Suction feeding of West African lungfish (Protopterus annectens): An XROMM analysis of jaw mechanics, cranial kinesis, and hyoid mobility

Abstract

Suction feeding in fishes is characterized by rapid movement of cranial elements, but extant lungfishes (Sarcopterygii: Dipnoi) exhibit a reduced number and mobility of cranial bones relative to actinopterygian fishes. Despite fusion of cranial elements, lungfishes are proficient at suction feeding, though the impacts of novel cranial morphology and reduced cranial kinesis on feeding remain poorly understood. We used X-ray Reconstruction of Moving Morphology (XROMM) to study the kinematics of six mobile skeletal elements (neurocranium, upper jaw, lower jaw, ceratohyal, clavicle, and cranial rib) and two muscles (costoclavicular portion of the hypaxialis and rectus cervicis) during the feeding strikes of West African lungfish (Protopterus annectens). We found that feeding by P. annectens on non-evasive prey is relatively slow, with a mean time to peak gape of 264 ms. Lower jaw depression and clavicular rotation were hinge-like, with one degree of freedom, but the ceratohyals rotated in a complex motion involving depression and long-axis rotation. We quantified the relative contributions to oral cavity volume change (RCVC) and found that oral cavity expansion is driven primarily by ceratohyal and clavicle motion. P. annectens suction feeds relatively slowly but successfully through muscle shortening of hypaxial and rectus cervicis muscles driving extreme hyoid mobility.

Occipital‐synarcual joint mobility in ratfishes (Chimaeridae) and its possible adaptive role

“…Retraction of the pectoral girdle (Bishop & Foxon, 1968) and neurocranial elevation (Bemis, 1986;Bemis & Lauder, 1986;Gartner et al, 2022) have also been described in lungfishes.…”