Heat stress does not induce wasting symptoms in the giant California sea cucumber (Apostichopus californicus)

Oceanic heatwaves have significant impacts on disease dynamics in marine ecosystems. Following an extreme heatwave in Nanoose Bay, British Columbia, Canada, a severe sea cucumber wasting event occurred that resulted in the mass mortality of Apostichopus californicus. Here, we sought to determine if heat stress in isolation could trigger wasting symptoms in A. californicus. We exposed sea cucumbers to (i) a simulated marine heatwave (22 degrees C), (ii) an elevated temperature treatment (17 degrees C), or (iii) control conditions (12 degrees C). We measured the presence of skin lesions, mortality, posture maintenance, antipredator defences, spawning, and organ evisceration during the 79-hour thermal exposure, as well as 7-days post-exposure. Both the 22 degrees C and 17 degrees C treatments elicited stress responses where individuals exhibited a reduced ability to maintain posture and an increase in stress spawning. The 22 degrees C heatwave was particularly stressful, as it was the only treatment where mortality was observed. However, none of the treatments induced wasting symptoms as observed in the Nanoose Bay event. This study provides evidence that sea cucumber wasting may not be triggered by heat stress in isolation, leaving the cause of the mass mortality event observed in Nanoose unknown.

Automated summary

Oceanic heatwaves can impact disease dynamics in marine ecosystems. Researchers investigated if heat stress alone could trigger wasting symptoms in sea cucumbers. However, the study found that none of the heat treatments induced wasting symptoms as observed in a mass mortality event, suggesting that the cause of the event remains unknown.