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Orchitophyra stellarum of Sea Stars

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Category 2 (In Canada and of Regional Concern)

Common, generally accepted names of the organism or disease agent

Orchitophyra stellarum, Ciliate disease of sea stars.

Scientific name or taxonomic affiliation

Orchitophyra stellarum, and Orchitophyra sp. parasitic scuticociliates of the Phylum Ciliophora and Family Orchitophryidae (based on morphometric observations and molecular methods, Goggin and Murphy (1997) suggest that more than one species may be involved with the species occurring on both sides of the Pacific Ocean being different from the species from Europe).

Geographic distribution

  1. Europe (English Channel, North Sea, Mediterranean Sea).
  2. N.W. Atlantic (Long Island Sound, Gulf of Maine, Prince Edward Island, Gulf of St. Lawrence).
  3. Pacific Canada (Howe Sound and Atrevida Reef near Powell River, British Columbia).
  4. Japan

Host species

  1. Asterias rubens, Sclerasterias richardi.
  2. Asterias forbesi, Asterias vulgaris
  3. Pisaster ochraceus.
  4. Asterias amurensis.

Impact on the host

These holotrich ciliates invade the host gonad causing atrophy of the gonad and castration in heavily infected sea stars. Infection is most prevalent in males and can reduce the proportion of males in a population. The reproductive potential in affected populations is decreased due to reduced male gamete production and the size structure of the population is altered. In addition, infections of O. stellarum were associated with a failure of coelomocytes to aggregate (clump) in A. forbesi (Childs 1970, Taylor and Bang 1978) and A. vulgaris (Bang 1982).

Diagnostic techniques

Gross Observations

Gonad of infected sea stars is often discoloured oratrophied.

Wet Mounts

Examine fluid from coelomic cavity or gonad tissue for numerous motile ciliates.


Cross-section through arm of small sea stars in area of gonad or section through gonadal tissue of larger sea stars showing elongate ciliates among the gametes.

Figure 1. Orchitophyra stellarum (0) beside a row of spermatogonia (s) and among developing sperm in the gonad of a male Pisaster ochraceus from Atrevida Reef, Strait of Georgia, British Columbia, Canada. Haematoxylin and eosin stain.

Figure 2. Several Orchitophyra stellarum among developing sperm in the same male Pisaster ochraceus illustrated in Fig. 1. Note that one O. stellarum is dividing (arrow). Haematoxylin and eosin stain.

Figure 3. Magnification of the dividing Orchitophyra stellarum in Fig. 2 with the two micronuclei indicated by arrows. Haematoxylin and eosin stain.

DNA Probes

The nucleotide sequence (495 bp) from the internal transcribed spacers (ITS1 and ITS2) and the 5.8S gene from the ribosomal RNA gene cluster of isolates of scuticociliate from 4 asteroid hosts (A. amurensis from Japan, P. ochraceus from British Columbia, Canada, A. vulgaris from Prince Edward Island, Canada; and A. rubens from The Netherlands) were identical for O. stellarum and had minor differences with Mesanophrys spp. and Anophtyoides haemophila from crustaceans. Thus, the internal transcribed spacer are highly conserved in this group of ciliates and unlikely to discriminate species or strains but may be useful to discriminate genera (Goggin and Murphy 2000).

Methods of control

No known methods of prevention or control.


Bang, F.B. 1982. Disease processes in seastars: a Metchnikoian challenge. The Biological Bulletin (Woods Hole, Mass.) 162: 135-148.

Bouland, C. and M. Jangoux. 1988. Infestation of Asterias rubens (Echinodermata) by the ciliate Orchitophrya stellarum: effect on gonads and host reaction. Diseases of Aquatic Organisms 5: 239-242.

Bouland, C., P. DePuytorac and E. Bricourt. 1986-1987. Orchitophyra stellarum, cilié prétendu astome, est un scuticocilié. Annales des Sciences naturelles, Zoologie, Paris, 13e série 8: 249-257.

Burrows, R.B. 1936. Further observations on parasitism in the starfish. Science (Washington D C) 84: 329.

Byrne, M. 1997. Parasitic castration of the sea star Asterias amurensis by the scuticociliate Orchitophyra stellarum: a caution against the use of this ciliate for biological control. In: M. Pascoe (ed.). 10th International Congress of Protozoology, The University of Sydney, Australia, Monday 21 July - Friday 25 July 1997, Programme & Abstracts. Business Meetings & Incentives, Sydney, p. 63.

Childs, J.N. 1970. Failure of coelomocytes of some Asterias forbesi to clump on glass. The Biological Bulletin (Woods Hole, Mass.) 139: 418. (Abstract).

Claereboudt, M.R. and C. Bouland. 1994. The effect of parasitic castration by a ciliate on a population of Asterias vulgaris. Journal of Invertebrate Pathology 63: 172-177.

Goggin, L.C. and N.E. Murphy. 1997. How many species of ciliates live in the gonads of seastars? In: M. Pascoe (ed.). 10th International Congress of Protozoology, The University of Sydney, Australia, Monday 21 July - Friday 25 July 1997, Programme & Abstracts. Business Meetings & Incentives, Sydney, p. 89.

Goggin, C.L. and N.E. Murphy. 2000. Conservation of sequence in the internal transcribed spacers and 5.8S ribosomal RNA among geographically separated isolates of parasitic scuticociliates (Ciliophora, Orchitophryidae). Diseases of Aquatic Organisms 40: 79-83.

Jangoux, M. 1987. Diseases of Echinodermata. I. Agents microorganisms and protistans. Diseases of Aquatic Organisms 2: 147-162.

Jangoux, M. 1990. Diseases of Echinodermata. In: Kinne, O. (eds), Diseases of Marine Animals. Volume III: Introduction, Cephalopoda, Annelida, Crustacea, Chaetognatha, Echinodermata, Urochordata. Biologische Anstalt Helgoland, Hamburg, Germany, pp. 439-567 (specifically see pgs 454-455).

Leighton, B.J., J.D.G. Boom, C. Bouland, E.B. Hartwick and M.J. Smith. 1991. Castration and mortality in Pisaster ochraceus parasitized by Orchitophrya stellarum (Ciliophora). Diseases of Aquatic Organisms 10: 71-73.

Piatt, J. 1935. Discovers important parasite of starfish. Fisheries Service Bulletin, U.S. Department of Commerce, Washington 247: 3-4.

Smith, G.F.M. 1936. A gonad parasite of the starfish. Science (Washington D C) 84: 157.

Taylor, C.E. and F.B. Bang. 1978. Alteration of blood clotting in Asterias forbesi associated with a ciliate infection. The Biological Bulletin (Woods Hole, Mass.) 155: 468-469. (Abstract).

Vevers, H.G. 1951. The biology of Asterias rubens L. II. Parasitization of the gonads by the ciliate Orchitophrya stellarum Cépède. Journal of the Marine Biological Association of the United Kingdom 29: 619-625.

Citation Information

Bower, S.M. (2004): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Orchitophyra stellarum of Sea Stars.

Date last revised: June 2004
Comments to Susan Bower

Date modified: