Comparative anatomy and functional implications of variation in the buccal mass in coleoid cephalopods

Abstract

In contrast to the well‐studied articulated vertebrate jaws, the structure and function of cephalopod jaws remains poorly known. Cephalopod jaws are unique as the two jaw elements do not contact one another, are embedded in a muscular mass and connected through a muscle joint. Previous studies have described the anatomy of the buccal mass muscles in cephalopods and have proposed variation in muscle volume depending on beak shape. However, the general structure of the muscles has been suggested to be similar in octopuses, squids, and cuttlefish. Here we provide a quantitative analysis of the variation in the buccal mass of coleoids using traditional dissections, histological sections and contrast‐enhanced computed tomography scans. Our results show that the buccal mass is composed of four main homologous muscles present in both decapodiforms and octopodiforms as suggested previously. However, we also report the presence of a muscle uniquely present in octopodiforms (the postero‐lateral mandibular muscle). Our three dimensional reconstructions and quantitative analyses of the buccal mass muscles pave the way for future functional analyses allowing to better model jaw closing in coleoids. Finally, our results suggest differences in beak and muscle function that need to be validated using future in vivo functional analyses.

Wear patterns of radular teeth in Loligo vulgaris (Cephalopoda; Mollusca) are related to their structure and mechanical properties

“…This species has a broad food spectrum and feeds on fish, crustaceans, smaller squids and polychaets [53][54][55][56][57][58][59][60] and specimens in larger quantities are easily accessible. Cephalopods mainly cut and disable their prey with their chitinous beaks [53,[61][62][63] (for reviews on cephalopod feeding, see [64][65][66]; for review on beaks, see [67]). The radula is rather used for the piercing of the prey, to clean crustacean carapaces .…”