Suction-feeding performance in invasive alien giant salamanders within the functional framework of Andrias

Hybridisation between Andrias japonicus and A. cf. davidianus lineages is a major conservation concern in Japan, but whether hybrid individuals retain the suction-feeding pattern described for non-hybrid Andrias remains unclear. We analysed suction feeding in six hybrid giant salamanders using 20 captive feeding events recorded with lateral and frontal high-speed videography. Skull, lower jaw, hyobranchial and prey movements were digitised to quantify trajectories, velocities and accelerations during the active expansion phase of prey capture. The hybrids displayed the characteristic suction-feeding sequence described for cryptobranchids, including mandibular opening, hyobranchial expansion, prey acceleration and capture once suction was initiated. Event-level variation occurred in relation to prey position, attack configuration and individual morphometrics, highlighting the flexibility of suction feeding performance among hybrid specimens. Overall, hybrid specimens retained suction-feeding kinematics within the functional pattern previously described for Andrias, suggesting that hybridisation does not disrupt the core biomechanical organisation of prey capture within the functional range examined here. When compared with published data for non-hybrid A. davidianus and A. japonicus, these results indicate a broadly conserved suction feeding mechanism rather than a distinct hybrid-specific feeding mode. Therefore, any potential ecological advantage of hybrids is unlikely to result from a fundamental change in the suction feeding sequence alone.