[Extract] The cleaner wrasse, Labroides dimidiatus, is a highly specialized reef fish that removes and consumes ecto-parasites, and occasionally dead tissues, from the bodies of other fishes – which we call "clients" (Figure 1; Grutter 2004; Grutter and Irving 2007). This species is the most widespread of all obligate cleaners, occurring from Africa to French Polynesia, but it has historically remained largely confined to the tropics. Although it cleans over 100 different fish species on the Great Barrier Reef (Bansemer et al. 2002), 99% of the food items it consumes are ectoparasitic crustaceans (gnathiid isopods; Grutter and Irving 2007), so this wrasse apparently has a very specific diet.