Biology subjects

Marquez, F.

Publications and source records attributed to Marquez, F..

5 recordsLinked to original sources

bioRxiv2024

Otolith shape variability of labrid fish from Rapa Nui (Easter Island), southeastern Pacific

Fish otolith shape provides valuable insights into the taxonomic, phylogenetic, and ecological traits of fish species. This study aimed to assess and compare the phenotypic variation in otolith shape among four labrid species (Anampses femininus, Coris debueni, Pseudolabrus fuentesi and Thalassoma lutescens) inhabiting Rapa Nui (Easter Island) in the southeastern Pacific Ocean, utilizing geometric morphometrics and aging methods. Age estimation based on otolith structure indicated that collected specimens were adults, ranging between 1 and 3 years old. Allometric analysis revealed low but significant variation (5.40%), primarily driven by changes in otolith width, resulting in distinct morphologies. Principal Component Analysis (PCA) of sagittal otoliths elucidated significant morphospace variation among species, with the first two PCs explaining 60.3% of the total variance. PC1 distinguished between elongated sagittal shapes (e.g., P. fuentesi) and robust sagittae (e.g., T. lutescens), while PC2 correlated with otolith roundness, delineating variations within species. Canonical variate analysis further highlighted differences in otolith shape, with significant variations detected among all species. The Discriminant function analysis showed high levels of discrimination accuracy for most of species pairs. Except for C. debueni-P. fuentesi (89%) and C. debueni-T. lutescens (96%), all other species pairs achieved 100% discrimination, highlighting the reliability of otolith shape as a distinguishing characteristic for the studied species. Overall, our findings emphasize the value of otolith shape analysis for characterizing and distinguishing Rapa Nui labrid species. This offers potential applications such as identifying prey within the digestive systems of large fish or bird predators in the vicinity of this isolated island in the South Pacific Ocean or archaeofauna studies.

zoology↗

bioRxiv2023

The Shape of Cannabis sativa L. Seeds for the Differentiation of Commercial Medicinal Cultivars from Argentina.

The Cannabis sativa L. plant has been used since ancient times as food, a source of fiber, and medicine, resulting in crosses that led to hybridization that currently does not allow for morphological differentiation among the three varieties of the genus (sativa, indica, and ruderalis). Currently, three chemotypes are differentiated based on their cannabinoid content (THC/CBD). Starting in the year 2023, seeds of two contrasting chemotype medicinal cultivars developed by CONICET (National Council for Scientific and Technical Research) and registered with INASE (National Institute of Seeds) can be commercialized in Argentina. In a previous study, we reported a relationship between the shape of Cannabis seeds and the chemical fingerprint associated with the chemotype. The objective of this study is to morphometrically characterize the seeds of two cultivars of Cannabis sativa L. with contrasting chemotypes: type I (high THC) and type III (high CBD). For this purpose, 2D geometric morphometrics based on landmarks and semilandmarks were used, allowing for the independent study of shape and size variation. Seed size between cultivars was compared using univariate statistics of an unbiased size estimator. To understand the magnitude and direction of shape change and determine shape characters that maximize separation between cultivars, a multivariate statistical approach was employed. Seeds belonging to the Malvina cultivar (type I cultivar, THC only) had, on average, smaller size and a rounded shape, whereas seeds from the Pachamama cultivar (type III, high CBD content) had larger size and a tendency towards an elongated oval shape. The use of a discriminant function based on seed shape allowed for over 97% correct assignments between cultivars. Our results could be used for implementing seed shape as a quality and authenticity seal for registered cultivars in the Argentine Cannabis market.

plant biology↗

bioRxiv2022

Posterior white matter hyperintensities are associated with reduced medial temporal lobe subregional integrity and long-term memory in older adults

White matter hyperintensities are a marker of small vessel cerebrovascular disease that are strongly related to cognition in older adults. Similarly, medial temporal lobe atrophy is well-documented in aging and Alzheimers disease and is associated with memory decline. Here, we assessed the relationship between lobar white matter hyperintensities, medial temporal lobe subregional volumes, and hippocampal memory in older adults. We collected MRI scans in a sample of 139 older adults without dementia (88 females, mean age (SD) = 76.95 (10.61)). Participants were administered the Rey Auditory Verbal Learning Test (RAVLT). Regression analyses tested for associations among medial temporal lobe subregional volumes, regional white matter hyperintensities and memory, while adjusting for age, sex, and education and correcting for multiple comparisons. Increased occipital white matter hyperintensities were related to worse RAVLT delayed recall performance, and to reduced CA1, dentate gyrus, perirhinal cortex (Brodmann area 36), and parahippocampal cortex volumes. These medial temporal lobe subregional volumes were related to delayed recall performance. The association of occipital white matter hyperintensities with delayed recall performance was fully mediated statistically only by perirhinal cortex volume. These results suggest that white matter hyperintensities may be associated with memory decline through their impact on medial temporal lobe atrophy. These findings provide new insights into the role of vascular pathologies in memory loss in older adults and suggest that future studies should further examine the neural mechanisms of these relationships in longitudinal samples.

neuroscience↗

bioRxiv2021

Shell shape as an indicator of phenotypic stocks of Tehuelche scallop (Aequipecten tehuelchus) in Northern Patagonia, Argentina

Tehuelche scallop, Aequipecten tehuelchus, is a commercially exploited species in Northern Patagonia, Argentina. Without genetic differentiation at the species level, A. tehuelchus presents three morphotypes: tehuelchus, madrynensis, and a non-common variant felipponei. The main goal of this study was to analyze the shell shape variation of Tehuelche scallop to differentiate and identify the phenotypic stocks. The shape differences between and within the two main morphotypes (tehuelchus and madrynensis) were assessed using geometric morphometrics in nine localities. The shell shape presented variability at geographic scale, with the morphologic traits that maximized the differentiation among localities between the tehuelchus and madrynensis morphotypes. Scallops from madrynensis morphotype presented higher and circular shell discs with smaller auricles than those from tehuelchus morphotype. Morphometric differentiation was also detected among localities of each morphotype, wherein most of the variability was related to the disc circularity and the symmetry of the auricles. The presence of morphologic variation in San Matias and San Jose gulfs, wherein a single genetic pool is shared, evidenced the plastic nature of the species. Given the distribution of this resource in distinct provincial jurisdictions, the differentiation of phenotypic stocks has relevance in the context of fishery management, especially if zoning and rotational strategies are implemented.

ecology↗

bioRxiv2020

Mass mortality of foundation species on rocky shores: another reason why monitoring programs are relevant

Global concern around substantial losses of biodiversity has led to the development of a number of large-scale long-term monitoring programs. In the past few decades, networks were established to obtain appropriate data on the spatial and temporal variation of marine species on rocky shores. Recently, the Marine Biodiversity Observation Network Pole to Pole of the Americas program (MBON P2P) was established and is coordinating biodiversity surveys along coastal areas throughout the continent. In this context, the goal of this paper was to demonstrate whether the proposed MBON P2P sampling protocol is capable of detecting rapid declines in cover of foundation species on Patagonian rocky shores. Changes in mussel beds cover were studied on monitored sites in northern Patagonia. Concurrently, long-term mussel bed dynamics were assessed based on existing data. Results showed that a mussel mortality event could be detected with this methodology. It took less than a year for mussel cover to drop from 90 to almost 0% despite the fact that significant changes in mussel bed cover were not registered in the previous 20 years at the study area. Therefore, yearly monitoring is needed, as a minimum, in order to timely perceive this kind of process. Real-time detection offers the opportunity of properly understanding the causes that lead to the loss of key community components such as these foundation species. Furthermore, it would provide early warning to decision makers enhancing the chances of conservation of natural environments and their key ecosystem services.

systems biology↗