Fight, flight or freeze Tonic immobility in sharks

摘要

Tonic immobility (TI) is an inherited and reversible status of motoric immobility that can be provoked in a variety of terrestrial and aquatic animal species, including sharks. In sharks, this behavior, which is originally natural behavior, can be induced by putting external pressure on the fins and turning the animal on its back, after which the sharks will display reduced muscle tone and will temporarily not respond to environmental stimulation. It can be expected that this state has an effect on the physiology of the animal. In sharks, it can induce lowered ventilation efficiency with impact on blood parameters, it can cause a stress response and disrupt the osmolarity of the blood. Nonetheless, this TI state in sharks has its applications in scientific and veterinary (clinical) research, blood sampling and wound treatment. However, tonic immobility in sharks remains an enigmatic phenomenon that should be studied in detail using an interdisciplinary approach.