Study
Cleaner fish really do clean
Grutter, Alexandra S.
Nature, 1999
Cleaner wrasse were removed from experimental reef patches and absent for an extended period, with comparable patches left intact as controls. Parasite loads on client fish were then measured on both.
- Studied in
- Labroides dimidiatus, Hemigymnus melapterus
- Sample size
- reef patches with cleaners experimentally removed, against controls
Client fish on reefs without cleaners carried substantially more parasites than those on control reefs.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
Cleaning interactions have a real effect on client parasite loads rather than being merely a conspicuous behaviour.
How NatureHQ reads it
Included because the obvious claim had gone untested for decades. Fish visiting cleaners, cleaners picking at them, and parasites on the reef were all long documented; that the interaction actually reduced parasite loads was assumed. Removing the cleaners and counting is what turned an appearance into an effect.
- Particular reef patches and client species; effect sizes differ between systems and later studies.
- Removal changes more than cleaning — client movement and visit patterns change too.
Taking the cleaners off a reef
Cleaner fish are seen picking parasites off other fish. Does that measurably reduce how many parasites those fish carry?
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Published by: Nature PortfolioPublished in a Nature Portfolio journal.
Checked against Crossref on 2026-09-28, and they agree on the title, the authors and the year.
NatureHQ summarises research in its own words and does not reproduce published text. Reviewed 2026-09-03.