Stereom microstructure of teeth in brittle stars: 3D reconstruction and quantifications using synchrotron microcomputed tomography data.

TITSCHACK, J.; BAUM, D.; SABOROWSKI, R.; BOOS, K.; SORIANO, C.; STOCK, S.R.; BROGGER, M.I.; BERECOECHEA, J.J.

Rhodes

Simposio; 51st European Marine Biology Symposium; 2016

In brittle stars (Ophiuroidea, Echinodermata), dietary differences and feeding mechanisms are, among others, reflected in a variety of morphologically different teeth. These are modified calcite stereom ossicles, typically arranged in vertical series of one or more rows along the inner sides of the jaws. Despite a wide range of known feeding modes, detailed morphological descriptions of the microstructure of teeth are scarce and their actual functioning when manipulating or handling food is largely unknown. Nonetheless, knowledge on the role, the function and the mechanical properties of teeth is highly relevant, because the teeth ultimately represent the final manipulating structures prior to food intake and digestion and therefore shed light on the animal?s role in local food chains. Here we present first results on 3D reconstructions from high resolution X-ray synchrotron microComputed Tomography (μCT) data as an advanced non-invasive tool for morphological visualization of complex three-dimensional structures such as the calcite stereom teeth in brittle stars. We use the concept of ambient occlusion for the segmentation of the intrapore space and the stereom classification. Presently, we focus on different infaunally living and deposit-feeding amphiurid species known to possess so called ?compound teeth?. In these, the proximal area of the tooth is loosely fenestrated, but the distal part as well as proximally located insertion and fixation hunches (i.e. where the tooth is inserted into the dental plate) are of solid imperforate calcite. In addition, we provide quantifications from the reconstructions for architectural properties of the teeth for standardized comparisons, such as porosity, amount and relation of fenestrated and imperforate calcite and gradients of porosity within a tooth from basal to distal. The results will allow for intra (- and inter) specific comparisons of different species with respect to their known feeding modes and life styles. Overall, the results will lead to a better understanding of the significance of structural differences in teeth of brittle stars, their overall feeding ecology and, ultimately, their roles in different marine benthic ecosystems.