Leptochiton rugatus, the Dwarf Chiton.
Dr Julia Sigwart from the UCD School of Biology and Environmental Science has utilised morphology imaging techniques to gain new insights into the internal organs of distinctive metal-toothed marine animals. These tiny shellfish in the molluscan class Polyplacophora are commonly known as chitons or coat-of-mail shells (ciotón máille as Gaeilge).
“The fossil record of these distinctive marine animals shows that their external shape has changed very little over the last 300 million years. But what is not known is how much the shape of their internal organs may have changed, or how much variation exists among the 1,000 living species,” said Dr Sigwart.
To investigate the anatomy of these 'living fossils', Sigwart recently travelled to use the state-of-the-art morphology imaging facilities in the Zoologische Staatssammlung München (Bavarian State Collection of Zoology, Munich) in Germany where she carried out the research in collaboration with Dr Michael Schrödl.
“The technique involves cutting the 5mm animals into more than 3,000 serial sections, and then using computer imaging to reconstruct the three dimensional shape of the internal organs from a 'stack' of two dimensional sections,” Sigwart explained.
View the reconstruction video of Leptochiton rugatus, the Dwarf Chiton.
Chitons live all over the world, mainly living on rocks in the intertidal. Specimens of the target species for this study, Leptochiton rugatus, the Dwarf Chiton, were collected by Sigwart in Canada. These creatures live on the under side of rocks embedded in the sand of the beach, and reach a maximum size of about 8mm long.
Most chitons use their special scraping tongue, called a radula, to graze on algae or bacterial mats growing on rocks. Because they constantly scrape on hard surfaces to eat, chitons have specially adapted teeth that actually contain iron. Metal teeth pose a technical challenge to slicing a chiton into sections without breaking the cutting blade.
Sigwart’s reconstruction shows all of the major organs, modelled in different colours for clarity. Future work will focus on modelling smaller scale aspects of the anatomy such as sensory systems.
