Browsing by Author "Medina, Matias H."

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    Effects of copper on early developmental stages of Lessonia nigrescens Bory (Phaeophyceae)
    (2007) Contreras, Loretto; Medina, Matias H.; Andrade, Santiago; Oppliger, Valeria; Correa, Juan A.
    Copper effects on the early developmental gametophytic and sporophytic stages of the kelp Lessonia nigrescens were tested in gradients of increasing concentrations of ASV-Iabile copper. The results demonstrated a high sensitivity to copper of all life-history stages of the alga, where even the lowest tested concentration affected spore release as well as their subsequent settlement. More significant, concentrations higher than 7.87 mu g L-1 totally interrupted the development of the spores after they settle. This effect led to a failure in the formation of male and female ametophytes and, as a consequence, to a complete disruption of the normal life cycle of the kelp. Thus, we suggest that the absence of L. nigrescens from copper-enriched environments results from the high sensitivity of its early life cycle stages, which limits growth and maturation of the gametophytic microscopic phase and, as a consequence, prevents development of the macroscopic sporophytic phase. (c) 2006 Elsevier Ltd. All rights reserved.
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    Experimental transplants of the large kelp Lessonia nigrescens (Phaeophyceae) in high-energy wave exposed rocky intertidal habitats of northern Chile
    (2006) Correa, Juan A.; Lagos, Nelson A.; Medina, Matias H.; Castilla, Juan C.; Cerda, Mauricio; Ramirez, Marco; Martinez, Enrique; Faugeron, Sylvain; Andrade, Santiago; Pinto, Raquel; Contreras, Loretto
    Potential for addressing ecological and physiological issues becomes severely limited when the organisms required to experimentally test specific hypotheses are absent from the study areas. This report describes a simple and inexpensive device for re-planting kelps into the lower intertidal zone of wave-swept rocky habitats, using Lessonia nigrescens Bory as a model organism. The device allows a wide range of plant sizes to be anchored by the holdfast. Transplanted kelps regenerated, re-attached to the substratum and overgrew the transplanting device. These results confirm the feasibility of using this technique to tackle a variety of highly relevant questions involving ecological, physiological, conservation, restoration and management issues. (c) 2006 Elsevier B.V. All rights reserved.
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    Intraspecific biogeographic pattern breakage in the snapping shrimp Betaeus emarginatus caused by coastal copper mine tailings
    (2008) Lardies, Marco A.; Medina, Matias H.; Correa, Juan A.
    Environmental gradients are common in nature, and geographically widespread species must cope with environmental differences between habitats. Environmental differences produce bio-geographic patterns that can involve morphological, physiological, and life-history traits. The Bergmann's rule has been described as one of these ecological and evolutionary patterns, predicting an increase in body size towards colder climates. Human-induced polluting events could impair the performance and/or fitness of exposed individuals and populations. Thus, we hypothesized that species undergoing exposure to pollutants will show a breakage of the natural biogeographical variation of their fitness-related life-history traits. In northern Chile, copper mine tailings have been dumped continuously for more than 60 yr. Because the snapping shrimp Betaeus emarginatus is commonly found in intertidal pools near this dumping site, it was used as a study model. This shrimp has a pelagic larva and a wide distribution along the Chilean coast. Different life-history traits were studied in 5 populations over a range of 19 degrees of latitude along the Chilean coast. Population mean values for female body mass, egg volume, and reproductive output were positively correlated with latitude. In contrast, egg number was negatively correlated with latitude and positively correlated with temperature. Shrimps from the dumping site showed life-history trait values significantly lower than the range observed in areas with no copper enrichment, breaking the biogeographical patterns predicted by the Bergmann's rule. Such studies emphasize the need for integrating different concepts of organism and population ecology and life-history theory in the assessment of anthropogenic pollution.