Do cleaning organisms reduce the stress response of client reef fish?

Abstract

Background: Marine cleaning interactions in which cleaner fish or shrimps remove parasites from visiting 'client' reef fish are a textbook example of mutualism. However, there is yet no conclusive evidence that cleaning organisms significantly improve the health of their clients. We tested the stress response of wild caught individuals of two client species, Chromis dimidiata and Pseudanthias squamipinnis, that had either access to a cleaner wrasse Labroides dimidiatus, or to cleaner shrimps Stenopus hispidus and Periclimenes longicarpus, or no access to cleaning organisms.

Does access to the bluestreak cleaner wrasse Labroides dimidiatus affect indicators of stress and health in resident reef fishes in the Red Sea?

“…Our data together with those of Bshary et al (2007) suggest that parasite removal by cleaner wrasses might not change average basal levels of cortisol substantially although it might reduce the peak levels of the hormone during stressful events. High peak levels of cortisol indicate a deficiency in the availability of metabolic resources under stressful conditions and this may have lasting and costly consequences for homeostatic processes, immunity, and reproductive behaviors (McEwen and Wingfield, 2003;Schreck, 2010).…”

“…An important element of this response in fish is the activation of the hypothalamus-pituitary-interrenal axis, which results in an increase in circulating levels of cortisol. Bshary et al (2007) showed for two client species (in the same study site as we used) Pseudanthias squamipinnis and Chromis dimidiatus that cortisol levels in response to a stressor were higher when these clients were resident on reef patches without cleaner access than with cleaner access. Here we aimed to test whether a similar effect could be measured in the basal levels.…”

“…Following the design of Bshary et al (2007), we selected 30 patches in 2-to 6-m depth with or without a cleaner wrasse as a resident. We aimed to sample 1-3 adult individuals per preselected resident species per patch.…”

“…In order to weigh such costs with the benefits of cleaner visits, more information about the effects of these visits on the overall condition and stress physiology of fish is necessary. In a first study to test the physiological effects of cleaner visits, Bshary et al (2007) compared reef fishes that lived on isolated small reef patches by comparing clients that did or did not have access to bluestreak cleaner wrasses. The cortisol levels in these fish in response to confinement stress were found to be reduced in client reef fishes with cleaner access in comparison to clients without cleaner access.…”

“…The cortisol levels in these fish in response to confinement stress were found to be reduced in client reef fishes with cleaner access in comparison to clients without cleaner access. We used the same method as used in the study of Bshary et al (2007) to address the question how the observed reduced stress response in clients with cleaner access is linked to condition and other physiological parameters, in particular the functioning of the immune system.…”