Marine sponges were examined from shallow waters of southeast Florida and the Florida Keys to determine species composition and distribution of commensal amphipod crustaceans from shallow reef, mangrove, and seagrass habitats. Twenty sponge species were investigated during this study, sixteen of which housed amphipods in the families Colomastigidae and/or Leucothoidae. Six species of commensal amphipods were identified. Leucothoe spinicarpa (Abildgaard) species complex was the most dominant amphipod commensal, representing 63% of the total amphipods collected. The L. spinicarpa complex contains four local morphotypes, which are diagnosed and briefly described. Common sponge hosts included Callyspongia vaginalis, Mycale sp., and Myriastra kallitetilla
