This study characterized shell occupation by two species of hermit crabs and analysed the occurrence of ectosymbionts on their shells, in a comparative way. The hermit crabs Clibanarius antillensis and Calcinus tibicen were selected for this comparative study because of their abundance and wide distributions. Specimens were collected manually during spring low tides every 2 months, from February 2011 to January 2012 in north-eastern Brazil (03°S), and in south-eastern Brazil (23°S). The populations showed different patterns of shell occupation and ectosymbiont coverage. The plasticity of these ecological traits is discussed in a broad context and possibly correlated to habitat differences.
