engleski

Sea urchin Paracentrotus lividus (Lamarck, 1816) (Echinodermata, Echinoidea) population of the southern Istria (Adriatic Sea)

Background and purpose: The sea urchin Paracentrotus lividus is one of the ecologically most important macrofaunal species in the biocoenosis of photophilic algae. As its populations have never been surveyed around the southern part of the Istrian peninsula the aim of this study was to obtain basic information on the local sea urchin distribution and densities patterns with special regard to the population structure and masking behaviour. Materials and methods: Field research at 12 stations was performed in summer time by skin and SCUBA diving along 50 m long transects. Benthic communities were analysed and sea urchins were collected on a square meter basis. Relevant taxonomic, morphometric and statistical analyses were done. Results and conclusions: In the area studied P. lividus preferred moderately exposed localities. The densest populations with a maximum of 102 specimens per square metre, usually small sized ones, occurred on denuded bedrocks till the maximum 2.8 m depth. Specimens with dark coloured spines usually prevail by about 90% . Most of the brightly coloured urchins were violet and brown, and only rarely green and red spined specimens were noted. The masking behaviour depended on habitat exposure and substrate features, and materials at disposal. Seaweed and seagrass fragments, molluscan shells and pebbles dominated in the masking materials used.

paracentrotus lividus ; ecology ; population structure ; Adriatic Sea ; masking behaviour

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