia had a coccidian-like structure and were the most frequent stages observed in the C. intestinalis pericardic bodies. The microorganism was considered as parasitic and represents a possible re-discovery of Cardiosporidium cionae , a sporozoan described early this century from the same host. Infection by the microparasite appeared implicated in the origin of the pericardic body, considered as an host response to infection.