An intertidal snail shows a dramatic size increase over the past century
- aDepartment of Biology, Queen's University, Kingston, Ontario K7L 3N6, Canada;
- bOcean Sciences Division, Bedford Institute of Oceanography, Dartmouth, Nova Scotia B2Y 4A2, Canada;
- cCheverus High School, Portland, ME 04103; and
- dDepartment of Biology, University of Pennsylvania, Philadelphia, PA 19104
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Edited by Juan Carlos Castilla, Pontificia Universidad Católica de Chile, Santiago, Chile and approved February 11, 2009 (received for review November 28, 2008)
Abstract
Changes in the shell architecture of marine snails enhance defenses and greatly improve survival against predators. In the northwest Atlantic Ocean, shorter and thicker shells have been reported for several species following the introduction of predatory Carcinus maenas crabs early in the 20th century. But we report that the shell lengths of Nucella lapillus actually increased by an average of 22.6% over the past century, with no evidence of shell thickening after correcting for shell length. The increases in shell length were greatest on sheltered shores, highlighting the interaction between wave exposure and the sampling period. Comparisons were based on archived shells collected in 1915–1922 from sites that were resampled in 2007. N. lapillus is an important member of North Atlantic marine ecosystems, and our results suggest that the impacts of historical changes in species' key morphological traits on marine ecosystems remain underappreciated.
Footnotes
- 1To whom correspondence should be addressed. E-mail: jonathan.fisher{at}queensu.ca
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Author contributions: J.A.D.F. and P.S.P. designed research; J.A.D.F., E.C.R., H.L., and P.S.P. performed research; J.A.D.F. and P.S.P. analyzed data; and J.A.D.F. and P.S.P. wrote the paper.
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The authors declare no conflict of interest.
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This article contains supporting information online at www.pnas.org/cgi/content/full/0812137106/DCSupplemental.
