Variation in the hemostatic complement (C5a) responses to in vitro nitrogen bubbles in monodontids and phocids
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ORIGINAL PAPER
Variation in the hemostatic complement (C5a) responses to in vitro nitrogen bubbles in monodontids and phocids Laura A. Thompson1 · Allyson G. Hindle2 · Sandra R. Black3 · Tracy A. Romano1 Received: 23 March 2020 / Revised: 30 June 2020 / Accepted: 10 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Immune responses to nitrogen gas bubbles, particularly activation of inflammation via the complement cascade, have been linked to the development of symptoms and damage associated with decompression sickness (DCS) in humans. Marine mammals were long thought not to be susceptible to such dive-related injury, yet evidence of DCS-like injury and new models of tissue nitrogen super-saturation suggest that bubbles may routinely form. As such, it is possible that marine mammals have protective adaptations that allow them to deal with a certain level of bubble formation during normal dives, without acute adverse effects. This work evaluated the complement response, indicative of inflammation, to in vitro nitrogen bubble exposures in several marine mammal species to assess whether a less-responsive immune system serves a protective role against DCS-like injury in these animals. Serum samples from beluga (Delphinapterus leucas), and harbor seals (Phoca vitulina) (relatively shallow divers) and deep diving narwhal (Monodon monoceros), and Weddell seals (Leptonychotes weddellii) were exposed to nitrogen bubbles in vitro. Complement activity was evaluated by measuring changes in the terminal protein C5a in serum, and results suggest marine mammal complement is less sensitive to gas bubbles than human complement, but the response varies between species. Species-specific differences may be related to dive ability, and suggest moderate or shallow divers may be more susceptible to DCS-like injury. This information is an important consideration in assessing the impact of changing dive behaviors in response to anthropogenic stressors, startle responses, or changing environmental conditions that affect prey depth distributions. Keywords Marine mammal · Dive physiology · Complement · Decompression sickness · Diving · Inflammation · Whale · Seal
Introduction Interest in whether marine mammals are susceptible to decompression sickness (DCS), or similar injury, was renewed following description of acute DCS-like injury in beaked whales (Ziphius cavirostris, Mesoplodon densirostris and europaeus), which stranded in close temporal and physical proximity to naval sonar exercises (Jepson et al. 2003). Communicated by H.V. Carey. * Laura A. Thompson [email protected] 1
Mystic Aquarium, a Division of SeaResearch Inc., Mystic, CT 06355, USA
2
University of Nevada, Las Vegas, Las Vegas, NV 89154, USA
3
University of Calgary, Calgary, AB T2N 1N4, Canada
Since this report, studies have focused on gas exchange, lung collapse and the potential for high tissue gas tensions and bubble formation in a variety of species (e.g. Zimmer and Tyack 2007; Bostrom et al. 2008; Kvadsheim et
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