Showing papers in "Naturwissenschaften in 1990"

Identification of a brood pheromone in honeybees

Abstract: 1. Reddy, G. R.: Can. J. Soil Sci. 44, 254 (1964) 2. Zacherl, B., Amberger, A.: VDLUFASchriftenr. 11, 55 (1984) 3. Amberger, A., Vilsmeier, K.: Z. P flanzenernaehr. Bodenkd. 142, 778 (1979) 4. Vilsmeier, K.: ibid. 143, 113 (1980) 5. Vilsmeier, K.: Z. Wasser-AbwasserForsch. 21, 140 (1988) 6. Rathsack, K. : Landw. Forsch. 6, SH, 116 (1955) 7. Hauser, M., Haselwandter, K.: Soil Biol. Biochem. 22, 113 (1990)

Controlled biosynthesis of greigite (Fe 3 S 4 ) in magnetotactic bacteria

Abstract: We report the presence of intracellular greigite crystals in two different types of rod-shaped single-celled magnetotactic bacteria collected from sulfide-rich sites

Enhancement of insect pheromone responses by green leaf volatiles

Abstract: verfahren wird fiir jede Beaufort-St/irkestufe und jedes Jahrzehnt durchgefiihrt, so dab man als Funktion der Zeit far jede Beaufort-St/irke einen Betrag des Luftdruckgradienten erh/ilt. Diesen kann man, etwa mit der heute am besten bestimmten Skala [5], auf Windgeschwindigkeit umrechnen. Damit ist die Umrechnung der Beaufort-St/irkeSch/itzungen friiherer Jahrzehnte auf Windgeschwindigkeiten m6glich. Es sei noch darauf hingewiesen, dab unsere Methode unabh/ingig yon der H~iufigkeitsverteilung des Windes in einem Seegebiet ist, da sie getrennt ftir jede Beaufort-Stufe durchgeftihrt wird. Die sich in einem Gebiet nach der Rekonstruktion ergebenden Wind~inderungen kOnnen daher als lokale Klima/inderungen angesehen werden. Als Beispiel wird hier die rekonstruierte Zeitreihe des Windes aus dem Feld vor der brasilianischen Kiiste wiedergegeben (Fig. 3). W/ihrend man von 1880 bis 1940 eine Zunahme um 0,5 m/s findet, ist nach 1950 praktisch kein von Null verschiedener Trend festzustellen. Diese Aussage gilt speziell fiir das Eingegangen am 17. Oktober 1989

Fat content as a Factor Inducing Migratory Behaviour in the Eel (Anguilla anguilla L.) to the Sargasso Sea

Abstract: Fat content as a factor inducing migratory behaviour in the eel (Anguilla anguilla L.) to the Sargasso Sea

Photocontrol of Weeds Without Herbicides

Abstract: (...) On the basis of 7 years of experience it is proposed to do the last harrowing before sowing or planting, and also these, during the time span between 1 h after sunset and 1 h before sunrise to lessen considerably the emerging weeds in crop fields. Further tillage should be carried out during bright daylight to photostimulate the germination of the weed seeds, and to diminish equivalently their seed bank. This method should allow the restriction of the herbicide load worldwide

Alkalinity: The link between anaerobic basins and shallow water carbonates?

Abstract: Anaerobic ocean basins were common features in earth history. Today, only one large anoxic basin exists, the deep Black Sea (480 000 km3). Massive calcareous deposits are often found in close regional and stratigraphic association with deposits of anoxic basins. The Aptian/Albian and Cenomanian/Turonian anoxic events were, for exarnaple, accompanied by widespread epicontinental chalk and reef limestone deposition. Therefore, one may ask if there is a causal relation between the two facies. In fact, such a connection has been proposed (e.g., [3, 6]). These models describe the general implications of shifting chemoclines and explore consequences of a Ca input, for example, from hydrothermal sources. Here, I present an alternative view which suggests that small changes in the concentration of the total dissolved inorganic carbon (~]CO2) could be responsible. Shifts in ~CO2 affect the supersaturation of CaCO 3 more effectively and therefore faster than the same change in Ca because the Ca concentration in seawater is about ten times that of ~-]CO2. Anaerobic basins are governed by sulfate reduction which mineralizes sinking algal organic matter (i.e., of a Redfield composition [ 12]):

On the presence of tricyclic terpane hydrocarbons in permian tasmanite algae

Abstract: Tricyclic terpane hydrocarbons have been identified as the major biomarkers in Tasmanian tasmanite of Permian age. The aliphatic series is comprised of 8/~, 13ot-dimethyl14/~-alkylpodocarpanes ranging from C19 to C33 and the aromatic series has the 13-methyl-14alkylpodocarpa-8,11,13-trienes from C19 to C40 as the dominant compounds. Other biomarkers (e.g., hopanes, steranes) are essentially absent. Tricyclic terpanes were first reported in the geologic record in bitumen from Green River Formation oil shale [1] and subsequently they have been found as important components of a number of sediment extracts and petroleums [2-13]. The series generally ranges from C19 to C30, with some exceptions to C45 [10, 14] and has proved useful for oil correlation studies (e.g. [4, 12]). The biogenic precursor compounds and the source organisms are not known. Tasmanian tasmanite (Permian, 220-227 Ma) is composed of compressed disks of Tasmanites or tasmanitids (e.g. [15]) and silt, with 29% total organic carbon and 27 %0 ash [16]. These unicellular organisms are thought to be green algae, i.e., zoosporangia of prasinophycean algae ([17]; Sarjeant, pers. commun.), with close biological affinities to the present-day marine organisms Pachysphaera pelagica [18] and other species of Pachysphaera [19]. The organic fossils in the sediments were interpreted to be thickwalled resting spores of such green algae and the associated bitumen their lipid residues [16, 20]. The tasmanitids are unique in that they are derived from a single species and hence were ex-

Sensory performance of blind Mexican cave fish after destruction of the canal neuromasts.

Abstract: 1. Herbst, C.: Mitt. zool. Stat. Neapel. 11, 136 (1893) 2. Hamburger, V.: A Manual of Experimental Embryology. Univ. Chicago Press 1942 3. Kao, K. R., Elinson, R. P.: Dev. Biol. 127, 64 (1988) 4. Klein, S. L., Moody, S. A.: Development 106, 599 (1989) 5. Jacobson, A. G.: J. exp. Morphol. 154, 273 (1963) 6. Harrison, R. G.: Genes, Cells and Organisms. Garland 1969 7. Lewis, E. R., Leverenz, E. L., Bialek, W. S. : The Vertebrate Ear. Boca Raton: CRC Press 1985 8. Shelton, P. M. J.: J. Embryol. exp. Morph. 24, 511 (1970) 9. Fritzsch, B., Wake, M. H.: Zoomorphology 108, 210 (1988) 10. Cooke, J., Smith, E. J.: Development 102, 85 (1988) 11. Starck, D.: Vergleichende Anatomie der Wirbeltiere. Berlin: Springer 1982 12. Jarvik, E.: Basic Structure and Evolution of Vertebrates. New York: Academic Press 1980 13. Berridge, M. J., Irvine, R. F.: Nature 341, 197 (1989) 14. Busa, W. B., Gimlich, R. L. : Dev. Biol. 132, 315 (1989) 15. Adams, R. J., Pollard, T. D.: Nature 340, 565 (1989) 16. Keller, R. E.: Dev. Biol. 51, 118(1976)

Optic flow-field variables trigger landing in hawk but not in pigeons.

Abstract: Received August 31 and November 8, 1989 1. Schmidt-Koenig, K.: Z. Tierpsychol. 18, 301 (1958); Avian Orientation and Navigation. London: Academic Press 1979 2. von Frisch, K.\" Experientia 5, 142 (1949); The Dance Language and Orientation of Bees. Harvard Univ. Press 1967 3. Fent, K.: J. Comp. Physiol. 158, 145 (1986) 4. Montgomery, K. C., Heinemann, E. G.: Science 116, 454 (1952) 5. Kreithen, M. L., Keeton, W. T.: J. Comp. Physiol. 89, 83 (1974) 6. Delius, J. D., Perchard, R. J., Emmerton, J.: J. Comp. Physiol. Psychol. 90, 560 (1976) 7. Delius, J. D., Emmerton J., in: Neural Mechanisms of Behaviour in the Pigeon, p. 51 (eds. Granda, A. M., Maxwell, J. H.). New York: Plenum 1979 8. Able, K. P.: J. Exp. Biol. 141, 241 (1989) 9. Moore, F. R.: Biol. Rev. 62, 65 (1987) 10. Helbig, A. J., Wiltschko, W. : Naturwissenschaften 76, 227 (1989) 11. Sandberg, R.: Condor 90, 267 (1988) 12. Hodos, W., Bessette, B. B., Macko, K. A., Weiss, S. R. B.: Vision Res. 25, 1525 (1985) 13. Umov, N.: Physik. Z. 6, 674 (1905) 14. Smith, J., in: Animal Psychophysics, p. 125 (ed. Stebbins, W. C.). New York: Appleton-Century-Crofts 1970 15. Wortel, J. F., Wubbels, R. J., Nuboer, J. F. W.: Vision Res. 24, 1107 (1984) 16. Campell, H. S., Smith, J. L.: Arch. Ophthal. 67, 501 (1962)

Pheromone production in a bark beetle independent of myrcene precursor in host pine species

Abstract: The California five-spined engraver, Ips paraconfusus (Coleoptera: Scolytidae), is an important pest of young pine forests in California and Oregon, where nearly all pine species within the range of this bark beetle are attacked [I]. The aggregation pheromone produced by males has been identified as a synergistic blend of three components (5')-( )-ipsenol, (5')-( + )-ipsdienol, and (45')-cis-verbenol 121. Ipsenol and ipsdienol accumulate only in males exposed to vapors of the host tree monoterpene, myrcene, in a logarithmic relationship 131. Recently emerged control males and females contain no volatile terpene compounds, neither pheromone components nor myrcene, while only myrcene is present in vapor-exposed females [3]. Hendry et al. [4] used deuterium-labeled myrcene to prove that myrcene could be converted by hydroxylation to ipsenol and ipsdienol in males exposed to vapors. Another host tree monoterpene, (-)-a-pinene, is converted in the vapor phase to cis-verbenol in both sexes 15, 61. A paradigm has been established that I. paraconfusus, and probably most other bark beetles of the genus Ips, use myrcene and a-pinene in their host tree as precursors to the aggregation pheromone components, ipsenol/ipsdienol and cis-verbenol, respectively [3 81. Host selection and host suitability may then depend, in part, on the concentration of myrcene and a-pinene in the tree 191. Pine trees exhibit a wide variation within and between species in their composition of myrcene and a-pinene, among other monoterpenes 110, 111. Thus, it has also been hypothesized that tree genotypes could have evolved to have lower titers of aggregation pheromone precursors as part of a resistance mechanism to bark beetles 181. We compared the relative attractiveness of five pine host species, ponderosa (Pinus ponderosa), sugar (P. lambertiana), Jeffrey (P. jeffreyl), digger (P. sabiniana), and lodgepole (P. contorta), that were infested with I. paraconfusus in order to detect possible differences in pheromone release and host suitability. Beetles were reared from naturally infested ponderosa pine collected from the Sierra National Forest, California. Fifty males were introduced (18:OO Aug. 29, 1985) to holes drilled in logs of each of the five host pines cut 2 days previously. These logs were wrapped with window screen and placed in sticky traps. A trap consisted of 6-mm mesh screen cylinders (19 cm, diam., 30.5 cm high) coated with Stikem Specialm at 1.2 m height. Traps were separated 10 m apart in a line (Sierra National Forest, California). Collections of flying beetles at each of the five infested logs were similar except for an approximate doubling of catch on the Jeffrey pine log (Fig. 1A). In all cases, attraction rates were significant since one to two or more females could have joined a male in his nuptial chamber if not intercepted by the traps, a natural pairing ratio in I. paraconfusus 1121. Another measure of the strength of a pheromone signal is the sex ratio of catch; a higher femalebiased ratio in I. paraconfusus indicates a higher release of pheromone, because high release rates cause inhibition of male response 1121. The collected sex ratios were similar to previous reports 1121, though the sex ratio on Jeffrey pine (a : Q = 1 : 15.6) was significantly higher than on the other pine species (Fig. lA), again indicating that a somewhat more potent attractant was released. Five days after introducing the males, the logs were dissected and no significant differences were noted in survival or in general appearance of nuptical chambers (43 47 per log). To determine the quantities of the pheromone components ipsenol, ipsdienol, and cis-verbenol in the feeding males, they were removed from nuptial chambers and their hindguts extracted in groups of eight in 150 p1 diethyl ether with 10 ng heptyl acetate per pl as an internal quantification standard. Monoterpenes, including myrcene and a-pinene, were extracted similarly from three samples of uninfested phloem (15-25 mg dry weight) from each of the infested logs using 250 p1 ether per sample, as well as from oleoresin (Table 1). Pheromone components and ipsenone in the males, and monoterpene hydrocarbons from the host were quantified by gas chromatography and mass spectrometry (GC-MS) using fused silica capillary columns (Fig. 1) and interpreted with respect to synthetic chemical standards (from Borregaard, Sarpsborg, Norway, and Aldrich Chemical Co., Milwaukee,

Hearing through the lungs: lung-eardrum transmission of sound in the frog Eleutherodactylus coqui.

Abstract: Des mesures laser montrent que les sons d'importance biologique entrent dans les poumons de E. c. et sont capables de stimuler le cote interne des osselets

Coral host improves photosynthesis of endosymbiotic algae

Abstract: We thank H. Lista of EICI-SOFT for all software used in this study; J .R . Lopez of Empresa de Equipos M6dicos for suggesting some time ago the possible relationship between air temperature and receptor physiology and for his valuable comments on the results; M. Villaverde of Facultad de Biologia for helping in the analysis of the Arrhenius relationship; and H . U . Kleindienst of the Max-Planck-Institut for Verhaltensphysiologie, Seewiesen, for help with graphs and comments on the results.

The vegetalizing factor belongs to a family of mesoderm-inducing proteins related to erythroid differentiation factor.

Abstract: steroid. In the dung/grain substrate the first flush of fruit bodies appeared remarkably earlier. Thus, whereas in the control the first sporocarps were produced within 4 to 5 weeks, the addition of the brassinosteroid caused a fruiting of the mycelia already in 3 to 3.5 weeks. Furthermore, a variation of the number of formed fruit bodies in the five flushes during fructification was observed, e.g., with brassinosteroid four to seven mushrooms were produced in the first flush compared to one to three in the control (Fig. 2). The steroid-treated cultures afforded also a remarkably higher dry mass than the control cultivations (3 .4 -3 .9 g versus 2 . 3 2.9 g/10 g substrate). The formation of incomplete fruit bodies, normally present in mushroom cultivation, was almost completely suppressed by the brassinosteroid. Interestingly, the added brassinosteroid also influenced the morphology of the formed fruit bodies which lacked the typical membranous annulus on the stems. In summary, the observed strong growth-promoting effect of 22S,23Shomobrassinolide in mycelial cultures of Psilocybe cubensis suggests that brassinosteroids could also play a physFig. 2. Fruit bodies of Psilocybe cubensis on dung/grain substrate, a) Five weeks after inoculation, b) with 22S,23S-homobrassinolide 3 weeks after inoculation

Do fungi building limestones exist in semi-arid regions?

Abstract: 2. Meier, W. M., Olson, D. H.: Atlas of Zeolite Structure Types. London: Butterworths 1987 3. Vogt, E. T. C., Richardson, J. W., Jr. : J. Solid State Chem. 87, 469 (1990) 4. Davis, M. E., Saldarriaga, C., Montes, C., Garces, J., Crowder, C. : Zeolites 8, 362 (1988) 5. Meier, W. M. : Molecular Sieves, p. 10. London: Society of Chemical Industry 1968 6. Richard, P., Perrault, G. : Acta Crystallogr. B28, 1994 (1972) 7. Bissert, G., Liebau, F. : Z. Kristaltogr. 179, 357 (1987) 8. Frost/ing, S.: Chem. Commun. Univ. Stockholm no 3 (1990); Eriksson, L., Frost/ing, S., Grins, J.: Acta Crystallogr. B (in press) 9. Hansen, S. : Nature 346, 799 (1990) 10. Brunner, G. O., Meier, W. M.: ibid. 337, 146 (1989) 11. Brunner, G. O.: J. Solid State Chem. 29, 41 (1979) 12. Zachariasen, W. H.: Sov. Phys. Crystallogr. 16, 1021 (1971) 13. Sabine, T. M., Hogg, S.: Acta Crystallogr. B25, 2254 (1969) 14. Meier, W. M. : Pure Appl. Chem. 58, 1323 (1986)

Mutations of mitochondrial DNA and human death.

Abstract: In the skeletal muscle of patients with mitochondrial myopathies (Kearns-Sayre syndrome and chronic progressive external ophthalmoplegia) and in the heart and skeletal muscle of healthy persons cells lacking cytochrome c oxidase are found. The respiratory-defective cells have the following features in common: onset of the defect at juvenile or adult age; progressive character of the defect with increasing age; and focal pattern of respiratory-deficient cells (fibers). A statistic mutation of mtDNA in affected cells is suggested to cause the defect of mitochondrial function. It is postulated that the continuous accumulation of respiratory-deficient cells, mainly in the human heart with increasing age, will finally limit the life-span of each human individual.

Courtship sounds of the polka-dot wasp moth,Syntomeida epilais

Abstract: Strasser, S.: Physiol. Entomol. 10, 337 (1985) 6. Wunderer, H., Smola, U. : Int. J. Insect Morphol. 11, 25 (1982) 7. Laughlin, S. B., et al., in: Photoreceptor Optics, p. 237 (Snyder, A. W., Menzel, R., eds.). Berlin: Springer 1975 8. Nilsson, D.-E., et al. : J. Comp. Physiol. A161, 645 (1987) 9. Meyer-Rochow, V. B.: Cytobiol. 4, 241 (1971) 10. Waterman, T. H., in: Handbook of Sensory Physiology, Vol . VII/6B, p. 281 (Autrum, H., ed.). Berlin: Springer 1981 11. Melamed, J., Trujillo-Cenoz, O. : J. U1trastruct. Res. 21, 313 (1968) 12. Wunderer, H., et al.: Cell Tiss. Res. 257, 565 (1989) 13. Strausfeld, N. J., Wunderer, H.: ibid. 242, 163 (1985); Labhart, T.: Nature 331, 435 (1988)

Endoparasitic larvae of conopid flies alter pollination behavior of bumblebees

Abstract: synthetically less suitable. The cooperation of the PhAR-amplifying mechanisms of the coral host and the photopigments of the symbionts may hypothetically be explained as follows. In the habitat the zooxanthellae need a critical density of PhAR photons for photosynthesis. This amount does not seem to exist below a depth of 1 0 0 m , but short wavelengths, outside the PhAR spectrum less suitable for photosynthesis, are potentially available. The critical photon flux density is obtained through photoadaptations of the host by transforming short wavelengths into longer ones and by scattering, through which the probability of photon absorption by algal pigments is amplified. As far as we know Kawaguti, studying shallowwater scleractinian coral species, was the first who took into account the possibility that host pigments may theoretically be involved in algal photosynthesis [9]. To judge the contributions of the PhAR-amplifying mechanisms of the host to the improvement of photosynthesis of the symbionts is not yet possible. For that purpose we need quantitative data on the availability of irradiance below 410nm in the habitat of L. fragilis. Wavelengths between 380 and 410nm evoke the most effective autofluorescence of host pigments [4, 5]. In L. fragilis the coral host evolved highly complex mechanisms to support photosynthesis of the symbiotic algae. This indicates that mutualistic associations might be discussed not only in terms of energy and effective recycling of nutrients within a single cell. In the case ofL. fragilis the host spends a considerable amount of energy (biosynthesis of chromatophores and pigments) for the maintenance and farming of the cytosymbiotic algae, and therefore it is most likely that the host depends essentially on specific metabolites or metabolic pathways of the symbionts. The studies were supported by the Deutsche Forschungsgemeinschaft (Fr. 369/7.1). The authors would like to thank Dr. H. Scharstein for valuable advice and help. The authors acknowledge the skillful technical assistance of H. Krisch. Thanks are also due to the crew of the research submersible GEO.

Comparison of the biosynthesis of the methanobacterial pseudomurein and the eubacterial murein.

Abstract: From cell extracts of the archaebacterium Methanobacterium thermoautotrophicum 11 putative precursors of the pseudomurein were isolated and characterized. On the basis of the isolated intermediates, a biosynthetic pathway of the pseudomurein is proposed. Compared to the eubacterial murein the biosynthetic stages follow different pathways as indicated by the occurrence of a nucleotide-activated disaccharide and nucleotide-activated peptides.

Reproductive competition involving oophagy in the socially nesting bee Xylocopa sulcatipes

Abstract: Several types of nesting associations, termed quasisocial (females more or less identical, no division of labor), semisocial (females of the same generation, with division of labor) and matrifilial (overlap of generations, with division of labor) are described in many primitively social hymenopteran species. In the latter two types, at least one potentially reproductive female forgoes her own reproduction in favor of that of a dominant female. Quasisociality is generally of a temporary nature, because dominance relations develop. It turns then into semisociality [11. The large carpenter bee Xylocopa sulcatipes in southern Israel has been described as forming both solitary and social nests [2, 3]. This paper shows that in certain associative nests founded by two females an extreme example of reproductive competition, oophagy, occurs. A X. sulcatipes egg measures approximately 11 mm in length and 2.2 mm in diameter; for an adult female of 22 mm body length, egg cannibalism therefore represents a significant loss of investment. X. su/catipes typically nests in twigs o f dead branches where the female excavates a straight tunnel. Females also use pre-existing cavities in stems of Arundo, Ferula and other plants existing naturally in the habitat. The female builds a linear array of cells [4]. Each is provisioned with pollen and nectar, and an egg is deposited upon the loaf-like food mass. Finally the cell is sealed with masticated wood. As part of a study on Xylocopa at Hazeva Field Centre, Arava Valley,

Activated State in the Lepidocrocite Structure During Thermal Treatment

Abstract: change of AMP against ATP and of calcium-flee calmodulin against calcium-loaded calmodulin the ATPase complex is workable again. Obviously, the energy transfer via calcium has the advantage that in case of emergency needs great amounts of free energy can be made available in a short time independently of the ATP supply. This is done by. flushing calcium-free calmodulin produced by continuous pumping and stored in the nearly calcium-flee cytosol with calcium coming from the periphery or any other calcium source of the cell. Thus the calcium/calmodulin system is part of a storage power station of the cell. In the pumping process based on the calcium transfer by calmodulin the lowest calcium concentration is set by the spontaneous dissociation of the calcium/calmodulin complex. This is consistent with the assumption made above to evaluate the upper limit of the free energy production by the calcium-loading of calmodulin. If a sustained stimulation results in a sustained reaction of the cell, the detour, via the cytosol, in the transport of calcium-loaded and calcium-flee calmodulin between the adenylate cyclase complex and the ATPase complex may be avoided. So the calcium cycling in the membrane region, described in [4] will be established. An increase in the concentration of calcium-loaded calmodulin in the cytosol not only starts the pumping process mentioned above but also activates phosphodiesterase which, as is well known, destroys cAMP by hydrolysis [2]. The main difference in the new concept as compared to the former models is seen in the fact that it attributes to calcium not only the function of a messenger but also the function of a transporter for the free energy needed to start endergonic reactions. The transfer of free energy by calcium does not need to be restricted to the production of cAMP for the initiation of chemical reactions. It can be expected that also for other endergonic processes in the cell, e.g., for the generation of mechanical work the transfer of free energy by calcium is of importance.

The pictographic molecular paradigm. Pictorial communication in the chemical and biological sciences.

Abstract: Chemistry, molecular biology and biology have turned into visive sciences in which ideas and information are communicated by artistic impressions and cartoons. These sciences have, in fact, become dominated by what we term the Pictographic molecular paradigm under which reality is acritically approximated by drawings of some kind. But it goes further than this and has both social and philosophical implications of which, we feel, there is insufficient general awareness. Important questions should be asked in connection with this way of doing science, including, for example, as to whether drawings of chemical formulae and graphical representation in biology meet the criterion of objectivity. This paper discusses some of the implications of the pictographic molecular paradigm and its limits and dangers.

Carrier-mediated uptake of digoxin by larvae of the cardenolide sequestering moth, Syntomeida epilais

Abstract: other signals, for instance mechanical ones, under natural conditions. It is important to point out that two compounds, MP and MN, appear to act at the same time as a pheromone for the honeybee and as a kairomone for the parasitic mite Varroa jacobsoni. These compounds, emitted by honeybee larvae, first attract the mites, and then the honeybee workers for the capping of the cells. The analysis of the composition of the pheromone blend and of the kairomone blend, in relation to the age of the larvae, is in progress. This work was supported by grants from the National Institute of Agricultural Research (INRA), the National Center of Scientific Research (CNRS), the French Ministry of Environment (SRETIE), the ECC (DG.VI), and Intermiel. We thank Drs. R. Brossut, C. Descoins, C. Noirot, J. Pain, G. Ourisson, and F. Ruttner for critical reading of the manuscript, and J. E. Walker for her assistance in the English translation.