Bubbles in live-stranded dolphins - PubMed (original) (raw)

Bubbles in live-stranded dolphins

S Dennison et al. Proc Biol Sci. 2012.

Abstract

Bubbles in supersaturated tissues and blood occur in beaked whales stranded near sonar exercises, and post-mortem in dolphins bycaught at depth and then hauled to the surface. To evaluate live dolphins for bubbles, liver, kidneys, eyes and blubber-muscle interface of live-stranded and capture-release dolphins were scanned with B-mode ultrasound. Gas was identified in kidneys of 21 of 22 live-stranded dolphins and in the hepatic portal vasculature of 2 of 22. Nine then died or were euthanized and bubble presence corroborated by computer tomography and necropsy, 13 were released of which all but two did not re-strand. Bubbles were not detected in 20 live wild dolphins examined during health assessments in shallow water. Off-gassing of supersaturated blood and tissues was the most probable origin for the gas bubbles. In contrast to marine mammals repeatedly diving in the wild, stranded animals are unable to recompress by diving, and thus may retain bubbles. Since the majority of beached dolphins released did not re-strand it also suggests that minor bubble formation is tolerated and will not lead to clinically significant decompression sickness.

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Figures

Figure 1.

Figure 1.

Common dolphin IFAW10-069Dd. Arrows indicate renal margins. (a) B-mode ultrasound image of the left kidney showing hyperechogenicities (white) and ring-down artefact around the renules. (b) B-mode ultrasound image of the right kidney in the same dolphin with a greater depth of field to enhance the ring-down artefacts. (c) Transverse CT image at the level of the kidneys showing gas (black) surrounding and within the kidneys. The animal's left is to the left of the image. Gas is also seen in this image within intestinal loops and adjacent to the spinal cord. The CT was performed within 2 h of death. Window Width (WW) 553, Window Level (WL) 62. Three millimetre slice thickness, soft tissue reconstruction algorithm.

Figure 2.

Figure 2.

Transverse CT images from the same animal as in figure 1. (a) Gas within the subarachnoid space or meningeal vasculature (arrows). (b) Gas between the blubber and muscle layers and in linear configurations consistent with intramuscular vasculature (arrows). Intestinal gas is also evident and is normal. Three millimetres slice thickness, soft tissue reconstruction algorithm. (a) WW500 WL50; (b) WW553 WL62.

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