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Histopathology of the alarm reaction in small odontocetes
1Department of Pathology, University of Texas Medical Branch, Galveston, TX, USA. dcowan@utmb.edu
Abstract:
Pathological changes in the organs and tissues of beach-stranded, net-caught or captive small odontocete cetaceans (whales and dolphins) are reported. These changes include contraction band necrosis of cardiac and smooth muscles, smooth muscle spasm, ischemic injury to the intestinal mucosa (especially the mucosa of the small intestine) and acute tubular necrosis (ATN) of the proximal tubules of the nephron. Spastic contraction of terminal bronchiolar muscular sphincters was also observed. The changes are consistent with multi-systemic injury caused by massive release of endogenous catecholamines or vasospasm leading to ischemic injury, followed by reperfusion and reperfusion injury. The histopathological findings suggest that the reflex response of an odontocete to any major perceived threat (the "alarm reaction") is to activate the physiological adaptations to diving or escape to an extreme or pathological level, resulting, if greatly prolonged, in widespread ischemic injury to tissues. These observations may explain why these species die abruptly from handling or transportation and why the mortality of highly stressed beach-stranded animals is very high.
Insights
Marine mammal stress responses can cause severe tissue injury. Pathological changes in stranded or captive cetaceans suggest an "alarm reaction" leading to widespread damage and mortality.
Area of Science:
- Veterinary Pathology
- Marine Mammal Science
- Physiology
Background:
- Small odontocete cetaceans (whales and dolphins) exhibit high mortality rates when stranded, captured, or handled.
- Understanding the physiological mechanisms behind this mortality is crucial for conservation efforts.
Purpose of the Study:
- To investigate the pathological changes in tissues and organs of stranded, net-caught, or captive small odontocete cetaceans.
- To correlate histopathological findings with physiological stress responses.
Main Methods:
- Histopathological examination of organs and tissues from deceased cetaceans.
- Analysis of pathological changes including necrosis, spasm, and tubular injury.
Main Results:
- Consistent pathological findings across various stress scenarios: contraction band necrosis, smooth muscle spasm, ischemic intestinal injury, and acute tubular necrosis (ATN).
- Observed spastic contraction of terminal bronchiolar muscular sphincters.
- Pathological changes are indicative of multi-systemic injury driven by massive endogenous catecholamine release or vasospasm, leading to ischemia and reperfusion injury.
Conclusions:
- The findings suggest that the odontocete "alarm reaction" to perceived threats involves extreme activation of diving/escape physiology.
- Prolonged activation of this response can result in widespread ischemic tissue injury.
- This mechanism likely explains abrupt mortality during handling/transport and high mortality in stressed, stranded animals.