Ascetosporea

Abstract

What are Ascetosporea? Chances are most readers will have never heard of Ascetosporea. Not that they are uninteresting, but for the simple reason that it is a poorly studied group of eukaryotes. Ascetosporea are hard to observe; they are unicellular eukaryotes (protists), exclusively parasites, often tiny (some have been known as microcells) and sometimes living an intracellular lifestyle. And unlike many other parasitic groups that include human or crop pathogens (for example Plasmodium, the malaria agent, or Phytophthora, the potato blight agent), Ascetosporea only infect invertebrates. But they have recently been put on the map of protists worth looking at. They are known from marine habitats where they cause mass mortalities in shellfi sh aquaculture, and they are also detected in freshwater and soils (although much less is known there). As a group, Ascetosporea has been gradually extended and consolidated following the discoveries of novel lineages, improved molecular phylogenies of long-known yet elusive parasites, and generally a much larger diversity than anticipated. Together, it is now clear that they represent a common and diverse group of globally distributed parasites.