Apostomatida

Apostomatida
SEM image of Collinia sp., which can cause mass mortality in affected krill populations
Scientific classification
Domain:	Eukaryota
Clade:	Diaphoretickes
Clade:	SAR
Clade:	Alveolata
Phylum:	Ciliophora
Class:	Oligohymenophorea
Subclass:	Apostomatia
Order:	Apostomatida Chatton & Lwoff, 1928
Families
Colliniidae Cépède, 1910 Cyrtocaryidae Corliss, 1979 Foettingeriidae Chatton, 1911 Pseudocolliniidae Chantangsi, Lynn, Rueckert, Prokopowicz, Panha & Leander, 2013

The Apostomatida are an order of ciliates from the class Oligohymenophorea. Individual organisms from this order are called apostomes. They are symbiotic with Crustacea. For majority of their life cycle they are dormant and encysted on their host's exoskeleton. The life cycle of apostomes varies; most genera will multiply through the biological process of fission causing the larvae to develop within the crustacean host. Physical characteristics may include a small cytostome (mouth), often accompanied by a glandular rosette and sparse hair like projections (cilia) arranged in spiral rows on the organism.

References

• Bradbury, Phyllis C.; Trager, William (October 1967). "Excystation of apostome ciliates in relation to molting of their crustacean hosts. II. Effect of glycogen" (PDF). Biological Bulletin. 133 (2): 310–6.
• "Apostome". Encyclopædia Britannica.