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

摘要

Interactions between the bluestreak cleaner wrasse Labroides dimidiatus and its client reef fish are a textbookexample of interspecific mutualism. The fact that clients actively visit cleaners and invite inspection, togetherwith evidence that cleaners eat many client ectoparasites per day, indeed strongly suggests a mutualisticrelationship. What remains unknown is how parasite removal affects the physiology of clients and therebytheir body condition, health, and immune function. Here we addressed these issues in a field study in RasMohammed National Park, Egypt. In our study area, small reef patches are inter-spaced with areas of sandysubstrate, thereby preventing many species (i.e., residents, including cleaner wrasses) from travellingbetween the reef patches. This habitat structure leads to a mosaic of resident clients with and without accessto bluestreak cleaner wrasses, further referred to as “cleaner access”, on which we focused our study. Wefound that residents with cleaner access had higher body condition than residents without cleaner access.However, indicators of stress like variation in cortisol levels corrected for handling time and various immuneparameters were apparently unaffected by cleaner access. In fact antibody responses were significantly higherin fishes without cleaner access. This suggests that cleaner access decreases the need for active immunityand that this releases resources that might be allocated to other functions such as somatic growth andreproduction.