The growth of the buccal mass in Sepia officinalis: functional changes throughout ontogeny

Due to their small size, juveniles are more likely to show lower absolute levels of performance leading to a potential competitive disadvantage compared to adults. Therefore, juveniles are expected to compensate by showing a higher relative performance, and/or partitioning resources to overcome this performance disadvantage. Here, we investigate the link between ontogeny and feeding performance in the common cuttlefish Sepia officinalis. We explore the changes in beak shape, wear pattern, mechanical properties, muscular anatomy, and bite force during growth from 3-month post hatching to adults. We show that both upper and lower beaks present important ontogenetic shape variation in the rostrum area that might be due to wear induced by feeding. The mechanical properties of the beaks in juveniles indicate greater resistance compared to adults. Tanning observed on the beaks provides reinforcement to areas under high load during biting. In addition, muscle development and relative bite force were found to differ between cuttlefish of different ages, resulting in juveniles having a similar bite force for their size but with a muscular advantage for opening. Finally, an isometric relation is found in the bite force of S. officinalis, with no sign of feeding performance compensation in juveniles. Feeding performance thus does not reflect the ontogenetic shift from a crustacean-based diet in juveniles to a fish-based diet in adults.

Automated summary

Due to their small size, juvenile cuttlefish may have lower absolute performance levels compared to adults, but they compensate by showing a higher relative performance and partitioning resources. In this study, we examined the ontogenetic changes in beak shape, wear pattern, mechanical properties, muscular anatomy, and bite force of the common cuttlefish Sepia officinalis. We found that both upper and lower beaks showed shape variation in the rostrum area, possibly due to wear induced by feeding. The mechanical properties of the beaks in juveniles indicated greater resistance compared to adults. Moreover, muscle development and relative bite force differed between cuttlefish of different ages, with juveniles having similar bite force for their size but an advantage for opening.