Life History & Behaviour

Clustering Behaviour of Clibanarius corallinus

Introduction: Very little research has been done on biology and ecology Clibanarius corallinus, and there are only a few on biogeographic distribution and physical description (Boone 1935;Tudge 1995), while none on behaviourial studies such as clustering behaviour particularly on this species.

Observation: Clibanarius corallinus were found in two clumps (one clump with 11 individuals, another clump with 14 individuals) on beach rock and rock pool of an inter-tidal zone on Heron Island.

Hypothesis: Clibanarius corallinus intended to form clumps to gain benefits such as reducing water loss and protection against predators.

Methods: 1. Field survey: Detailed survey on Clibanarius corallinus was carried out during low tide in rocky shore on Heron Island by randomly throwing six 1m x 1m quadrants within the inter-tidal zone (Image 1). Clibanarius corallinus appeared in each quadrant were found carefully by flipping boulders and shells. Number of clustered and separated individuals was recorded.
                2. Field experiment: Twenty four Clibanarius corallinus individuals were randomly separated into two groups, where 12 individuals were placed in a clump while another 12 individuals were placed around the clump in a circle with maximum separation. The experimental set-up were allowed to run for 15 minutes and number of clustered (clumps with more than 3 individuals) and separated individuals were recorded. Three trials were carried out each in wave-absence and wave-presence environment to examine the effects of waves on clustering behaviour of Clibanarius corallinus.

Results and Discussion: As shown in Figure 1, number of clustered Clibanarius corallinus individuals (Image 2) were significantly higher (P = 0.007) than number of clustered individuals in wave-absence environment . It is suggested that in wave-presence area, due to the small size of Clibanarius corallinus, individuals are being washed together by wave actions, so that clumps are formed and individuals stay together to avoid being washed away. However, fittingness of shell, which is one of the possible factors explaining clustering behaviour of hermit crabs (Gherardi & Benvenuto 2001), cannot be determined due to limitation of time.


Image 1: 1m x 1m quadrants were randomly placed in the inter-tidal zone of Heron Island


Image 2: Clustered Clibanarius corallinus individuals at the end of experimental period in a wave-presence environment