Revista de Saúde Pública (Jun 2003)
Modificación del coeficiente peso/área del pié en relación con la agregación en Tarebia granifera Change of the weight/ foot area coefficient in relation to aggregation in Tarebia granifera
Abstract
OBJETIVO: Analizar la dispersión de los ejemplares de una población de Tarebia granifera y su relación con la modificación de los parámetros morfométricos. METODOS: Se colectó por parcelas incluyendo dos tipos de substratos en condiciones opuestas de agregación y se comparó la abundancia relativa tanto entre muestreos, como entre sustratos. Se delimitaron 7 clases de alto a las cuales se les determinó el coeficiente peso/área del pié, el cual se correlacionó con la talla por clase. Se evaluó experimentalmente si los individuos con menor carga del pié tienen mayor persistencia en substratos emergidos, así como la interacción entre dos grupos de clases de alto. RESULTADOS: La diferencia de la abundancia entre los muestreos fue de t=5.874 (pOBJECTIVE: To analyze specimens dispersion in a population of Tarebia granifera and its relationship with the change of morphometric parameters. METHODS: Two samplings by parcels including two types of substrata in opposite aggregation conditions were carried out, and the specimen abundance was compared between both samplings and substrata. The samples were stratified into classes according to shell height and for each of these the coefficient weight/foot-area was calculated and correlated with class size. It was experimentally evaluated whether specimens with a lower foot load had a better persistence in emerged substratum as well as the interaction between two class groups of shell height. RESULTS: The abundance difference between samplings was t=5.874 (p<0.001), and t=10.15 (p<0.001) between emerged rocky and sandy substrata, only under conditions of high aggregation where foot load decreases with the size for higher specimens (r=-0.98, p<0.05). Experimentally, the abundance of specimens of opposed sizes were mutually limited (r=-0.87, p<0.01), waves' height limits the abundance of smaller snails (r=-0.94, p<0.01) but it is tolerated by larger ones (r=0.72, p<0.05), and foot load diminishes with the waves' height (r=-0.93, p<0.001). CONCLUSIONS: Under high aggregation conditions larger specimens emigrate toward substratum of difficult capture by smaller ones, which are limited by the environment's mechanical influence. The decrease of foot load facilitates specimens' dispersion.
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