Hlavním druhem posledního dílu horečkové části seriálu je hořeček nahořklý. Jde o široce rozšířený druh - Evropa, severní Asie až po střední Sibiř, Dálný východ, Severní Amerika. Počet lokalit a velikost populací tohoto druhu však v ČR v posledních dekádách dramaticky poklesl. V současné době je prokázán ze 71 lokalit (70 lokalit G. amarella subsp. amarella a jedna lokalita G. amarella subsp. lingulata). Z ČR je známo též několik horečkových kříženců. Do současnosti se zachovaly populace dvou z nich. U hořečků je známé synchronizované kolísání velikosti populací. V ČR lze tento jev dokumentovat na dvou druzích přežívajících dosud ve více populacích (G. praecox subsp. bohemica a G. amarella). Příčiny synchronizace nejsou známy. Jednou z hypotéz je masivní klíčení, růst a v dalším roce kvetení hořečků v mezerách nárazově vytvořených v jinak relativně zapojeném travním porostu. Synchronizované vytvoření mezer v porostu pak může být způsobeno přísuškem během vegetační sezóny., G. amarella is a widely distributed species (Europe, northern Asia to Central Siberia, the Far East and North America); however, the number of its sites and population size have decreased dramatically in the last few decades in the Czech Republic. At present, the species is documented from 71 sites here (70 sites of G. a. subsp. amarella, one site of G. a. subsp. lingulata). Several hybrids of Gentianella species are also known from the Czech Republic (two of them have survived so far). A synchronized inter-annual fluctuation in population size is documented for G. praecox subsp. bohemica and G. amarella in the Czech Republic. The reasons behind, however, remain unclear. Massive establishment, survival and flowering in the year following the creation of gaps in vegetation have been suggested as an explanation. Synchronized occurrence of gaps may be caused by a dry period during the growing season., Jiří Brabec., and Obsahuje seznam literatury
In the parthenogenetic monogeneans of the genus Gyrodactylus Nordmann, 1832, the genetic diversity within or between hosts is determined by the relative roles of lateral transmission and clonal propagation. Clonality and limited transmission lead to high-amplitude metapopulation dynamics and strong genetic drift. In Baltic populations of the three-spined stickleback Gasterosteus aculeatus Linnaeus, the local mitochondrial diversity of Gyrodactylus arcuatus Bychowsky, 1933 is very high, and spatial differentiation weak. To understand the transmission dynamics in a single location, the transmission of the parasite from adults to next generation sticklebacks was investigated in a northern Baltic brackish water location. By sequencing 777 nt of cox1, as many as 38 separate mitochondrial haplotypes were identified. In August, the intensity of gyrodactylid infection on adult hosts was high, the haplotype diversity (h) was extreme and differentiation between fish was negligible (total h = 0.926, mean h = 0.938). In October, only 46% of the juvenile sticklebacks carried G. arcuatus. The number of parasites per young fish followed a Poisson distribution 0.92 ± 1.04 (mean ± SD) on October 2, and was clearly overdispersed 2.38 ± 5.00 on October 25. The total haplotype diversity of parasites on juveniles was nearly as high as in adults (h = 0.916), but the mean per fish was only h = 0.364 (FST = 0.60), due to low intensity of infection and rapid clonal propagation of early arrivals. The initial first come first served advantage of the first gyrodactylid colonisers will be lost during the host adulthood via continuous transmission. Nesting and polygamy are suggested as factors maintaining the high genetic diversity of the parasite population. The transmission dynamics and, consequently, the population structure of Baltic G. arcuatus is fundamentally different from that of G. salaris Malmberg, 1957, on the Baltic salmon Salmo salar Linnaeus., Jaakko Lumme, Marek S. Ziętara., and Obsahuje bibliografii
Hmyzí hormonální soustava se skládá z několika typů žláz produkujících tři různé druhy hormonů – ekdysteroidy, juvenilní hormony a peptidické neurohormony. Struktura, funkční koordinace a vzájemné vztahy v této soustavě představují dobře organizovaný řídicí systém, který v zásadě pracuje stejně jako hormonální soustava obratlovců: řídí prakticky všechny životní projevy hmyzu. Jedna skupina hmyzích metabolických neurohormonů – adipokinetické hormony – hraje důležitou roli v odpovědi organismu na stresové podmínky. Tyto hormony zajišťují mobilizaci energetických zdrojů, stimulují pohybovou aktivitu, zvyšují činnost srdce, aktivují imunitní systém a nedůležité procesy odsouvají na pozdější dobu. Touto koordinovanou činností umožňují hmyzímu organismu vyrovnávat se s nepříznivými podmínkami vnějšího prostředí a podílet se tak na udržování homeostázy vnitřního prostředí., The insect hormonal system consists of several types of endocrine glands which produce three different hormones – ecdysteroids, juvenile hormones and peptidic neurohormones. The structure, functional coordination and mutual relationships within the system are a well organised control system resembling the hormonal system of vertebrates: it controls practically all aspects of insect life. One group of insect metabolic neurohormones called adipokinetic hormones plays an important role in the defence of the insect organism against stress. Those hormones control energy mobilization, stimulate locomotory activity and the heart beat, activate the immune system and postpone less important processes for later. That sophisticated system helps the insect organism to cope with negative environmental conditions and to retain the body homeostasis., and Dalibor Kodrík.
We deployed branch traps in an ash (Fraxinus) plantation to investigate how Agrilus planipennis behavior is associated with Fraxinus pennsylvanica condition and dispersal patterns. Data were collected from traps with or without the presence of beetle visual decoys, and from a yearly survey of exit holes. The traps were placed on trees that were either clearly declining, with most foliage arising from epicormic sprouting, or on apparently healthy trees, with little evidence of damage or decline. We calculated correlations of exit holes among neighboring tree rings and also between exit holes and male trap captures. The damaged trees the traps were hung upon had more cumulative exit holes observed than the corresponding healthy trees. However, there was otherwise no evidence that the experiment was biased by differences in exit hole patterns of the surrounding trees. Male captures were greater on decoy-baited traps than controls and this decoy effect was most clearly apparent late in the season when traps were placed on healthy trees. There were also patterns of correlations between male captures and exit hole numbers that may be indicative of short-range mate finding-and dispersal behaviors. Female captures were sparser, but were positively affected by decoys on healthy and declining trees early in the season. Thus, the results suggest that the placement of such traps on healthier trees will maximize detection, and the branch traps also show promise for further use in dispersal studies., Michael J. Domingue, Jennifer Berkebile, Kim Steiner, Loyal P. Hall, Kevin R. Cloonan, David Lance, Thomas C. Baker., and Obsahuje bibliografii
Aphis fabae and Myzus persicae (Hemiptera: Aphididae) are insect pests that damage sugar beet and bean crops. Both are responsible for losses in yield and transmission of viral diseases, and may be present on the same host at the same time. Three parasitoid species, Aphidius colemani, Lysiphlebus testaceipes and Lysiphlebus fabarum (Hymenoptera: Braconidae: Aphidiinae) have the potential to be used as biological control agents against at least one of these species of aphids. As a first step prior to the implementation of a biological control program, our aim was to understand the host selection behaviour of the parasitoids, particularly when both aphids are present. We recorded the host acceptance (number of insertions of the ovipositor / number of antennal contacts), suitability (number of mummies / the number of insertions of the ovipositor) and emergence (number of adults emerging from mummies) of these three aphid parasitoids when parasitizing the two aphids. We also analyzed the effect of the host plant on the host preference of the parasitoid. Females of each parasitoid species (n = 15) were exposed to 20 aphids of A. fabae or M. persicae, or a mixture of these two species of aphids, for 15 min, on a leaf disc of each of the two host plants, sugar beet and bean. Higher host acceptance and suitability were recorded for A. colemani attacking both species of aphid: A. fabae (43 and 46%) and M. persicae (43 and 46%) on beet and bean plants respectively, compared to L. testaceipes and L. fabarum. L. testaceipes and L. fabarum showed a clear preference for A. fabae. L. fabarum accepted M. persicae on both plants only when it was mixed with A. fabae, probably due to a confusion effect. We found that the host plant played a significant role in host acceptance, host suitability. We conclude that A. colemani is the better of the three parasitoids studied for the biological control in bean, and particularly, sugar beet crops. and Loulou Albittar, Mohannad Ismail, Claude Bragard, Thierry Hance.