STUDIES ON THE LIFE-HISTORY OF A NEOGREGARINE PARASITE FOUND IN LEPTOTHORAX ANTS FROM NORTH-AMERICA

Pupal stages of Leptothorax ants collected near West Yellowstone, MT, USA, displayed striking signs and symptoms of disease, i.e., grey to b lack coloration, irregular pigmentation of compound eyes and toothless mandibles. Light microscope studies revealed heavy infections by a ne ogregarine, the life history of which is described. The life cycle of the pathogen includes micronuclear and macronuclear schizogonies, game togony and sporogony. Schizonts of both types vary in size depending o n the number of nuclei which is usually defined by doubling, thus givi ng rise to 8, 16, 32, 64 or even 128 uninucleate merozoites. In smears and sections, micronuclear merozoites are typically arranged in roset tes. In the early transformation of zygotes, sickle-shaped development al stages have been encountered, so far undescribed from neogregarines . Two spores (oocysts), each developing eight sporozoites, evolve from each gametocyst, as is typical of the genus Mattesia. Mature lemon-sh aped spores measure 13.8 X 9.3 mu m in fresh preparations. Infections can be readily transmitted to healthy colonies and to other Leptothora x species by feeding crushed infected pupae. Vegetative life cycle sta ges grow and multiply in the haemocoel, only to some extent they infec t fat body cells. Macronuclear merozoites invade the hypodermis and th e fat body but also settle extracellularly in the haemocoel. The disea se process terminates with the death of the pupae that harbour abundan t spores. Infections of adults have not been observed. Despite some mi nor differences that may result from development of the pathogen in th is host, from the type, sequence and morphology of life cycle stages a nd from the signs and symptoms of disease, this Mattesia species is id entified with M. geminata, first discovered in the tropical fire ant, Solenopsis geminata (Fabricius).