VERTICAL-DISTRIBUTION OF CHITONS (MOLLUSCA, POLYPLACOPHORA) IN THE ROCKY INTERTIDAL ZONE OF CENTRAL CHILE
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1985
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Abstract
The patterns of vertical distribution of chitons in various exposed rocky shore habitats of central Chile are described. The density and size of the individuals were determined at different levels on intertidal rock walls, in pools and on boulders. A group of 4 spp. [Chiton barnesi, C. granosus, Callistochiton viviparus and Acanthopleura echinata] was found on rock walls while another group of 4 spp. [Ischnochiton pusio, Tonicia elegans f. lineata, Chilton cumingsi and C. latus] was found in tidal pools and on boulders. The species showed vertical separation on rock walls and segregation according to a range of increasing frequency of water movement in pools and on boulders. Only the 2 spp. with largest adult individuals (A. echinata (Barnes) and C. latus Sowerby) showed vertical segregation in size. Small-sized species and small individuals of large-sized species were found higher on rock walls or in zones where water movement is less; large chitons occur in zones of greatest water impact. This suggests that water movement may be a significant factor in setting the lower limits of distribution of these herbivores. Some of the species examined were extremely abundant (600 .cntdot. m-2) with densities of 1-2 orders of magnitude greater than for other chiton species elsewhere.