237 research outputs found
Epigenesis and epigenetics: Examples from the morphology of tadpoles
La epigenética, como una disciplina científica que explora los mecanismos que originan nuevos fenotipos sin alterar el genoma, parece una novedad más ligada a los avances tecnológicos de la Biología Molecular y la Genética del Desarrollo. Sin embargo, el concepto de epigénesis fue propuesto mucho antes que las ideas de evolución y el papel de los genes en la continuidad de la vida cobraran forma. En este artículo, se analizan los conceptos de epigénesis y epigenética desde una amplia perspectiva biológica y para ello se utilizan como caso de estudio anurosde ambientes semiáridos de Norteamérica de la familia Scaphiopodidae y de Sudamérica de la familia Ceratophryidae. En ambos casos, se presentan las causas de las modificaciones en el desarrollo embrionario-larval que determinan que los tractos digestivos de los renacuajos resulten muy diferentes a los de la mayoría de los anuros y también se plantean los mecanismos moleculares que determinan cómo ocurre esta modificación. Al introducir los términos de epigénesis y epigenética con estos ejemplos se pretende demostrar la riqueza de interpretaciones que emergen al integrar múltiples enfoques del desarrollo animal.The epigenetic, as a scientific discipline that explores the mechanisms that give rise to new phenotypes with no genome alteration, emerged as a new approach related to innovations in Molecular Biology and Developmental Genetics. However, the concept of epigenesis was proposed long before the paradigms of evolution and the role of genes in the continuity of life could achieve scientific reputations. Herein, I analyzed the concepts of epigenesis and epigenetic from a broad biological perspective. Therefore, I used as cases of study the anurans of semiarid environments of North America, family Scaphiopodidae, and South America, family Ceratophryidae. In both cases, I present the causes of changes in the embryo-larval development that determine differences in the digestive tracts of those tadpoles from most of the anurans and also I emphasize on the molecular mechanisms that determine how this change occurs. By introducing the terms of epigenesis and epigenetic with these examples I intend to demonstrate the value to integrate multiple approaches to the study of animal development.Fil: Fabrezi, Marissa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentin
A developmental staging table for physalaemus biligonigerus (Cope, 1861) (Anura: Leptodactylidae)
Physalaemus biligonigerus is a leptodactylid frog that is widely distributed in southern South America and a common member of anuran assemblages that breed in temporary ponds near human settlements. Herein, we analyzed its embryonic and larval morphology through the completion of metamorphosis and constructed a normal table of development. In addition, the timing of development and growth data are provided. Development of P. biligonigerus from fertilization through metamorphosis takes 20-24 days. We recognized 46 discrete developmental stages on the basis of readily discerned, unambiguous, external traits that can be identified in preserved specimens. In contrast with the standard Gosner developmental table, we recognized several particularities in the development of this species. The staging criterion based on external gill morphology presented here is a novel approach to distinguish pre- A nd post-hatching stages, which could also be employed in other anuran species. We found that anal tube loss in P. biligonigerus occurs earlier than Gosner Stage 41; this trait is highly variable among species and should not be used as a standard criterion. Our analysis demonstrates the value of detailed specific staging tables to characterize anuran life cycles. Furthermore, we point out that the use of generalized standard tables might mask the richness of phenotypic variation during the ontogeny of anuran species.Fil: Chuliver Pereyra, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Fabrezi, Marissa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentin
Evolutionary and developmental considerations of the diet and gut morphology in ceratophryid tadpoles (Anura)
Background: Before metamorphosis, almost all anuran tadpoles are omnivores. Larval carnivory occurs in some species and, it is associated with distinctive morphotypes. Obligatory carnivorous tadpoles exhibit structural changes in the gastrointestinal tract compared to larvae that are predominately omnivores. The most distinctive feature of the anuran family Ceratophyridae (three genera) overall is the enormous gape of adults. This feature increases their ability to capture extremely large and active prey. The larvae of Ceratophyrid genera are remarkably distinct from each other and carnivory has diversified in a manner unseen in other anurans. The larvae of onegenus, Lepidobatrachus, has a massive gape like the adult. Herein, we report on larval developmental variation, diet, gross morphology of the gastrointestinal tract, and histology of the cranial segment of the gut before, during and after metamorphosis in larval series for the following ceratophryid species: Chacophrys pierottii, Ceratophrys cranwelli, Lepidobatrachus laevis and Lepidobatrachus llanensis. Results: We described patterns of larval development with variation in growth with consequence to the final size at the end of metamorphosis. These patterns seem to be influenced by food quantity/quality, and most predominant by animal protein. Prey items found in pre and post-metamorphic Lepidobatrachus spp. are similar. Tadpoles of Ceratophrys and Chacophrys (and other anurans) share a short cranial segment of the gut with an internal glandular, mucous secreting epithelium, a double coiled intestine and the sequence of metamorphic changes (tract is empty, the stomach differentiates and the intestine shortens abruptly). In contrast, Lepidobatrachus tadpoles have a true stomach that acquires thickness and increased glandular complexity through development. As larvae they have a short intestine without double coils, and the absence of intestine shortening during metamorphosis. Conclusions: The larval development of the gastrointestinal tract of Lepidobatrachus is unique compared with that of other free-living anuran larvae. An abrupt metamorphic transformation is missing and most of the adult structural features start to differentiate gradually at the beginning of larval stages.Fil: Fabrezi, Marissa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta-Jujuy. Instituto de Bio y Geociencias del Noroeste Argentino. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Instituto de Bio y Geociencias del Noroeste Argentino; ArgentinaFil: Cruz, Julio César. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta-Jujuy. Instituto de Bio y Geociencias del Noroeste Argentino. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Instituto de Bio y Geociencias del Noroeste Argentino; Argentin
Tópicos sobre la evolución
Surgió así este conjunto de contribuciones que decidimos llamar "Tópicos sobre la Evolución" que intenta presentar a la Evolución como un cuerpo de conocimientos que en su tiempo, Darwin trató de organizar e interpretar. También\ud
resaltamos algunos acontecimientos previos, como el nacimiento de la Geología como disciplina científica y el trabajo de los anatomistas comparados, que favorecieron y dieron argumentos a las ideas de Darwin.\ud
Desde su nacimiento, la obra de Darwin mantiene su vigencia y se enriquece. Si nos preguntamos qué es la evolución tendremos una infinidad de respuestas: para algunos es adaptación con especialización; para otros es la persistencia a lo largo del tiempo; hay quienes la consideran el resultado de una diversificación exitosa; y\ud
hay quienes enfatizan en las extinciones como un componente fundamental de los procesos evolutivos. Estas distintas miradas, parciales pero no equivocadas, tienden a responder preguntas que son inherentes a nuestra curiosidad
Morphology and function of the forelimb in arboreal frogs: specializations for grasping ability.
Frogs are characterized by a unique morphology associated with their saltatory lifestyle. Although variation in the form and function of the pelvic girdle and associated appendicular system related to specialized locomotor modes such as swimming or burrowing has been documented, the forelimbs have typically been viewed as relatively unspecialized. Yet, previous authors have noted versatility in forelimb function among arboreal frogs associated with feeding. Here we study the morphology and function of the forelimb and hand during locomotion in two species of arboreal frogs (Litoria caerulea and Phyllomedusa bicolor). Our data show a complex arrangement of the distal forelimb and hand musculature with some notable differences between species. Analyses of high‐speed video and video fluoroscopy recordings show that forelimbs are used in alternating fashion in a diagonal sequence footfall pattern and that the position of the hand is adjusted when walking on substrates of different diameters. Electromyographic recordings show that the flexors of the hand are active during substrate contact, suggesting the use of gripping to generate a stabilizing torque. Measurements of grasping forces in vivo and during stimulation experiments show that both species, are capable of executing a so‐called power grip but also indicates marked differences between species, in the magnitude of forces generated. Stimulation experiments showed an increased control of digit flexion in the more specialized of the two species, allowing it to execute a precision grip paralleled only by that seen in primates.Fil: Manzano, Adriana Silvina. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; ArgentinaFil: Abdala, Virginia Sara Luz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Biodiversidad Neotropical. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Biodiversidad Neotropical. Instituto de Biodiversidad Neotropical; ArgentinaFil: Herrel, Anthony. University of Antwerp; Bélgic
Phenotypic variation through ontogeny: thyroid axis disruption during larval development in the frog pleurodema borellii
Studies of the effects of thyroid hormones on larval development in the frog Xenopus spp. have provided baseline information to identify developmental constraints and elucidate genetic and hormonal mechanisms driving development, growth, and life history transitions. However, this knowledge requires data based on other anurans to complete a comprehensive approach to the understanding of larval developmental diversity and phenotypic variation through ontogeny. Mesocosm experiments provide realistic data about environmental conditions and timing; this information is useful to describe anuran larval development and/or analyze endocrine disruption. In this study, mesocosm experiments of the larval development of the frog Pleurodema borellii were conducted to explore the consequences of thyroid axis disruption; the sensitivity of tadpoles to the methimazole (2.66 mg/l) and thyroxine (T4) (1.66 μg/l) was compared. These concentrations were selected based on previous studies in Pleurodema borellii. We test the effects of methimazole and thyroxine on development in early exposure (from beginning of larval development) and late exposure, 18 days after hatching, with doses administered every 48 h. Tadpoles were evaluated 31 days after hatching. Methimazole caused moderate hypertrophy of the thyroid gland, alteration in the growth rates, differentiation without inhibition of development, and an increase of developmental variability. Thyroxine produced slight atrophy of the thyroid gland, accelerated growth rates and differentiation, and minor developmental variability. In tadpoles at stages previous to metamorphose, skull development (differentiation of olfactory capsules, appearance of dermal bones, and cartilage remodeling) seemed to be unaltered by the disruptors. Moreover, similar abnormal morphogenesis converged in specimens under methimazole and thyroxine exposures. Abnormalities occurred in pelvic and pectoral girdles, and vent tube, and could have been originated at the time of differentiation of musculoskeletal tissues of girdles. Our results indicate that premetamorphic stages (Gosner Stages 25–35) are sensitive to minimal thyroid axis disruption, which produces changes in developmental rates; these stages would also be critical for appendicular musculoskeletal morphogenesis to achieve the optimal condition to start metamorphosis.Fil: Fabrezi, Marissa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Cruz, Julio Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentin
Heterocronía y variación morfológica en anuros
El concepto de heterocronía está ligado a la variación en la ontogenia y es frecuente en estudios de morfología comparada, involucra tanto a caracteres individuales como a todo el organismo,al tamaño y a la forma y lleva implícito el tiempo en el cual ocurre una trayectoria ontogenética. El estudio de la heterocronía ha generado un conjunto de términos, definicionesy modelos en los que se confunde el origen de la variación (cambio heterocrónico) con sus consecuencias morfológicas en procesos evolutivos. En este trabajo se revisan algunos conceptos muy usados en el estudio de la heterocronía con ejemplos de la variación durante el desarrollo en anuros.Asociación Herpetológica Argentina (AHA
Anatomía craneal de larvas de Gastrotheca gracilis (Anura: hylidae)
Comprende el estudio del condrocráneo y aparato hiobranquial de larvas de Gastrotheca gracilis como fuente de caracteres taxonómicos.Asociación Herpetológica Argentin
Developmental changes and novelties in ceratophryid frogs
The Neotropical frog genera Ceratophrys, Chacophrys and Lepidobatrachus form the monophyletic family Ceratophryidae. Although in- and out-group relationships are not fully resolved, the monophyly of the three genera is well supported by both morphological and molecular data. Much is known about the morphology of the ceratophryids, but there is little comparative information on how modification of a common ancestral developmental pathway played a role in shaping their particular body plans. Herein, we review morphological variation during ceratophryid ontogeny in order to explore the role of development in their evolution. The ceratophryids are collectively characterized by rapid larval development with respect to other anurans, yet the three genera differ in their postmetamorphic growth rates to sexual maturity. Derived traits in the group can be divided into many homoplastic features that evolved in parallel with those of anurans with fossorial/burrowing behaviors in semiarid environments, and apomorphies. Morphological novelties have evolved in their feeding mechanism, which makes them capable of feeding on exceptional large prey. Lepidobatrachus is unusual in having reduced the ecomorphological differences between its larvae and adults. As a result, both the larvae and the frog are similarly able to capture large prey underwater. Some unique features in Lepidobatrachus are differentiated in the tadpole and then exaggerated in the adult (e.g., the posterior displaced jaw articulation) in a manner unobserved in any other anurans.Fil: Fabrezi, Marissa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Quinzio, Silvia Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Goldberg, Francisco Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Cruz, Julio Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Chuliver Pereyra, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Wassersug, Richard J.. Dalhousie University Halifax; Canad
El condocráneo larval en algunos leptodactylidae
Se realizó la descripción del cráneo y aparato hiobranquial de larvas de Ceratophrys cranwelli en estadíos comprendidos entre 31-35 de la tabla de Gosner (1960), previa transparentación y coloración de cartilagos siguiendo la técnica de Wassersug (1976).El presente documento es un resumen del trabajoAsociación Herpetológica Argentin
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