Marine & Environmental Sciences Faculty Proceedings, Presentations, Speeches, Lectures


Development and Functional Variation of Barnacle Penis Morphology

Event Name/Location

Society for Integrative and Comparative Biology 2007 Meeting, Phoenix, Arizona, January 3-7, 2007

Document Type

Conference Proceeding

Publication Date



Barnacles are simultaneous hermaphrodites that reproduce by copulating with neighbors. To accomplish this, barnacles must extend their penis into the water column, locate receptive functional females and deposit sperm. This may take several minutes, during which the mating individuals are vulnerable to predators or disruption by wave action. This presentation addresses variation in penis functional morphology across environments and mating aggregations. First, I followed the development of the penis over the course of the year from barnacles in several locations. Confocal and traditional microscopy revealed the rapid growth of the penis within the month prior to the brief mating season and variation in musculature across environment. I measured the fertilization success rates of barnacles with different mate distances across a gradient of wave exposure to determine how far penises could reach. I then compared differences in morphology and condition of the penis to reveal functional consequences of penis variation. The data suggest that penises grow relatively longer when mates are more distant, but the increase in reach does not increase linearly. The ability to reach distant mates also decreases as wave action increases. Local mate competition theory for simultaneous hermaphrodites predicts changes in relative allocation to the sex roles based on mating group size. My data allows precise measurement of mating group potential for an individual barnacle and I discuss how this can be used to predict sex allocation within different environments.

This document is currently not available here.