Kevin D. Lafferty Jack O’Brien Just Cebrian Kate L. Sheehan 2011 The grass shrimp, <i>Palaemonetes pugio</i>, harbors a number of symbionts within its North American range. Here, we document the distribution and seasonality of 4 taxonomic groups that use <i>P. pugio</i> as a host in coastal Alabama. We conducted a regional survey of 4 symbionts of <i>P. pugio</i> over 3 seasons and compared assemblages across space and time. The most common parasite was the metacercarial stage of the microphallid trematode <i>Microphallus turgidus</i>, which remained consistently prevalent over the 3 seasons surveyed. We also monitored the prevalence of <i>M. turgidus</i> at 2 sites monthly. Prevalence fluctuated significantly among seasons at these sites, but spatial heterogeneity appears to have a stronger influence on regional parasite prevalence. Distributions of 3 of 4 symbionts overlapped in a single geographic area (Mon Louis Island, Alabama, U.S.A.); however, multispecies infections of individual hosts were normally distributed within host populations. Sites surrounding Mon Louis Island had substantially higher parasite prevalence, particularly in the summer months. This area had a high quantity of <i>Spartina</i> marsh habitat, which we found influenced parasite prevalence, suggesting a role for wetland habitat in structuring parasite communities for this host. application/pdf 10.1654/4427.1 en The Helminthological Society of Washington Parasite distribution, prevalence, and assemblages of the grass shrimp, Palaemonetes pugio, in Southwestern Alabama, U.S.A. article