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Enduring muscular courtship

Physiology
Several species of male amphibians and reptiles hold tight to their partners, possibly to prevent them mating with their rivals. The southern alligator lizard ( Elgaria multicarinata ) clamps its mate's head in its jaws for hours. This extreme muscular performance runs counter to expectations of reptilian muscle resilience. Nguyen et al. tested the sustained bite force of the adductor muscles of the lizard's jaw for fatigue. Muscle fibers can specialize, in terms of performance, into fast-acting twitch fibers and into slow-acting tonic fibers that are capable of fatigue-resistant contraction. Tonic fibers also exhibit slow calcium fluxes and relax slowly. The lizards' jaw muscle appears to have evolved to comprise fast-twitch fibers for eating and slow-tonic fibers that can sustain an extended courtship grip.

Proc. R. Soc. London Ser. B 287 , 20201578 (2020).