Browsing by Author "Opitz, Tania"

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    Effects of predation risk on survival, behaviour and morphological traits of small juveniles of Concholepas concholepas (loco)
    (2013) Manriquez, Patricio H.; Elisa Jara, Maria; Opitz, Tania; Carlos Castilla, Juan; Lagos, Nelson A.
    In marine systems, water-borne chemical cues may induce anti-predator responses that influence not only performance and survival of the prey, but also population dynamics and species interaction. The early life stages of marine species with complex life-cycles settle into unpredictable habitats, and therefore may be expected to exploit reliable chemical cues emanating from both prey and predators in order to promote plastic responses to the local conditions. We compared the behavioural responses, survival and growth of early ontogenetic stages of Con cholepas concholepas exposed to the risk of predation by natural predators that commonly co-occur with it in the intertidal: the crabs Homalaspis plana and Acanthocyclus hassleri and the asteroid Heliaster helianthus. Y-maze experiments indicated that C. concholepas use water-borne cues both to detect prey and deploy strong anti-predator behaviour. Our results indicate lower survival rates of small specimens of C. concholepas when they were maintained in the direct presence of predators rather than under control conditions. Similar results and growth inhibition were found with C. concholepas exposed to seawater in which the predators had been maintained. Quantification of feeding activity and shell thickness in response to predation risk indicated lower prey consumption and thicker shells when C. concholepas were exposed to crab odours compared to control conditions. Our results suggest that this behavioural receptiveness to water-borne cues may be responsible, in part, for the early plasticity of species with complex life-cycles such C. concholepas under natural conditions, facilitating predator avoidance and thus enhancing survival.
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    Geographic variation in trace-element signatures in the statoliths of near-hatch larvae and recruits of Concholepas concholepas (loco)
    (2012) Manriquez, Patricio H.; Galaz, Sylvana P.; Opitz, Tania; Hamilton, Scott; Paradis, George; Warner, Robert R.; Carlos Castilla, Juan; Labra, Fabio A.; Lagos, Nelson A.
    Spatial variation of trace elements in calcified structures (otoliths, statoliths, and shells) has been used to track the movements of individuals among habitats, and connectivity between marine populations. In the present study, we used laser ablation-inductively coupled plasma mass spectrometry to quantify the concentrations of trace elements in statoliths of prehatch larvae and recruits of the gastropod Concholepas concholepas from 3 regions in Chile. We also examined spatial variation in chemical signatures deposited during larval life and at the time of settlement in intertidal habitats. We found significant differences between 3 geographic regions in the trace element concentrations recorded in natal statoliths of near-hatch larvae and in natal core and edge areas of recruit statoliths. Discriminant function analysis indicates that natal signatures of near-hatch larvae and the cores and edges of recruit statoliths show spatial segregation among regions. High levels of reclassification success of larvae to the origin region suggest potential for assigning recruits to the corresponding matching region. Concentrations of trace elements in the natal cores of recruit statoliths fell relatively close but did not overlap with the discriminant space occupied by larvae, and at regional scales the pattern of geographic variation of recruit statoliths resembles that of larval statoliths. This suggests population grouping and little population interchange at this regional scale. Assessing population stocks and connectivity of this species at smaller scales along the Chilean coast will only be possible with more finely structured sampling and a better understanding of temporal variation in the chemical environment.