title: Cheating the Locals: Invasive Mussels Steal and Benefit from the Cooling Effect of Indigenous Mussels.
abstract: The indigenous South African mussel Perna perna gapes during periods of aerial exposure to maintain aerobic respiration. This behaviour has no effect on the body temperatures of isolated individuals, but when surrounded by conspecifics, beneficial cooling effects of gaping emerge. It is uncertain, however, whether the presence of the invasive mussel Mytilus galloprovincialis limits the ability of P. perna for collective thermoregulation. We investigated whether varying densities of P. perna and M. galloprovincialis influences the thermal properties of both natural and artificial mussel beds during periods of emersion. Using infrared thermography, body temperatures of P. perna within mixed artificial beds were shown to increase faster and reach higher temperatures than individuals in conspecific beds, indicating that the presence of M. galloprovincialis limits the group cooling effects of gaping. In contrast, body temperatures of M. galloprovincialis within mixed artificial mussel beds increased slower and exhibited lower temperatures than for individuals in beds comprised entirely of M. galloprovincialis. Interestingly, differences in bed temperatures and heating rates were largely dependent on the size of mussels, with beds comprised of larger individuals experiencing less thermal stress irrespective of species composition. The small-scale patterns of thermal stress detected within manipulated beds were not observed within naturally occurring mixed mussel beds. We propose that small-scale differences in topography, size-structure, mussel bed size and the presence of organisms encrusting the mussel shells mask the effects of gaping behaviour within natural mussel beds. Nevertheless, the results from our manipulative experiment indicate that the invasive species M. galloprovincialis steals thermal properties as well as resources from the indigenous mussel P. perna. This may have significant implications for predicting how the co-existence of these two species may change as global temperatures continue to rise.
authors.affiliation: Department of Zoology and Entomology, Rhodes University, Grahamstown 6140, South Africa.
authors.forename: Justin A
authors.initials: JA
authors.lastname: Lathlean
authors.affiliation: Centre National de la Recherche Scientifique, CNRS UMR 8187 LOG, 28 avenue Foch, BP 80, 62930 Wimereux, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Seuront
authors.affiliation: Department of Zoology and Entomology, Rhodes University, Grahamstown 6140, South Africa.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: McQuaid
authors.affiliation: The Swire Institute of Marine Science and School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China.
authors.forename: Terence P T
authors.initials: TP
authors.lastname: Ng
authors.affiliation: Department of Zoology and Entomology, Rhodes University, Grahamstown 6140, South Africa.
authors.forename: Gerardo I
authors.initials: GI
authors.lastname: Zardi
authors.affiliation: CCMAR-Centro de Ciencias do Mar, CIMAR Laboratório Associado, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal.
authors.forename: Katy R
authors.initials: KR
authors.lastname: Nicastro
mesh_terms: D000818:Animals; D057231:Climate Change; D003080:Cold Temperature; D058865:Introduced Species; D049878:Mytilus / Q000502:physiology*; D049883:Perna / Q000502:physiology*