Microsporidiosis in peppermint shrimp (decapoda: Hippolytidae: Lysmata spp.)

Microsporidia are a diverse, parasitic phylum closely related to fungi. They infect a broad range of host species and tissues. This report describes microsporidiosis infection in a captive, wild-caught peppermint shrimp (Lysmata spp.). The animal was found dead in its enclosure approximately 5 days after molting. Grossly, the skeletal musculature was diffusely swollen, opaque, and pale tan to white. Histologically, skeletal myofibers were replaced by large aggregates of sporophorous vesicles containing up to eight spores and earlier stages of sporogony. Tissue inflammation was minimal. Spores had positive staining with Luna's, Giemsa, Fites acid fast, and Brown and Brenn Gram stains. Ultrastructurally, spores were ovoid with an exo- and endospore, lamellar polaroplast, and polar tube arranged in 9 to 14 basilar, bilayered coils with a straight, apical manubrium. Spores and earlier stages of sporogony were contained within sporophorous vesicles. This is the first report of microsporidiosis in a shrimp from the family Hippolytidae.