Browsing by Author "RODRIGUEZ, SR"

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    DISTRIBUTION PATTERNS OF TETRAPYGUS-NIGER (ECHINODERMATA, ECHINOIDEA) OFF THE CENTRAL CHILEAN COAST
    (1993) RODRIGUEZ, SR; OJEDA, FP
    We investigated spatial distribution and temporal occurrence patterns of Tetrapygus niger in the subtidal zone off the central Chilean coast from March to November 1990. The shallowest portion of the subtidal zone and the shallowest edge of the kelp forest of Lessonia trabeculata appeared to be important recruitment zones for this species. We found a significant number of recruits along the bed border, and a marked decrease of urchin abundance toward the center of the kelp. Data obtained in September and November outside the kelp bed showed juvenile urchins [i.e. <24 mm test diameter (TD)] strongly associated with crevices. Size-frequency distributions at 2 m depth for those months also showed a large trough of intermediate-sized individuals (i.e. 15 to 30 mm TD). Temporal analysis of size-frequency distributions of individuals collected outside the kelp showed a relatively slow shift of modes between March and September and a major modal shift from September to November. Density values of urchins found in November were relatively low; however, the individuals appeared aggregated.
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    METAMORPHOSIS OF LABORATORY-REARED LARVAE OF CONCHOLEPAS-CONCHOLEPAS (MOLLUSCA, GASTROPODA)
    (1994) CAMPOS, EO; PINTO, A; BUSTOS, E; RODRIGUEZ, SR; INESTROSA, NC
    Metamorphosis of laboratory-reared larvae of the gastropod Concholepas concholepas was observed under the influence of K+ ions. After 64 h of incubation at 10 degrees C, 58% of larvae metamorphosed in response to 20 mM K+ final concentration in seawater, 11 mM above ambient. No effect was observed at 15 mM K+. Likewise, larvae were unable to survive when exposed to 25 mM K+. Metamorphosed individuals of C. concholepas migrated to the water-air interface within 28 h of their metamorphosis. This study reports the first successful experiment on the induction of metamorphosis in laboratory-reared larvae of C. concholepas. The advantages of mass production of larvae with metamorphic capacity of this economically important resource, related to its eventual culture on a pilot scale are discussed.