Are cleaner fishes replaceable on coral reefs as consumers of fish
Specialist species have evolved to fill narrow niches but are especially
susceptible to environmental change. With sufficient functional
redundancy, ecosystem services can persist without specialists. Grooming
behaviors are common in both terrestrial and aquatic organisms. However,
in aquatic systems there is a heavy reliance on intraspecific mutualisms
where specialist species groom or “clean” parasites off host fishes.
Here, we sampled the gut contents of 709 fishes, representing 61 species
and including both cleaner and non-cleaner fishes, to compare their
consumption of gnathiid isopods, the most common fish ectoparasites. We
found that cleaner fishes eat significantly more gnathiids, and eat them
more frequently, compared to non-cleaner fishes. Our results highlight
the importance of both dedicated and facultative cleaners as consumers
of ectoparasites and show that their role cannot be supplanted by
generalist consumers. Furthermore, we suggest that different cleaner
species act as complementary rather than redundant specialists.