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Homoxenous life cycle for Sarcocystis : QUESTION

Alex Jeffries ajeffrie at waite.adelaide.edu.au
Tue Jul 19 01:04:27 EST 1994

Dear protozoologists,

Norman Levine has written (Journal of Parasitology _72_, 372-382 (1986). The
Taxonomy of Sarcocystis (Protozoa Apicomplexa) Species);

"Some earlier papers (e.g., Theobald Smith (1901, 1905) for S. muris and J. W.
Scott (1943) for sheep species(1)) have reported a homoxenous life cycle, stating
that sarcocysts in 1 animal produce some sort of stage in the feces that can
infect another host animal of the same species.  If this is really true and
does not merely reflect ignorance of the role of cats or sheep-dogs in the life
cycle, it contradicts our present belief(2).  The work should be repeated,
using animals apart from possible vectors."

(1) From the reference title this appears to be S. tenella

(2) As part of the descriptions for the higher taxa of sarcocystis a
heteroxenous life cycle is used at the Family level (Sarcocystidae Poche 1913)
and an obligatorily heteroxenous life cycle is used at the Subfamily level
(Sarcocystinae Poche 1913).

My questions are these...Have the necessary investigations been conducted since
1986 to confirm or deny the monoxenous life cycles for S. muris and S. tenella?
If, for arguments sake, a monoxenous life cycle is/was proven, what are peoples
opinions on whether these species should remain in the Family Sarcocystidae?
Would they fit better into a sister Family (considering only this life cycle
aspect)?  Could such a life cycle difference warrent the construction of a new
taxanomic group for these species?

I hope this can generate some interesting discussion and I look forward to it

Alex Jeffries
Department of Microbiology
School of Biological and Biomedical Sciences
University of Technology, Sydney
Westbourne Street
GORE HILL       NSW     2065

Ph. (02) 330 4014
FAX (02) 330 4003
e-mail a.jeffries at uts.edu.au

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