Browsing by Author "Sepulveda, Roger D."

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    Differential ecological responses to environmental stress in the life history phases of the isomorphic red alga Gracilaria chilensis (Rhodophyta)
    (2013) Guillemin, Marie-Laure; Sepulveda, Roger D.; Correa, Juan A.; Destombe, Christophe
    In order to better understand the alternation of generations that characterizes haploid-diploid life cycles, we assessed the existence of ecological differences between the two phases (haploid gametophyte and diploid tetrasporophyte) in Gracilaria chilensis, a rhodophyte with a typical Polysiphonia-type life cycle. We investigated the effect of light intensity and salinity on viability and growth of both phases at different ontogenetic stages: juveniles and adults. In our study, the survival of juvenile gametophytes (n) was higher than the survival of juvenile tetrasporophytes (2n) despite culture conditions; however, low salinity had greater effect on carpospores (2n) than on tetraspores (n). On the other hand, a complex interaction between salinity and light intensity within each life history phase generated observed differences between juvenile growth rates. Low light was shown to trigger early onset of alteration of the holdfast growing pattern. In addition, adult tetrasporophytes showed, despite the conditions, a faster vegetative growth than female and male gametophytes. These differences between phases could have led to the complete dominance of tetrasporophyte fragments of fronds observed in G. chilensis farms. We hypothesize that Chilean fishers could have unknowingly selected for tetrasporophyte thalli during domestication of the species, thus enhancing the natural trend of tetrasporophytes dominance already present in estuarine natural populations of free-floating plants.
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    Masculinized females produce heavier offspring in a group living rodent
    (2016) Correa Kaempfe, Loreto Alejandra; León Letelier, Cecilia Alejandra; Ramírez Estrada, Juan Carlos; Soto Gamboa, Mauricio; Sepulveda, Roger D.; Ebensperger Pesce, Luis Alberto
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    On some ecological aspects of the lugworm Abarenicola affinis chiliensis Wells, 1963 (Polychaeta: Scolecida: Arenicolidae) from shallow soft bottoms of northern Chile
    (2007) Moreno, Rodrigo A.; Rozbaczylo, Nicolas; Sepulveda, Roger D.; Marinkovic, Milko I.; Arntz, Wolf E.; Thatje, Sven
    We conducted an ecological study of a population of the polychaete Abarenicola affinis chiliensis in the shallow subtidal zone of Caleta Guardiamarina Riquelme in northern Chile. The study area is characterized by a hypoxic bottom consisting of fine sands and a silt-clay mixture, with high values of total organic matter content (TOM > 20%). During the two study periods (spring 1996 and 1997), the numerical contribution of A. affinis chiliensis to the total macrofauna was greater than 80%. A similar pattern was recorded for biomass, with A. affinis chiliensis surpassing 95% of the total macrofauna biomass. Statistical analyses did not detect significant differences in environmental and biotic variables between years (with the exception of salinity, which increased slightly), indicating temporal stability of these variables over the study period. Our results do not support the hypothesis of Wells that seawater temperatures act as a physical barrier impeding the dispersal of Abarenicola species. This hypothesis should be reexamined for some representatives of Abarenicola on the Pacific coast of South America.
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    Thorson's rule, life-history evolution, and diversification of benthic octopuses (Cephalopoda: Octopodoidea)
    (2018) Ibanez, Christian M.; Rezende Landaeta, Enrico; Sepulveda, Roger D.; Avaria-Llautureo, Jorge; Hernandez, Cristian E.; Sellanes, Javier; Poulin, Elie; Cecilia Pardo-Gandarillas, M.