Efecto del manejo forestal en la herpetofauna de un bosque templado del occidente de Oaxaca, México / Effect of forest management on the herpetofauna of a temperate forest of western Oaxaca, Mexico

ResumenEl desarrollo de técnicas y tratamientos silvícolas tiene como objetivo principal el aumento de la productividad forestal, al mismo tiempo que minimiza el impacto sobre la diversidad. A pesar de ello, estas actividades modifican la estructura de la vegetación, así como el clima local, alterando la composición de las comunidades. El efecto de estos cambios puede ser mayor en aquellos grupos taxonómicos con alta sensibilidad a las alteraciones del hábitat, como es el caso de los anfibios y reptiles, que al ser los únicos vertebrados terrestres ectotermos, pueden verse seriamente afectados por las variaciones de clima local. El presente trabajo tiene como objetivo conocer las diferencias en diversidad de anfibios y reptiles en un bosque templado bajo dos tratamientos silvícolas (uno intensivo y otro de baja intensidad) y con diferentes tiempos de regeneración (uno, cinco y diez años) en la Sierra Sur del estado de Oaxaca, México. Se obtuvieron registros de 21 especies de herpetofauna (seis anfibios y 15 reptiles). La riqueza total de especies fue similar en ambos tratamientos; sin embargo, la composición varió entre sitios con diferentes tiempos de recuperación. La mayor abundancia de anfibios se presentó en los sitios con el tratamiento de baja intensidad, mientras que los reptiles fueron más abundantes en los sitios con el tratamiento intensivo. Se observó un mayor número de especies raras en los sitios intervenidos con el tratamiento intensivo, aunque los valores de diversidad verdadera de anfibios fueron similares entre tratamientos con intensidades diferentes, mientras que en los reptiles se observó una diversidad 33 % menor en los sitios bajo el tratamiento intensivo y un 28 % en los sitios con baja intensidad respecto al sitio control. Un Análisis de Complementariedad mostró una diferencia de hasta 86 % de disimilitud entre la composición de especies en sitios con el tratamiento intensivo. La intensidad del tratamiento estuvo asociada con un aumento en el número de especies, sin embargo la manera en que responden ante las modificaciones de hábitat depende en gran medida de las características poblacionales de cada especie, así como su habilidad de adaptación a las nuevas condiciones del hábitat.

Abstract:The development of silvicultural techniques has as main objective to maximize the production of timber, whereas at the same time minimize the impact generated during and after forest intervention in the local diversity. However, these activities change local climate, and this, in turn, alter the composition of natural communities. The effect of these changes may be greater in those taxonomic groups with high sensitivity to habitat disturbance, such as amphibians and reptiles, which are the unique terrestrial ectothermic vertebrates. The present study aims to know the differences in diversity of amphibians and reptiles in a temperate forest under two silvicultural treatments, one of low and the other of high intensity, as well as from one, five and ten years of regeneration since the last logging event, Sierra Sur of Oaxaca, Mexico. Records of 21 species of herpetofauna (six amphibians and 15 reptiles) were obtained. The total species richness was similar in both treatments; however, the composition varied between sites with different recovery times. Higher abundance of amphibian was presented on sites with the low-intensity treatment, while reptiles were more abundant at sites with intensive treatment. Compared to a mature forest without management, sites with intensive treatment have more rare species, although the values of true diversity of amphibians were similar between treatments with different intensities, while for reptiles sites under treatment showed less diversity that unmanaged site: 33 % for intensive treatment and 28 % at sites with low intensity with respect to one control site. Complementary Analysis showed a difference of 86 % between the compositions of species in sites with intensive treatment. The treatment intensity was associated with an increase in the number of species, but the way they respond to changes in habitat depends largely on the population characteristics of each species and its ability to adapt to new conditions. Rev. Biol. Trop. 64 (3): 931-943. Epub 2016 September 01.

Characteristics of hemolytic activity induced by skin secretions of the frog Kaloula pulchra hainana

Background: Previous works had shown that scorpion venom induced neurotransmitter elevation and an inflammatory response associated with various anatomo-pathological modifications. The most dangerous scorpions species in Algeria responsible for these effects are Androctonus australis hector (Aah) and Androctonus amoreuxi (Aam). Results: Comparison of the physiopathological effects induced by the two venoms showed differences in the kinetic of cytokine release and in lung injury. The lung edema was only observed in response to Aah venom and it was correlated with cell infiltration. In order to better understand the involved mechanism in inflammatory response, we used two antagonists, atropine (non-selective muscarinic antagonist) and propranolol (ß adrenergic antagonist), which lead to a decrease of cell infiltration but has no effect on edema forming. Conclusion: These results suggest another pathway in the development of lung injury following envenomation with Aam or Aah venom.(AU)

Physiological response of American bullfrog tadpoles to stressor conditions of capture and hypoxia / Resposta fisiológica de girinos de rã-touro americana submetidos aos mecanismos estressores de captura e hipóxia

The American bullfrog (Rana catesbeiana), recently named Lithobates catesbeianus is currently farmed for commercial purposes throughout various regions of Brazil. Stressful situations such as problems of management, inadequate facilities and environmental changes with consequent reduction of immunity are common in intensive production. The assessments of these situations of stress allow us detect these problems decreasing the injuries causes by confinement. The main objective of this study was to use the biological markers of plasma cortisol and glucose level and hematological parameters to evaluate the response of bullfrog tadpoles submitted to stressed mechanisms of capture and hypoxia. The animals were subjected to three treatments: stress due to individual capture with a hand net; stress due to batch capture with a hand net; and stress due to capture by emptying. The results obtained demonstrated that there were no statistically significant differences in the parameters tested when comparing the treatments with and without exposure to air (normoxia and hypoxia). Based on these results we can conclude that the stressful stimuli tested were not adequate to alter the biomarker tested. For the cortisol, probably this should have occurred due to the synergistic action between this hormone and thyroxin, which induces metamorphosis in these animals.

A rã-touro americana (Rana catesbeiana) recentemente denominada Lithobates catesbeianus é cria da com propósito comercial em várias regiões do Brasil. Situações estressantes tais como problemas de manejo, criação inadequada e alterações ambientais com consequente redução da imunidade são comuns em produções intensivas. A avaliação destas situações de estresse permite-nos detectar estes probemas e diminuir as injurias causadas pelo confinamento. O principal objetivo deste estudo foi utilizar os marcadores biológicos de cortisol, glicemia e dados hematológicos para avaliar a resposta de girinos de rã-touro submetidos aos mecanismos estressores de captura e hipóxia. Os animais foram distribuídosem três tratamentos: estresse por captura individual com puçá; estresse por captura em massa com puçá e estresse por captura por escoamento. Os resultados obtidos demostraram não haver diferenças estatisticamente significativas entre os parametros avaliados quando comparou-se os grupos com e sem exposição ao ar (normoxia e hipoxia). Com base nestes resultados pode-se concluir que os estímulos estressores avaliados não foram adequados para alterar os valores plasmáticos dos marcadores biológicos testados. Para o cortisol, isto ocorreu provavelmente em virtude da ação sinérgica deste hormônio e a tiroxina, que induz a metamorfose nestes animais.

Autonomic control of cardiorespiratory interactions in fish, amphibians and reptiles

Control of the heart rate and cardiorespiratory interactions (CRI) is predominantly parasympathetic in all jawed vertebrates, with the sympathetic nervous system having some influence in tetrapods. Respiratory sinus arrhythmia (RSA) has been described as a solely mammalian phenomenon but respiration-related beat-to-beat control of the heart has been described in fish and reptiles. Though they are both important, the relative roles of feed-forward central control and peripheral reflexes in generating CRI vary between groups of fishes and probably between other vertebrates. CRI may relate to two locations for the vagal preganglionic neurons (VPN) and in particular cardiac VPN in the brainstem. This has been described in representatives from all vertebrate groups, though the proportion in each location is variable. Air-breathing fishes, amphibians and reptiles breathe discontinuously and the onset of a bout of breathing is characteristically accompanied by an immediate increase in heart rate plus, in the latter two groups, a left-right shunting of blood through the pulmonary circuit. Both the increase in heart rate and opening of a sphincter on the pulmonary artery are due to withdrawal of vagal tone. An increase in heart rate following a meal in snakes is related to withdrawal of vagal tone plus a non-adrenergic-non-cholinergic effect that may be due to humoral factors released by the gut. Histamine is one candidate for this role.

Control of respiration in fish, amphibians and reptiles

Fish and amphibians utilise a suction/force pump to ventilate gills or lungs, with the respiratory muscles innervated by cranial nerves, while reptiles have a thoracic, aspiratory pump innervated by spinal nerves. However, fish can recruit a hypobranchial pump for active jaw occlusion during hypoxia, using feeding muscles innervated by anterior spinal nerves. This same pump is used to ventilate the air-breathing organ in air-breathing fishes. Some reptiles retain a buccal force pump for use during hypoxia or exercise. All vertebrates have respiratory rhythm generators (RRG) located in the brainstem. In cyclostomes and possibly jawed fishes, this may comprise elements of the trigeminal nucleus, though in the latter group RRG neurons have been located in the reticular formation. In air-breathing fishes and amphibians, there may be separate RRG for gill and lung ventilation. There is some evidence for multiple RRG in reptiles. Both amphibians and reptiles show episodic breathing patterns that may be centrally generated, though they do respond to changes in oxygen supply. Fish and larval amphibians have chemoreceptors sensitive to oxygen partial pressure located on the gills. Hypoxia induces increased ventilation and a reflex bradycardia and may trigger aquatic surface respiration or air-breathing, though these latter activities also respond to behavioural cues. Adult amphibians and reptiles have peripheral chemoreceptors located on the carotid arteries and central chemoreceptors sensitive to blood carbon dioxide levels. Lung perfusion may be regulated by cardiac shunting and lung ventilation stimulates lung stretch receptors.

Simulation of physiology experiments--an alternative to animal use.

Amphibian experiments on nerve-muscle preparation and heart are essential as per first year MBBS practical syllabus, for learning basic concepts in Physiology. Need was felt to design and develop computer based simulation software as an alternative to animal use, due to growing concern and stringent laws imposed by animal ethical bodies. Computer algorithms were developed for 13 amphibian experiments, by manually tracing the graphs obtained through mechanical experimentation and storing the X, Y coordinates for the end points of each line segment as data base tables. By retrieving the data base tables, one for each experiment, the computer simulated graphs were drawn using Visual Basic 6 with timer control and Macromedia Flash for animation effects. A CD-ROM consisting of the software for computer simulation of all the amphibian experiments, as an alternative to the conventional animal experiments, has been developed for the benefit of medical students across the country, as a useful active learning tool.

Un modelo anfibio para el estudio evolutivo del control respiratorio / Anphibian model study for evolutionary respiratory control

Los enormes progresos de la medicina perinatal han permitido la sobrevivencia de recién nacidos prematuros en estadios de desarrollo cada vez más precoces. Estos pequeños pacientes requieren de medios muy sofisticados y costosos para paliar su inmadurez respiratoria. Además de las complicaciones asociadas al desarrollo pulmonar, la inestabilidad respiratoria y las apneas asociadas a la inmadurez de los circuitos nerviosos productores del control respiratorio, contribuyendo éstos últimas, como factor principal de morbilidad, a las prolongadas hospitalizaciones que presenta esta tan vulnerable población. Éstos imperativos médicos combinados a la curiosidad fisiológica han contribuido al desenvolvimiento de novedosas investigaciones en neurobiología respiratoria. Si bien la mayoría de los trabajos realizados en éste campo utilizan a los múridos como modelos experimentales, las investigaciones recientes efectuadas a partir del tronco cerebral aislado de anfibios (Rana catesbeiana) han revelado las ventajas técnicas de este modelo animal, para mostrar los principales fenómenos que rigen el funcionamiento y el desarrollo del sistema de control respiratorio entre los vertebrados. El presente artículo se propone repasar los avances más recientes realizados en la investigación de la neurobiología evolutiva del control respiratorio, prestando una atención particular a la respiración episódica, así como al rol que desempeñan la modulación serotoninérgica y Gabaérgica de la actividad respiratoria en el curso del desarrollo.

Recent perinal advances have made possible that premature newborns survive increasingtly in earlier developmental stages. This babies requires sophisticated and costly critical intensive care to address the problems associated with inmadurity of the respiratory system. In addition respiratory instability and apnea reflecting inmaturity of the respiratory control system are major causes of morbidity and prolonged hospitalization in this highly vulnerable group of patients. These concerns have contributed to the development of research in respiratoy evolutionary neurobiology. While the majority of researchers working in this field use rodents as an animal model, recent research using in vitro brainstem preparations from bullfrog (Rana catesbeiana) have reveled the technical advantages of this model to study the basic principles underlying respiratory control and its ontogeny between vertebrates. The present article review the recent advances in the area of research with special interest on episodic breathing and the role of serotoninergic and GABAergic modulation of respiratory control during development.

Digestive Phenotypic Flexibility in Post-Metamorphic Amphibians: Studies on a Model Organism

Studies of phenotypic flexibility are central to the understanding of evolutionary and comparative physiology. Research conducted on many vertebrate species has shown that the digestive system is highly responsive and sensitive to environmental cues. However, amphibians, which are a standard and classic model organism for the study of many physiological processes, have been poorly considered in the study of ecological consequences on digestive flexibility. Here we review and analyze the current information on this topic for amphibians. We identify three major bodies of empirical evidence: a) seasonal changes in gut development, b) lack of dietary modulation of gut attributes in adult individuals, c) a relationship between feeding habits and the magnitude of digestive performance regulation. Once the natural history characteristics of the species under study are taken into account, all the evidence is in full agreement with the predictions of digestive theory. We propose that evolutionary and comparative physiology could benefit greatly from the study of phenotypic flexibility in amphibians.

Aggrecan structure in amphibian cartilage

The structure of the large proteoglycan present in the bullfrog epiphyseal cartilage was studied by immunochemical and biochemical methods. The isolated monomer showed a polydisperse behavior on Sepharose CL2B, with a peak at Kav = 0.14. Chondroitin sulfate chains were identified by HPLC analysis of the products formed by chondroitinase digestion and mercuric acetate treatment. These chains have approximately 38 disaccharides, a Di45:Di68 ratio of 1.6 and GalNAc4S + GalNAc4,6S are the main non-reducing terminals. Keratan sulfate was identified by the use of two monoclonal antibodies in Western blots after chondroitinase ABC treatment. A keratan sulfate-rich region (~110 kDa) was isolated by sequential treatment with chondroitinase ABC and proteases. We also employed antibodies in Western blotting experiments and showed that the full length deglycosylated core protein is about 300 kDa after SDS-PAGE. Domain-specific antibodies revealed the presence of immunoreactive sites corresponding to G1/G2 and G3 globular domains and the characterization of this large proteoglycan as aggrecan. The results indicate the high conservation of the aggrecan domain structure in this lower vertebrate

Evolution of circadian organization in vertebrates

Circadian organization means the way in which the entire circadian system above the cellular level is put together physically and the principles and rules that determine the interactions among its component parts which produce overt rhythms of physiology and behavior. Understanding this organization and its evolution is of practical importance as well as of basic interest. The first major problem that we face is the difficulty of making sense of the apparently great diversity that we observe in circadian organization of diverse vertebrates. Some of this diversity falls neatly into place along phylogenetic lines leading to firm generalizations: i) in all vertebrates there is a "circadian axis" consisting of the retinas, the pineal gland and the suprachiasmatic nucleus (SCN), ii) in many non-mammalian vertebrates of all classes (but not in any mammals) the pineal gland is both a photoreceptor and a circadian oscillator, and iii) in all non-mammalian vertebrates (but not in any mammals) there are extraretinal (and extrapineal) circadian photoreceptors. An interesting explanation of some of these facts, especially the differences between mammals and other vertebrates, can be constructed on the assumption that early in their evolution mammals passed through a "nocturnal bottleneck". On the other hand, a good deal of the diversity among the circadian systems of vertebrates does not fall neatly into place along phylogenetic lines. In the present review we will consider how we might better understand such "phylogenetically incoherent" diversity and what sorts of new information may help to further our understanding of the evolution of circadian organization in vertebrates.

Regulation of acid-base status in ectothermic vertebrates: the consequences for oxygen pressures in lung gas and arterial blood

Extensive literature reports a negative deltapHa/deltat in ectothermic vertebrates, but data are scarce as to its consequences for O2 transport. In reptiles, the negative delta-pHa/delta-t results from an elevated lung gas PCO2 (PACO2) at higher temperatures, implying a corresponding fall of PAO2. In parallel, arterial PO2 rises with temperature, due to a combination of central vascular shunt and decreasing Hb O2 affinity. As a result, the PO2 gradient between lung gas and blood (PA-aO2) becomes reduced at higher temperatures. In amphibians, the negative delta-pHa/delta-t results from combined cutaneous and pulmonary CO2 elimination. We propose that this leads to a rather temperature-independent lung gas PO2. Moreover, our calculations suggest that resting reptiles and amphibians maintain a relatively large PA-aO2 also at high temperatures. The negative delta-pHa/delta-t in teleost fish is generally considered to be a result of modulated plasma [HCO3-]. Recent data from our laboratory suggest that acute pH adjustments at high temperatures may involve alterations of PaCO2 through gill ventilation, leading to a decrease of PaO2 with rising temperature.

Estivation in South American amphibians and reptiles

A number of amphibians and reptiles have cyclic behavior, becoming inactive with the coming of the dry season. In South America this pattern of activity is common, particularly in savannah-like vegetation. During the dry season amphibians burrow into the mud or soil, and either form a cocoon or increase the osmotic concentration of body fluids to reduce evaporative water loss. Some phyllomedusid tree frogs coat their body surface with skin secretion and excrete uric acid to minimize water loss. Reptiles also retreat into shelter deep enough to avoid temperature fluctuation during estivation or reduce metabolic response to temperature. Reduction of temperature sensitivity of the metabolism seems to be a strategy common to estivating amphibians and reptiles. Despite seasonal change of the environment, some species of reptiles are active all year round.

Perfiles séricos e hipofisarios de alfa-melanotrofina y prolactina durante el ciclo reproductor de Leptodactylus ocellatus / Serum and hypophyseal profiles of alpha-melanotropin and prolactin during the reproductive cycle of Leptodactylus ocellatus

Con el presente trabajo se estudian las concentraciones sérica e hipofisaria de las hormonas alfamelanotrofina y prolactina en Leptodactylus ocellatus macho de la provincia de Córdoba en un período anual completo. Este anfibio presenta un ciclo reproductor continuo con una onda de mayor actividad espermatogénica en los meses tempranos de verano (Diciembre-Enero). Los resultados obtenidos en ambas hormonas muestran un patrón mu semejante; ambas presentan su valor sérico máximo en el período Dicembre-Enero coincidente con la mayor onda espermatogénica. Las concentraciones hipofisarias preceden en sus valores máximos en 2 meses a las concentraciones séricas. Aunque no está bien determinada la influencia de las hormonas estudiadas sobre la espermatogénesis en anfibios, las observaciones aquí descriptas podrían indicar que tanto alfa-melanotrofina como prolactina cumplirían algún rol en el proceso espermatogénico de Leptodactylus ocellatus