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.
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
Článek shrnuje dosavadní znalosti o druhové diverzitě, bionomii a rozšíření rodu Purpuricenus (Coleoptera, Cerambycidae) na území Íránu s dílčími poznámky o jejich výskytu a ekologii., The article summarises recent knowledge related to the diversity, bionomy and distribution of species of the genus Purpuricenus (Coleoptera, Cerambycidae) in Iran. Some previously less known occurence data and ecological notes are briefly mentioned., and Jiří Simandl.
Společenstva mravenců většinou reagují na změny jejich biotopů méně výrazně než společenstva jiných organismů. V biotopech měnících se pozvolněji (např. neobhospodařované louky) se zpravidla dlouho zachovává původní druhová skladba myrmekofauny, zatímco výměna druhů z jiných skupin (rostlin i většiny bezobratlých) je mnohem rychlejší. Podobně na člověkem výrazně pozměněných lokalitách typu výsypek, odkališť nebo pískoven společenstvo mravenců velmi často sestává pouze z několika běžných druhů, zatímco mezi ostatními organismy se obyčejně najde řada druhů z Červené knihy. Mezi příčiny těchto rozdílů patří zejména značná schopnost mravenců regulovat podmínky panující v hnízdě, jejich agresivita a způsob šíření. Nově vzniklou lokalitu nejrychleji osídlí druhy mravenců běžné v okolí, kdežto obecně vzácnější specialisté mají zpoždění a již existující kolonie dříve příchozích je na lokalitu nepustí. Na druhou stranu z výskytu kolonií druhů na místech pro ně nevhodných může ukazovat, že na těchto lokalitách panovaly v uplynulých letech podmínky odlišné., Ant assemblages are usually less affected by environmental alteration than other organisms. They persist without obvious changes in slowly changing habitats (e.g. unmanaged meadows) much longer than assemblages of plants or most invertebrates. Similarly, communities of ants consist of several common species in anthropogenic habitats (spoil dumps, coal ash settling basins or sandpits) whereas assemblages of other organisms usually contain some rare and endangered species. The ability of ants to regulate environmental conditions in nests, their agressivity and mode of dispersion play an important role in this respect. A new locality is often first colonised by common ant species. The occurrence of colonies of certain species in habitats with suboptimal conditions can indicate the past changes of local environmental conditions., and Pavel Pech.
The nature and rate of juvenile hormone (JH) biosynthesis and effects of allatostatins and allatotropin have been investigated in isolated corpora allata (CA) of adults and larvae of the noctuid tomato moth, Lacanobia oleracea. In adult female CA, mean rates of synthesis were relatively constant (10-16 pmol/pr/h) at all times. However, the range of JH synthesis by individual CA of similarly aged insects was quite large (2-30 pmol/pr/h). High performance liquid chromatography (HPLC) separation shows that adult female moth CA synthesise predominantly JH I and JH II. Rates of JH synthesis in vitro are dependent on methionine concentration. Synthetic Manduca sexta allatostatin (Mas-AS) caused a dose-dependent inhibition of JH synthesis by adult female CA but only to a max. of 54%, whilst 10 µM synthetic M. sexta allatotropin caused a 37% stimulation of CA activity. At 1 mM the cockroach allatostatin, Dip-allatostatin-2, had no significant effect on JH synthesis. In larval L. oleracea, rates of JH biosynthesis were very low., Neil Audsley, Robert J. Weaver, John P. Edwards, and Lit
Vybrat vhodnou metodu sběru hmyzu tak, aby byla efektivní a přitom poskytovala relevantní data, není vůbec snadné. Na základě rozsáhlého datového souboru se ukázalo, že zemní pasti, standardně používaná metoda při ekologickém výzkumu epigeických členovců, zaznamenaly jen polovinu druhů střevlíků ve srovnání s metodou individuálního sběru. Výrazně se lišily i vlastnosti zaznamenaných druhů, v pastech převládaly druhy velké, kdežto ve vzorcích z individuálního sběru druhy drobné. Ale i metoda individuálního sběru má své mouchy, protože její účinnost do značné míry závisela na terénních zkušenostech sběratele. Ideálním řešením zajišťujícím co nejkompletnější záznam společenstev střevlíků se zdá být kombinace obou metod sběru dat., The selection of a proper sampling technique for ecological research into insect assemblages is a tough nut to crack. Based on extensive field study, I have shown that the commonly employed "pitfall trapping" technique recorded just half the number of carabid species compared to the individual collection technique. There were also differences in species trait representation in samples originating from each particular technique. Pitfall traps efficiently recorded large species but missed smaller ones, which were frequently recorded by individual collection. The main shortcoming of the individual collection technique is the dependence of its efficiency on the field experiences of each particular researcher. A combination of both investigated sampling techniques seems to be the best way to gain as complete records of carabid assemblages as possible., and Michal Knapp.
Climate features that influence life cycles, notably severity, seasonality, unpredictability and variability, are summarized for different polar zones. The zones differ widely in these factors and how they are combined. For example, seasonality is markedly reduced by oceanic influences in the Subantarctic. Information about the life cycles of Arctic and Antarctic arthropods is reviewed to assess the relative contributions of flexibility and programming to life cycles in polar regions. A wide range of life cycles occurs in polar arthropods and, when whole life cycles are considered, fixed or programmed elements are well represented, in contrast to some recent opinions that emphasize the prevalence of flexible or opportunistic responses. Programmed responses ale especially common for controlling the appearance of stages that are sensitive to adverse conditions, such as the reproductive adult. The relative contribution of flexibility and programming to different life cycles is correlated with taxonomic affinity (which establishes the general lifecycle framework for a species), and with climatic zone, the habitats of immature and adult stages, and food., Hugh V. Danks, and Lit
Vodní toky v ČR jsou v posledních sto letech vystaveny intenzivnímu antropogennímu tlaku. Tyto činnosti se projevují také na populaci druhu marše pobřežní (Tetrix tuerki), který se vyskytuje se pouze na štěrkových lavicích podhorských potoků a řek. Národní přírodní památka Skalická Morávka je ideálním místem pro tento druh. Dynamika štěrkových lavic je velmi důležitá pro existenci tohoto druhu., Water flows have been under intensive anthropogenic pressure over the last 100 years. These activities also influenced populations of Tetrix tuerki, which only occurs on gravel benches of streams and rivers (dynamics of the benches are crucial for its existence). The National Natural Monument Skalická Morávka provides an ideal habitat., and Kateřina Kuřavová.
In view of the extremely high metabolic rates involved, insect flight offers a fascinating model system for studying metabolism during exercise, including its regulation by metabolic neurohormones. In our laboratory the African migratory locust, Locusta migratoria, well-known for its long-distance flights, is used as an internationally recognized model insect. The insect is mass-reared under controlled conditions; its size permits convenient handling in vivo and in vitro, while flight activity can be easily evoked. In addition, research on this pest insect may be of economical importance.
A survey of the energy metabolism during locust flight is presented in Fig. 1. Flight activity stimulates the neurosecretory adipokinetic cells in the glandular lobes of the corpus cardiacum, a neuroendocrine gland connected with the insect brain, to release peptide neurohormones, the adipokinetic hormones (AKHs). The target for these hormones is the fat body. Via signal transduction processes, the action of the hormones ultimately results in the mobilization of both carbohydrate and lipid reserves as fuels for flight. Carbohydrate (trehalose) is mobilized from glycogen reserves, implying hormonal activation of the key enzyme, fat body glycogen phosphorylase, by phosphorylation. Similarly, on the lipid side, sn-1,2-diacylglycerol (DAG) is mobilized from stored triacylglycerol (TAG), by hormonal activation of the fat body TAG lipase. The carbohydrate and lipid substrates are transported in the hemolymph to the contracting flight muscles. Carbohydrate provides most of the energy for the initial period of flight, whereas at a later stage, lipid substrate in the blood is increased and gradually takes over. The transport of DAG requires specific lipoprotein carriers (lipophorins) which differ in several respects from the lipoproteins in mammals, and act as a lipid shuttle.
This review is focused on three interrelated topics, covering recent data on the biosynthesis and release of the AKHs, their signal transduction mechanisms in the fat body cells, and the changes in the lipophorin system induced by the AKHs during flight., Dick J. Van Der Horst, Wil J.A. Van Marrewijk, Henk G.B. Vullings, Jacques H.B. Diederen, and Lit