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

Nicastro KR, Zardi GI, McQuaid CD, Pearson GA, Serrão EA - PLoS ONE (2012)

Bottom Line: Although made up of individual members, an aggregation often displays novel effects that do not manifest at the level of the individual organism.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.

View Article: PubMed Central - PubMed

Affiliation: CCMAR-CIMAR Laboratório Associado, Universidade do Algarve, Faro, Portugal.

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.

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Related in: MedlinePlus

Schematic diagram of the experimental design of the laboratory group experiment.The experiment consisted of three treatments: P. perna bed, M. galloprovincialis bed and solitary individuals. Three replicates of each treatment were set up and the whole experiment was performed twice.
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pone-0047382-g001: Schematic diagram of the experimental design of the laboratory group experiment.The experiment consisted of three treatments: P. perna bed, M. galloprovincialis bed and solitary individuals. Three replicates of each treatment were set up and the whole experiment was performed twice.

Mentions: Robomussels mimic the thermal characteristics of living mussels (see [35]) and were used in all group gaping experiments to avoid potential disruption of the behaviour caused by wires passing over the beds. They were made by placing a temperature logger (iButtons®, Maxim Integrated Products, Dallas Semiconductor, USA) between two empty mussel valves (length ∼5 cm) filled with silicone sealant and left to dry at air temperature for 48 hours before being employed in trials. For the experiment, three artificial mussel beds were made using live mussels for each species, each bed with two robomussels placed in the center of the bed and two at the edge. The artificial beds were circular (diameter of ∼15 cm) and made up of mussels (5 cm±0.5 in length; n∼55) arranged vertically to mimic their position in natural beds. Partially rigid, white PVC net (mesh size 4 cm) was placed around and under the beds to keep the mussels in position. Three sets of robomussels (each consisting of two robomussels 20 cm apart) were placed outside the beds to mimic mussels in isolated positions (referred to as solitary robomussels; Fig. 1). At the beginning of the experiment, bed and solitary treatments were positioned on tiles and aerially exposed to 35°C and 60% humidity for six hours. All laboratory experiments were conducted in a controlled temperature-humidity walk-in room. The temperature chosen is commonly experienced by intertidal mussels on the South African south coast [36]. An additional set of two temperature and two humidity loggers (iButtons®, Maxim Integrated Products, USA) were placed among the mussels at the center of the bed and next to the solitary robomussels for the duration of the experiment.


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

Nicastro KR, Zardi GI, McQuaid CD, Pearson GA, Serrão EA - PLoS ONE (2012)

Schematic diagram of the experimental design of the laboratory group experiment.The experiment consisted of three treatments: P. perna bed, M. galloprovincialis bed and solitary individuals. Three replicates of each treatment were set up and the whole experiment was performed twice.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3472978&req=5

pone-0047382-g001: Schematic diagram of the experimental design of the laboratory group experiment.The experiment consisted of three treatments: P. perna bed, M. galloprovincialis bed and solitary individuals. Three replicates of each treatment were set up and the whole experiment was performed twice.
Mentions: Robomussels mimic the thermal characteristics of living mussels (see [35]) and were used in all group gaping experiments to avoid potential disruption of the behaviour caused by wires passing over the beds. They were made by placing a temperature logger (iButtons®, Maxim Integrated Products, Dallas Semiconductor, USA) between two empty mussel valves (length ∼5 cm) filled with silicone sealant and left to dry at air temperature for 48 hours before being employed in trials. For the experiment, three artificial mussel beds were made using live mussels for each species, each bed with two robomussels placed in the center of the bed and two at the edge. The artificial beds were circular (diameter of ∼15 cm) and made up of mussels (5 cm±0.5 in length; n∼55) arranged vertically to mimic their position in natural beds. Partially rigid, white PVC net (mesh size 4 cm) was placed around and under the beds to keep the mussels in position. Three sets of robomussels (each consisting of two robomussels 20 cm apart) were placed outside the beds to mimic mussels in isolated positions (referred to as solitary robomussels; Fig. 1). At the beginning of the experiment, bed and solitary treatments were positioned on tiles and aerially exposed to 35°C and 60% humidity for six hours. All laboratory experiments were conducted in a controlled temperature-humidity walk-in room. The temperature chosen is commonly experienced by intertidal mussels on the South African south coast [36]. An additional set of two temperature and two humidity loggers (iButtons®, Maxim Integrated Products, USA) were placed among the mussels at the center of the bed and next to the solitary robomussels for the duration of the experiment.

Bottom Line: Although made up of individual members, an aggregation often displays novel effects that do not manifest at the level of the individual organism.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.

View Article: PubMed Central - PubMed

Affiliation: CCMAR-CIMAR Laboratório Associado, Universidade do Algarve, Faro, Portugal.

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.

Show MeSH
Related in: MedlinePlus