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Thursday, November 3, 2011

Egg spots on Cichlids

Bernd Egger and coauthors report in a recent issue of the online journal PLoS ONE that female haplochromine cichlids exhibit a pre-existing sensory bias for egg-shaped structures and egg coloration (red, yellow and orange), which may have been enough to trigger the evolution of egg spots in the anal fins of the male fish.

Egg spots or egg dummies are round or oval-shaped markings found on the anal fins in males of approximately 1500 haplochromine cichlid species.  The markings consist of a conspicuous yellow, orange, or reddish inner circle and a transparent outer ring.

Given that these markings resemble real fish eggs, it has been proposed that they mimic freshly laid eggs in order to attract females and to maximise fertilisation success.

The authors test the hypothesis that the exploitation of a pre-existing bias in female haplochromine cichlids has triggered the evolution of this male trait.

Using the Egyptian mouthbrooder (Pseudocrenilabrus multicolor) as their experimental organism, the authors conducted a series of mate choice experiments to test if the females showed a bias for egg-shaped spots and egg colour. The Egyptian mouthbrooder is a basal (i.e. ‘primitive’) haplochromine whose males do not possess egg spots....READ MORE>>


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