Body size evolution in South American Liolaemus lizards of the boulengeri clade: a contrasting reassessment

Bergmann's rule predicts larger body sizes in species living in higher latitudes and altitudes. This rule appears to be valid for endotherms, but its relevance to ectotherm vertebrates has largely been debated. In squamate reptiles (lizards and snakes), only one study, based on Liolaemus species of the boulengeri clade, has provided phylogenetic evidence in favour of Bergmann's clines. We reassessed this model in the same lizard clade, using a more representative measure of species body size and including a larger number of taxa in the sample. We found no evidence to support Bergmann's rule in this lineage. However, these non-significant results appear to be explained only by the inclusion of further species rather than by a different estimation of body size. Analyses conducted on the 16 species included in the previous study always revealed significant relationships between body size and latitude-altitude, whereas, the enlarged sample always rejected the pattern predicted by Bergmann's rule.     

Requirements for obtaining maximum indices of photosynthesis and transpiration in attached leaves of willow plants grown in short-rotation forest

The results of multiyear studies of gas exchange in intact attached leaves of several willow species (Salix sp.) were analyzed. Measurements were performed with a portable Li-6400 infrared gas analyzer both on plants in their natural environment and on rooted cuttings grown in a greenhouse. Individual attached leaves were placed into the leaf chamber where climatic conditions were either similar to or different from those outside the chamber. The maximal rates of net photosynthesis (P _n) and transpiration (E) were only observed with the provision that the environmental variables inside and outside the chamber were identical. On rainy or cloudy days, the P _n and E values observed under optimum conditions inside the leaf chamber were lower than their potential maxima by 12–18% and 35–45%, respectively. Deviation of temperature in the chamber by 5–7°C from the external level and fluctuations of ambient temperature affected P _n but not E rates of tested leaves. Variations in relative air humidity in the chamber directly influenced E but had no effect on P _n of attached leaves. It was shown that the maximum rates of gas exchange in the attached willow leaf could be only attained by providing optimum conditions for the whole plant.     

Daily temperature gradients and processes of organogenesis in apical meristem of <Emphasis Type="Italic">Cucumis sativus</Emphasis> L.

We studied the influence of daily temperature gradients on organogenesis in apical and axil shoot meristems at different developmental stages in Cucumis sativus L. The level of organogenic activity of meristems was determined according to the number of leaf primordia on the main and lateral shoots, number of 2nd order shoots, and rudiments of flowers of different levels of development. At the studied ontogenetic stages (mesotrophic seedling or juvenile state), plants were grown under the controlled conditions: photoperiod 12 h, light intensity 100 Wt/m², range of mean daily temperatures 20…30°C, and daily temperature gradients ?20…+20°C. After the temperature treatment, some plants were returned to the optimal, for growth and development, conditions for two weeks (aftereffect). Three types of organogenic activity of meristems in response to the influence of variable daily temperatures were described: stimulation, inhibition, or absence of effect. The phenomenon of stimulation includes two subtypes: optimization, when a maximum effect, observed at other constant temperatures, was attained under the influence of variable temperatures and maximization, when maximum values markedly exceeded those at constant temperatures. The patterns described are preserved on the whole in the aftereffect of daily temperatures.     

Seasonal dynamics of fish assemblage structures in a surf zone on an exposed sandy beach in Japan

Seasonal dynamics in fish assemblage structure, comprising postlarval to early adult stages, in the surf zone on an exposed sandy beach on the Kashimanada coast were studied over a 2-year period. A total of 32 species and two higher group taxa were found. In terms of abundance, Salangichthys ishikawae, Mugil cephalus cephalus, Plecoglossus altivelis altivelis, and Engraulis japonicus were the four most dominant species. The results of cluster analysis and canonical correspondence analysis using 12 dominant species in terms of abundance revealed that water temperature and wind factor (wind speed × wind direction) had significant independent associations on species occurrence patterns for 11 species; that is, occurrence of 11 species was significantly related to water temperature and occurrence of 7 species was related to wind factor. Two species (S. ishikawae and P. altivelis altivelis) showed clear monthly increases in size, consequently suggesting their use of the surf zone as a nursery area. In contrast, M. cephalus cephalus and E. japonicus showed few increases in standard length, indicating their use of the surf zone only in their postlarval and/or juvenile stage. It is suggested that numerous fish species use the surf zone as shelter and/or a nursery area, even in the harsh conditions of an exposed sandy beach with great wave action.     

Habituation and habitat changes can moderate the impacts of human disturbance on shorebird breeding performance

Disturbance by humans is widely expected to reduce the reproductive fitness of nesting birds if disturbance reduces nest attentiveness, and unattended eggs experience increased risk of predation or exposure to potentially lethal temperature extremes. Yet, relatively few studies have examined the physiological or behavioural mechanisms whereby disturbance influences reproductive fitness, or the extent to which the costs of disturbance may be reduced through habituation. We compared the behavioural responses, egg temperatures and reproductive success of shore-nesting white-fronted plovers Charadrius marginatus to disturbance at two breeding sites experiencing low versus high human recreational activity, respectively. Daytime nest attentiveness decreased with increasing experimental disturbance at both sites, but this relationship differed between sites; for any given level of disturbance, incubating birds at the more disturbed site had greater nest attentiveness. They achieved this through habituation, allowing a closer human approach before leaving the nest, and returning to the nest faster after a disturbance event. Despite lower average daytime nest attentiveness at the more disturbed site, incubation temperatures did not differ significantly between sites. Nest mortality, mostly by natural mammalian and corvid predators, was significantly lower at the site experiencing high recreational activity. However, chick mortality was significantly greater at the more disturbed site, most likely because of predation by domestic dogs. Chick mortality may have been increased by the habitation of chicks, whose escape responses were much reduced at the more disturbed site. Nonetheless, annual fecundity was substantially higher at the more disturbed site, showing that the overall reproductive fitness of wild birds is not always compromised by human disturbance and urbanization.     

Effect of pH, temperature and nutrient limitations on growth and leukotoxin production by Mannheimia haemolytica in batch and continuous culture

AIMS: Quantification of the effects of pH, temperature and nutrient limitations on the growth and leukotoxin (LKT) production parameters of Mannheimia haemolytica in batch and chemostat culture. METHODS AND RESULTS: Mannheimia haemolytica strains OVI-1 and PH12296 were grown aerobically in two semi-defined media. In amino acid-limited cultures, the LKT concentration and yield in terms of biomass (Y(LKT/x)) were up to eightfold greater than in carbon-limited cultures. Supplementing amino acid-limited chemostat cultures with cysteine, glutamine, ferric iron and manganese further enhanced the Y(LKT/x) values up to threefold. Supplementation of an amino acid-limited batch culture of M. haemolytica strain OVI-1 with these nutrients resulted in an LKT concentration of 1.77 g l(-1) that was 45-fold greater than that obtained in RPMI 1640 medium. Aerobiosis enhanced LKT production. High acetic acid concentrations were produced under carbon-sufficient conditions. The highest maximum specific growth rates were recorded in the range of pH 6.8 to 7.8 and 37 to 40 degrees C. CONCLUSIONS: An amino acid-limited culture medium greatly improved LKT production in aerobic batch culture, which could be further enhanced by supplementation with cysteine, glutamine, ferric iron and manganese. SIGNIFICANCE AND IMPACT OF THE STUDY: It was demonstrated that LKT production by M. haemolytica could be dramatically increased through manipulation of the culture medium composition, which could benefit the production of LKT-based vaccines against bovine shipping fever pneumonia.     

昼间亚高温下番茄叶中糖含量与蔗糖代谢相关酶的活性日变化

研究番茄品种‘辽园多丽’幼苗在昼间35℃亚高温条件下叶中糖含量及蔗糖代谢相关酶活性日变化的结果表明,昼间亚高温处理后的幼苗叶中果糖、葡萄糖和淀粉含量下降,蔗糖含量升高。与蔗糖代谢相关的酶活性有明显的昼夜节律性变化,转化酶、蔗糖合成酶呈现昼间活性低、夜间活性高的节律性,而蔗糖磷酸合成酶活性在进入夜间时立刻升高。35℃昼间亚高温处理后的幼苗叶中,转化酶活性下降,蔗糖合成酶活性明显升高,蔗糖磷酸合成酶活性则略有升高。     

温度对大猿叶虫发育、存活和繁殖的影响

在光周期14L:10D、75%RH的条件下研究不同温度对大猿叶虫Colaphellus bowringi Baly生长发育、存活率和繁殖的影响。结果表明,卵、幼虫和蛹的发育起点温度分别为11·86,11·17和10·15℃,有效积温分别为61·6,110·8和65·3日·度;22℃时卵的孵化率和蛹的羽化率最高,分别达96·04%和94·26%;滞育后成虫寿命雌虫普遍长于雄虫,25℃下的产卵期11～34d,每雌产卵量平均861粒,最高达1527粒。     

药材甲发育起点温度和有效积温

在恒温条件下用新鲜药材甘遂饲养药材甲Stegobium paniceum(L.),测定药材甲各虫态(龄)的发育历期,结果表明,该虫卵、幼虫、蛹、产卵前期及世代发育起点温度分别是5.05,8.45,9.06,8.36和8.01℃,有效积温分别是177.9,745.5,127.9,37.8和1094.1日.度。