The Caribbean fruit fly, Anastrepha suspensa (Diptera: Tephritidae) is a pest of tropical fruits in Florida. Hemocytes from 1 st-3 rd instars, adults, and larval fat body were infected with an unidentified protozoan. We utilized light microscopy to evaluate fresh hemolymph and hemocytes cultured in vitro. Our goal was to describe the developmental stages of the parasite relative to their morphology and behavior. We found 1) spherical spores (2-3 µm) with a well defined membrane and a centrally placed nucleus, 2) rod-shaped binucleate spores (5-7 x 2-2.5 µm) that occurred singly or in chains, 3) oval spores (10-15 x 5-6 µm) with a less dense exospore and opaque endospore with a nucleus and posteriorly located vacuole, and 4) septate filaments of different lengths. Spherical spores occurred within the hemocytes of all larvae and oval spores were free in the hemolymph of 1 st–3 rd instars. Oval spores also aggregated around septate filaments that arose from lysed cells. Rod-shaped binucleate spores occurred in and were released from the disintegrated hemocytes of 3 rd instars. Infected cells initially formed aggregates and the membranes of the innermost ones were the first to disintegrate. Peripheral cells exhibited blebbing and cytoplasmic protrusions, and eventually lysed. Since 1 st instars were infected, we hypothesized that the eggs from which they hatched were also infected, suggesting that the parasite may be transovarially transmitted. Future studies of this parasite will focus on its life cycle, transmission pathways, and impact on the fitness of adult flies. The infecting organism is probably a microsporidian, and as such would be the first protozoan parasite reported from Caribbean fruit fly hemocytes. Support from the National Science Foundation grants, IBN 9514583 and 9986076 to POL is gratefully acknowledged.
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA