Browsing by Author "Manriquez, Patricio H."

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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.
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    Roles of larval behaviour and microhabitat traits in determining spatial aggregations in the ascidian Pyura chilensis
    (2007) Manriquez, Patricio H.; Castilla, Juan Carlos
    The large edible ascidian Pyura chilensis Molina, 1782 is a sessile suspension feeder that occurs in intertidal and subtidal habitats along the Chilean and Peruvian coasts. In these habitats the species, although solitary, is commonly found in highly aggregated assemblages and is seldom isolated. The results of a study to determine whether the observed field aggregations could be explained by larval behaviour, microhabitat with quiescent hydrodynamics, or both, are reported. Our laboratory experiments showed that P. chflensis larvae have a short pre-settlement period when maintained in the presence of artificial substratum conditioned with adult conspecific extract. Moreover, R chilensis larvae tended to settle in shaded areas. In the control treatment without conspecifics, or in illuminated areas, low numbers of P. chilensis settlers were found. In a 5-armed radial maze, under still water and low seawater flow regimens, larvae of F chilensis tended to swim toward and settle in chambers that contained water in which conspecific adults had been placed. In the field, we tested the hypothesis that larval settlement in P. chilensis differs depending on microhabitat traits such as water flow, mechanical disturbance and light intensity. We conducted quadrat sampling on low rocky platforms in contrasting microhabitats, such as around holdfasts of the kelp Lessonia nigrescens, kelp whiplash zones and between holdfasts. The majority of P. chilensis settlers were found on top of conspecific adults inhabiting shaded microhabitats and around kelp holdfasts. These results suggest that protected habitats and chemical cue-mediated larval response to waterborne conspecifics during the settlement period contribute to the formation of intertidal and shallow subtidal aggregations of P. chilensis. Given that the edible ascidian P. chilensis supports an important small-scale fishery and hosts an important associated community of macro- and micro-invertebrates, we suggest that our results should be considered when determining fisheries regulatory and management practices for this species.