ABSTRACT: Ghost shrimp, Lepidophthalmus louisianensis (Schmitt 1935) and Sergio trilobata (Biffar 1970) are 2 common burrowing decapod crustaceans in Tampa Bay, Florida, which affect the benthic community through bioturbation. The burrowalso plays a crucial role in determining benthic community structure, since it may house several symbionts, one of which is the copepod Clausidium dissimile Wilson, 1921. This study was conducted to investigate factors that affect the density ofC. dissimile on ghost shrimp specimens both in the field and in the laboratory. Collections of L. louisianensis and S. trilobata were made over a 15 mo period to determine the prevalence of C. dissimile in the field. Analysisof monthly field data showed that host shrimp (p = 0.0001), and sampling month (p = 0.0310) were significantly correlated with the host-size adjusted density of the symbiont C. dissimile, with more copepods preferring specimens of S.trilobata over L. louisianensis. Although host sex did not have a significant effect on host-size adjusted copepod density, percentage prevalence of copepods was significantly higher for females than males in S. trilobata (p <0.0001). Laboratory experiments supported observations from the field in that C. dissimile significantly preferred S. trilobata over L. louisianensis (p < 0.001). However, unlike the field data, copepods did not appear to preferfemale over male hosts when size was held constant. Higher colonization of females than males in the field may instead be attributed to differences in size and behavior between the sexes.