Patterns of shell utilization by hermit crabs as a proxy of gastropod population dynamics

ABSTRACT

Hermit crabs are known to use empty gastropod shells, which allows them to grow and avoid predation and desiccation stress. However, shell benefits lessen with crab growth and natural damages so that hermit crabs are always in search for new and better-quality shells. This makes these organisms dependent on the input of newer shells, presenting adaptations to locate new released shells, as perception of chemical cues liberated by predated gastropods. The allocation from older to newer shells suggests that the patterns of shell utilization by hermit crabs may reflect populational changes of gastropod species. In this scenario, we aimed to investigate whether a recognized population decline of the intertidal gastropod Olivella minuta in summer can be explained by mortality or intertidal migration. To do so, we analysed patterns of shell availability and use (number and quality) by hermit crabs before and after the population decline. Contrary to our mortality hypothesis, there was no increase in availability and occupancy of newer shells in the area, as well as no increase in shell quality after the period of population decline of gastropods. There were also no general changes in the size distribution of available and occupied shells. Thus, it is likely that O. minuta migrates towards lower areas of the intertidal to avoid thermal stress and mortality due to summer higher temperatures.

KEYWORDS:

• Pagurus
• Olivella
• benthic ecology
• vacancy chains

Acknowledgments

The authors would like to thank the Center for Marine Biology (CEBIMar), the Oceanographic Institute (IO) and the Management, Ecology and Marine Conservation Laboratory from the University of São Paulo, which have provided all the infrastructure for the field and laboratory work; and respective staff, for their always kind support. We also thank Leandro and Douglas who voluntarily helped with the fieldwork.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ) via postdoctorate grant for HHC [Proc. 150316/2018-6] and research grant for AT [Proc. 309697/2015-8] and the Fundação de Amparo à Pesquisa do Estado de São Paulo (Fapesp) via scholarship grant to LID [Proc. 2013/14889-0] and post doctorate grant to LQY [Proc. 2009/15893-5].