Bacillus sonorensis sp. nov., a close relative of Bacillus licheniformis, isolated from soil in the Sonoran Desert, Arizona.
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Eight Bacillus strains isolated from Sonoran Desert soil were shown to belong to a previously unidentified species, for which the name Bacillus sonorensis sp. nov. is proposed. The type strain is strain L87-10T (= NRRL B-23154T). On the basis of phenotypic and genetic data, B. sonorensis is most closely related to Bacillus licheniformis. B. sonorensis can be distinguished from B. licheniformis by salt tolerance, pigmentation, multilocus enzyme electrophoresis, reassociation of genomic DNA and sequence differences in protein-coding genes and 16S rRNA. (+info)
Genomic dissection of genotype x environment interactions conferring adaptation of cotton to arid conditions.
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The interaction of genotype with environment is of primary importance in many aspects of genomic research and is a special priority in the study of major crops grown in a wide range of environments. Water deficit, the major factor limiting plant growth and crop productivity worldwide, is expected to increase with the spread of arid lands. In genetically equivalent cotton populations grown under well-watered and water-limited conditions (the latter is responsible for yield reduction of approximately 50% relative to well-watered conditions), productivity and quality were shown to be partly accounted for by different quantitative trait loci (QTLs), indicating that adaptation to both arid and favorable conditions can be combined in the same genotype. QTL mapping was also used to test the association between productivity and quality under water deficit with a suite of traits often found to differ between genotypes adapted to arid versus well-watered conditions. In this study, only reduced plant osmotic potential was clearly implicated in improved cotton productivity under arid conditions. Genomic tools and approaches may expedite breeding of genotypes that respond favorably to specific environments, help test roles of additional physiological factors, and guide the isolation of genes that protect crop performance under arid conditions toward improved adaptation of crops to arid cultivation. (+info)
Egocentric information helps desert ants to navigate around familiar obstacles.
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Homing ants have been shown to associate directional information with familiar landmarks. The sight of these local cues might either directly guide the path of the ant or it might activate a landmark-based vector that points towards the goal position. In either case, the ants define their courses within allocentric systems of reference. Here, we show that desert ants, Cataglyphis fortis, forced to run along a devious path can use egocentric information as well. The ants were trained to deviate from their straight homebound course by a wide inconspicuous barrier that was placed between the feeding and nesting sites. At a distant test area, the ants were confronted with an identical barrier rotated through 45 degrees. After passing the edge of the obstacle, the ants did not proceed in the trained direction, defined by the skylight compass, but rotated their courses to match the rotation of the barrier. Visual guidance could be excluded because, as soon as the ants turned around the end of the barrier, the visual cue it provided vanished from their field of view. Instead, the ants must have maintained a constant angle relative to their previous walking trajectory along the obstacle and, hence, must have determined their new vector course in an egocentric way. (+info)
Physiological responses of Houbara bustards to high ambient temperatures.
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Desert birds often experience a scarcity of drinking water and food and must survive episodes of high ambient temperature (T(a)). The physiological mechanisms that promote survival during extended periods of high T(a) have received little attention. We investigated the physiological responses of wild-caught and captive-reared Houbara bustards, Chlamydotis macqueenii, to T(a) values ranging from below 0 degrees C to 55 degrees C, well above those in most previous studies of birds. Captive-reared Houbara bustards (mass 1245+/-242 g, N=7, mean +/- S.D.) in summer have a resting metabolic rate (RMR) of 261.4 kJ day(-1), 26 % below allometric predictions, and a total evaporative water loss (TEWL) at 25 degrees C of 25.8 g day(-1), 31 % below predictions. When T(a) exceeded body temperature (T(b)), the dry heat transfer coefficient decreased, a finding supporting the prediction that birds should minimize dry heat gain from the environment at high T(a) values. Houbara bustards withstand high T(a) values without becoming hyperthermic; at 45 degrees C, T(b) was on average 0.9 degrees C higher than at 25 degrees C. RMR and TEWL of captive-bred Houbara bustards were 23 % and 46 % higher in winter than in summer, respectively. Captive-reared Houbara bustards had a 17 % lower RMR and a 28 % lower TEWL than wild-born birds with similar genetic backgrounds. Differences in body composition between wild-caught and captive-reared birds were correlated with differences in physiological performance. (+info)
The visual centring response in desert ants, Cataglyphis fortis.
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When negotiating their way through cluttered environments, desert ants, Cataglyphis fortis, tend to run along the midlines of the alleys formed by adjacent low shrubs. This 'centring response' was investigated by inducing foraging ants to walk through artificial channels. The sidewalls of the channel were either homogeneously black or provided with stationary or moving black-and-white gratings. The speed of motion and the spatial period of the gratings and the height of the walls could be varied independently on the left-hand and right-hand sides of the channel. The results clearly show that the ants, while exhibiting their centring responses, try to balance neither the self-induced image speeds nor the contrast frequencies seen in their left and right visual fields, but the vertical angle subtended by the landmarks on either side. When manoeuvring through the channel, the ants always adjust the lateral positions of their walking trajectories in such a way that the vertical angles subtended by the walls are identical for both eyes. (+info)
The use of ground-borne vibrations for prey localization in the Saharan sand vipers (Cerastes).
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Sand vipers of the genus Cerastes are specialized semi-fossorial snakes that launch predatory strikes at rodents and lizards while partially buried in the soft sand of the Saharan desert. This study attempted to document which environmental stimuli are used by these snakes as a trigger for the ambush behavior. Denervating the olfactory and vomeronasal organs produced no changes in prey capture behavior in Cerastes cerastes. Occluding the eyes of the denervated specimens resulted in significant decreases in strike distance, diversity of strike angle and strike accuracy, demonstrating the importance of visual stimuli for target acquisition in this species. Nevertheless, every olfactory-denervated, temporarily blinded specimen succeeded in capturing free-ranging mice in every trial. Presentation of chemosensory-neutral targets to the olfactory-denervated, temporarily blinded specimens resulted in similar predatory behaviors, whether the target was isothermic to the environment or heated to mammalian body temperature. Collectively, these results provide evidence for the importance of visual stimuli during foraging in C. cerastes, the first experimental evidence for foraging by vibration detection in snakes and the strongest evidence to date that snakes are capable of 'hearing' vibrational stimuli. (+info)
Metabolic rate and respiratory gas-exchange patterns in tenebrionid beetles from the Negev Highlands, Israel.
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This study correlates the pattern of external gas exchange with the diel activity of nine species of tenebrionid beetle from the Negev Desert, Israel. The study species are active throughout the summer months when daytime temperatures are high and no rain falls. There were no differences in standard metabolic rate, determined by flow-through respirometry, among the nine species. All the nocturnally active beetles exhibited a form of continuous respiration, whereas the two diurnally active and one crepuscular species exhibited a cyclic form of respiration referred to as the discontinuous gas-exchange cycle (DGC). The DGCs recorded have a long flutter period consisting of miniature ventilations, and 29-48 % of the total CO(2) output occurred during this period. In this study, the flutter period played an important role in the modulation of metabolic rate, in contrast to other studies in which the burst period has been shown to be important. We suggest that the long flutter period is important in reducing respiratory water loss in arid-dwelling arthropods. This study lends support to the hypothesis that discontinuous gas exchange is important in reducing respiratory water loss from beetles that need to minimise dessication because of the high water vapour pressure gradient they experience. If the use of underground burrows were responsible for the evolution of discontinuous gas exchange, then we would expect all nine tenebrionid species to use DGCs since both the nocturnally and diurnally active species bury in the sand during periods of inactivity. We conclude that the activity patterns of the beetles are more important than their habitat associations in designating the type of respiration used. (+info)
Preweaning growth of F1 tropically adapted beef cattle breeds x Angus and reproductive performance of their Angus dams in arid rangeland.
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The objective of this study was to determine the preweaning performance of F1 Brahman (Bos indicus)-, Senepol (Bos taurus)-, and Tuli (Sanga)-Angus calves under semiarid south Texas conditions and to evaluate the reproductive performance of their Angus dams. Four hundred eighty-nine records collected over 4 yr were analyzed. The statistical model for performance traits included the effects of breed of sire, year, sex, age of dam, and breed of sire x year. Year effects were important (P < 0.05) for performance traits but could be explained, at least partially, by differences between years in rainfall patterns. Brahman F1 calves were 13% less (P < 0.05) vigorous at birth, 4.7 kg heavier (P < 0.05) at birth, 13.5 kg heavier (P < 0.05) at weaning, 0.25 units lower (P < 0.05) in body condition score (BCS) at weaning, and 1.75 units greater (P < 0.05) in frame score (scores of 1 to 9) at weaning than Tuli and Senepol F1 calves. Senepol F1 calves were intermediate (P < 0.05) between the Brahman and Tuli F1 calves for birth and weaning weight but had 11% more (P < 0.05) vigor at birth than the other two crossbreds. Tuli and Senepol F1 were similar (P > 0.05) in BCS and frame size at weaning. Males were 3.3 kg heavier (P = 0.12) at birth than females, especially for the F1 Brahman males that were 4.5 kg heavier (P < 0.05) than their counterparts. Brahman F1 weaned 19.9 kg heavier (P < 0.05) than the average of the other two F1 in the year of the greatest rainfall (1994), whereas the average advantage in other years was 11.4 kg. This difference gave rise to a breed of sire x year interaction (P < 0.003). Brahman F1 were heavier at every measurement and appeared to be later-maturing and more able to excel under good forage conditions than the other two F1 breed types; Senepol and Tuli F1 were similar (P > 0.05) in these respects but appeared to be more competitive in relative growth rate to the Brahman F1 calves in years of greater nutritional stress. Angus females were observed to have a relatively low reproductive rate and high apparent fetal loss at the first (27.5%) and second (19.2%) compared with the third or later pregnancy (11.2%). Angus females that gave birth to Brahman F1 calves had 20.1% lower (P < 0.05) pregnancy rates in the succeeding year than those that had given birth to the other two breeds. (+info)