Observations on two infectious agents found within the rootlets of the parasitic barnacle, Sacculina carcini

Two types of infectious agent within rootlet cells of the parasitic barnacl e, Sacculina carcini have been recognized by transmission electron microsco py. The rootlets were dissected from the common shore crab. Carcinus maenas , collected from two locales-Plymouth and Pwllheli. Yeast cells were identi fied within cells of S. carcini rootlets from crabs collected at both locat ions and an iridovirus was also found, but only in rootlets from Plymouth c rabs. These infectious agents were never found co-occurring in the rootlets from Plymouth crabs. Both agents, when present in rootlets? were also pres ent in the respective host crab tissues. It is therefore concluded that S. carcini rootlets are susceptible to invasion from natural infectious agents of the host crab.