Browsing by Author "AVILA, M"

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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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    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.
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    PHOTOPERIOD AND TEMPERATURE REGULATION OF THE LIFE-HISTORY OF PORPHYRA-COLUMBINA (RHODOPHYTA, BANGIALES) FROM CENTRAL CHILE
    (1986) AVILA, M; SANTELICES, B; MCLACHLAN, J
    The effects of temperature (10, 15, 20.degree. C) and photoperiod (8:16, 12:12. 16:8 (hours of light:hours of dark)) on the growth and reproduction of different stages in the life history of Porphyra columbina Montagne were assessed. The conchocelis phase had higher growth rates at 12 h light: 12 h dark, 45 .mu.mol m-2s-1, and 15.degree. C. Under all the temperatures and photoperiods tested, the conchocelis phase could propagate either by monospores or vegetative fragmentation. Conchosporangia were formed only at 10.degree. C and 8 h light: 16 h dark or at 15.degree. C and either 8 h light:16 h dark or 12 h light: 12 h dark. Long photoperiods inhibited conchosporangia formation at all temperatures tested with the exception of 20.degree. C and 16 h light: 8 h dark, where sporangia was formed once. Conchospores were released when the temperature was decreased (15 to 10.degree. C) maintaining the photoperiod, Conchospore germination occurred under the three photoperiods and temperatures tested. Growth of juvenile fronds was maximum at 15.degree. C and either 12 h light: 12 h dark of 16 h light: 8 h dark. Fronds formed carpospores and spermatia at 15.degree. C and 16 h light: 8 h dark only. With optimum conditions the life history was completed in 60 days. Spermatia had three chromosomes (n = 3).