OBSERVATIONS ON AN ENDAMBA PARASITIZING OPALINID CILIATES

¹ From the Zoölogical Laboratory, University of Pennsylvania, Osborn Zoölogical Laboratory, Yale University, and the Marine Biological Laboratory, Woods Hole, Massachusetts

1. Observations are presented on an Endamba living in the opalinid ciliates from anuran hosts.

2. Large numbers of frogs and toads from widely separated regions have been examined. The endambæ have been found in some of the opalinids collected from the United States (Arizona and Utah), Panama (Panama City), Brazil (states of São Paulo and Rio de Janeiro), Chile (near Coquimbo), Uruguay and Ceylon. In a given locality, only certain species of anurans and a certain percentage of individuals of a given species contain the parasitized opalinids.

3. Within some individual anuran hosts, 91 per cent of the ciliates are infected. There may be a single, a few, many, or over a hundred of these ambæ within a single opalinid. Usually in any one ciliate all the ambæ are in the same stage of development, either cysts or trophozoites.

4. The ambæ seem to produce no serious effect on the opalinids, as the latter swim actively about in the saline solution and were seen to undergo binary fission even though heavily parasitized.

5. The trophozoites range in diameter from 5.3 µ-14.3 µ, averaging 8.0 µ. They appear to feed on the endospherules of the opalinids and a number of dividing stages have also been observed in the trophozoites.

6. The cysts are less variable in size and are slightly larger on the average (9.4 µ) than the trophozoites, though some trophozoites are larger than any cysts. Only uninucleate cysts have been found within the opalinids although uninucleate, binucleate and quadrinucleate ones were found outside the ciliates. The chromatoids vary in appearance; many are splinter-shaped, while others are bar-shaped. Glycogen vacuoles are present in many cysts.

7. In the zelleriellas from Pleurodema bibroni from Chile and in Bufo marinus from Panama, some of the endambæ were invaded by a Sphærita-like organism, which was also observed in the cytoplasm of some of the ciliates.