Browsing by Author "CORREA, J"

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    BENTHIC ALGAL SPORES SURVIVING DIGESTION BY SEA-URCHINS
    (1983) SANTELICES, B; CORREA, J; AVILA, M
    Present ideas on benthic algal adaptations to animal herbivory focus mainly on defensive and escape mechanisms of settled plants, and disregard the ability of algal reproductive bodies to escape from digestion by animals. To test this hypothesis, 150 individuals of the common Chilean sea urchin, T. niger Molina, were collected over a period of 7 mo., covering spring through fall. Fifty were examined for gut contents which revealed a total of 31 algal species, 62.9% of which could be categorized as opportunists and 37.1% as late successional forms. When the contents of fecal pellets were cultured the resulting algal species that had successfully resisted digestion by means of incomplete digestion or protective spore walls showed 84.6% as opportunists and 15.4% as late successional forms. There was no significant correlation between frequency of occurrence in the gut contents and in the fecal cultures, indicating that digestion survival depended on factors other than abundance. The capacity to survive digestion may play a role in the abundance of these species in overgrazed areas.
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    DIFFERENTIAL SURVIVAL OF MACROALGAE TO DIGESTION BY INTERTIDAL HERBIVORE MOLLUSKS
    (1985) SANTELICES, B; CORREA, J
    This study evaluates the capacity of algal propagules to survive digestion by 7 intertidal herbivore mollusks. Individual [30] Littorina peruviana, 36 of Siphonaria lessoni, 35 of Collisella ceciliana, and 25 each of C. zebrina, Chiton granosus, Fissurella crassa and F. limbata were collected at different dates between Oct., 1983 and April, 1984. About half of the individuals of each species were examined for gut contents and the other half was used to provide fecal pellets for culture. Diet of these grazers ranged from 8 macroalgal species in Collisella zebrina to 17 in F. limbata. Macroalgal propagules of 56% of the 27 algal species found in these gut contents survive digestion. There was no positive correlation between diet and number of algal taxa growing in the respective fecal cultures. Survival through L. peruviana and Chiton granosus was low (20-30% of the algal species consumed) while it was high (75-83%) through the 2 spp. of Collisella. No significant correlation was found between frequency of algae in the gut contents and its frequency in the fecal cultures. Algal capacity to survive digestion was almost exclusively restricted to opportunistic species, especially in the Chlorophyta and Phaeophyta. Survival of algal propagules through the digestive tract of generalist grazers may be a rather random phenomenon.
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    EFFECTS OF SOME ENVIRONMENTAL-FACTORS ON GROWTH OF SPORELINGS IN 2 SPECIES OF GELIDIUM (RHODOPHYTA)
    (1985) CORREA, J; AVILA, M; SANTELICES, B
    The effects of temperature, photoperiod and photon-flux density on growth of sporelings of 2 spp. of the economically important [agar production] red algal genus Gelidium [G. lingulatum, G. chilense] were evaluated, and a basic set of abiotic conditions for growing these sporelings was defined.