''Urastoma cyprinae'' is a turbellarian that infects the gills of numerous species. It has been reported as free-living organism in marine mud and on algae. ''Urastoma cyprinae'' is reported as an opportunistic mantle inhabitant
/ref> on the gills of various bivalve species, including the clams ''

Tridacna maxima The maxima clam (''Tridacna maxima''), also known as the small giant clam, is a species of bivalve mollusc found throughout the Indo-Pacific region.MolluscaBase eds. (2022). MolluscaBase. Tridacna maxima (Röding, 1798). Accessed through: Worl ...

'' and ''

Tridacna gigas The giant clams are the members of the clam genus ''Tridacna'' that are the largest living bivalve mollusks. There are actually several species of "giant clams" in the genus ''Tridacna'', which are often misidentified for ''Tridacna gigas'', th ...

'', and the mussels ''

Mytilus edulis The blue mussel (''Mytilus edulis''), also known as the common mussel, is a medium-sized edible marine (ocean), marine bivalve mollusc in the family (biology), family Mytilidae, the mussels. Blue mussels are subject to commercial use and intensiv ...

'' and ''

Mytilus galloprovincialis The Mediterranean mussel (''Mytilus galloprovincialis'') is a species of bivalve, a marine mollusc in the family Mytilidae. It is an invasive species in many parts of the world, and also an object of aquaculture. Systematics ''Mytilus galloprov ...

''. They are also found throughout the gill surface of ''C. virginica'' and is attracted by mucus that coats the gills of oysters. However, the nature of the host-parasite relationship remains unknown.

Morphology

''Urastoma cyprinae'' is a ciliated

turbellarian The Turbellaria are one of the traditional sub-divisions of the phylum Platyhelminthes (flatworms), and include all the sub-groups that are not exclusively parasitic. There are about 4,500 species, which range from to large freshwater forms more ...

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 Chlamydia, or more specifically a chlamydia infection, is a sexually transmitted infection caused by the bacterium ''Chlamydia trachomatis''. Most people who are infected have no symptoms. When symptoms do appear they may occur only several wee ...

''-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 The bacterial order Chlamydiales includes only obligately intracellular bacteria that have a chlamydia-like developmental cycle of replication and at least 80% 16S rRNA or 23S rRNA gene sequence identity with other members of Chlamydiales. Chlam ...

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 Mollicutes is a class of bacteria distinguished by the absence of a cell wall. The word "Mollicutes" is derived from the Latin ''mollis'' (meaning "soft" or "pliable"), and ''cutis'' (meaning "skin"). Individuals are very small, typically only 0. ...

References

{{DEFAULTSORT:Urastoma Cyprinae Turbellaria Animals described in 1883