Shell choice and occupation by the hermit crab (Crustacea: Diogenidae) in laboratory environment

Abstract

The Neotropical hermit crabs’ behaviour is rarely studied, although it is an important tool for the conservation of these invertebrates. In this context, the present study aimed to describe the hermit crab ethogram on its behaviour in the choice and dispute by shells. 60 specimens of hermit crabs were collected that were occupying mollusc shells Cerithium atratum , in sandstone reefs. In the laboratory, 30 hermit crabs were removed from their host shells by heating, the rest remained in their shells. The specimens were submitted to five experimental tests: (I) behaviour, (II) shell dispute, (III) shell preference, (IV) specimen behaviour with and without shell, and (V) shell contention between individuals with and without shell. The ethogram was built and evaluated by the Ad Libitum type of observational sampling methods and by the scanning type, for 30 uninterrupted minutes, records every two minutes, in total 15 observations per each observer. There were eight behavioural acts divided into 4 categories: immobility, interaction between specimen, environment exploration, and shell occupation. The most frequent behaviour was walking, for both hermit crabs (54.2%) and those without shell (59.3%), followed by the rest of the individuals with and without shell, 16.9% and 12.4%, respectively. All hermits preferred mollusc shell Bulla striata , when offered in conjunction with the shell of Astrea tecta . However, all specimens returned to C. atratum shells when it was experimentally offered with all shells. Studies with hermits have shown that the species has preferences of gastropods shell C. atratum .