Sensory systems form the first point of contact between animals and their surroundings. The study of sensory systems is both a rich and diverse anatomical and behavioural field, and a potentially invaluable tool in evolutionary biology. This thesis examines four systems in three molluscan classes and ophiuroid echinoderms, addressing novel or poorly-understood systems and examining evolutionary trends by assessing the anatomy of more familiar structures in a phylogenetic context. The primary study system is a novel discovery reported herein throughout the chiton order Lepidopleurida, named the Schwabe organ. By combining detailed anatomical study, electrophysiology and behavioural experiments, 1 demonstrated that the Schwabe organ mediates light-avoidance behaviour and likely shares developmental origins with the chiton larval eye. A similar integrative approach was applied to a putative ‘visual* system in the ophiuroid Ophiocoma wendtii. Anatomical and behavioural results indicated that animals may use an extensive network of dermal photoreceptors for image formation, however this system differs substantially from the established model. The two final chapters focus on sensory and nervous systems in evolution. A re-description of scaphopod neuroanatomy in Rhabdus rectius demonstrates the potential power of a neurocladistic approach in solving deep phylogenetic questions, highlighting important similarities with cephalopod neural architecture and prompting the re-assignment of the major body axes in adult scaphopods. Finally, a study of eye reduction and eye loss in deep sea solariellid gastropods found surprising morphological diversity and differential progression between independent eye reductions, even within genera. This thesis makes several important contributions to our knowledge of four sensory systems and their evolution across two major invertebrate phyla: the Schwabe organ, extra-ocular photoreception in 0. wendtii, the Steiner organ and gastropod eyes. Overall, it also demonstrates the powerful nature of cross-disciplinary projects as well as the versatile role of sensory biology in broader evolutionary studies.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:709845 |
| Date | January 2016 |
| Creators | Sumner-Rooney, Lauren Héloïse |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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