Home About us Contact
|
Home About us Contact | ||
|
|
||
Ectothermic Vertebrates (ectothermic + vertebrate)
Selected AbstractsTemperature-induced plasticity at cellular and organismal levels in the lizard Anolis carolinensisINTEGRATIVE ZOOLOGY (ELECTRONIC), Issue 3 2010Rachel M. GOODMAN Abstract Among ectotherms, individuals raised in cooler temperatures often have larger body size and/or larger cell size. The current study tested whether geographic variation in cell size and plasticity for cell size exist in a terrestrial, ectothermic vertebrate, Anolis carolinensis Voigt, 1832. We demonstrated temperature-induced plasticity in erythrocytes and epithelial cells of hatchlings lizards derived from the eggs of females sampled from four populations and incubated at multiple temperatures. Larger cells were produced in hatchlings from cooler treatments; however, hatchling body size was unaffected by temperature. Therefore, temperature-induced plasticity applies at the cellular, but not organismal, level in A. carolinensis. In addition, reaction norms for cell size differed among populations. There was a latitudinal trend in cell size and in plasticity of cell size among our study populations. The two southernmost populations showed plasticity in cell size, whereas the two northernmost ones did not. We suggest that selection pressure for larger cell size in northern, cooler environments has restricted plasticity in A. carolinensis applied at the cellular level in response to variable incubation environments. [source] Recovering the Reptile Community after the Mine-Tailing Accident of Aznalcóllar (Southwestern Spain)RESTORATION ECOLOGY, Issue 5 2009Rocío Márquez-Ferrando Abstract Ecosystem restoration requires that habitat requirements of all species be considered. Among animal communities in Mediterranean ecosystems, reptiles, as ectothermic vertebrates, need refuges for avoidance of extreme environmental temperatures, concealment from predators, and oviposition sites. In 1998, a massive amount of tailings broke out of the holding pond of the Aznalcóllar mine (southwestern Spain) and polluted the Guadiamar river valley. After the accident, a soil- and vegetation restoration program began, and the Guadiamar Green Corridor was created to connect two huge natural areas, Doñana National Park and the Sierra Morena. Within this corridor, the reptile community remained dramatically impoverished, probably because of elimination of all natural refuges during the soil restoration program. To test this hypothesis, we set an array of artificial refuges (logs) in a large experimental plot. During the 5 years of the experiment (2002,2006), the area managed with artificial refuges exhibited a better and faster recovery of the reptile community in species richness and individual abundance than did the control area with no artificial refuges. Moreover, reptile colonization of the Guadiamar Green Corridor was transverse rather than lineal,that is, it did not act as a corridor for reptiles, at least in the first stages of colonization. This suggests that landscape restoration programs should not neglect refuge availability, a limiting resource for reptile species. [source] Predicted impact of climate change on threatened terrestrial vertebrates in central Spain highlights differences between endotherms and ectothermsANIMAL CONSERVATION, Issue 4 2010P. Aragón Abstract Climate change can induce shifts in species ranges. Of special interest are range shifts in regions with a conflict of interest between land use and the conservation of threatened species. Here we focus on the 94 threatened terrestrial vertebrates occurring in the Madrid region (Central Spain) and model their distributions using data for the whole peninsular Spain to evaluate which vertebrate groups are likely to be more sensitive to climatic change. First, we generated predictive models to quantify the extent to which species distributions are explained by current climate. We then extrapolated the models temporally to predict the effects of two climate-change scenarios on species distributions. We also examined the impact on a recently proposed reserve relative to other interconnected zones with lower protection status but categorized as Areas of Community Importance by the European Union. The variation explained by climatic predictors was greater in ectotherms. The change in species composition differed between the proposed reserve and the other protected areas. Endothermic and ectothermic vertebrates had different patterns of changes in species composition but those of ectotherms matched with temperature departures predicted by climate change. Our results, together with the limited dispersal capacity of herptiles, suggest that trade-offs between different design criteria accounting for animal group differences are necessary for reserve selection. [source] Resistance to chytridiomycosis varies among amphibian species and is correlated with skin peptide defensesANIMAL CONSERVATION, Issue 4 2007D. C. Woodhams Abstract Innate immune mechanisms of defense are especially important to ectothermic vertebrates in which adaptive immune responses may be slow to develop. One innate defense in amphibian skin is the release of abundant quantities of antimicrobial peptides. Chytridiomycosis is an emerging infectious disease of amphibians caused by the skin fungus, Batrachochytrium dendrobatidis. Susceptibility to chytridiomycosis varies among species, and mechanisms of disease resistance are not well understood. Previously, we have shown that Australian and Panamanian amphibian species that possess skin peptides that effectively inhibit the growth of B. dendrobatidis in vitro tend to survive better in the wild or are predicted to survive the first encounter with this lethal pathogen. For most species, it has been difficult to experimentally infect individuals with B. dendrobatidis and directly evaluate both survival and antimicrobial peptide defenses. Here, we demonstrate differences in susceptibility to chytridiomycosis among four Australian species (Litoria caerulea, Litoria chloris, Mixophyes fasciolatus and Limnodynastes tasmaniensis) after experimental infection with B. dendrobatidis, and show that the survival rate increases with the in vitro effectiveness of the skin peptides. We also observed that circulating granulocyte, but not lymphocyte, counts differed between infected and uninfected Lit. chloris. This suggests that innate granulocyte defenses may be activated by pathogen exposure. Taken together, our data suggest that multiple innate defense mechanisms are involved in resistance to chytridiomycosis, and the efficacy of these defenses varies by amphibian species. [source] Animal performance and stress: responses and tolerance limits at different levels of biological organisationBIOLOGICAL REVIEWS, Issue 2 2009Karin S. Kassahn ABSTRACT Recent advances in molecular biology and the use of DNA microarrays for gene expression profiling are providing new insights into the animal stress response, particularly the effects of stress on gene regulation. However, interpretation of the complex transcriptional changes that occur during stress still poses many challenges because the relationship between changes at the transcriptional level and other levels of biological organisation is not well understood. To confront these challenges, a conceptual model linking physiological and transcriptional responses to stress would be helpful. Here, we provide the basis for one such model by synthesising data from organismal, endocrine, cellular, molecular, and genomic studies. We show using available examples from ectothermic vertebrates that reduced oxygen levels and oxidative stress are common to many stress conditions and that the responses to different types of stress, such as environmental, handling and confinement stress, often converge at the challenge of dealing with oxygen imbalance and oxidative stress. As a result, a common set of stress responses exists that is largely independent of the type of stressor applied. These common responses include the repair of DNA and protein damage, cell cycle arrest or apoptosis, changes in cellular metabolism that reflect the transition from a state of cellular growth to one of cellular repair, the release of stress hormones, changes in mitochondrial densities and properties, changes in oxygen transport capacities and changes in cardio-respiratory function. Changes at the transcriptional level recapitulate these common responses, with many stress-responsive genes functioning in cell cycle control, regulation of transcription, protein turnover, metabolism, and cellular repair. These common transcriptional responses to stress appear coordinated by only a limited number of stress-inducible and redox-sensitive transcription factors and signal transduction pathways, such as the immediate early genes c-fos and c-jun, the transcription factors NF,B and HIF - 1,, and the JNK and p38 kinase signalling pathways. As an example of environmental stress responses, we present temperature response curves at organismal, cellular and molecular levels. Acclimation and physiological adjustments that can shift the threshold temperatures for the onset of these responses are discussed and include, for example, adjustments of the oxygen delivery system, the heat shock response, cellular repair system, and transcriptome. Ultimately, however, an organism's ability to cope with environmental change is largely determined by its ability to maintain aerobic scope and to prevent loss in performance. These systemic constraints can determine an organism's long-term survival well before cellular and molecular functions are disturbed. The conceptual model we propose here discusses some of the crosslinks between responses at different levels of biological organisation and the central role of oxygen balance and oxidative stress in eliciting these responses with the aim to help the interpretation of environmental genomic data in the context of organismal function and performance. [source] | ||||||||||