If you think that algae do not suffer from illness, you’re wrong. On the photo the central cell of the centric diatom chain of Guinardia delicatula (Bacillariophyceae) is infected by eight pathogens. The invader, the flagellate Cryothecomonas aestivalis, really likes the large chloroplasts of this diatom and has attacked the cell in an earlier stage. One specimen has penetrated, fed itself with chloroplasts and divided three times after feeding. The eight newly developed well-fed pathogens are three times larger than the original attacker. Because the pathogens do not ingest the nucleus, infected cells may survive the attack and carry on growing.