DOI: 10.5061/dryad.8gtht76ss
title: Data from: Whole-body variational modularity in the zebrafish: An inside-out story of a model species

description: Actinopterygians are the most diversified clade of extant vertebrates.
 Their impressive morphological disparity bears witness to tremendous
 ecological diversity. Modularity, the organization of biological systems
 into quasi-independent anatomical/morphological units, is thought to
 increase evolvability of organisms and facilitate morphological
 diversification. Our study aims to quantify patterns of variational
 modularity in a model actinopterygian, the zebrafish (Danio
 rerio), using 3D-geometric morphometrics on osteological
 structures isolated from micro-CT scans. 72 landmarks were digitised along
 cranial and postcranial ossified regions of 30 adult zebrafishes. Two
 methods were used to test modularity hypotheses, the covariance ratio and
 the distance matrix approach. We find strong support for two modules, one
 comprised of paired fins and the other comprised of median fins, that are
 best explained by functional properties of subcarangiform swimming. While
 the skull is tightly integrated with the rest of the body, its intrinsic
 integration is relatively weak supporting previous findings that the fish
 skull is a modular structure. Our results provide additional support for
 the recognition of similar hypotheses of modularity identified based on
 external morphology in various teleosts, and at least two variational
 modules are proposed. Thus, our results hint at the possibility that
 internal and external modularity patterns may be congruent.
description: Osteological data were
 obtained using X-ray micro-tomography (Skyscan 1173, Bruker-microCT,
 Belgium) on 30 alcohol-preserved wild-type specimens of adult
 <em>Danio rerio</em>. Scans were reconstructed using NRecon
 v1.6.6 and image segmentation was performed using Drishti Paint v.2.6.4.
 Fin and body shape variation among specimens was quantified using
 landmark-based geometric morphometrics. 72 homologous 3D-landmarks were
 digitised across 48 skeletal elements and 11 sutures or articulations
 between bones using Stratovan Checkpoint v.2018.08.07 (Stratovan Corporation). Landmarks'
 descriptions are available in Table S1 (see supplementary information of
 the article) and coordinates are available in TPS
 files.  Seven <em>a priori</em> hypotheses
 of modularity were formulated. A full description of the hypotheses is
 available in Table S3 (see supplementary
 information of the article).
 Landmark coordinates were
 scaled, translated, and rotated by performing a Procrustes
 superimposition. Two different methods were used to test these hypotheses:
 (1) the covariance ratio (CR) (Admas and Collyer, 2019); and (2) the
 distance matrix approach (Klingenberg and Monteiro,
 2005; Magwene, 2001, 2009; Monteiro et al., 2005; Zelditch et al.,
 2009). To describe patterns of morphological
 integration, we quantified integration between modules for each hypothesis
 using partial least square (PLS) analyses (Adams and Collyer, 2016). We also estimated the global integration for
 the entire landmark configuration, as well as for the subsets comprising
 the skull and the postcranial regions. All statistical analyses were performed in R
 v.3.6.3 using the packages
 ‘morpho’,
 ‘geomorph’, and
 ‘ggm’.
description: R Programming software.