Mechanical properties and elemental composition of the beak in selected cephalopod species: patterns and variability

Cephalopod beaks are remarkable organic structures that play a crucial role in the feeding ecology of these marine molluscs. This study investigates the mechanical properties, microstructure, and elemental composition of beaks from four commercially available cephalopod species: Eledone cirrhosa, Sepia officinalis, Loligo vulgaris, and Sepioteuthis lessoniana. Using nanoindentation, we measured the elastic modulus of the rostrum, revealing that lower beaks are stiffer than upper beaks across all species. Notably, L. vulgaris exhibited the highest stiffness. The study highlights significant intra- and interspecific variability in beak properties, suggesting ecological implications regarding diet and environmental factors. Scanning electron microscopy (SEM) showed a fibrous microstructure with nanoparticles of different sizes, while energy dispersive spectroscopy (EDS) identified carbon, oxygen, and nitrogen as primary elements, along with trace elements like silicon and calcium. These initial results suggest that the relationships between beak structure, composition, and biomechanical properties are likely to be complex and species-specific, underscoring the need for more comprehensive analyses to better understand beak function and its adaptive implications. This research provides new baseline data for comparative studies on cephalopod functional morphology and raises the potential of beaks as tools for ecological and environmental monitoring. We recommend that future studies incorporate larger and developmentally diverse samples to refine our understanding of cephalopod feeding adaptations and their interaction with changing marine environments.