Molecular and functional bases of coordination in early branching metazoans – insights from physiology and investigations of potassium channels in the Porifera

• Author / Creator

  Tompkins MacDonald, Gabrielle Jean

• Sponges are filter feeders that lack nerves and muscle but are nonetheless able to
  respond to changes in the ambient environment to control their feeding current.
  Cellular sponges undergo coordinated contractions that effectively expel debris.
  Syncytial sponges propagate action potentials through their tissue, causing
  immediate flagellar arrest. Understanding the basis of this coordination in sponges
  is of interest for the insight it provides on mechanisms of coordination in early
  branching animals. However, when I began this thesis no ion channels had been
  described from the Porifera. I adopted a multifaceted approach to studying the
  conduction system of sponges. This included cloning and characterizing
  potassium channels as a means to understanding the underlying ionic currents,
  and monitoring regulation of the sponge feeding current in response to
  environmental stimuli. The latter experiments provided a functional context. The
  glass sponges Rhabdocalyptus dawsoni and Aphrocallistes vastus arrest feeding in
  response to mechanical disturbance and to sediment in the incurrent water –
  suggesting a protective role. Monitoring patterns of feeding current arrests also
  revealed several features of the glass sponge conduction system: pacemaker
  activity, mechanosensitivity, distinct excitability thresholds, and tolerance to
  repeated stimuli. With access to the genome of the demosponge Amphimedon
  queenslandica I have also cloned and characterized the first sponge ion channels.
  Inward rectifier potassium (Kir) channels were prioritized for their role in
  regulating excitability. Kir channels cloned from A. queenslandica shared critical
  residues and a strong rectifying phenotype with Kir channels typically expressed
  in excitable cells. A variety of potassium channels from A. queenslandica indicate
  great diversity and a foundation for coordination at the dawn of the Metazoa

• Subjects / Keywords

  • Potassium channels
  • Sponge
  • Filter feeder
  • Porifera
  • Coordination systems
  • Sediments

• Graduation date

  Fall 2010

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R34Q4V

• 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.