School of Biological Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
Biol Lett. 2011 Apr 23;7(2):292-4. doi: 10.1098/rsbl.2010.0916. Epub 2010 Nov 17.
Mucus performs numerous protective functions in vertebrates, and in fishes may defend them against harmful organisms, although often the evidence is contradictory. The function of the mucous cocoons that many parrotfishes and wrasses sleep in, while long used as a classical example of antipredator behaviour, remains unresolved. Ectoparasitic gnathiid isopods (Gnathiidae), which feed on the blood of fish, are removed by cleaner fish during the day; however, it is unclear how parrotfish and wrasse avoid gnathiid attacks at night. To test the novel hypothesis that mucous cocoons protect against gnathiids, we exposed the coral reef parrotfish Chlorurus sordidus (Scaridae) with and without cocoons to gnathiids overnight and measured the energetic content of cocoons. Fish without mucous cocoons were attacked more by gnathiids than fish with cocoons. The energetic content of mucous cocoons was estimated as 2.5 per cent of the fish's daily energy budget fish. Therefore, mucous cocoons protected against attacks by gnathiids, acting like mosquito nets in humans, a function of cocoons and an efficient physiological adaptation for preventing parasite infestation that is not used by any other animal.
黏液在脊椎动物中具有多种保护功能，在鱼类中可能会保护它们免受有害生物的侵害，尽管证据常常相互矛盾。许多鹦嘴鱼和隆头鱼睡觉时睡在黏液茧中，这一现象长期以来一直被用作抗捕食行为的经典例子，但它的功能仍未得到解决。以鱼类血液为食的外寄生虫食虱鱼（Gnathiidae）在白天会被清洁鱼清除；然而，目前尚不清楚鹦嘴鱼和隆头鱼如何在夜间避免食虱鱼的攻击。为了验证黏液茧可以保护鱼类免受食虱鱼攻击这一新颖假说，我们将有和没有黏液茧的珊瑚礁鹦嘴鱼（Scaridae）暴露于食虱鱼中过夜，并测量了黏液茧的能量含量。没有黏液茧的鱼比有茧的鱼更容易受到食虱鱼的攻击。黏液茧的能量含量估计为鱼类每日能量预算的 2.5%。因此，黏液茧可以保护鱼类免受食虱鱼的攻击，就像人类的蚊帐一样，这是黏液茧的一种功能，也是一种防止寄生虫感染的有效生理适应，其他动物都没有这种功能。
