World Congress of Malacology Antwerp ... - Unitas Malacologica

morphological variants of the shallow species, or a different species with a bathyal distribution (S.
Gofas and co-workers).
Proboscis morphology in Caenogastropoda:
Does the neogastropod proboscis have a homologue?
Golding, Rosemary E.
Department of Anatomy and Histology, University of Sydney, NSW 2006, Australia and Australian
Museum, Sydney, NSW 2000, Australia,
Email: rgol8300@anatomy.usyd.edu.au
The Neogastropoda are united by several synapomorphies of the alimentary system, but the proboscis
found in all neogastropod taxa is also present in a number of other caenogastropod families. The
Tonnoidea, Ficoidea, Cypraeoidea, Calyptraeoidea, Naticoidea and Ptenoglossa (and their close
allies) all consist of proboscate taxa in which the anterior head and alimentary system is modified in
association with a carnivorous diet. Neogastropod phylogeny is underpinned, to a large extent, by
comparative morphological studies of the proboscis, and it is likely that the group is derived from
another proboscate lineage within Caenogastropoda. This study aims to provide comparative
morphological descriptions of the proboscis and the organs contained within it, for diverse
caenogastropod taxa, and to assess the utility of this system in identifying the putative sister-group to
Neogastropoda. Proboscis morphology varies with regard to structures including; proboscis retractor
muscles (number, origin, point of insertion); proboscis wall (muscle layers); attachment of the buccal
mass to the proboscis wall; passage of the anterior aorta (connection to buccal mass, connection to
proboscis wall); passage of the buccal muscles (relative to the nerve ring, proboscis retractor muscles,
anterior aorta); presence of a rhynchodeum external to the proboscis; mode of retraction of the
proboscis. Current schemes of proboscis classification refer only to the manner in which the
proboscis retracts, divided into acrembolic, pleurembolic, intraembolic and polyembolic forms. These
categories do not necessarily reflect the underlying morphology of the proboscis, are frequently
misapplied, and are of little use in inferring phylogenetic relationships. However, detailed analysis of
the individual structural components of the caenogastropod proboscis may provide valuable insight
into phylogenetic relationships.
Micro-CT—3D analysis of molluscan anatomy
Golding, Rosemary E. 1 ; Jones, Allan S. 2
1. Department of Anatomy and Histology, University of Sydney, NSW 2006, Australia,
Email: rgol8300@anatomy.usyd.edu.au
2. Electron Microscope Unit, University of Sydney, NSW 2006, Australia,
Email: allanj@emu.usyd.edu.au
X-ray microcomputed tomography (micro-CT) is a fine-resolution 3D imaging technique which has
been developed for the materials science industry. In a biological context, micro-CT is particularly
suited to imaging dense materials such as bone and teeth. However, we have applied high atomic
weight stains (osmium tetroxide and phosphomolybdic acid) which allow for the visualisation of softtissue
anatomy. This is a rapid, non-destructive alternative to the painstaking process of 3D
reconstruction from histological sections. Soft-tissue micro-CT has not previously been applied to
molluscan specimens, although some species are well suited to this method of examination due to
their small size, external shell and complex, asymmetrical anatomy. The Skyscan 1172 microCT has
a maximum voxel resolution of 3.5 µm at a maximum specimen size of approximately 3.5 x 7 x 7
mm. Many micromolluscan specimens are within this size range, and soft-tissue micro-CT is a
promising new technology for studying the anatomy of these groups. We have generated images of
several micromolluscan species and of juvenile specimens of larger species, including assimineids
and chitons. Preliminary analyses of the data sets have generated complex, 3D models and serial
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