The impact of metamorphosis and size on the aquatic feeding kinematics of the Iberian ribbed newt ( Pleurodeles waltl Michahelles, 1830)

Metamorphosis involves abrupt morphological changes separating larval and adult stages. The adaptive decoupling hypothesis proposes that metamorphosis breaks the correlations among the phenotypes expressed at the different life stages, enabling their independent evolution. This should be reflected in differences in functional performance linked to the body parts remodelled during metamorphosis. Moreover, changes in body size throughout ontogeny, can also influence functional performance. We investigated the influence of metamorphosis and size on suction feeding kinematics in larvae and metamorphs of Iberian ribbed newts using high-speed video analyses. Our results suggest that Iberian ribbed newts' ability to capture larger prey increases throughout ontogeny. Furthermore, apart from buccal expansion metrics, all feeding variables were significantly affected by the interaction between size and developmental stage. Notably, most duration variables increased with size in larvae, while decreasing with size in metamorphs. This pattern may reflect greater cranial ossification after metamorphosis, enabling more direct muscle force transmission and consequently, faster movements relative to size. Finally, although requiring further investigation, our results suggest that larvae may enhance suction and prey retention through labial lobes and gill slits, whereas metamorphs may compensate for the loss of these larval structures through faster movements enabled by cranial ossification.