Adult reproductive Latrodectus geometricus, Araneae: Theridiidae (Koch), succumbing to a zygomycetous fungus

A population of brown widow spiders, Latrodectus geometricus, was collected from various sites within and near the University of Florida during the winter season. During the following months, a sudden string of mortalities occurred within the population resulting in the loss of approximately 80% of the collected specimens. A white fungal growth was observed and documented from the infected members. Refusal to eat and probable dehydration lead to the loss of most of the infected before proper culturing could occur, as the spiders did not exhibit fungal growth after succumbing to the infection. Success in culturing was managed after the loss of most of the population. Samples were taken from a spider while still living, in addition to samples taken from a culture and the deceased body and were processed for DNA extraction and ITS sequencing. Sequencing indicated that a zygomycetous fungus, Mucor fragilis was the probable match for the apparent infection in the spiders. Although a previous record of a single Mucor sp. infecting arachnids is documented, no other Mucor sp. has been documented as a pathogen. Instead, Mucor sp. are most often representated as widely distributed saprophytic normal flora. To verify this pathogen, five trials of 12 inoculated spiders and three control members (per trial) were tested on the basis of Koch’s postulate in an attempt to support Mucor fragilis as the specific cause of mortality within reproductive adult Latrodectus geometricus.