 But cleaning sessions do not always end up well, because wrasses (or wrasse-mimicking parasitic sabre-toothed blennies) may cheat and eat the nutritious body mucus of their clients, rather than just the ectoparasites, something that makes the client jolt and sometimes flee.This system has been the subject of extensive observations which have suggested cognitive abilities on the part of the cleaner wrasses and their clients.For example, clients refrain from soliciting a cleaning session if they have witnessed the cleaning session of the previous client ending badly.