The colony as a Network: Graph-Theoretic Morphometrics in Eunicella cavolini (Cnidaria: Octocorallia)
B. Coda and P. Apolloni
Kanazawa University, University of Trento
Eunicella cavolini is one of the most ecologically prominent gorgonian corals in the Mediterranean, growing in intricate branching shapes that usually encode structural information at multiple levels. Despite this complexity, extracting topologically meaningful descriptors using quantitative frameworks is not common practice. This study addresses the following research question: does Eunicella cavolini express a conserved colony-level architectural blueprint quantifiable through terminal branch fraction and branch length distribution structure?
We present a morphometric pipeline applied to eleven colonies sampled across three sites along the coast of Barcelona, Spain. We acknowledge that this sample size limits statistical generalization; knowing this, results should be interpreted as hypothesis-generating rather than confirmatory. Non-destructive field measurements, such as total colony height, width, and individual branch lengths, were used as inputs throughout.
The analytical pipeline operates at two levels. First, Strahler stream ordering quantifies architectural self-similarity within each colony. Second, each colony is modeled as a weighted arborescence, a directed tree graph, in which nodes represent branching junctions and tips, and edge weights correspond to measured branch lengths. From this representation, we derive degree distribution, mean path length and betweenness centrality. This last metric is of particular functional interest: branches with high centrality constitute structural bottlenecks whose removal would fragment a great portion of the colony, providing a proxy for mechanical and ecological vulnerability.
Preliminary results reveal that the proportion of terminal leaf nodes is at 73–74% of total segments across individuals, suggesting a species-level topological constraint. Additionally, branch length distributions maintain a consistent relative structure, with segment counts showing an approximately constant ratio at the most peripheral tier. Both findings require validation on a larger, environmentally stratified dataset. Nevertheless, they suggest that E. cavolini expresses a conserved architectural blueprint at both the topological and morphometric levels.
Keywords: Eunicella cavolini, Gorgonian Network Architecture, Gorgonian Morphometrics.