Morphological and biochemical characterization of the trypanosomatids Crithidia desouzai and Herpetomonas anglusteri

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Abstract
Two species of trypanosomatids, Crithidia desouzai and Herpetomonas anglusteri, were recently isolated from Diptera in Minas Gerais, Brazil. The Crithidia species was found to harbor bacterium-like endosymbionts in the cytoplasm. To biochemically characterize these two species of trypanosomatids, and to try to verify the evolutionary meaning of the presence of endosymbionts, an electrophoretic study was undertaken whereby the two species were compared with eight other species in the same family. Horizontal 12.5% starch gel electrophoresis was used to resolve the isozymes of eight enzyme systems: acid phosphatase, glucose-6-phosphate dehydrogenase, hexokinase, malate dehydrogenase, malic enzyme, 6-phosphogluconate dehydrogenase, phosphoglucose isomerase, and phosphoglucomutase. Ten other enzyme systems were assayed without yielding any reproducible activity. The isozymes observed were conservatively interpreted as being due to the activity of 44 different alleles. All species studied differed in at least one enzyme system. The phenetic (Jaccard similarity index, UPGMA grouping) analysis produced a tree in which the species of Crithidia and Herpetomonas clustered separately, forming monophyletic groupings. All the endosymbiont-bearing species formed a monophyletic cluster, indicating that the presence of bacterium-like endosymbionts may be a synapomorphy of that group, and may represent, therefore, a unique event in the evolution of the genus.

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