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
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
The monophyly of the subgenus Leptempis Collin of the genus Empis L. is established on the basis of a male hypopygial character, and the possibility of a close relationship between the subgenera Leptempis Collin, Planempis Frey and Kritempis Collin is discussed. Seven new species belonging to Empis (Leptempis) rustica-group are described from France, Germany, Greece and Spain: E. (L.) abdominalis sp. n., E. (L.) lamellata sp. n., E. (L.) multispina sp. n., E. (L.) pandellei sp. n., E. (L.) lamellimmanis sp. n., E. (L.) sinuosa sp. n. and E. (L.) trunca sp. n. A key to the E. (L.) rustica-group is presented., Christophe Daugeron, and Lit
Myotropic neuropeptides were isolated from the retrocerebral complex of the stick insect, Carausius morosus, by using three HPLC steps. Bioactivity during purification was measured by heterologous bioassays monitoring the contractions of the hyperneural muscle and hindgut of the American cockroach. Additionally, fractions not active in these bioassays were tested in a homologous bioassay evoking contractions of the hindgut of C. morosus. Peptide sequence analysis and mass spectrometry yielded the following structures: Pro-Phe-Cys-Asn-Ala-Phe-Thr-Gly-Cys-NH2 (CCAP), pGlu-Thr-Phe-Gln-Tyr-Ser-His-Gly-Trp-Thr-Asn-NH2 (His7-corazonin) and Asp-Glu-Gly-Gly-Thr-Gln-Tyr-Thr-Pro-Arg-Leu-NH2 (Cam-PK-1). These neuropeptides are the first myotropins isolated from C. morosus. The most bioactive compound in the homologous bioassay, the C. morosus-hindgut assay, was CCAP., Reinhard Predel, Roland Kellner, Gerd Gäde, and Lit
Teploty vzduchu okolo 100 °C, erupce sopek, blesky, dopady masivních asteroidů, silné ultrafialové zářeni. Jak v takovém pekle na Zemi před čtyřmi miliardam ilet mohl vzniknou život? Otazek je více než odpovědí a pátrání po původu živoat zůstává dobrodružnou disciplínou, v níž spolu soupeří zastánci různých teorii. and Luděk Svoboda, Stanislava Kyselová.