Hemodynamics of tonic immobility in the American alligator (Alligator mississippiensis) identified through Doppler ultrasonography

Young, Bruce A.; Adams, James Truslow; Segal, Solomon; Kondrashova, Tatyana

doi:10.1007/s00359-018-1293-x

Cited by 4 publications

(2 citation statements)

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“…Bradycardia has been reported during both tonic immobility in A. mississippiensis and death-feigning in the Eastern hognose snake (Heterodon platyrhinos). In both species, the cessation of the behavior is immediately preceded by a period of tachycardia [24,25]. There is chemical evidence for a barostatic response in alligators [26], but the full basis of the baroreflex remains unclear [27].…”

Section: Introductionmentioning

confidence: 99%

The Influence of Gravitational Gradients on the American Alligator (Alligator mississippiensis)

Knoche¹,

Young²,

Kondrashova³

2019

Anat Physiol

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Background Cranial fluids of vertebrae mammals are composed of arterial blood, venous blood, and cerebrospinal fluid that can be altered by orthostatic pressures; head‐down postures can elevate intracranial pressure and carotid/jugular luminal area while head up postures produce opposite effects. Previous studies on aquatic and terrestrial snakes showed cardiovascular variation while arboreal snakes showed little cardiovascular variation during orthostatic transitions. Little experimental work regarding orthostatic transitions has been done on alligators. Alligators are known to have unique blood flow patterns due to active regulation of blood flow. The purpose of this study is to investigate the effects of gravitational tilt on vessel luminal diameter and ICP in alligators. Methods Live adult alligators (n = 5, 165 – 183 cm total length) were subjected to gravitational tilts between 45° head‐up to 45° head‐down in 15° increments. Short (30 s) and long (120 s) duration tilts were performed to assess barostatic reflex and ICP using ocular ultrasonography, respectively. Vascular ultrasonography was also used to assess luminal diameter of the carotid artery and jugular vein. Instantaneous heart rate was inferred from EKG recordings throughout tilts. Results Throughout orthostatic transitions, ocular ultrasonography revealed an increase in optic nerve sheath diameter (head down tilts) and a decrease in optic nerve sheath diameter (head up tilts). Head down tilts resulted in jugular and carotid dilation while head up tilts resulted in various jugular luminal diameters and minimal change in carotid diameter. Heart rate increased at the onset of all orthostatic transitions. There was no evidence for a barostatic response. Conclusions Ocular ultrasonography was used to non‐invasively assess intracranial pressure of reptiles. There was a linear relationship between orthostatic transitions and intracranial pressure due to redistribution of CSF. Compared to previous studies, orthostatic transitions produced similar results on vessel flow and diameter. Variations of vessel flow and diameter may be attributed to unusual patters of heart rate or blood shunts in the cephalic venous system. Increases in heart rate in all rotations may be due to a fear response. Additional studies are needed to further understand the underlying regulatory mechanisms that give rise to the alligator's heart rate and blood flow patterns. Support or Funding Information Funding: The Influence of Gravitational Gradients on American Alligators (Alligator Mississippiensis) project has been funded by A.T. Still University's Masters in Biomedical Sciences program. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

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Section: Introductionmentioning

confidence: 99%

The Influence of Gravitational Gradients on the American Alligator (Alligator mississippiensis)

Knoche¹,

Young²,

Kondrashova³

2019

Anat Physiol

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“…With redu ced possibilities to escape, restraint from the neck while freezing would have led to tonic im mobility (Hagenaars et al, 2014). This may inhibit further attack or subjugation by preda tors (Humphreys & Ruxton, 2018), and was in frequently reported as a crocodilian behaviour: tonic immobility can be induced in American al ligators (A. mississippiensis) when inverted, being the mechanism a fear vasovagal syncope (Young et al, 2018) some studies on Crocodylus niloticus (Laurenti, 1768) [Handler et al, 2021; Subalusky et al, 2017. Additional field data are anecdotal, for instance in A. mississippiensis (Nifong et al, 2011), C. acutus (Cuvier, 1807) [CupulMagaña et al, 2005; EscobarLasso et al, 2016, C. ni loticus [Cott, 1961; Moleón et al, 2015, C. pa lustris (Lesson, 1831) [Murugan et al, 2020; Vyas, 2012, and C. porosus [Lim, 2015; Gal lagher et al, 2018.…”

Section: Scavengingmentioning

confidence: 99%

Capture methods of Caiman latirostris Daudin, 1802 (Crocodylia, Alligatoridae) in northern Uruguay, with notes of defensive and feeding behaviours

Borteiro¹,

Gutiérrez²,

Tedros³

et al. 2023

Rev. Biol. Neotrop.

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Caiman latirostris is a Neotropical crocodilian for which there is scarce natural history information in regard to other species, as also about survey methods used by field researchers. In this work we report the capture methodology implemented during population monitoring in northern Uruguay and some observations about defensive and feeding behaviours. We found the use of a metallic clamp as very useful for capturing juveniles and subadult individuals (< 120 cm total length) in vegetated habitats, while a wire snare was used for adults. Regardless locomotor escape, we provide a reappraisal of defensive behaviours in the presence of humans, with particular comments on tonic immobility. In addition, we suggest an apparent case of carcass consumption (scavenging) for the species, a presumedly common behaviour but sometimes hard to observe in wild crocodilians.

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Autonomic correlates of defense responses, including tonic immobility (TI)

Carli

Farabollini

2022

Progress in Brain Research

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Hemodynamics of tonic immobility in the American alligator (Alligator mississippiensis) identified through Doppler ultrasonography

Cited by 4 publications

References 56 publications

The Influence of Gravitational Gradients on the American Alligator (Alligator mississippiensis)

The Influence of Gravitational Gradients on the American Alligator (Alligator mississippiensis)

Capture methods of Caiman latirostris Daudin, 1802 (Crocodylia, Alligatoridae) in northern Uruguay, with notes of defensive and feeding behaviours

Autonomic correlates of defense responses, including tonic immobility (TI)

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