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 / Physiology, Cell and Developmental Biology
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:AEU.10048/1365 |
| Date | 11 1900 |
| Creators | Tompkins MacDonald, Gabrielle Jean |
| Contributors | Sally Leys, Biological Sciences, Andy Spencer (deceased), Biological Sciences, Sally Leys, Supervisor, Biological Sciences, Warren Gallin, Biological Sciences, Andrew Waskiewicz, Biological Sciences, Peter Light, Pharmacology, Peter Anderson, External Examiner, Whitney Laboratory for Marine Bioscience |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 19090709 bytes, application/pdf |
| Relation | Tompkins-MacDonald et al. 2009. Journal of Experimental Biology 212: 761-767., Tompkins-MacDonald and Leys 2008. Marine Biology 154: 973-984 |
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