The farmer fish
Another feeding habitThe researchers underline that the loss of this ligament is not linked to a change of life with regard to the proximity of the reef area. Some species which do not have the ligament do not wander far from the reef, like most damselfishes. “And even so, when we are talking about species that live in the water column, they remain quite close to the reefs, do not wander more than a few meters from it and only develop in shallow water. At night, they return to sleep among the coral reefs or rocky anfractuosities. The morphological evolution is therefore not linked to a change of habitat but to a dietary specialization”, continues Damien Olivier. Usually, damselfishes are quite opportunistic when it comes to eating as the observations of the young researcher have shown in the context of his thesis. According to the species, they have developed three different types of diet. The first consists of algae attached to the substrate, a second, consists of zooplankton in the water column, and a third which groups together a series of intermediate species. “What we noticed, however, was that all the species lacking the ligament are exclusively zooplanktivorous. Among the species with the ligament, the three types of diet were observed. During the course of evolution, some lineages went from being zooplanktivorous to algivorous and vice versa. Once they lost the ligament however, they no longer ate algae. It seems that there was no going back after the loss of the ligament”. A more rapid morphological evolution without the cerato-mandibular ligamentThe discovery of the ligament and its role in the feeding habits of damselfish makes it possible to identify its presence as a veritable functional adaptation. It was a key innovation which enabled damselfishes to forge a place in the coral reefs by adopting this ‘farming’ behavior. Within fifty million years, the damselfishes successfully radiated in the modern coral reef ecosystems. This success can be partly explained by this morphological trait. |
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© 2007 ULi�ge
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