Facultad de Ciencias de la Vida

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http://repositorio.unab.cl//handle/ria/2068

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En 2018 se fusionan la Facultad de Ciencias Biológicas, con la Facultad de Ecología y Recursos Naturales y se crea la Facultad de Ciencias de la Vida (Fac.CV)

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Detection of antimicrobial-resistant Enterobacterales in insectivorous bats from Chile
(Royal Society Publishing, 0023-11) Rojas-Sereno, Zulma Esperanza; Streicker, Daniel G; Suarez-Yana, Tania; Lineros, Michelle; Yung, Verónica; Godreuil, Sylvain; Benavides, Julio A
Enterobacterales of clinical importance for humans and domestic animals are now commonly detected among wildlife worldwide. However, few studies have investigated their prevalence among bats, particularly in bat species living near humans. In this study, we assessed the occurrence of Extended-spectrum beta-lactamase-producing (ESBL) and carbapenemase-resistant (CR) Enterobacterales in rectal swabs of bats submitted to the Chilean national rabies surveillance program from 2021 to 2022. From the 307 swabs screened, 47 (15%) harboured cefotaxime-resistant Enterobacterales. Bats carrying these bacteria originated from 9 out of the 14 Chilean regions. Most positive samples were obtained from Tadarida brasiliensis (n = 42), but also Lasiurus varius, L. cinereus and Histiotus macrotus. No Enterobacterales were resistant to imipenem. All ESBL-Enterobacterales were confirmed as Rahnella aquatilis by MALDI-TOF. No other ESBL or CR Enterobacterales were detected. To our knowledge, this is the first screening of antibiotic-resistant bacteria in wild bats of Chile, showing the bat faecal carriage of R. aquatilis naturally resistant to cephalosporins, but also including acquired resistance to important antibiotics for public health such as amoxicillin with clavulanic acid. Our results suggest unknown selective pressures on R. aquatilis, but low or no carriage of ESBL or CR Escherichia coli and Klebsiella spp. Future studies should assess the zoonotic and environmental implications of R. aquatilis, which are likely present in the guano left by bats roosting in human infrastructures. © 2023 The Authors.
NEDD4-1 deficiency impairs satellite cell function during skeletal muscle regeneration
(BioMed Central Ltd, 0023-12) Cabezas, Felipe; Cabello-Verrugio, Claudio; González, Natalia; Salas, Jeremy; Ramírez, Manuel J.; de la Vega, Eduardo; Olguín, Hugo C
Background: Satellite cells are tissue-specific stem cells primarily responsible for the regenerative capacity of skeletal muscle. Satellite cell function and maintenance are regulated by extrinsic and intrinsic mechanisms, including the ubiquitin–proteasome system, which is key for maintaining protein homeostasis. In this context, it has been shown that ubiquitin-ligase NEDD4-1 targets the transcription factor PAX7 for proteasome-dependent degradation, promoting muscle differentiation in vitro. Nonetheless, whether NEDD4-1 is required for satellite cell function in regenerating muscle remains to be determined. Results: Using conditional gene ablation, we show that NEDD4-1 loss, specifically in the satellite cell population, impairs muscle regeneration resulting in a significant reduction of whole-muscle size. At the cellular level, NEDD4-1-null muscle progenitors exhibit a significant decrease in the ability to proliferate and differentiate, contributing to the formation of myofibers with reduced diameter. Conclusions: These results indicate that NEDD4-1 expression is critical for proper muscle regeneration in vivo and suggest that it may control satellite cell function at multiple levels. © 2023, The Author(s).
Removal of a partial genomic duplication restores synaptic transmission and behavior in the MyosinVA mutant mouse Flaile
(BioMed Central Ltd, 0023-12) Bustos, Fernando J.; Pandian, Swarna; Haensgen, Henny; Zhao, Jian-Ping; Strouf, Haley; Heidenreich, Matthias; Swiech, Lukasz; Deverman, Benjamin E.; Gradinaru, Viviana; Zhang, Feng; Constantine-Paton, Martha
Background: Copy number variations, and particularly duplications of genomic regions, have been strongly associated with various neurodegenerative conditions including autism spectrum disorder (ASD). These genetic variations have been found to have a significant impact on brain development and function, which can lead to the emergence of neurological and behavioral symptoms. Developing strategies to target these genomic duplications has been challenging, as the presence of endogenous copies of the duplicate genes often complicates the editing strategies. Results: Using the ASD and anxiety mouse model Flailer, which contains a partial genomic duplication working as a dominant negative for MyoVa, we demonstrate the use of DN-CRISPRs to remove a 700 bp genomic region in vitro and in vivo. Importantly, DN-CRISPRs have not been used to remove genomic regions using sgRNA with an offset greater than 300 bp. We found that editing the flailer gene in primary cortical neurons reverts synaptic transport and transmission defects. Moreover, long-term depression (LTD), disrupted in Flailer animals, is recovered after gene editing. Delivery of DN-CRISPRs in vivo shows that local delivery to the ventral hippocampus can rescue some of the mutant behaviors, while intracerebroventricular delivery, completely recovers the Flailer animal phenotype associated to anxiety and ASD. Conclusions: Our results demonstrate the potential of DN-CRISPR to efficiently remove larger genomic duplications, working as a new gene therapy approach for treating neurodegenerative diseases. © 2023, BioMed Central Ltd., part of Springer Nature.
Reduced microbial diversity of the nasopharyngeal microbiome in household contacts with latent tuberculosis infection
(Nature Research, 0023-12) Ruiz-Tagle, Cinthya; Ugalde, Juan A.; Naves, Rodrigo; Araos, Rafael; García, Patricia f; Balcells, María Elvira
The upper respiratory tract is an obliged pathway for respiratory pathogens and a healthy microbiota may support the host's mucosal immunity preventing infection. We analyzed the nasopharyngeal microbiome in tuberculosis household contacts (HHCs) and its association with latent tuberculosis infection (TBI). A prospective cohort of HHCs was established and latent TBI status was assessed by serial interferon-γ release assay (IGRA). Nasopharyngeal swabs collected at baseline were processed for 16S rRNA gene sequencing. The 82 participants included in the analysis were classified as: (a) non-TBI [IGRA negative at baseline and follow-up, no active TB (n = 31)], (b) pre-TBI [IGRA negative at baseline but converted to IGRA positive or developed active TB at follow-up (n = 16)], and (c) TBI [IGRA positive at enrollment (n = 35)]. Predominant phyla were Actinobacteriota, Proteobacteria, Firmicutes and Bacteroidota. TBI group had a lower alpha diversity compared to non-TBI (padj = 0.04) and pre-TBI (padj = 0.04). Only TBI and non-TBI had beta diversity differences (padj = 0.035). Core microbiomes’ had unique genera, and genus showed differential abundance among groups. HHCs with established latent TBI showed reduced nasopharyngeal microbial diversity with distinctive taxonomical composition. Whether a pre-existing microbiome feature favors, are a consequence, or protects against Mycobacterium tuberculosis needs further investigation. © 2023, The Author(s).
Ursodeoxycholic acid induces sarcopenia associated with decreased protein synthesis and autophagic flux
(BioMed Central Ltd, 0023-12) Orozco-Aguilar, Josué; Tacchi, Franco; Aguirre, Francisco; Valero-Breton, Mayalen; Castro-Sepulveda, Mauricio; Simon, Felipe; Cabello-Verrugio, Claudio
Background: Skeletal muscle generates force and movements and maintains posture. Under pathological conditions, muscle fibers suffer an imbalance in protein synthesis/degradation. This event causes muscle mass loss and decreased strength and muscle function, a syndrome known as sarcopenia. Recently, our laboratory described secondary sarcopenia in a chronic cholestatic liver disease (CCLD) mouse model. Interestingly, the administration of ursodeoxycholic acid (UDCA), a hydrophilic bile acid, is an effective therapy for cholestatic hepatic alterations. However, the effect of UDCA on skeletal muscle mass and functionality has never been evaluated, nor the possible involved mechanisms. Methods: We assessed the ability of UDCA to generate sarcopenia in C57BL6 mice and develop a sarcopenic-like phenotype in C2C12 myotubes and isolated muscle fibers. In mice, we measured muscle strength by a grip strength test, muscle mass by bioimpedance and mass for specific muscles, and physical function by a treadmill test. We also detected the fiber’s diameter and content of sarcomeric proteins. In C2C12 myotubes and/or isolated muscle fibers, we determined the diameter and troponin I level to validate the cellular effect. Moreover, to evaluate possible mechanisms, we detected puromycin incorporation, p70S6K, and 4EBP1 to evaluate protein synthesis and ULK1, LC3 I, and II protein levels to determine autophagic flux. The mitophagosome-like structures were detected by transmission electron microscopy. Results: UDCA induced sarcopenia in healthy mice, evidenced by decreased strength, muscle mass, and physical function, with a decline in the fiber’s diameter and the troponin I protein levels. In the C2C12 myotubes, we observed that UDCA caused a reduction in the diameter and content of MHC, troponin I, puromycin incorporation, and phosphorylated forms of p70S6K and 4EBP1. Further, we detected increased levels of phosphorylated ULK1, the LC3II/LC3I ratio, and the number of mitophagosome-like structures. These data suggest that UDCA induces a sarcopenic-like phenotype with decreased protein synthesis and autophagic flux. Conclusions: Our results indicate that UDCA induces sarcopenia in mice and sarcopenic-like features in C2C12 myotubes and/or isolated muscle fibers concomitantly with decreased protein synthesis and alterations in autophagic flux. © 2023, The Author(s).
Ontogenetically distinct neutrophils differ in function and transcriptional profile in zebrafish
(Nature Research, 0023-12) García-López, Juan P.; Grimaldi, Alexandre; Chen, Zelin; Meneses, Claudio; Bravo-Tello, Karina; Bresciani, Erica; Banderas, Alvaro; Burgess, Shawn M.; Hernández, Pedro P; Feijoo, Carmen G
The current view of hematopoiesis considers leukocytes on a continuum with distinct developmental origins, and which exert non-overlapping functions. However, there is less known about the function and phenotype of ontogenetically distinct neutrophil populations. In this work, using a photoconvertible transgenic zebrafish line; Tg(mpx:Dendra2), we selectively label rostral blood island-derived and caudal hematopoietic tissue-derived neutrophils in vivo during steady state or upon injury. By comparing the migratory properties and single-cell expression profiles of both neutrophil populations at steady state we show that rostral neutrophils show higher csf3b expression and migration capacity than caudal neutrophils. Upon injury, both populations share a core transcriptional profile as well as subset-specific transcriptional signatures. Accordingly, both rostral and caudal neutrophils are recruited to the wound independently of their distance to the injury. While rostral neutrophils respond uniformly, caudal neutrophils respond heterogeneously. Collectively, our results reveal that co-existing neutrophils populations with ontogenically distinct origin display functional differences. © 2023, Springer Nature Limited.
Impact of KDM6B mosaic brain knockout on synaptic function and behavior
(10.1038/s41598-024-70728-5, 0024-12) Brauer, Bastian; Ancatén-González, Carlos; Ahumada-Marchant, Constanza; Meza, Rodrigo C.; Merino-Veliz, Nicolas; Nardocci, Gino; Varela-Nallar, Lorena; Arriagada, Gloria; Chávez, Andrés E.; Bustos, Fernando J.
Autism spectrum disorders (ASD) are complex neurodevelopmental conditions characterized by impairments in social communication, repetitive behaviors, and restricted interests. Epigenetic modifications serve as critical regulators of gene expression playing a crucial role in controlling brain function and behavior. Lysine (K)-specific demethylase 6B (KDM6B), a stress-inducible H3K27me3 demethylase, has emerged as one of the highest ASD risk genes, but the precise effects of KDM6B mutations on neuronal activity and behavioral function remain elusive. Here we show the impact of KDM6B mosaic brain knockout on the manifestation of different autistic-like phenotypes including repetitive behaviors, social interaction, and significant cognitive deficits. Moreover, KDM6B mosaic knockout display abnormalities in hippocampal excitatory synaptic transmission decreasing NMDA receptor mediated synaptic transmission and plasticity. Understanding the intricate interplay between epigenetic modifications and neuronal function may provide novel insights into the pathophysiology of ASD and potentially inform the development of targeted therapeutic interventions. © The Author(s) 2024.
Global transcriptome profiles provide insights into muscle cell development and differentiation on microstructured marine biopolymer scaffolds for cultured meat production
(Nature Research, 0024-12) Bezjak, Dragica; Orellana, Nicole; Valdivia, Guillermo; Acevedo, Cristian A.; Valdes, Jorge H.
Biomaterial scaffolds play a pivotal role in the advancement of cultured meat technology, facilitating essential processes like cell attachment, growth, specialization, and alignment. Currently, there exists limited knowledge concerning the creation of consumable scaffolds tailored for cultured meat applications. This investigation aimed to produce edible scaffolds featuring both smooth and patterned surfaces, utilizing biomaterials such as salmon gelatin, alginate, agarose and glycerol, pertinent to cultured meat and adhering to food safety protocols. The primary objective of this research was to uncover variations in transcriptomes profiles between flat and microstructured edible scaffolds fabricated from marine-derived biopolymers, leveraging high-throughput sequencing techniques. Expression analysis revealed noteworthy disparities in transcriptome profiles when comparing the flat and microstructured scaffold configurations against a control condition. Employing gene functional enrichment analysis for the microstructured versus flat scaffold conditions yielded substantial enrichment ratios, highlighting pertinent gene modules linked to the development of skeletal muscle. Notable functional aspects included filament sliding, muscle contraction, and the organization of sarcomeres. By shedding light on these intricate processes, this study offers insights into the fundamental mechanisms underpinning the generation of muscle-specific cultured meat. © The Author(s) 2024.
A Deep Dive into the Trophic Ecology of Engraulis ringens: Assessing Diet Through Stomach Content and Stable Isotope Analysis
(Multidisciplinary Digital Publishing Institute (MDPI), 0024-12) Cárcamo, Carolina; Schultz, Eric T.; Leiva, Francisco; Saavedra, Alvaro; Klarian, Sebastian A.
Our study investigates the trophic ecology of the anchoveta (Engraulis ringens). The anchoveta plays a key role in the Greater Humboldt Ecosystem and is extensively exploited by countries from the south-eastern Pacific Ocean. For a comprehensive study of trophic ecology, we employed a combined approach that included stomach content analysis, stable isotope analysis, and scaled mass index of body condition. Our results showed that the multivariate composition of the diet varies significantly between life stage and fishing zones in Chile. Copepods and euphausiids emerged as the dominant prey found in the stomachs across all fisheries zones. Stable isotope analysis revealed significant differences among different zones. The scaled mass index values were higher in the northern zone compared to the southern zones, for both juveniles and adults. This research carries significant implications for fisheries management and conservation efforts, such as the development of targeted management strategies that address variations in the trophic structure of anchoveta across different life stages and fishing zones. © 2024 by the authors.
Unrolling the Systematics of a Southeastern Pacific Chiton
(Multidisciplinary Digital Publishing Institute (MDPI), 0024-12) Ibáñez, Christian M.; Sirenko, Boris
The species Chiton echinatus was first described by Barmes in 1824. Subsequently, it has been allocated to several widely distributed genera (e.g., Acanthopleura, Enoplochiton, Mesotomura) within the subfamily Acanthopleurinae. In order to resolve this species’ taxonomic uncertainty, specimens were collected throughout its entire distribution (i.e. from Peru and Chile) and subjected to a series of morphological and phylogenetic analyses. Scanning electron microscopy was used to improve this species’ morphological description, whereas publicly available sequences were used to infer its phylogenetic position. Morphological and phylogenetic analyses suggest that this species merits its own genus, endemic to the Southeastern Pacific. Of the aforementioned genera, Mesotomura appears to be the most appropriate designation. Therefore, it is proposed that the name Mesotomura echinata be restored, and the range of this species be extended to 39° S. © 2024 by the authors.
Large-scale molecular survey for piroplasmids in Iberian wild carnivores
(Springer Science and Business Media Deutschland GmbH, 0024-12-13) Millán, Javier; Checa, Rocío; Oleaga, Álvaro; Rodríguez, Alejandro; Negre, Nieves; Llaneza, Luis; Velarde, Roser; Miró, Guadalupe
Piroplasmids are vector-borne hemoprotozoan parasites belonging to the phylum Apicomplexa that are of veterinary and medical importance. Wild carnivores are hosts for diverse piroplasmids, some of which are highly pathogenic for domestic dogs and cats. A large-scale survey including samples from 244 individuals belonging to eleven different species that were opportunistically obtained between 1993 and 2015 in four Autonomous Regions in Spain were tested for piroplasmid DNA with two different nested-PCR assays targeting the 18S rRNA gene. Sixty of 85 Eurasian badgers (Meles meles), 11 of 42 red foxes (Vulpes vulpes), and 1 of 10 stone martens (Martes foina) resulted positive. In contrast, 46 wolves (Canis lupus), 26 genets (Genetta genetta), 22 pine martens (Martes martes), and other less-represented species were negative. Sequencing revealed that all foxes and one badger were parasitized by Babesia vulpes, and the remaining badgers and the stone marten by Babesia sp. badger type A (BBTA). The prevalence of BBTA in Catalonian badgers was significantly lower in Alpine than in Continental and Mediterranean climates. This study confirms that badgers and ref foxes constitute the natural hosts of BBTA and B. vulpes, respectively, with occasional spillovers to other species. © The Author(s) 2024.
Hydatigera parva population genetics in Iberian rodents provides insights into its introduction from Africa
(Cambridge University Press, 0025) Miljević, Milan; Rajičić, Marija; Marco, Javier; Blagojević, Jelena; Rodríguez-Pastor, Ruth; Bajić, Branka; Millán, Javier
This study investigated the prevalence and genetic diversity of Hydatigera parva in 341 native rodents in a riparian habitat in the Mediterranean part of Spain. Polycephalic larvae were found in 32% of wood mice (Apodemus sylvaticus; n=84) and 0.4% of Algerian mice (Mus spretus; n=257) examined, with a significantly higher prevalence in the former. No significant differences in infection prevalence in wood mouse were found between sex and age groups, habitats (agricultural vs natural), or seasons. Genetic analysis of 25 cysts using cox1 sequences revealed low nucleotide (0.00110) and haplotype diversity (0.380), suggesting limited genetic variation. Phylogenetic analysis showed that the studied H. parva isolates were genetically distinct from other species within the genus Hydatigera. The results support the hypothesis that H. parva was introduced to Europe from Africa, possibly with its final host, the common genet (Genetta genetta), an abundant predator in the study area, and suggest a lower genetic diversity in Europe than in African populations. This study is the first population genetic study of H. parva in the Iberian Peninsula. It provides insights into the population structure of the parasite and its interaction with rodent hosts, and thereby constitutes an example of the potential identification of an introduction route of a parasite with its definitive host. It also confirms the importance of the wood mouse as an intermediate host for the maintenance of the parasite's life cycle in Europe and forms the basis for further studies on the distribution and genetic diversity of H. parva. © The Author(s), 2025.
Production of minicell-like structures by Escherichia coli biosynthesizing cadmium fluorescent nanoparticles: a novel response to heavy metal exposure
(BioMed Central Ltd, 0025) Valenzuela-Ibaceta, Felipe; Álvarez, Sergio A.; Pérez-Donoso, José M.
The bacterial synthesis of fluorescent semiconductor nanoparticles or quantum dots (QDs), presents a sustainable method for producing nanomaterials with customized optical properties and significant technological potential. However, the underlying cellular mechanisms for this process remain elusive. Specifically, the role of cellular structures in QD generation has not been thoroughly investigated. In this study, we examined the morphological changes in Escherichia coli during the biosynthesis of cadmium sulfide (CdS) QDs, using a strain overexpressing the gshA gene to promote QD biosynthesis through increased glutathione (GSH) levels. Microscopy analyses revealed that fluorescence emission associated with QDs was concentrated at the cell poles, along with fluorescence emission from small spherical cells, a phenomenon exclusively detectable during QD biosynthesis. Transmission electron microscopy (TEM) revealed electron-dense nanomaterials localized at the cell poles. Furthermore, it was demonstrated the formation of minicell-like structures (∼ 0.5 μm in diameter) originating from these poles under biosynthesis conditions. These minicells encapsulated nanometric electron-dense material. Additional analyses indicated that minicells contained inclusion bodies, likely formed due to gshA overexpression and cadmium stress. Our findings confirms the role of minicells as a bacterial mechanism for sequestering cadmium at the cell poles and expelling the metal in the form of nanoparticles. This underscores the importance of minicells in bacterial physiology and stress responses, introducing a novel mechanism for heavy metal detoxification in bacteria. © The Author(s) 2025.
SNX5 promotes antigen presentation in B cells by dual regulation of actin and lysosomal dynamics
(Life Science Alliance, LLC, 0025-01) Cabrera-Reyes, Fernanda; Contreras-Palacios, Teemly; Jara-Wilde, Jorge; Caballero, Mia; Quiroga, Clara; Feijoo, Carmen G.; Díaz-Muñoz, Jheimmy; Yuseff, María-Isabel
B cells rapidly adapt their endocytic pathway to promote the uptake and processing of extracellular antigens recognized through the B-cell receptor (BCR). The mechanisms coupling changes in endomembrane trafficking to the capacity of B cells to screen for antigens within lymphoid tissues remain unaddressed. We investigated the role of SNX5, a member of the sorting nexin family, which interacts with endocytic membranes to regulate vesicular trafficking and macropinocytosis. Our results show that in steady state, B cells form SNX5-rich protrusions at the plasma membrane, which dissipate upon interaction with soluble antigens, whereas B cells activated with immobilized antigens accumulate SNX5 at the immune synapse where it regulates actin-dependent spreading responses. B cells silenced for SNX5 exhibit enlarged lysosomes, which are not recruited to the synaptic membrane, decreasing their capacity to extract immobilized antigens. Overall, our findings reveal that SNX5 is critical for actin-dependent plasma membrane remodeling in B cells in-volved in antigen screening and immune synapse formation, as well as endolysosomal trafficking required to promote antigen extraction and presentation. © 2024 Cabrera-Reyes et al.
Production of minicell-like structures by Escherichia coli biosynthesizing cadmium fluorescent nanoparticles: a novel response to heavy metal exposure
(BioMed Central Ltd, 0025-12) Valenzuela-Ibaceta, Felipe; Álvarez, Sergio A.; Pérez-Donoso, José M.
The bacterial synthesis of fluorescent semiconductor nanoparticles or quantum dots (QDs), presents a sustainable method for producing nanomaterials with customized optical properties and significant technological potential. However, the underlying cellular mechanisms for this process remain elusive. Specifically, the role of cellular structures in QD generation has not been thoroughly investigated. In this study, we examined the morphological changes in Escherichia coli during the biosynthesis of cadmium sulfide (CdS) QDs, using a strain overexpressing the gshA gene to promote QD biosynthesis through increased glutathione (GSH) levels. Microscopy analyses revealed that fluorescence emission associated with QDs was concentrated at the cell poles, along with fluorescence emission from small spherical cells, a phenomenon exclusively detectable during QD biosynthesis. Transmission electron microscopy (TEM) revealed electron-dense nanomaterials localized at the cell poles. Furthermore, it was demonstrated the formation of minicell-like structures (∼ 0.5 μm in diameter) originating from these poles under biosynthesis conditions. These minicells encapsulated nanometric electron-dense material. Additional analyses indicated that minicells contained inclusion bodies, likely formed due to gshA overexpression and cadmium stress. Our findings confirms the role of minicells as a bacterial mechanism for sequestering cadmium at the cell poles and expelling the metal in the form of nanoparticles. This underscores the importance of minicells in bacterial physiology and stress responses, introducing a novel mechanism for heavy metal detoxification in bacteria. © The Author(s) 2025.
Effect of drought disturbance in a sclerophyll forest on the micromammal community in the Río Clarillo National Park, Metropolitan Region, Chile
(0716078X, 0025-12) Fletcher, Susan; Sarmiento, Carlos; Stotz, Gisela C.; Quirici, Verónica
Background: Micromammals play an important role in mediterranean ecosystems. The “megadrought” in the sclerophyll forest has caused a “browning” that implies, among other things, the reduction of canopy cover. The effects of forest browning on the taxonomic and functional diversity of micromammals were evaluated. Methods: Forests with high and low disturbance degree were characterized based on the level of browning and canopy cover. To study the community of micromammals in these forests, the Capture-Mark-Recapture method was used with Sherman traps. Community indices such as Shannon–Wiener and Pielou were calculated. The Coefficient of Variation was used to study functional diversity for each trait separately. Multivariate measures FRic, FEve and FDiv were used to determine multidimensional diversity. Results: We observed differences in species composition and in richness, diversity, and cover variables between forest types. However, micromammal communities were similar in taxonomic and functional diversity in highly and slightly disturbed forests. Discussion: The micromammal community appears to show some resistance to forest changes due to disturbance, which could be related to their generalist diet and high dispersal capacity. The presence of the genus Rattus could entail a decrease in native rodent diversity and could have a greater effect than the disturbance of the forest due to drought. These results are an invitation to conduct long-term studies to better understand the potential vulnerability of the different micromammal species to disturbed sclerophyll forests affected by drought. © The Author(s) 2025.
Respuesta productiva de la trucha arcoiris (Oncorhynchus mykiss) alimentadas con dietas extruidas isoproteicas con distintos niveles de energía
(Universidad Andres Bello, 1995) Barra Toro, Felipe E. de la.; Galleguillos Munizaga, Carlos; Facultad de Ingeniería; Escuela de Ingeniería en Acuicultura
Se midió la respuesta productiva de la trucha arcoiris con un peso inicial de 80 g por 90 días, frente a 3 dietas de distinto tenor lipídico, 16, 22 y 30% , obteniendo niveles energéticos de 3500 , 4000 y 4600 Kcal EM/Kg de alimento respectivamente. El aporte protéico fue de 40% para todas las dietas. La dieta de mayor energía logró una mejor respuesta en la variable consumo de alimento y eficiencia de conversión alimenticia. Los indicadores productivos ganancia de peso y tasa de crecimiento diario no evidenciaron diferencias entre los distintos tratamientos. El rendimiento de la canal al final del ensayo fue superior para la dieta de menor energía. Referente al análisis químico de los filetes, éste arrojó un mayor contenido de grasa y menor tenor protéico a medida que se incrementó el nivel lipídico de la dieta.
Variación de los parámetros nutricionales de las microalgas de cultivo masivo
(Universidad Andrés Bello, 1996) Pino Osses, María Soledad; Farías Molina, Ana; Facultad de Ciencias Básicas y Humanas; Escuela de Ingeniería en Acuicultura
El cultivo de microalgas ha sido largamente estudiado desde principios de siglo. Sin embargo, el cultivo en el ámbito comercial se ha ido masificando en los últimos años.· Como este cultivo es auxiliar al de bivalvos, es necesario conocer los requerimientos de ellos para establecer las dietas microalgales a entregar, basándose en tipo de especie, tamaño y calidad nutricional. El trabajo realizado corresponde a establecer como varían los parámetros nutricionales de las microalgas más usadas en cultivo masivo como Jsochrysis galbana y Chaetoceros gracilis a través de su crecimiento. Los parámetros medidos fueron cuantificados como lípidos, proteínas y carbohidratos totales, usando los métodos de Bling & Dyer (1959), Bames & Blackstock (1973) modificado por Utting(l985) para Iípidos, Lowry et.al. (1951 ) modificado con TCA para proteínas y Dubois (1956) modificado por Hellebust & Craige (1978) para carbohidratos. Además se estableció como influyen los factores externos en la calidad nutricional de los cultivos. Los resultados obtenidos indican que los parámetros bioquímicos si varían a través de la curva de crecimiento de las especies y se ven influenciadas por fotoperíodo, temperatura y momento de cosecha. Estos fueron analizados estadísticamente usando un ANO VA Multifatorial (Statgraph 4.0). Puede concluirse que el maneJo de variables tales como temperatura y fotoperíodo para la obtención de cultivos de una buena calidad nutricional, va a depender de las especies que se estén cultivando, así como de los medios de cultivos utilizados. Por otro lado, el establecer en que etapa de crecimiento es mejor cosechar microalgas, va a influir directamente en la calidad nutricional de los cultivos.
Características reproductivas de los machos de salmón salar variación temporal
(Universidad Andrés Bello, 1996) Izurieta Gimeno, Rodrigo Javier; Díaz, Nelson; Facultad de Ciencias de la Vida
Basado en el escaso éxito, no superior al 50% de sobrevida, de producción de ovas embrionadas de salmón del Atlántico con reproductores criados en Chile, y el reducido estudio de los gametos de los: machos y sus variaciones dentro de una misma temporada de desove, se hace necesario determinar la variación de calidad y cantidad de los gametos masculinos y su influencia en la fecundación de las ovas. La determinación de las variaciones de la calidad y cantidad del semen se realizó en un grupo de 126 machos, donde se estudiaron la producción total de semen, su color y textura, para cada ejemplar y la motilidad de los espermios bajo el microscopio, con activador símil al líquido ovárico controlando además la muerte del 75 y 100% de los espermios, por muestra. Para determinar la densidad espermática se utilizó un método espectrofotométrico, midiéndose absorvancia a 505 nm, interpolando luego los valores en una curva de calibración que relaciona densidad óptica con número de espermios por ml. Para el análisis de la capacidad fecundante se usó el método de ácido acético al 4% a las 110 UTA y "shocking" a 250 UTA, con un posterior control volumétrico de las ovas vivas.
Respuesta productiva de la trucha arcoiris (Oncorhynchus mykiss) frente a distintas tasas de alimentación
(Universidad Andrés Bello, 1997) Longa Cordero, Marcia A.; Galleguillos Munizaga, Carlos; Facultad de Ecología y Recursos Naturales; Escuela de Ciencias del Mar
Se estudió el efecto de distintas tasas de alimentación (1,4- 1,7- 2,0%) de una dieta extruida para la fase de engorda en trucha arcoiris (Oncorhynchus mykiss) tipo pan- size, desde los 70 +/- 5 gr. por 90 días, evaluando su respuesta productiva, rendimiento de la canal, composición química corporal, mortalidad, índice de condición y conveniencia económica del uso de restricción alimenticia. La respuesta productiva se evaluó a través de las variables peso vivo, ganancia de peso, consumo de alimento, eficiencia de conversión alimenticia y tasa de crecimiento diario. Se encontraron diferencias estadísticamente significativas (P < 0,05 ) a favor del grupo alimentado al 1,4% , para consumo de alimento y eficiencia de conversión alimenticia. Para las variables ganancia de peso y tasa de crecimiento diario los resultados fueron similares para los grupos con mayores tasas de alimentación; sin embargo, ambos evidenciaron diferencias estadísticamente significativas (P < 0,05 ) , respecto al tratamiento alimentado al 1,4%. El rendimiento de la canal, la mortalidad y el índice de condición no presentaron diferencias significativas (P > 0,05) entre los tres tratamientos. La composición química de los filetes no se vio afectada en cuanto al nivel de proteínas (P > 0,05 ); sin embargo, se observó diferencias estadísticamente significativas (P < 0,05 ) en el tenor graso entre el grupo de mayor alimentación frente a los restantes tratamientos. El análisis de costos evidenció diferencias estadísticamente significativas (P < 0,05 ) en los tres grupos, siendo el tratamiento con menor tasa de alimentación el que logró inferiores costos en la producción del kg. de trucha bruto y neto.

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