Closing the gap between science and management of cold-water refuges in rivers and streams

Human activities and climate change threaten coldwater organisms in freshwater ecosystems by causing rivers and streams to warm, increasing the intensity and frequency of warm temperature events, and reducing thermal heterogeneity. Cold-water refuges are discrete patches of relatively cool water that are used by coldwater organisms for thermal relief and short-term survival. Globally, cohesive management approaches are needed that consider interlinked physical, biological, and social factors of cold-water refuges. We review current understanding of cold-water refuges, identify gaps between science and management, and evaluate policies aimed at protecting thermally sensitive species. Existing policies include designating cold-water habitats, restricting fishing during warm periods, and implementing threshold temperature standards or guidelines. However, these policies are rare and uncoordinated across spatial scales and often do not consider input from Indigenous peoples. We propose that cold-water refuges be managed as distinct operational landscape units, which provide a social and ecological context that is relevant at the watershed scale. These operational landscape units provide the foundation for an integrated framework that links science and management by (1) mapping and characterizing cold-water refuges to prioritize management and conservation actions, (2) leveraging existing and new policies, (3) improving coordination across jurisdictions, and (4) implementing adaptive management practices across scales. Our findings show that while there are many opportunities for scientific advancement, the current state of the sciences is sufficient to inform policy and management. Our proposed framework provides a path forward for managing and protecting cold-water refuges using existing and new policies to protect coldwater organisms in the face of global change.     

Inhibition of rat perirenal preadipocyte differentiation

The process of adipose differentiation uniquely endows fat cells to accrue triacylglycerols under conditions of nutrient energy surfeit and to release fatty acids during energy deprivation. The object of this investigation was to study influences on this process in perirenal preadipocytes, grown in primary culture or first subculture and derived from male Sprague-Dawley rats, 180-200 g. Supplementation of the culture medium with 1-methyl-3-isobutylxanthine, corticosterone, and insulin induced differentiation in practically all perirenal preadipocytes, as indicated morphologically and by rising glycerophosphate dehydrogenase activity. Appreciable differentiation was induced even in the absence of methylisobutylxanthine. Transforming growth factor beta (1-1000 pM), cachectin (tumour necrosis factor alpha) (1-1000 pM), and basic fibroblast growth factor (0.063-63 nM) inhibited adipose differentiation significantly, almost completely at the higher concentrations. Direct inhibition, rather than a persisting mitogenic effect of fibroblast growth factor, was confirmed using demecolcine (Colcemid). The fact that transforming growth factor beta and cachectin inhibit differentiation in preadipocytes from postpubertal rats suggests that this effect probably also occurs in vivo, thus diverting energy from adipose depots in certain neoplastic and inflammatory states. We propose that the anterior pituitary, through fibroblast growth factor(s), modulates the pool of preadipocytes and other mesenchymal cells. The mitogenic effect would be complemented by a concerted function, inhibition of adipose differentiation, resulting in the retention of a greater number of potentially replicative cells. Then, depending on the subject's nutritional and endocrine status, extrapituitary factors would regulate the specific process of differentiation.     

Marsh Harriers Circus aeruginosus target Teals Anas crecca at roosts according to potential availability of vulnerable prey

Capsule The mean daily rate of foraging flyovers by Marsh Harriers in a given site is better predicted by the number of vulnerable Teal they can force to take flight (equivalent to patch size) than by the total number of Teal present.     

RELATIONS BETWEEN SUNFLECK SEQUENCES AND PHOTOINHIBITION OF PHOTOSYNTHESIS IN A TROPICAL RAIN FOREST UNDERSTORY HERB

We report the photosynthetic characteristics of a C₃ shade plant native to the tropical rain forest understory. It was shown that Elatostema repens Lour. (Hall) f. (Urticaceae) presents a large light adjustment capacity. The effects of several lightfleck sequences on photoinhibition of photosynthesis and carbon gain are analyzed. Photoinhibition is measured both as a decrease in leaf net CO₂ uptake in limiting light (shown to be linearly correlated to quantum yield of O₂ evolution measured at saturating CO₂) and as a decrease of the ratio of variable fluorescence (Fv) to maximum fluorescence (Fmax) measured in liquid nitrogen. It is shown that lightflecks (from 10 to 30 min in duration) of 700 μmol m^–2 s^–1 (high light) induce photoinhibition, and that the effects of those successive high light periods are additive; there is apparently no recovery from photoinhibition during the low light periods (from 10 to 45 min in duration). In contrast, the Fv/Fmax ratio, though decreasing similarly to quantum yield of net CO₂ uptake on leaves submitted to a continuous illumination of 700 μmol m^–2 s^–1, is only decreased a little on leaves submitted to lightfleck sequences of the same photon flux density. Lightflecks of 250 μmol m^–2 s^–1 are not photoinhibitory. Compared to the control maintained under light growth condition (40 μmol m^–2 s^–1) carbon gain is increased on leaves submitted to lightflecks; this gain remains high throughout the light cycles on leaves submitted to nonphotoinhibitory lightflecks and to the photoinhibitory lightflecks followed by the shortest low light period. In the other cases, carbon gain, higher than that of the control at the beginning of the treatments, decreases and becomes lower than the control carbon gain. Finally, the relevance of photoinhibition in the tropical rain forest understory environment is discussed.     

Alphavirus Mutator Variants Present Host-Specific Defects and Attenuation in Mammalian and Insect Models

Arboviruses cycle through both vertebrates and invertebrates, which requires them to adapt to disparate hosts while maintaining genetic integrity during genome replication. To study the genetic mechanisms and determinants of these processes, we use chikungunya virus (CHIKV), a re-emerging human pathogen transmitted by the Aedes mosquito. We previously isolated a high fidelity (or antimutator) polymerase variant, C483Y, which had decreased fitness in both mammalian and mosquito hosts, suggesting this residue may be a key molecular determinant. To further investigate effects of position 483 on RNA-dependent RNA-polymerase (RdRp) fidelity, we substituted every amino acid at this position. We isolated novel mutators with decreased replication fidelity and higher mutation frequencies, allowing us to examine the fitness of error-prone arbovirus variants. Although CHIKV mutators displayed no major replication defects in mammalian cell culture, they had reduced specific infectivity and were attenuated in vivo. Unexpectedly, mutator phenotypes were suppressed in mosquito cells and the variants exhibited significant defects in RNA synthesis. Consequently, these replication defects resulted in strong selection for reversion during infection of mosquitoes. Since residue 483 is conserved among alphaviruses, we examined the analogous mutations in Sindbis virus (SINV), which also reduced polymerase fidelity and generated replication defects in mosquito cells. However, replication defects were mosquito cell-specific and were not observed in Drosophila S2 cells, allowing us to evaluate the potential attenuation of mutators in insect models where pressure for reversion was absent. Indeed, the SINV mutator variant was attenuated in fruit flies. These findings confirm that residue 483 is a determinant regulating alphavirus polymerase fidelity and demonstrate proof of principle that arboviruses can be attenuated in mammalian and insect hosts by reducing fidelity.     

Effects of carbohydrate addition on the induction of somatic embryogenesis in Hevea brasiliensis

Plant Cell, Tissue and Organ Culture (PCTOC) - The effect of different carbohydrates was tested on early somatic embryogenesis of Hevea brasiliensis. Sucrose was replaced with maltose, fructose or...     

Cardiovascular and adrenaline-releasing effects of the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin in streptozotocin diabetic rats.

The 5-hydroxytryptamine1A (5-HT1A) receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) has been reported to trigger sympathoinhibition, as evidenced by its cardiovascular effects, and adrenal catecholamine secretion. The purpose of this study was to analyze the cardiovascular and adrenaline-releasing effects of 8-OH-DPAT in 1 week streptozotocin diabetic rats. 8-OH-DPAT-induced changes in mean arterial pressure (MAP) and heart rate (HR) were determined directly in anesthetized rats, whilst changes in plasma adrenaline (and plasma corticosterone and glucose) levels were analyzed in conscious rats. Resting blood pressure and heart rate were diminished in diabetics, when compared with controls. These changes were associated with a decrease in body weight and a marked increase in resting plasma glucose levels. Diabetes did not affect MAP response to 8-OH-DPAT, except for a decrease in the amplitude of MAP maximal fall, which was associated with a diminished bradycardic response to 8-OH-DPAT. Blood pressure response to prazosin (0.5 mg/kg) in 8-OH-DPAT-pretreated rats was also diminished in diabetics. Lastly, diabetes prevented the adrenaline-releasing and hyperglycemic effects of 8-OH-DPAT (250 ug/kg).     

Correlation between 2 methods of measuring cutaneous blood flow: photoplethysmography and xenon 133

Photoplethysmography, cutaneous blood flow measurement by Xenon 133 were carried out before and after resolution by Puva therapy on a lesion and on the symmetrical healthy skin area of 29 psoriatic subjects. The increase of the blood pulsatility and cutaneous blood flows found before treatment, disappears after resolution. The correlation between the two methods is studied.     

Notes on reptiles of Tunesia. VII. Observations on a double-headed snake Natrix (Reptilia: Colubridae)

A case of a double-headed Viperine Snake Natrix maura (Linné, 1758) hatching is reported. Its two heads are side by side, about equally and perfectly developed and the neck is dual for the 8 first vertebras. Two post-pharyngeal fistulas and dissymetries in the cephalic markings and scales are noted. The origin of such an anterior dichtomy is discussed.