Love thy neighbour: group properties of gaping behaviour in mussel aggregations

PLoS One. 2012;7(10):e47382. doi: 10.1371/journal.pone.0047382. Epub 2012 Oct 16.

Abstract

By associating closely with others to form a group, an animal can benefit from a number of advantages including reduced risk of predation, amelioration of environmental conditions, and increased reproductive success, but at the price of reduced resources. Although made up of individual members, an aggregation often displays novel effects that do not manifest at the level of the individual organism. Here we show that very simple behaviour in intertidal mussels shows new effects in dense aggregations but not in isolated individuals. Perna perna and Mytilus galloprovincialis are gaping (periodic valve movement during emersion) and non-gaping mussels respectively. P. perna gaping behaviour had no effect on body temperatures of isolated individuals, while it led to increased humidity and decreased temperatures in dense groups (beds). Gaping resulted in cooler body temperatures for P. perna than M. galloprovincialis when in aggregations, while solitary individuals exhibited the highest temperatures. Gradients of increasing body temperature were detected from the center to edges of beds, but M. galloprovincialis at the edge had the same temperature as isolated individuals. Furthermore, a field study showed that during periods of severe heat stress, mortality rates of mussels within beds of the gaping P. perna were lower than those of isolated individuals or within beds of M. galloprovincialis, highlighting the determinant role of gaping on fitness and group functioning. We demonstrate that new effects of very simple individual behaviour lead to amelioration of abiotic conditions at the aggregation level and that these effects increase mussel resistance to thermal stress.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Behavior, Animal*
  • Bivalvia / physiology*
  • Body Temperature
  • Environment
  • Stress, Physiological

Grant support

This research was supported by post-doctoral fellowships from FCT, Portugal (to GIZ) and funded by project PTDC/BIA-BEC/103916/2008 from FCT (to GIZ). This work is based upon research supported by the South African Research Chairs Initiative of the Department of Science and Technology and the National Research Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.