Microsporidiosis in the Caribbean spiny lobster Panulirus argus from southeast Florida, USA

Two specimens of the Caribbean spiny lobster Panulirus argus captured by lobster fishers offshore of southeast Florida, USA, between late 2007 and early 2008 had completely white abdominal muscle tissue with a 'cooked' appearance. Wet-mount examination of the skeletal muscle tissue revealed masses of microsporidian spores. Histopathology of longitudinally sectioned skeletal muscle showed that the microsporidian spores displaced much of the muscle mass, but were interspersed with small empty vacuoles (approximately 5 microm in diameter) found adjacent to necrotic skeletal muscle. Skeletal muscle showed both liquefactive and coagulative necrosis. Transmission electron microscopy of the microsporidian spores revealed characteristics--including microvilli extending from the surface of the exospore, a unikaryotic spore (width 1.0 +/- 0.13 microm, range 0.8 to 1.4 microm; length 1.4 +/- 0.11 microm, range 1.2 to 1.6 microm; mean +/- SD, N = 16), and an isofilar polar filament-consistent with the genus Ameson, which is known to infect other palinurid lobsters. Microsporidiosis in Caribbean spiny lobsters has rarely been reported within the lobster's range, with only one brief report coming from the Florida Keys in 1976. Potential risks to the lobster fishery are unknown but warrant further study.