Most studies of responses of insects to elevated carbon dioxide have been made using short-term exposures to treated food plants and have involved measurements of responses in growth, reproduction, food consumption and efficiencies of conversion at specific stages in the life cycle. These will be reviewed in the light of longer-term studies recently published where whole generations have been reared in chambers with simultaneous treatment of plants and where insects have been free to select their food and microenvironment. Factors such as seasonal change in plants, choice of food plant, mode of feeding, timing of exposure, temperature, the role of natural enemies are considered and the whole placed in the context of other aspects of climate change.
It is concluded that in studies to date, the only feeding guild in which some species have shown increases in population density in elevated carbon dioxide are the phloem feeders. Chewing insects (both free-living,and mining) generally have shown no change or reduction in abundance, though relative abundance may be greatly affected. Compensatory feeding is common in these groups., John B. Whittaker, and Lit
Insect cold tolerance mechanisms are often divided into freezing tolerance and freeze intolerance. This division has been criticised in recent years; Bale (1996) established five categories of cold tolerance. In Bale's view, freezing tolerance is at the extreme end of the spectrum of cold tolerance, and represents insects which are most able to survive low temperatures. Data in the literature from 53 species of freezing tolerant insects suggest that the freezing tolerance strategies of these species are divisible into four groups according to supercooling point (SCP) and lower lethal temperature (LLT): (1) Partially Freezing Tolerant-species that survive a small proportion of their body water converted into ice, (2) Moderately Freezing Tolerant-species die less than ten degrees below their SCP, (3) Strongly Freezing Tolerant-insects with LLTs 20 degrees or more below their SCP, and (4) Freezing Tolerant Species with Low Supercooling Points which freeze at very low temperatures, and can survive a few degrees below their SCP. The last 3 groups can survive the conversion of body water into ice to an equilibrium at sub-lethal environmental temperatures. Statistical analyses of these groups are presented in this paper. However, the data set is small and biased, and there are many other aspects of freezing tolerance, for example proportion of body water frozen, and site of ice nucleation, so these categories may have to be revised in the future. It is concluded that freezing tolerance is not part of Bale's (1996) continuum, but rather a parallel, alternative strategy of cold tolerance., Brent J. Sinclair, and Lit
In the laboratory, not all females of the seed bug Lygaeus simulans Deckert, 1985, produced fertilized eggs after copulation: 26.7% of the females were not inseminated and 5% were inseminated but did not lay fertilized eggs; only in 40% of the couples did copulation result in fertile eggs. The remaining 28.3% of couples refrained from mating. Duration of copulation was associated with insemination and fertilization: (i) fertile eggs were produced by only one couple that copulated for less than 60 min and all those that copulated for more than 360 min, (ii) probability of fertilization increased steadily with duration of copulation between 60 and 360 min, and (iii) duration of copulation was significantly different for couples that showed different insemination status.
A possible morphological explanation for this rime dependency was revealed by examining the genitalia of 69 couples freeze-fixed in copula after different periods in copulation. Because of the intricate structure of the genitalia in L. simulans, a male takes a long time to manoeuver its intromittent organ into the narrow insemination duct of the female. Only if completely inserted is the tip of the intromittent organ close enough for successful ejaculation of sperm into the spermatheca. The freeze-fixing experiment revealed that it usually took the male more than 30 min to locate the entrance to the insemination duct and another 30 min for full penetration. This explains why copulations that lasted less than 60 min failed, since insemination began only after intromission was complete.
The experiments, therefore, indicated that there is a relationship between the complex morphology of the genitalia and the low rates of insemination and fertilization in L. simulans., Thomas Micholitsch, Peter Krügel, Günther Pass, 7 obrázků, 1 tab., and Lit.
The intertidal collembolan Anurida maritima can endure periods of twice-daily submergence by seawater. The air-breathing terrestrial apterygote insect has developed specific adaptations to prevent respiratory failure during hypoxic stress. When submerged, the animal is initially enclosed by an air-bubble. This bubble lasts three times longer than the small amount of stored oxygen would allow. The air bubble acts not only as an oxygen store but also as a compressible gas gill. This was demonstrated by an O2-needle electrode technique which allowed recordings of pO2 changes in the watery medium close to the animal. Oxygen uptake in A. maritima follows an aerial mode of respiration during the first three hours of submergence. Oxygen consumption rate at decreasing ambient O2 partial pressures showed oxyregulating behaviour during severe hypoxia., Dietmar Zinkler, Raimund Rüssbeck, Marc Biefang, Horst Baumgärtl, and Lit
Larval Manduca prothoracic gland cells in vitro responded to prothoracicotropic hormone (PTTH) from neurosecretory cells of the brain with an increase of intracellular free calcium. This effect is reversible and dose-dependent. Preincubation of the glands with TMB-8 and dantrolene, which inhibit the release of calcium from intracellular stores, did not decrease the PTTH-stimulated increase in calcium, indicating that intracellular calcium stores are not involved in the control of ecdysteroidogenesis. Pharmacological studies of the PTTH effect with calcium channel blockers revealed that the increase in calcium was totally blocked by cadmium, partially inhibited by nickel and lanthanum and by amiloride, an antagonist of T-type calcium channels. All other inhibitors tested were ineffective, suggesting that the increase in cytosolic calcium is induced by opening of calcium channels, presumably of the T-type, in response to PTTH. The action of PTTH on these channels may be mediated by a G-protein as shown by the effect of mastoparan, a G-protein activator, which increased the concentration of cytosolic calcium comparable to that evoked by PTTH., Heiner Birkenbeil, and Lit
Jméno dostal teprve v roce 1986, takže tu s námi zdánlivě není dlouho. Nevzal se ale jen tak odnikud, na člověka se přenesl ze šímpanzů na přelomu 19. a 20. století. HIV řadíme mezi lentiviry, které jsou - v širším slova smyslu - mnohem starší. V roce 2008 odvodil tým ze Stanfordovy univerzity stáří jejich předchůdců na 14 milionů let. Experti z Ústavu molekulární genetiky AV ČR je však nejnovějším výzkumem datují ještě mnohem hlouběji do minulosti. Mohl být vzdálený předchůdce viru HIV současníkem dinosaurů? Nebo je dokonce napadat? and Viktor Černoch.
Vede Výzkumné centrum Dvory a rezidence ve středověku, píše odborné knihy o životě na středověkých dvorech a překládá veršované eposy ze staré němčiny 13. století. Zároveň si však umí ušít středověké šaty dobovou technikou nebo vyzkoušet vaření podle dochovalých středověkých receptů. Bádání v historických pramenech i méně obvyklé experimentální přistupy pomáhají Daně Dvořáčkové-Malé z Historického ústavu AV ČR lépe pochopit vytyčený objekt věděckého zájmu - každodenní život panovníckých dvorů a obyvatel středověku. and Leona Matušková, Stanislava Kyselová, Václav Kořínek.