Telling your partner to watch her weight is not recommended-unless you're a male cleaner fish, reports a new study in Proceedings of the Royal Society B.
Cleaner fish feed in male-female pairs by removing parasites from larger 'client' fish. While providing this cleaning service, cleaners may get greedy and bite clients rather than sticking to parasites. This cheating by cleaners causes mealtimes to come to an abrupt end as the disgruntled client fish swims off. Females that bite clients receive aggressive punishment from their male partners for such greedy behaviour.