Fish hypnosis: Induction of an atonic immobility reflex

Abstract

An immobility reflex may be induced in fish by a vigorous flow of water through the branchial chamber. The reflex was observed in 22 species representing bony and cartilaginous fishes from diverse habitats, and was invariably characterised by loss of caudal muscle tone and limp posture. The immobilised state may be maintained for many hours, and revival is instantaneous. The critical flow rate for induction increases with increasing body size in the snapper, Pagrus auratus, and heart rate falls below the resting rate. In addition, haematological parameters, and plasma lactate after 6 h were typical of resting fish. Although the mechanism is unclear, and the selective advantage for the fish unknown, pressure-sensitive receptors in the branchial chamber are likely to be involved. Application in live fish transport, and recovery from handling and exercise stressors is suggested.

Home range size and patterns of space use by lingcod, copper rockfish and quillback rockfish in relation to diel and tidal cycles

“…dorsal side down) in a chamois-lined, v-shaped foam 'bed', which was placed within a larger, water filled plastic container to allow for irrigation of the gills during surgery. After approximately 1 min in this position, the fish entered a state of tonic immobility (Henningsen 1994, Holland et al 1999, Wells et al 2005) and became nonresponsive. A small 2 to 3 cm long incision was made anterior of the anus and the acoustic tag inserted.…”

Could thermal sensitivity of mitochondria determine species distribution in a changing climate?

“…Water pumped into the buccal cavity induced atonic immobility (Wells et al, 2005) and fish were then held for 3 h prior to experiments to dissipate any associated handling stress. Heart rates were measured non-invasively by fetal Doppler probes (Sonotrax B, Contec Medical Systems, Qinhuangdao, China) to avoid anaesthetics.…”

Tonic immobility in the zebra shark, Stegostoma fasciatum, and its use for capture methodology

“…As such, it may act as a mechanism to invoke female acquiesence during mating rituals (Pratt and Carrier 2001;Kunze and Simmons 2004;Brunnschweiler and Pratt Jr 2008), as well as having a role in anti-predator responses. In those shark species that do show tonic immobility it is usually induced by rapid dorso-ventral inversion (Watsky and Gruber 1990), but can also be induced by pumping water into the branchial chamber (Wells et al 2005). In zebra sharks, Stegostoma fasciatum, tonic immobility can be induced not only by dorso-ventral inversion, but also by applying pressure to the distal end of the tail (Henningsen 1994;Dudgeon et al 2013), and usually occurs immediately following pressure.…”

“…Tonic immobility is an innate, reversible, coma-like stasis displayed by a large number of wildlife taxa (Gallup 1974;Hennig et al 1979; Thompson et al 1981;Wells et al 2005). It is characterized by a reversible catatonic motionless posture, immobility, and an unresponsiveness to noxious or injurious stimulation.…”

“…It is characterized by a reversible catatonic motionless posture, immobility, and an unresponsiveness to noxious or injurious stimulation. Tonic immobility causes muscle hypertonicity in terrestrial vertebrates but relaxed muscle tone and a 'limp' posture develops in fish species (Thompson et al 1981;Whitman et al 1986;Wells et al 2005;Marx et al 2008;Brooks et al 2011). Tonic immobility can be induced by several stimuli, but external pressure and physical restraint are the most common (Bayard 1957;Jones 1986).…”