High-Density Three-Dimensional Morphometric Analyses Reveal Predation-Based Disparity and Evolutionary Modularity in Spider ‘Jaws’

• Published in: Evolutionary biology 2022-12, Vol.49 (4), p.389-402
• Main Authors: Kallal, Robert J., Wood, Hannah M.
• Format: Article
• Language: English
• Subjects: Analysis; Animal Genetics and Genomics; Appendages; Axial skeleton; Biomedical and Life Sciences; Chelicerae; Computed tomography; Developmental Biology; Ecology; Evolutionary Biology; Human Genetics; Jaw; Life Sciences; Marriage; Predation; Predation (Biology); Prey; Research Article; Spiders
• ISSN: 0071-3260; 1934-2845
• DOI: 10.1007/s11692-022-09576-y

Understanding complex morphological shape differences has been revolutionized by the marriage of three-dimensional morphometric techniques and micro-computed tomography scanning. In animals, a major focus of this work has been the vertebrates, particularly the axial skeleton, while shape diversity in arthropods, by comparison, is less well explored. For example, the chelicerae (fanged, jaw-like mouthpart appendages) of spiders exhibit a wide degree of variation and may be expected to differ across the diversity of spider sizes and hunting strategies (e.g., active hunters versus relying on a web to intercept and capture prey) as well as in comparison to other structures on the same organism. We characterize and quantify the shapes of the carapace and chelicerae of 40 spiders across the spider tree of life and look for differences based on how those spiders attain their prey and whether their shapes coevolved or are modular. We found evidence for differences in cheliceral shape and related structures in spiders with different predation strategies as well as evidence for both integration and modularity in those structures. This suggests different pressures on the chelicerae including but not limited to predation mode. Furthermore, while differences in the structures were observed, they still must work in concert.