DSpace Angular :: Browsing by Author "Fernandez, Miriam"

Browsing by Author "Fernandez, Miriam"

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EMBRYONIC DEVELOPMENT, FEEDING AND INTRACAPSULAR OXYGEN AVAILABILITY IN TROPHON GEVERSIANUS (GASTROPODA: MURICIDAE)
(OXFORD UNIV PRESS, 2011) Cumplido, Mariano; Pappalardo, Paula; Fernandez, Miriam; Averbuj, Andres; Bigatti, Gregorio
Large-scale patterns of encapsulated embryo development and causal factors determining developmental success in the marine environment have been relevant issues of research for decades. We studied the embryonic development and intracapsular oxygen availability of Trophon geversianus in egg capsules from northern Patagonia (Golfo Nuevo, Argentina). The intracapsular embryonic development had a mean duration of 112 days (at 12-14 degrees C). The initial number of eggs per capsule was 197 (mean diameter 270 mu m), but on average only four embryos per capsule reached the juvenile stage. Embryos fed on nurse eggs (which disintegrated spontaneously 48 h after oviposition). The sequence of intracapsular developmental stages was recorded from egg to hatching occurred at the crawling stage (mean shell length 2.8 mm). Maximum growth rate was observed at the 'veliger' stage, while nurse eggs were consumed. A decrease in embryo number was observed between prehatching and hatching. Cannibalism was recorded in an egg capsule containing a prehatching embryo, which showed signs of shell drilling by the accessory boring organ. Intracapsular oxygen availability decreased from 90% during the cleavage stage to 45% of air saturation in the final stages of development (at 13 degrees C). Abnormal embryos were recognized in egg capsules, probably associated with food competition or oxygen limitation.
Integration of biophysical connectivity in the spatial optimization of coastal ecosystem services
(ELSEVIER, 2020) Ospina Alvarez, Andres; de Juan, Silvia; Davis, Katrina J.; Gonzalez, Catherine; Fernandez, Miriam; Navarrete, Sergio A.
Ecological connectivity in coastal oceanic waters is mediated by dispersion of the early life stages of marine organisms and conditions the structure of biological communities and the provision of ecosystem services. Integrated management strategies aimed at ensuring long-term service provision to society do not currently consider the importance of dispersal and larval connectivity. A spatial optimization model is introduced to maximise the potential provision of ecosystem services in coastal areas by accounting for the role of dispersal and larval connectivity. The approach combines a validated coastal circulation model that reproduces realistic patterns of larval transport along the coast, which ultimately conditions the biological connectivity and productivity of an area, with additional spatial layers describing potential ecosystem services. The spatial optimization exercise was tested along the coast of Central Chile, a highly productive area dominated by the Humboldt Current. Results show it is unnecessary to relocate existing management areas, as increasing no-take areas by 10% could maximise ecosystem service provision, while improving the spatial representativeness of protected areas and minimizing social conflicts. The location of protected areas was underrepresented in some sections of the study domain. principally due to the restriction of the model to rocky subtidal habitats. Future model developments should encompass the diversity of coastal ecosystems and human activities to inform integrative spatial management. Nevertheless, the spatial optimization model is innovative not only for its integrated ecosystem perspective, but also because it demonstrates that it is possible to incorporate time-varying biophysical connectivity within the optimization problem, thereby linking the dynamics of exploited populations produced by the spatial management regime. (C) 2020 Elsevier B.V. All rights reserved.
Microsatellite evidence for sperm storage and multiple paternity in the marine gastropod Crepidula coquimbensis
(ELSEVIER SCIENCE BV, 2011) Brante, Antonio; Fernandez, Miriam; Viard, Frederique
In gregarious species with copulation and internal fertilization, male-male competition and female cryptic choice may affect reproductive success of both sexes. We carried out a molecular analysis to study paternity and sperm use by females in the protandrous marine brooding gastropod Crepidula coquimbensis. In the field, a single female inhabits an empty hosting shell with up to six males. This gregarious behavior may promote intra-brood multiple paternity if females can store sperm from several consecutive copulations with the surrounding males. To study female sperm usage, the males sharing shelters with five different adult females were collected and preserved for paternity analysis. Females were transported alive to the laboratory and isolated for six months. After that, an additional male was offered to each of the five study females. Once the females had laid capsules, a total of 528 embryos from the five females were assigned paternity based on five microsatellite loci. Paternity analysis showed that every male sharing the empty hosting shell of a female as well as the additional male were assigned fatherhood of embryos laid by this specific female. Females can thus use sperms from multiple males including sperms stored for at least six months. In addition, in four out of the five offspring arrays, a similar contribution of each male to the brood was observed, a pattern associated with the close relationship between the number of fathers observed and the effective paternity index calculated. These results contrast with those of paternity analyses carried out in another species of the same genus. C. fornicata which is characterized by a stacking behavior in which the closest male to the female achieves the highest reproductive success. Male reproductive success may be largely influenced by the aggregation pattern and male mating opportunities in the Crepidula complex, a hypothesis to be examined further by studying other species exhibiting different grouping behavior. (C) 2010 Elsevier B.V. All rights reserved.
Navigating transformations in governance of Chilean marine coastal resources
(NATL ACAD SCIENCES, 2010) Gelcich, Stefan; Hughes, Terry P.; Olsson, Per; Folke, Carl; Defeo, Omar; Fernandez, Miriam; Foale, Simon; Gunderson, Lance H.; Rodriguez Sickert, Carlos; Scheffer, Marten; Steneck, Robert S.; Castilla, Juan C.
Marine ecosystems are in decline. New transformational changes in governance are urgently required to cope with overfishing, pollution, global changes, and other drivers of degradation. Here we explore social, political, and ecological aspects of a transformation in governance of Chile's coastal marine resources, from 1980 to today. Critical elements in the initial preparatory phase of the transformation were (i) recognition of the depletion of resource stocks, (ii) scientific knowledge on the ecology and resilience of targeted species and their role in ecosystem dynamics, and (iii) demonstration-scale experimental trials, building on smaller-scale scientific experiments, which identified new management pathways. The trials improved cooperation among scientists and fishers, integrating knowledge and establishing trust. Political turbulence and resource stock collapse provided a window of opportunity that triggered the transformation, supported by new enabling legislation. Essential elements to navigate this transformation were the ability to network knowledge from the local level to influence the decision-making processes at the national level, and a preexisting social network of fishers that provided political leverage through a national confederation of artisanal fishing collectives. The resultant governance scheme includes a revolutionary national system of marine tenure that allocates user rights and responsibilities to fisher collectives. Although fine tuning is necessary to build resilience of this new regime, this transformation has improved the sustainability of the interconnected social-ecological system. Our analysis of how this transformation unfolded provides insights into how the Chilean system could be further developed and identifies generalized pathways for improved governance of marine resources around the world.
Phylogeography and Biogeography Concordance in the Marine Gastropod Crepipatella dilatata (Calyptraeidae) along the Southeastern Pacific Coast
(OXFORD UNIV PRESS INC, 2012) Brante, Antonio; Fernandez, Miriam; Viard, Frederique
The biogeography and phylogeography concordance hypothesis suggests that the same factors, for instance physical barriers or environmental gradients, shape both species assemblages and intraspecific genetic structure. In the marine realm, previous studies have however suggested that phylogeographic patterns are also explained by the life-history strategy of the species. However, evidence is contradictory and comes mainly from the northern hemisphere, which is characterized by specific environmental conditions and evolutionary histories of species. In this work, we evaluated the concordance hypothesis in the southern Pacific using the marine gastropod Crepipatella dilatata as a case study. This intertidal species with direct development exhibited a restricted dispersal potential, a feature that contrasts with previous species studied in the same area. Using the gene cytochrome oxidase I, we analyzed 253 individuals sampled at 10 locations covering 543 km of the coast of Chile. The study sites also incorporated 2 biogeographic regions separated by a well-studied biogeographic break (at 30 degrees S). Populations of C dilatata displayed a high degree of genetic structure and a perfect match between phylogeographic and biogeographic breaks at 30 degrees S. When comparing our data with previous research over the same geographic range, life history traits related to dispersal ability seem to be a good proxy for explaining the concordance between biogeography and phylogeography along the southeastern pacific coast. In addition, in this and other marine invertebrate species, gene flow limitations across both sides of the 30 degrees S break may act as a driver of the speciation process.
Territorial User Rights for Fisheries as Ancillary Instruments for Marine Coastal Conservation in Chile
(WILEY-BLACKWELL, 2012) Gelcich, Stefan; Fernandez, Miriam; Godoy, Natalio; Canepa, Antonio; Prado, Luis; Carlos Castilla, Juan
Territorial user rights for fisheries have been advocated as a way to achieve sustainable resource management. However, few researchers have empirically assessed their potential as ancillary marine conservation instruments by comparing them to no-take marine protected areas. In kelp (Lessonia trabeculata) forests of central Chile, we compared species richness, density, and biomass of macroinvertebrates and reef fishes among territorial-user-right areas with low-level and high-level enforcement, no-take marine protected areas, and open-access areas in 42 100-m subtidal transects. We also assessed structural complexity of the kelp forest and substratum composition. Multivariate randomized permutation tests indicated macroinvertebrate and reef fish communities associated with the different access regimes differed significantly. Substratum composition and structural complexity of kelp forest did not differ among access regimes. Univariate analyses showed species richness, biomass, and density of macroinvertebrates and reef fishes were greater in highly enforced territorial-user-right areas and no-take marine protected areas than in open-access areas. Densities of macroinvertebrates and reef fishes of economic importance were not significantly different between highly enforced territorial-user-right and no-take marine protected areas. Densities of economically important macroinvertebrates in areas with low-level enforcement were significantly lower than those in areas with high-level enforcement and no-take marine protected areas but were significantly higher than in areas with open access. Territorial-user-right areas could be important ancillary conservation instruments if they are well enforced.
Thermal tolerance of larval stages of the Chilean kelp crab Taliepus dentatus
(INTER-RESEARCH, 2011) Storch, Daniela; Fernandez, Miriam; Navarrete, Sergio A.; Poertner, Hans Otto
Physiological responses of larval stages can differ from those of the adults, affecting key ecological processes. Therefore, developing a mechanistic understanding of larval responses to environmental conditions is essential vis-a-vis climate change. We studied the thermal tolerance windows, defined by lower and upper pejus (Tp) and critical temperatures (Tc), of zoea I, II, and megalopa stages of the Chilean kelp crab Taliepus dentatus. Tp limits determine the temperature range where aerobic scope is maximal and functioning of the organism is unrestrained, and were estimated from direct observations of larval activity. Tc limits define the transition from aerobic to anaerobic metabolism, and were estimated from the relationship between standard metabolic rate and temperature. Zoea I showed the broadest, zoea II an intermediate, and megalopae the narrowest tolerance window (Tp). Optimum performance in megalopae was limited to Tp between 11 and 15 degrees C, while their Tc ranged between 7 and 19 degrees C. Although Tc may be seldom encountered by larvae, the narrower Tp temperatures can frequently expose larvae to unfavorable conditions that can drastically constrain their performance. Temperatures beyond the Tp range of megalopae have been observed in most spring and summer months in central Chile, and can have important consequences for larval swimming performance and impair their ability to avoid predators or settle successfully. Besides the well-documented effects of temperature on development time, variability in field temperatures beyond Tp can affect performance of particular larval stages, which could drive large-scale variability in recruitment and population dynamics of T. dentatus and possibly other invertebrate species.

Browsing by Author "Fernandez, Miriam"

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