Description of Sarcocystis falcatula Stiles, 1893, a Parasite of Birds and Opossums1

Abstract
S. falcatula Stiles, 1893 is re-described. Intermediate hosts of the parasite which was earlier described as S. debonei Vogelsang, 1929 are species of passeriform, psittaciform and columbiform birds. In these birds, muscle zoites are 6.88 .times. 2.19 (4.8-8.4 .times. 1.2-3.6) .mu.m and are enclosed in a cyst wall with regular protrusions, 1-5 .mu.m long. The convoluted primary wall has multiple thin areas in the osmiophilic layer. Microtubules originate in the ground substance and extend to the tips of the protrusions. The only known definitive host is the opossum. D. virginiana; rats, cats, a dog and a ferret could not be infected from muscle cysts. Sporocysts from opossums infected from 5 different infected avian sources measure 11.2 .times. 7.4 (9.6-12.0 .times. 6.0-8.4) .mu.m.