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

  • Author / Creator
    Barazandeh, Marjan
  • 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.

  • Subjects / Keywords
  • Graduation date
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
  • Institution
    University of Alberta
  • Degree level
  • Department
  • Specialization
    • Systematics and Evolution
  • Supervisor / co-supervisor and their department(s)
  • Examining committee members and their departments
    • Gallin, Warren J. (Biological Sciences)
    • Grosberg, Richard K. (Biological Sciences, University of California at Davis)
    • Proctor, Heather C. (Biological Sciences)
    • Davis, Corey S. (Biological Sciences)
    • Coltman, David W. (Biological Sciences)