DOI: 10.5061/dryad.xksn02vc2
title: Data for: Three-dimensional characterization of osteocyte volumes at multiple scales, and its relationship with bone biology and genome evolution in ray-finned fishes

description: Osteocytes, cells embedded within the bone mineral matrix, inform on key
 aspects of vertebrate biology. In particular, a relationship between
 volumes of the osteocytes and bone growth and/or genome size has been
 proposed for several tetrapod lineages. However, the variation in
 osteocyte volume across different scales is poorly characterised, and
 mostly relies on incomplete, two-dimensional information. In this study,
 we characterise the variation of osteocyte volumes in ray-finned fishes
 (Actinopterygii), a clade including more than half of modern vertebrate
 species in which osteocyte biology is poorly known. We use X-ray
 synchrotron micro-computed tomography (SRµCT) to achieve a
 three-dimensional visualisation of osteocyte lacunae and direct
 measurement of their size (volumes). Our specimen sample is designed to
 characterise variation in osteocyte lacuna morphology at three scales:
 within a bone, among the bones of one individual and among species. At the
 intra-bone scale, we find that osteocyte lacunae vary noticeably in size
 between zones of organised and woven bone (being up to six times larger in
 woven bone), and across cyclical bone deposition. This is probably
 explained by differences in bone deposition rate, with larger osteocyte
 lacunae contained in bone that deposits faster. Osteocyte lacuna volumes
 vary 3.5-fold among the bones of an individual, and this cannot readily be
 explained by variation in bone growth rate or other currently observable
 factors. Finally, we find that genome size provides the best explanation
 of variation in osteocyte lacuna volume among species: actinopterygian
 taxa with larger genomes (polyploid taxa in particular) have larger
 osteocyte lacunae (with a nine-fold variation in median osteocyte volume
 being measured). Our findings corroborate previous two-dimensional studies
 in tetrapods that also observed similar patterns of intra-individual
 variation and found a correlation with genome size. This opens new
 perspectives for further studies on bone evolution, physiology and
 palaeogenomics in actinopterygians, and vertebrates as a whole.
description: These data sheets (in the .csv format) are generated from the
 software VGStudioMax. They stem from the segmenting of tomograms (digital
 'slices') obtained with PPC-SRµCT (synchrotron microtomography)
 of modern ray-finned fish bones. The osteocyte lacunae (bone cell spaces)
 were segmented out of the bone mineral matrix, and analysed with the
 'Porosity/Inclusion' module to automatically obtain a set of
 measurements. These include (but are not limited to): osteocyte lacuna
 volumes (µm³), position in the x, y and z axis and range of tomogram gray
 values. Each data sheet corresponds to one set of
 segmented objects (osteocytes lacunae and a few, mostly smaller,
 unidentified objects) from each PPC-SRµCT tomogram (list of specimens and
 scans in the accompanying article), with two segmenting thresholds
 ('min' and 'max') for each tomogram.
 The name of each file corresponds to the following convention: 
 'Genus name' _ 'Species name' _ 'Specimen
 number'_ 'Bone' _ 'Location in bone (when
 appropriate)' _ 'Segmenting threshold'