Urastoma cyprinae

Morphology

Urastoma cyprinae is a ciliated turbellarian measuring between 0.4 and 0.8 mm in length.

Life cycle

They live and feed and grow in the mussels, but their complete life cycle stumped researchers because eggs were never observed in these hosts. Researchers in Spain recently discovered that when U. cyprinae is ready to lay eggs, it leaves the bivalve, secretes a protective cocoon around itself and produces an egg sac. About 24 days later, the young hatch out (shown in the photo), make their way out of the cocoon and swim off to find new mussel hosts. The adults sometimes appear to just die in the cocoons, but sometimes also were observed to escape from it themselves and head off to lay more eggs.

Prevention

There are no known methods of prevention or control.

Pathogenicity

Urastoma cyprinae is believed to feed on the mucus secreted by its host and its presence alters the protease composition of gills in C. virginica. Urastoma cyprinae is negatively phototatic and is more attracted to oysters when compared to other mollusc species such as mussels and clams. Urastoma cyprinae attaches its anterior end to gill filaments, presumably in a feeding posture, and arches its body back and forth, wagging its posterior end, which bears the terminal orogenital pore, within the mucus that flows over the gills. Ingestion of foods is likely to be driven by the sphincters on the orogenital atrium. Urastoma cyprinae exhibits a marked seasonal pattern, with the highest levels of infection occurring during the summer and autumn, coinciding with the highest abundance of juvenile worms in the gills, and the lowest in winter.

Histological examinations revealed prokaryotic infections within the digestive gland of both mussel specimens and in the digestive tract of Urastoma cyprinaeis. In the worm Urastoma cyprinaeis, 2 types of microorganisms were observed within sub-segmentary cells, a Chlamydia-like organism (CLO) and a myco-plasma-like organism (MLO). The CLO found in Urastoma cyprinaeis is the first infectious agent described in this species. It exhibits some similarities with the Chlamydiales reported in marine invertebrates, but differs in the morphology of its elementary bodies. The second intracellular microorganism found in Urastoma cyprinae appears closely related to the Mollicutes.

References

References

1. [http://www.pac.dfo-mpo.gc.ca/science/species-especes/shellfish-coquillages/diseases-maladies/pages/maldisoy-eng.htm McGladdery, S.E. and Bower, S.M. (1999) Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Malpeque Disease of Oysters.]
2. Nicole T. Brun. (1999). "Attraction of ''Urastoma cyprinae'' Graff, 1882 (Turbellaria: Urastomidae) to the Eastern Oyster ''Crassostrea virginica''". [[Diseases of Aquatic Organisms]].
3. (2010-10-20). "Parasite of the Day: October 20 - Urastoma cyprinae".
4. (1999). "Musculature of the facultative parasite ''Urastoma cyprinae'' (Platyhelminthes)". [[Journal of Morphology]].
5. Celia Crespo-González. (2010). "Seasonal dynamics and microhabitat distribution of ''Urastoma cyprinae'' in ''Mytilus galloprovincialis'': implications for its life cycle". [[Journal of Shellfish Research]].
6. (1999). "Procaryotic infections in the mussel ''Mytilus galloprovinciallis'' and in its parasite the turbellarian ''Urastoma cyprinae''". [[Diseases of Aquatic Organisms]].