Hot Habitat Research Articles

Savanna Plants Have a Lower Hydraulic Efficiency than Co-Occurring Species in a Rainforest

A plant species can have diverse hydraulic strategies to adapt to different environments. However, the water transport divergence of co-occurring species in contrasting habitats remains poorly studied but is important for understanding their ecophysiology adaptation to their environments. Here, we investigated whole-branch, stem and leaf water transport strategies and associated morphology traits of 11 co-occurring plant species in Yuanjiang valley-type savanna (YJ) with dry–hot habitats and Xishuangbanna tropical seasonal rainforest (XSBN) with wet–hot habits and tested the hypothesis that plants in YJ have a lower water transport efficiency than co-occurring species in XSBN. We found high variation in whole-branch, stem and leaf hydraulic conductance (Kshoot; Kstem and Kleaf) between YJ and XSBN, and that Kstem was significantly higher than Kleaf in these two sites (Kstem/Kleaf: 16.77 in YJ and 6.72 in XSBN). These plants in YJ with significantly lower Kshoot and Kleaf but higher sapwood density (WD) and leaf mass per area (LMA) showed a lower water transport efficiency regarding less water loss and the adaptation to the dry–hot habitat compared to co-occurring species in XSBN. In contrast, these co-occurring plants in XSBN with higher Kshoot and Kleaf but lower WD and LMA tended to maximize water transport efficiency and thus growth potential in the wet–hot habitat. Our findings suggest that these co-occurring species employ divergent hydraulic efficiency across YJ and XSBN so that they can benefit from the contrasting hydraulic strategies in adaptation to their respective habitats.

Targeted α-Therapy Using 225Ac Radiolabeled Single-Domain Antibodies Induces Antigen-Specific Immune Responses and Instills Immunomodulation Both Systemically and at the Tumor Microenvironment.

Targeted radionuclide therapy (TRT) using targeting moieties labeled with α-particle-emitting radionuclides (α-TRT) is an intensely investigated treatment approach as the short range of α-particles allows effective treatment of local lesions and micrometastases. However, profound assessment of the immunomodulatory effect of α-TRT is lacking in literature. Methods: Using flow cytometry of tumors, splenocyte restimulation, and multiplex analysis of blood serum, we studied immunologic responses ensuing from TRT with an antihuman CD20 single-domain antibody radiolabeled with 225Ac in a human CD20 and ovalbumin expressing B16-melanoma model. Results: Tumor growth was delayed with α-TRT and increased blood levels of various cytokines such as interferon-γ, C-C motif chemokine ligand 5, granulocyte-macrophage colony-stimulating factor, and monocyte chemoattractant protein-1. Peripheral antitumoral T-cell responses were detected on α-TRT. At the tumor site, α-TRT modulated the cold tumor microenvironment (TME) to a more hospitable and hot habitat for antitumoral immune cells, characterized by a decrease in protumoral alternatively activated macrophages and an increase in antitumoral macrophages and dendritic cells. We also showed that α-TRT increased the percentage of programmed death-ligand 1 (PD-L1)-positive (PD-L1pos) immune cells in the TME. To circumvent this immunosuppressive countermeasure we applied immune checkpoint blockade of the programmed cell death protein 1-PD-L1 axis. Combination of α-TRT with PD-L1 blockade potentiated the therapeutic effect, however, the combination aggravated adverse events. A long-term toxicity study revealed severe kidney damage ensuing from α-TRT. Conclusion: These data suggest that α-TRT alters the TME and induces systemic antitumoral immune responses, which explains why immune checkpoint blockade enhances the therapeutic effect of α-TRT. However, further optimization is warranted to avoid adverse events.

Physiological adjustment of the genus Limicolaria (Gastropoda: Pulmonata) during aestivation and activity in tropical agro-ecosystem

ABSTRACTComparisons of sympatric species inhabiting the same ecological habitat may elucidate adaptive processes. We studied the physiological patterns of two species of the genus Limicolaria (L. aurora and L. flammea) that thrive in a hot tropical habitat. We examined changes in water content, biochemical fuel reserves and haemolymph enzyme activities during aestivation and activity. Our results indicate that both species had the potential to conserve body water during aestivation. A definite pattern in foot muscle biochemical fuel reserves was observed. Both species depleted glycogen during aestivation while building up lipids. Catabolism of protein was observed during aestivation. Lactate levels and the activity of lactate dehydrogenase both decreased during aestivation, and both variables later increased at the onset of activity. Significantly higher enzyme activities were recorded during aestivation than during the active period. Stepwise discrimination analysis revealed lactate as the significant predictor of differences between the two periods, with 97.9% of the cases correctly classified. No significant correlation was observed between the measured variables and climatic data. Our results suggest that the physiological adaptation of Limicolaria is not environmentally predictable, rather it is inherently determined for ensuring physiological adjustment for survival in the tropics.

Stronger cooling effects of transpiration and leaf physical traits of plants from a hot dry habitat than from a hot wet habitat

Abstract Leaf temperature exerts an important impact on the microenvironment and physiological processes of leaves. Plants from different habitats have different strategies to regulate leaf temperature. The relative importance of physical traits and transpiration for leaf temperature regulation in the hot habitat is still unclear. We investigated 22 leaf physical traits, transpiration, and thermal properties of 38 canopy species of seedlings in a greenhouse, including 18 dominant species from a hot wet habitat (HW) and 20 dominant species from a hot dry habitat (HD). To separate the impact of transpiration and leaf physical traits on leaf temperature, we measured the diurnal courses of leaf temperatures with and without transpiration. The temperature of a reference leaf beside each individual was measured simultaneously to render temperatures comparable. Generally, the species from HD showed lower leaf temperatures than the species from HW under the same conditions. Both transpiration capacity and cooling effect of leaf physical traits were stronger for the plants from HD. Active transpiration provides a suitable thermal environment for photosynthesis, while xeromorphic leaves can dampen heat stress when transpiration is suppressed. Higher vein density and stomatal pore area index (SPI) facilitated higher transpiration capacity of the plants from HD. Meanwhile, shorter leaves and thinner lower epidermis of the plants from HD were more efficient in heat transfer, although relationships were much weaker than the synergic effect of all the physical traits. Our results confirmed that transpiration and leaf physical traits provided double insurance for avoiding overheating, particularly for plant from HD. We emphasize that transpiration is a more effective way to cool leaves than physical traits when water is sufficient, which may be an important adaptation for plant from HD where rainfall is sporadic. Our results provide further insight into the relationship between physical traits and transpiration for the regulation of leaf temperature, and the co‐evolution of gas exchange and thermal regulation of leaves. A plain language summary is available for this article.

Leveraging Clustering Techniques to Facilitate Metagenomic Analysis

AbstractMachine learning clustering algorithms provide excellent methods for conducting metagenomic analysis with efficiency. This study uses two machine learning algorithms, the self-organizing map and the K-means algorithms, to cluster data from an environmental sample collected from a hot springs habitat and to provide a visual analysis of that data. A data processing pipeline is described that uses the clustering algorithms to identify which reference genomes should be included for further analysis in determining possible organisms that are present in a metagenomic sample. The clustering revealed probable candidates for additional analysis, including a thermophilic, anaerobic bacterium, which is likely to be found in a hot springs environment and serves to validate the functionality of these tools. The machine learning techniques discussed here can serve as a launching point for elucidating protein sequences that could serve as possible reference comparisons to a specific metagenomic sample and lead t...

ADAPTIVE MORPHOMETRY VARIATION IN LIZARDS OF THE GENUS AGAMA IN ISRAEL

ABSTRACT The genus Agama in Israel is represented by five taxa which are distributed in different habitats and different zoogeographical regions of the country. An attempt was made to analyze these taxa according to various morphometric characteristics and to correlate these variables with habitat quality as well as with thermal characteristics. The results indicate that the five Agama taxa in Israel segregate on the basis of morphometric and thermal features. Among the morphometric characteristics, the ratios between the length of fore—and hindlimbs and body length were dominant discriminating features, especially between A. sinaita from a hot rocky habitat and all other four species. Body temperature was the main thermal feature accounting for taxon segregation. These results revealed a high compatibility between morphometric attributes and habitat features.

Temperature-related diversity of shell colour in the intertidal gastropod Batillaria

The intertidal snail Batillaria exhibits remarkable variation in the shell colour within and among populations. Field study was conducted to determine the factors in maintaining observed shell colour polymorphism. Geographical variations in shell colour polymorphisms in B. attramentaria were significantly correlated with the temperature of the locality of the population. Darker morphs were predominant in colder regions, whereas lighter morphs increase their proportion in warmer regions. A consistent association was also found in B. multiformis that co-existed with B. attramentaria. Strong predatory pressure imposed by digenean trematode parasites was observed in B. attramentaria. However, it is unlikely to affect the colour variations, because no correlation exists between colour morphs and trematode parasitism. Although visual selection may also contribute to colour variation in Batillaria, no evidence is found for the existence of visual predators that affect colour patterns of these snails. The deficit of variation in cold regions is possibly due to selection against brighter morphs, because bright colours reflect heat. Although dark shells absorb sunlight and may therefore be exposed to the risks of overheating and drying up in a hot habitat, the darkest morph was frequently observed in the warmer regions, suggesting that physical selection on the colour morphs can be relaxed in the warmer environment. Our results suggest that climatic selection is one of the significant factors maintaining shell colour polymorphism in these intertidal snails.

Temperature Regulation in Great Frigate Birds Fregata minor

Great frigate birds are large black tropical seabirds. Those breeding on Midway Atoll absorb more than 90% of the incoming solar radiation and yet can remain on their nest exposed to intense solar radiation for up to 16 days. Despite experiencing air temperatures as high as 33.3 C and environmental temperatures ($T_{e}'s$, an index of total heat load) up to 51.7 C, the birds maintained body temperature within relatively narrow limits, averaging 39.3 ± 0.5 C. They reduce overheating by using gular fluttering and by assuming three distinct postures, which were used sequentially as $T_{e}$ increased. The most common posture was erected feathers, followed by open wing and droop wing. Despite sexual dimorphism in size and plumage, there were no sexual differences in posturing, dorsal absorptivity to solar radiation, or response to $T_{e}$. The postures evidently contribute to water conservation in the hot breeding habitat of frigate birds, as the birds appear to have low rates of water loss.

Environment of Deposition and Uranium Host Rock Potential of Jurassic Morrison Formation, Northeastern New Mexico: ABSTRACT

A stratigraphic examination of the Morrison Formation in northeastern New Mexico indicates that its sediments were deposited in either a semiarid or arid environment when the area was located below 30°N lat. and was under the influence of the Northeast Trades. The dry environment and the prevailing northeasterly flow adversely affected the chance of commercial quantities of uranium from being incorporated into Morrison sediments. Dinosaurs that lived in the area were adapted to living in a dry and hot habitat. End_of_Article - Last_Page 563------------