Phenotypic and reproductive trade-offs of colonial invertebrates to salinity
Extreme or seasonal climatic events can lead to abrupt changes in environmental conditions. These events can produce a range of phenotypic responses that may help to protect local-scale populations against changes in climate. However, empirical studies relating dramatic shifts in environmental conditions with reproductive variation in traits are rare. We performed laboratory experiments under varying episodic and chronic salinity regimes using the botryllid ascidians, Botrylloides nigrum and Botryllus planus. Our study illustrates trait variation, indicative of an adaptive plastic response to salinity and species-specific differences in salinity tolerances. Forty and twenty percent of B. nigrum and B. planus colonies exhibited a distinct physical behavior when exposed to low salinity treatments. They distended their cloacal cavities, showing their pharyngeal baskets and neural glands. Salinity negatively affected reproduction, heart rates and survival in both B. nigrum and B. planus, with speciesspecific recovery that suggests a trade-off between reproduction and recovery from environmental stress. Our study revealed that continued reproduction may delay recovery of colonies during periods of osmotic stress as their physiology may be working harder to maintain normal metabolic functions. These results suggest these species can directly respond to fine-scale environmental processes such as those associated with adaptive plasticity that may aid their persistence in a future where flood events are likely to be more common and acute.
Journal or Conference Title
International Invasive Sea-Squirt Conference
October 29-31, 2014
Woods Hole, MA
J. A. Dijkstra and Simkanin, C., “Phenotypic and reproductive trade-offs of colonial invertebrates to salinity”, International Invasive Sea-Squirt Conference. Woods Hole, MA, 2014.