THERMAL EVOLUTION OF EGG SIZE IN DROSOPHILA MELANOGASTER

We measured the size of eggs produced by populations of Drosophila melanogaster that had been collected along latitudinal gradients in different continents or that had undergone several years of culture at different temperatures in the laboratory. Australian and South American populations from higher latitudes produced larger eggs when all were compared at a standard temperature. Laboratory populations that had been evolving at 16.5°C produced larger eggs than populations that had evolved at 25°C or 29°C, suggesting that temperature may be an important selective agent in producing the latitudinal clines. Flies from laboratory populations produced larger eggs at an experimental temperature of 16.5°C than at 25°C, and there was no indication of genotype-environment interaction for egg size. Evolution of egg size in response to temperature cannot be accounted for by differences in adult body size between populations. It is not clear which life-history traits are direct targets of thermal selection and which are showing correlated responses, and disentangling these is a task for the future.     

Non-reciprocal cross-incompatibility in Trichogramma deion

In non-reciprocal cross-incompatibility (NRCI), the crossing of a female of a strain A with a male of a strain B results in hybrid offspring, whereas the reciprocal cross produces few or no hybrids. Only females are of hybrid origin in Hymenoptera because they arise from fertilized eggs; males arise from unfertilized (haploid) eggs. Crosses between many strains of Trichogramma deion showed some degree of NRCI. Crosses between a T. deion culture collected in Seven Pines, California (SVP) with one from Marysville, California (MRY) showed an extreme form of NRCI in which practically no female offspring was produced when MRY females were crossed with SVP males. The reciprocal cross produced a close to normal proportion of female and male offspring. Detailed studied of this cross indicated that 1) the female offspring produced in the compatible interstrain cross were not the result of parthenogenesis but were true hybrids, 2) the incompatible interstrain cross did not produce female offspring because fertilized eggs died during development, 3) the death of these eggs could not be prevented by either antibiotic or temperature treatment, 4) cytoplasmically inherited factors causing NRCI could be discounted because backcrossed females with the genome of MRY and the cytoplasm of SVP, exhibit the NRCI relationship characteristic of their genome. Therefore the NRCI between these strains appears to be caused by a modification coded for by the nuclear genes of MRY that results in incompatibility when SVP sperm fertilizes MRY eggs. In addition the level of incompatibility in crosses between the SVP females and MRY males is temperature sensitive, the higher the rearing temperature the lower the level of compatibility.     

Temperature influence on cohort parameters and demographic characteristics of the two cowpea coreids Clavigralla tomentosicollis and C. shadabi

Age-specific life tables of two important pests of cowpea, Vigna unguiculata (L.) Walp., the pod sucking bugs Clavigralla tomentosicollis Stål and C. shadabi Dolling (Heteroptera: Coreidae), were obtained from observations carried out at different temperatures. A biophysical model was found satisfactory to describe the temperature-response of developmental and mortality rates of egg and nymphal stages, with a peak developmental rate around 34°C in both species. The variability in development times was small and the experimental data did not permit any conclusion with regard to the Erlang probability density function. Survival of eggs and nymphs remained high between 20° and 30°C for both species. At temperatures above 34°C, C. tomentosicollis survivorship and fecundity was higher than that of C. shadabi, which in turn laid more eggs at temperatures between 20° and 30°C. Maximum fecundity is estimated to be at 29°C for C. tomentosicollis (99 eggs/female) and 26°C for C. shadabi (261 eggs/female). At 30°C, the intrinsic rate of increase reached a maximum in both species, 0.152 per day for C. tomentosicollis and 0.145 per day for C. shadabi, and remained high for C. tomentosicollis until 36°C. C. tomentosicollis performed significantly better on pigeonpea, Cajanus cajan Millsp., than on cowpea at higher temperatures.     

The role of β- and α-adrenoreceptors on blood flow and temperature of brown adipose tissue and involvement of nitric oxide in their effects

1. o

2. 1. Isoproterenol increased interscapular brown adipose tissue (BAT) blood flow and temperature.

3. 2. Phenylephrine increased BAT temperature, but did not affect blood flow. The effect was completely suppressed by N^ω-nitro- -arginine methyl ester ( -NAME), an inhibitor of endogenous NO synthesis.

4. 3. Isoproterenol plus phenylephrine increased BAT blood flow and temperature earlier than isoproterenol alone.

5. 4. CL316,243 increased BAT blood flow and temperature. These effects were also inhibited by -NAME.

6. 5. These data suggest that BAT blood flow as well as thermogenesis is regulated mainly by β-adrenoreceptors and partly by α₁-adrenoreceptors, and NO may be a common mediator for their regulations.

     

Neuropeptide Y perfused in the preoptic area of rats shifts extracellular efflux of dopamine,norepinephrine and serotonin during hypothermia and feeding

This study examined the localized action of neuropeptide Y (NPY) on monoamine transmitter activity in the hypothalamus of the unrestrained rat as this peptide induced hypothermia, spontaneous feeding or both responses simultaneously. A guide tube was implanted in the anterior hypothalamic pre-optic area (AH/POA) of Sprague-Dawley rats. Then either control CSF vehicle or NPY in a dose of either 100 ng/μl or 250 ng/μl was perfused by push-pull cannulae in this structure in the fully sated, normothermic rat. Successive perfusions were carried out at a rate of 20 μl/min for 6.0 min with an interval of 6.0 min elapsing between each. Samples of perfusate were assayed by HPLC for their levels of dopamine (DA), norepinephrine (NE), serotonin (5-HT) and their respective metabolites. Whereas control CSF was without effect on body temperature (T_b) or feeding, repeated perfusions of NPY over 3.0 hr caused dose—dependent eating from 4 to 39 g of food, hypothermia of 0.9 to 2.3°C or both responses concurrently. As the rats consumed 11–39 g of food, the efflux of NE, MHPG, DOPAC and 5-HT was enhanced significantly, whereas during the fall in T_b the efflux of NE, DOPAC and 5-HIAA from the AH/POA increased. When the T_b of the rat declined simultaneously with eating behavior, the levels in perfusate of DOPAC and HVA increased significantly while MHPG declined. During perfusion of the AH/POA with NPY the turnover of NE declined while DA and 5-HT turnover increased during hypothermia alone or when accompanied by feeding. These results demonstrate that the sustained elevation in NPY within the AH/POA causes a selective alteration in the activity of the neurotransmitters implicated in thermoregulation, satiety and hunger. These findings suggest that both DA and NE comprise intermediary factors facilitating the action of NPY on neurons involved in thermoregulatory and ingestive processes. The local activity of NPY on hypothalamic neurons apparently shifts the functional balance of serotonergic and catecholaminergic neurons now thought to play a primary role in the control of energy metabolism and caloric intake.     

不同温度对三带喙库蚊卵的保存及不同食料对幼虫发育的影响

用不同温度对三带喙库蚊卵的保存进行了试验,发现蚊卵在10℃条件下仅可保存两天,而2℃、5℃、11℃以上等其他温度均不宜保存．因此证实该蚊卵不能在任何温度下作长时间保存。通过实验观察了以6种不同配方的食料饲养三带喙库蚊幼虫,结果显示用鱼粉、面粉、酵母粉组合成的6号组食料经综合分析优于其他组食料。进一步说明动物蛋白的种类、配比对蚊幼虫的存活、健康关系极大。     

温度对粘虫产生和释放性信息素规律的影响

在21℃饲养的粘虫雌蛾腺体提取物中Zll－16：Aid含量峰值时间是羽化后第8～9天;25℃是羽化后第4～5天,27℃是羽化后第3～4天。低温不仅推迟了粘虫雌蛾求偶和释放性信息素的时间,而且降低了腺体中性信息素的滴度。在27℃,粘虫雌蛾腺体中Zll－16：Ald峰值的平均值达15ng;在25℃时为10ng,而在21℃时,只有5ng。由此可见,低温环境明显抑制粘虫雌蛾的性发育,延缓了性成熟。     

Free Air Temperature Increase (FATI): a new tool to study global warming effects on plants in the field

A new technique, called Free Air Temperature Increase (FATI), was developed to artificially induce increased canopy temperature in field conditions without the use of enclosures. This acronym was chosen in analogy with FACE (Free Air CO₂ Enrichment), a technique which produces elevated CO₂ concentrations [CO₂] in open field conditions. The FATI system simulates global warming in small ecosystems of limited height, using infrared heaters from which all radiation below 800 nm is removed by selective cut-off filters to avoid undesirable photomorpho-genetic effects. An electronic control circuit tracks the ambient canopy temperature in an unheated reference plot with thermocouples, and modulates the radiant energy from the lamps to produce a 2.5°C increment in the canopy temperature of an associated heated plot (continuously day and night). This pre-set target differential is relatively-constant over time due to the fast response of the lamps and the use of a proportional action controller (the standard deviation of this increment was <1°C in a 3 week field study with 1007 measurements). Furthermore, the increase in leaf temperature does not depend on the vertical position within the canopy or on the height of the stand. Possible applications and alternative designs are discussed.     

Cold requirement for maximal activity of the bacterial ice nucleation protein INAZ in transgenic plants

The bacterial ice nucleation gene inaZ confers production of ice nuclei when transferred into transgenic plants. Conditioning of the transformed plant tissue at temperatures near 0°C greatly increased the ice nucleation activity in plants, and maximum ice nucleation activity was achieved only after low-temperature conditioning for about 48 h. Although the transgenic plants contain similar amounts of inaZ mRNA at both normal and low temperatures, low temperatures are required for accumulation of INAZ protein. We propose that the stability of the INAZ protein and thus ice nucleation activity in the transgenic plants is enhanced by low-temperature conditioning.