Effects of crowding and wave exposure on penis morphology of the acorn barnacle, Semibalanus balanoides
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Wave action and low population density can strongly reduce the ability of sessile acorn barnacles to find mates and copulate. For Semibalanus balanoides, penis morphology varies with wave exposure and with characteristics of the mating neighborhood. Field experiments were conducted at five intertidal sites on Long Island, New York, USA from July to December 2005 to determine how wave exposure and aggregation structure influence the length, diameter, mass, and number of annulated folds of the penis. Sparsely crowded barnacles had more annulations in the penis and are inferred to have greater ability to stretch. At higher wave exposure, the diameter of the penis was greater, but the mass was not. This study identifies density of crowding as the most important cue that barnacles respond to when perceiving their mating group and details how penis morphology varies in response to wave exposure.
Valuable ideas were incorporated into this manuscript deriving from conversations with J. Levinton, D. Padilla, D. Rand, R. Strathmann, J. True, and B. Yuen. This manuscript was meaningfully improved thanks to comments from the associate editor and anonymous reviewers. Help in the field was provided by B. Allen, P. Bourdeau, L. Brown, A. Ehmer, M. Fung, R. Junkins, C. McGlynn, B. Rodgers and E. Woo. Laboratory assistance was provided by E. O’Donnell, W. Wang and B. Yuen. Laboratory work was carried out in the Levinton Laboratory at Stony Brook University and the Functional Ecology Research and Training Lab (FERTL) in the department of Ecology and Evolution at Stony Brook University. Logistical support was provided by M. Doall. Assistance with statistical analysis was provided by Paulette Johnson at the FIU Statistical Consulting Center. Funding was provided by a Grant-in-aid-of-research from the Society for Integrative and Comparative Biology, a Student Research Fellowship from the Crustacean Society and a Doctoral Dissertation Improvement Grant from the National Science Foundation. An earlier version of this manuscript appears as a chapter in the author’s PhD dissertation.
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