![]() These mechanisms have yet to be discovered. This leads to the hypothesis that band formation is controlled by a precise genetic mechanism and depends on the antero-posterior polarity of the fish. These results suggest that the chronological loss of the bands during evolution was constrained by the sequence of appearance of the bands during development and that there is a strong link between phylogenesis (evolutionary history) and ontogenesis (individual development). These bands are then lost in the reverse order that they evolved, from tail to head. ocellaris in the larval stage, with the successive appearance of three white bands from head to tail, while adult individuals have only one. frenatus shows the same development as A. See also: This MIT-Made Robot Fish Will Study the World’s Fragile Coral ReefsĪ second surprising observation was that A. That is, in the reverse order that they disappeared for some species during the process of evolution. ocellaris appear in a well-defined order during its transformation from larva to young adult - first that of the head, then the body, and finally on the tail. frenatus, which has only one stripe, on its head. ocellaris, which has three stripes, and A. To understand why some stripe combinations do not exist in clownfish, we looked at the development of two species with two different colored patterns in adulthood, A. And Away They Go Over the Course of Evolution Looking at the patterns that have developed, it’s clear that diversity is constrained: while the four combinations listed above are seen, biological mechanisms do not allow a species to have others - for example, a single stripe on the tail. Genetic analysis integrating the evolutionary history of clownfish revealed that their common ancestor had three white bands, and that during their diversification, clownfish lines successively lost the tail band, then the body band, and finally the head band, thus giving four possible combinations: To understand the mechanism leading to the diversity of pigment patterns, we grouped each clownfish species according to their number of vertical bands. From top to bottom and left to right: Amphiprion ephippium, Amphiprion frenatus, Amphiprion bicinctus and Amphiprion ocellaris. What can explain the difference in the number of bands between these species?įour clownfish illustrating the species’ colour patterns. Amphiprion ocellaris, the famous Nemo, has three stripes. ![]() Thus, some species have no stripes ( Amphiprion ephippium), only one ( Amphiprion frenatus), or just two ( Amphiprion sebae). In addition to other physical characteristics, clownfish species are distinguished by their number of vertical white stripes. Their color pattern is characterized by a yellow, orange, brown, or black color with vertical white stripes composed of light-reflecting cells called iridophores. Nemo, alias Amphiprion ocellaris, belongs to the clownfish group, which includes about 30 species. The study was published in the September 2018 edition of the journal BMC Biology. More precisely, how are the patterns formed and what are the roles of the colors? To answer these questions, a research team from the Banyuls-sur-Mer Observatory (France) and the University of Liège (Belgium), decided to study the clownfish and its cousins. This small fish, which lives in symbiosis with the sea anemone, is easily recognizable thanks to its bright orange body and wide white stripes.ĭespite the coral fishes’ popularity and wide distribution, we do not understand yet why they have such myriad and different color patterns. One of the most famous examples of coral fish is the clownfish, which starred in the animated Pixar film Finding Nemo in 2003. On the left is the copperband butterflyfish, on the right the Picasso triggerfish. ![]()
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