Shell colour polymorphism in the chiton Ischnochiton striolatus (Gray, 1828) (Mollusca: Polyplacophora) and habitat heterogeneity |
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Authors: | LETÍCIA RIBEIRO GONÇALVES RODRIGUES RICARDO SILVA ABSALÃO |
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Institution: | Departamento de Zoologia, Instituto de Biologia, CCS, Universidade Federal do Rio de Janeiro, Ilha do Fundão, Rio de Janeiro, RJ 21941-570, Brazil; Departamento de Zoologial, Instituto de Biologia, Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier 524, Maracanã, Rio de Janeiro, RJ 20550-900, Brazil |
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Abstract: | Shell colour polymorphism was examined in a population of the polyplacophoran Ischnochiton striolatus (Gray, 1828) living on intertidal rocks in Búzios, Rio de Janeiro State, Brazil. Nine shell colours were identified: green (most common), grey, pink, cream, brown, orange, white, black and purple. The species habitat was also examined using three rock characteristics: volume; turnover frequency, caused by hydrodynamic disturbance; and chromatic composition. Chitons were most frequently encountered on the undersides of rocks of intermediate volume which experienced medium-intensity hydrodynamic disturbance, and which harboured a chromatically rich biotic community. These findings were in agreement with the Intermediate Disturbance Hypothesis. As chitons depend on the biotic community on rocks for food and shelter, a greater variety of colours could increase the chances of camouflage of the morphs against the background, favouring crypsis. It is likely that the frequency at which intermediate-volume rocks are overturned ? thus exposing the chitons on them to light ? would be sufficient for visual predators to act as selective agents. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 543–548. |
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Keywords: | crypsis hydrodynamic disturbance negative phototaxia rocky bottom south-east Brazil |
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