Abstract
Many barnacles have phenotypically plastic cirri and penises. We studied this ability in Chthamalus stellatus over a range of wave exposure, height and population density along the John U. Lloyd State Park jetty. We also examined specialized, serrated bristles found on the cirri to determine functionality of these bristles, as well as to document any variation. We observed no meaningful variation in penis or cirrus morphology with wave exposure, height or crowding. However both correlate with body size, which is greatest in the middle of their vertical range. Barnacles in the middle of their vertical range also had more denticulate setae. These setae were only present on the first and second cirri. The second cirri had more setae than the first. Within the paired appendages that make cirrus #I, we found that the shorter ramus had more denticulate setae while the longer essentially had none. Both rami of cirrus #II had many denticulate bristles with the shorter having slightly more. Greater than 97% of penises were tucked between cirri #I and #II. The lack of plasticity amongst these barnacles may be a result of the sites sampled having lower variation in the properties of the sites compared to other parts of their geographic range. Self-fertilization may reduce the need for such a response as well. High rates of fertilization in non-crowded specimens also supports this. The denticulate setae may function as a grooming device for the penis and possibly to comb food particles out of the cirral net.
Faculty Sponsors
J. Matthew Hoch, Ph.D.
Project Type
Event
Location
Alvin Sherman Library
Start Date
4-10-2015 1:00 PM
End Date
4-10-2015 5:30 PM
Morphological Variation of the Penis and Cirral as well as Potential Denticulated Bristle Function in the Barnacle, Chthamalus stellatus
Alvin Sherman Library
Many barnacles have phenotypically plastic cirri and penises. We studied this ability in Chthamalus stellatus over a range of wave exposure, height and population density along the John U. Lloyd State Park jetty. We also examined specialized, serrated bristles found on the cirri to determine functionality of these bristles, as well as to document any variation. We observed no meaningful variation in penis or cirrus morphology with wave exposure, height or crowding. However both correlate with body size, which is greatest in the middle of their vertical range. Barnacles in the middle of their vertical range also had more denticulate setae. These setae were only present on the first and second cirri. The second cirri had more setae than the first. Within the paired appendages that make cirrus #I, we found that the shorter ramus had more denticulate setae while the longer essentially had none. Both rami of cirrus #II had many denticulate bristles with the shorter having slightly more. Greater than 97% of penises were tucked between cirri #I and #II. The lack of plasticity amongst these barnacles may be a result of the sites sampled having lower variation in the properties of the sites compared to other parts of their geographic range. Self-fertilization may reduce the need for such a response as well. High rates of fertilization in non-crowded specimens also supports this. The denticulate setae may function as a grooming device for the penis and possibly to comb food particles out of the cirral net.
