ABSTRACT
Los embriones de tortugas marinas son susceptibles a perturbaciones ambientales, las cuales se traducen en anomalías en su fenotipo. Uno de los principales parámetros para la medición de estas perturbaciones es la asimetría en los carapachos (caparazones), que puede ser obtenida a través del Índice de Inestabilidad de Desarrollo (DIx, por sus siglas en inglés). La temperatura juega un rol importante, influenciando no solo en la futura supervivencia de los neonatos en temperaturas extremas (altas o bajas), sino en atributos específicos, tales como la determinación del sexo, o incluso puede ser la causa del incremento en el número de apéndices dérmicos (escudos) sobre la parte dorsal del carapacho. Este estudio evaluó la relación entre la temperatura de incubación con la asimetría de carapacho de los neonatos de Lepidochelys olivacea incubados en condiciones relocalizadas en el tortugario del Área de Usos Múltiples Hawaii en Santa Rosa, Guatemala. Para lograrlo, se replicaron las condiciones de anidación seleccionadas por las hembras anidadoras en nidos relocalizados, utilizando dispositivos termosensitivos para la toma de la temperatura durante el período de incubación. A través del cálculo del DIx en 210 neonatos, y mediante las pruebas de correlación de Kendall y Jockheere-Terpstra, se obtuvo que en valores de temperaturas extremas tanto altas (Kendall tau = .23, p < .001; JT = 2,891, p < .001), como bajas (Kendall tau u= -.21, p < .001; JT = 5,005, p < .001), así como en altos rangos de variación durante el período de desarrollo embrionario (Kendall tau = .23, p < .001; JT = 6,619, p < .05), los neonatos presentan una mayor asimetría.
Sea turtle embryos are susceptible to environmental disturbances, which result in abnormalities in their phenotype. One of the main parameters for measuring these disturbances is the asymmetry in the carapaces, which can be obtained through the Developmental Instability Index (DIx). Temperature plays an important role, influencing not only the future survival of hatchlings in extreme temperatures (high or low), but also specific attributes, such as sex determination, or it can even be the cause of the increase in the number of dermal appendages (shields) on the dorsal part of the carapace. This aimed to evaluate the relationship between incubation temperature and carapace asymmetry of Lepidochelys olivacea hatchlings incubated in relocated conditions in the Hawaii Multiple Use Area turtle rookery in Santa Rosa, Guatemala. To achieve this, the nesting conditions selected by the nesting females were replicated in relocated nests, using thermosensitive devices to measure the temperature during the incubation period. îrough the calculation of DIx in 210 hatchlings, and using Kendall and Jockheere-Terpstra correlation tests, it was obtained that hatchlings present greater asymmetry in values of extreme temperatures, for both, high (Kendall: p<.05, tau = .232 ; JT p<.05, JT=2891) and low (Kendall: p<.05, tau= -.211 ; JT p<.05, JT=5005); as well as in high ranges of variation (Kendall: p<.05, tau= .231 ; JT p<.05, JT=6619), during the embryonic development period
ABSTRACT
ABSTRACT The population dynamics of a species tends to change from the core to the periphery of its distribution. Therefore, one could expect peripheral populations to be subject to a higher level of stress than more central populations (the center–periphery hypothesis) and consequently should present a higher level of fluctuating asymmetry. To test these predictions we study asymmetry in wing shape of five populations of Drosophila antonietae collected throughout the distribution of the species using fluctuating asymmetry as a proxy for developmental instability. More specifically, we addressed the following questions: (1) what types of asymmetry occur in populations of D. antonietae? (2) Does the level of fluctuating asymmetry vary among populations? (3) Does peripheral populations have a higher fluctuating asymmetry level than central populations? We used 12 anatomical landmarks to quantify patterns of asymmetry in wing shape in five populations of D. antonietae within the framework of geometric morphometrics. Net asymmetry – a composite measure of directional asymmetry + fluctuating asymmetry – varied significantly among populations. However, once net asymmetry of each population is decomposed into directional asymmetry and fluctuating asymmetry, most of the variation in asymmetry was explained by directional asymmetry alone, suggesting that populations of D. antonietae have the same magnitude of fluctuating asymmetry throughout the geographical distribution of the species. We hypothesize that larval development in rotting cladodes might play an important role in explaining our results. In addition, our study underscores the importance of understanding the interplay between the biology of a species and its geographical patterns of asymmetry.
ABSTRACT
La capacidad de un organismo para producir un fenotipo ideal, pese a las perturbaciones encontradas durante su desarrollo, es el mecanismo causal de la estabilidad del desarrollo (ED). Esta capacidad es utilizada para evaluar variedad de tipos de estrés y la capacidad genotípica de corregirlos. La herramienta de medición más utilizada para estimar la ED es la asimetría fluctuante (AF), siendo esta una medida de las pequeñas desviaciones al azar que ocurren entre el lado izquierdo y derecho de rasgos bilateralmente simétricos. El estudio de AF, por su simplicidad de manejo y rapidez en la obtención de resultados, se ha convertido en un foco de interés para la biología, y durante los últimos años el aumento en artículos publicados usando AF para evaluar perturbaciones en la ED ha sido progresivo, pero aun así existen muchas interrogantes de cuales son las causas subyacentes que generan la AF. La presente revisión recopila información sobre el avance en los estudios del uso de la AF, su metodología, mecanismos, ventajas y controversias en el tiempo, y propone que es estrictamente necesario generar una mejor comprensión de esta herramienta, producto de eso, la utilización de modelos más exactos de estudio que signifiquen (o justifiquen) un enfoque unificado en el análisis de los patrones en AF y ED.
The ability of an organism to produce an ideal phenotype, despite the disturbances encountered during its development is the causal mechanism of the developmental stability (DS). This ability is used to evaluate a variety of stress types and the genotypic ability to correct them. The measurement tool mostly used to estimate the DS is the fluctuating asymmetry (FA), this being a small measure of random deviations that occur between the left and right sides of bilaterally symmetrical features. The study of FA management in its simplicity and speed in obtaining results has become the focus of interest in biology, and during the last years, and although there has been a progressive increase in published articles using FA to evaluate disturbances in the DS, many questions remain as to what constitutes the underlying causes that generate FA. This review compiles information on the progress in studies of FA use, its methodology, mechanisms, benefits and controversies in time, and proposes that it is strictly necessary to generate a better understanding of this tool, and as a result the use of more precise study models that justify a unified approach to the analysis of patterns in FA and DS.