Browsing by Author "Manriquez, Patricio H."

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    Behavioural traits of competent Concholepas concholepas (loco) larvae
    (2011) Manriquez, Patricio H.; Carlos Castilla, Juan
    Swimming activity of competent Concholepas concholepas (Bruguiere, 1789) larvae, under different photoperiod, water turbulence and settlement cues were investigated in laboratory experiments. At night, larvae mainly swam to the water surface and then sank passively to the bottom. During the day, regardless of the photoperiod, larvae mainly stayed on the bottom, occasionally exhibiting upward movements. During the swimming period, larvae displayed the capacity to adhere to floating substrata through several mechanisms, including the secretion of a long and sticky mucous thread, air bubble capture or taking advantage of the water tension. The presence of C. concholepas prey, such as the mussel Semimytilus algosus and the chthamaloid barnacle Notochthamalus scabrosus, significantly influenced the swimming activity of competent C. concholepas larvae, inducing them to stay close to the bottom where prey were present. C. concholepas prey also triggered the initiation of larvae crawling, a characteristic of the early benthic life of C. concholepas. Although our laboratory experiments are proxies of nature, they are in good agreement with field observations in shallow nearshore areas (< ca. 0.5 km from shore) that recorded higher abundances of competent C. concholepas larvae (which are often associated with floating substrata) captured by surface planktonic tows during the night rather than day. Similarly, competent C. concholepas larvae abundances were higher in tows through inner nearshore foam slicks than in non-slick areas. The results suggest that the presence of endogenous swimming behaviour in these larvae may be a key factor enhancing adherence to floating substrata. The laboratory discovery of vertical buoyancy provides new information leading to a better understanding of the distribution and abundance patterns of these larvae in inner nearshore waters.
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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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    Fertilization efficiency and gamete viability in the ascidian Pyura praeputialis in Chile
    (2010) Manriquez, Patricio H.; Carlos Castilla, Juan
    In Chile, the ascidian Pyura praeputialis is an introduced species that occurs in intertidal and subtidal habitats restricted to Antofagasta Bay where it commonly forms extensive colonies that dominate mainly the rocky intertidal. Here we report the results of laboratory experiments conducted to determine the patterns of gamete spawning, and the consequences of the mode of reproduction, sperm age and sperm concentration on fertilization success. Our laboratory experiments indicate that the synchronous release of gametes takes place after the specimens are exposed to air, which is then followed by the formation of a biofoam in the rearing containers. Self fertilization with gametes obtained either by stripping or natural spawning failed to produce larvae or normal development, which occurred only when allosperm were used. Under laboratory conditions, fertilization success significantly decreased with sperm age and sperm concentration. Under field conditions, we recorded a negative effect of distance from areas with biofoam associated with spawning individuals on fertilization success. These findings suggest that it is selectively advantageous for this broadcast species to release gametes at low tide or after a period of emersion followed by biofoam formation. We suggest that this mechanism might have evolved to mitigate the difficulties of fertilization in turbulent aerated seawater, and to maximize fertilization success of short-lived gametes.
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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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    Morphological, physiological and behavioral responses of an intertidal snail, Acanthina monodon (Pallas), to projected ocean acidification and cooling water conditions in upwelling ecosystems
    (2022) Duarte, Cristian; Jahnsen-Guzman, Nicole; Quijon, Pedro A.; Manriquez, Patricio H.; Lardies, Marco A.; Fernandez, Carolina; Reyes, Miguel; Zapata, Javier; Garcia-Huidobro, M. Roberto; Lagos, Nelson A.
    Ocean acidification (OA) is expected to rise towards the end of the 21st century altering the life history traits in marine organisms. Upwelling systems will not escape OA, but unlike other areas of the ocean, cooling effects are expected to intensify in these systems. Regardless, studies evaluating the combined effects of OA and cooling remain scarce. We addressed this gap using a mesocosm system, where we exposed juveniles of the intertidal muricid snail Acanthina monodon to current and projected pCO(2) (500 vs. 1500 ppm) and temperature (15 vs. 10 degrees C) from the southeast Pacific upwelling system. After 9 weeks of experimental exposure to those conditions, we conducted three estimations of growth (wet weight, shell length and shell peristomal length), in addition to measuring calcification, metabolic and feeding rates and the ability of these organisms to return to the normal upright position after being overturned (self-righting). Growth, feeding and calcification rates increased in projected cooling conditions (10 degrees C) but were unaffected by pCO(2) or the interaction between pCO(2) and temperature. Instead, metabolic rates were driven by pCO(2), but a significant interaction with temperature suggests that in cooler conditions, metabolic rates will increase when associated with high pCO(2) levels. Snail self-righting times were not affected across treatments. These results suggest that colder temperatures projected for this area would drive this species growth, feeding and calcification, and consequently, some of its population biology and productivity. However, the snails may need to compensate for the increase in metabolic rates under the effects of ocean acidification. Although A. monodon ability to adjust to individual or combined stressors will likely account for some of the changes described here, our results point to a complex dynamic to take place in intertidal habitats associated with upwelling systems.
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    Ocean acidification alters anti-predator responses in a competitive dominant intertidal mussel
    (2022) Jahnsen-Guzman, Nicole; Lagos, Nelson A.; Quijon, Pedro A.; Manriquez, Patricio H.; Lardies, Marco A.; Fernandez, Carolina; Reyes, Miguel; Zapata, Javier; Roberto Garcia-Huidobro, M.; Labra, Fabio A.; Duarte, Cristian
    Widespread intertidal mussels are exposed to a variety of natural and anthropogenic stressors. Even so, our understanding of the combined influence of stressors such as predation risk and ocean acidification (OA) on these species remains limited. This study examined the response of the purple mussel (Perumytilus purpuratus), a species distributed along Pacific southeastern rocky shores, to the effects of predation risk and OA. Using a laboratory 2 x 2 cross design, purple mussels were either devoid or exposed to predator cues from the muricid snail Acanthina monodon, while simultaneously exposing them to current (500 ppm) or projected OA conditions (1500 ppm). The response of purple mussels to these factors was assessed using growth, calcification, clearance, and metabolic rates, in addition to byssus production. After 60 d, the presence of predator cues reduced mussel growth in width and length, and in the latter case, OA enhanced this response making the effects of predator cues more severe. Calcification rates were driven by the interaction between the two stressors, whereas clearance rates increased only in response to OA, likely explaining some of the growth results. Mussel byssus production also increased with pCO(2) but interacted with predation risk: in the absence of predator cues, byssus production increased with OA. These results suggest that projected levels of OA may alter and in some cases prevail over the natural response of purple mussels to predation risk. Considering the role played by this mussel as a dominant competitor and ecosystem engineer in rocky shores, these results have community-wide implications.
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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.