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 crabsClibanarius antillensisandCalcinus tibicenwere 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.