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New insights about barnacle reproduction: Spermcast mating, aerial copulation and population genetic consequences Open Access


Other title
Single Nucleotide Polymorphism
Penis size
Rocky intertidal shores
Molecular markers
Aerial copulation
Chthamalus dalli
Population genetics
Balanus glandula
Tidal conditions
Acorn barnacles
Mating behavior
Mitochondrial DNA
Wave exposure
Shore height
Stalked barnacles
Spermcast mating
Pollicipes polymerus
Type of item
Degree grantor
University of Alberta
Author or creator
Barazandeh, Marjan
Supervisor and department
Palmer, A. Richard (Biological Sciences)
Examining committee member and department
Proctor, Heather C. (Biological Sciences)
Coltman, David W. (Biological Sciences)
Grosberg, Richard K. (Biological Sciences, University of California at Davis)
Gallin, Warren J. (Biological Sciences)
Davis, Corey S. (Biological Sciences)
Department of Biological Sciences
Systematics and Evolution
Date accepted
Graduation date
Doctor of Philosophy
Degree level
Barnacles are mostly hermaphroditic and they are believed to mate via copulation or, in a few species, by self-fertilization. However, isolated individuals of two species that are thought not to self-fertilize, Pollicipes polymerus and Balanus glandula, nonetheless carried fertilized embryo-masses. These observations raise the possibility that individuals may have been fertilized by waterborne sperm, a possibility that has never been seriously considered in barnacles. Using molecular tools (Single Nucleotide Polymorphisms; SNP), I examined spermcast mating in P. polymerus and B. glandula as well as Chthamalus dalli (which is reported to self-fertilize) in Barkley Sound, British Columbia, Canada. Embryo masses of isolated individuals and isolated pairs of all three species had alleles that were not present in the genome of the parents or of immediate partners, which indicates that spermcast mating occurred. However, the rate of fertilization by spermcasting was higher in P. polymerus (100% and 24% in isolated individuals and pairs, respectively), followed by B. glandula (100% and 7.7%) and C. dalli (70% and 9.1%). The relatively shorter size of the penis — and hence lower copulation rates — in P. polymerus compared to the other two species could favor higher rates of spermcasting. Moreover, lower apparent spermcasting in C. dalli could reflect a higher incidence of self-fertilization. Surveys of the sperm release process in P. polymerus using a belt-transect method, indicated that tidal and weather conditions did not affect sperm release, however, lower barnacle density (less opportunity for copulation) and higher wave action of the low shore (more chance to disperse sperm) compared to high shores was associated with more sperm release. By videotaping P. polymerus, I found that — unlike all other known barnacles — they copulate mostly in air, during the incoming tides. Extended times of aerial copulation were observed in barnacles on less wave-exposed shores. Using mitochondrial DNA markers, I tested for genetic divergence among P. polymerus populations experiencing different wave exposures and shore heights that might be associated with observed differences in spermcasting and copulation. However, none of the analyses indicated any genetic differentiation among populations or between shore levels. These novel observations raise many questions about some long-established beliefs regarding barnacle reproductive biology.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Barazandeh, M., Davis, C.S., Neufeld, C.J., Coltman, D.W., Palmer, A.R., 2013. Something Darwin didn't know about barnacles: Spermcast mating in a common stalked species. Proc. R. Soc. B-Biol. Sci. 280 (1754), 20122919.Barazandeh, M., Davis, C.S., 2012. Identification and characterization of 16 single nucleotide polymorphisms (SNPs) in the northeast intertidal gooseneck barnacle, Pollicipes polymerus. Conserv. Genet. Res. 4, 217-219.

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