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1.
A molecular phylogeny based on DNA/DNA hybridization revealed that the Sylvia-Parisoma complex is monophyletic and includes three main groups of species, the “mid-European” warblers, the genus Parisoma, and the “eu-Mediterranean” Sylvia species sensu stricto. The latter can be assigned to three main clusters, a “West-Mediterranean” group, a “Central-Mediterranean group”, and an “East-Mediterranean” group. The radiation of the whole complex is much more ancient than formerly believed. It started ca 12–13 Ma ago and the ancestors of the main extant groups differentiated during the Pliocene. Only speciation events within the “eu-Mediterranean” lineages occurred during the Pleistocene. The paleoclimatical and paleoecological history of the Mediterranean region is too complicated to provide any evidence for direct relationships between past events and evolutionary steps of these taxa which did not leave any reliable fossil record. However, some major speciation events may be related to well documented climatical crises as well as paleobotanical data. The largely man-induced extension of matorrals over several millenia presumably extended the range of several species that were formerly much more restricted, which complicates reconstruction of the spatio-temporal course of speciation.  相似文献   

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A new species of the eel cod Muraenolepis kuderskii sp. nova from the Scotia Sea, South Georgia, from depths of 440–605 m is described. The species belongs to the group of “few-rayed” species having less than 150 rays in the dorsal fin and less than 114 rays in the anal fin. According to general body proportions, M. kuderskii is closely related to high-latitude Antarctic species M. trunovi; however, it differs from the latter and all other species of the group of “few-rayed” eel cods in a short chin barbel, small sizes of the eye, a short antebranchial distance, a short anteanal distance, and a long postanal distance.  相似文献   

4.
The relative appearance of the parietal muscles in the development of the zooids has been studied in several ctenostomatous and “cheilostomatous” species. A comparison of the different on-togenetical sequences demonstrated that a “cheilostomatous” type of organization of the zooids with a great probability has been achieved in minimum three times independentl and originated from different ctenostomatous sub-grous: the Membranidea from plesiomorgic victorelloids (ancestors of Bulbella with not yet developed peristomial tube), the Inoviceiata (Aetea) from advanced forms of victorelloids with reduced primary parietal muscles (perhaps stcies related to Pottsiella), and Penetrantia from arachnidioid or vesicularioid ancestors (?). Therefore, the classical orders α“Ctenostomata” and “Cheilostomata” represent only “stage groups” but no monohyletic systematical units. Because of the new concept and interpretation I propose a new name for the united group: Cteno-Cheilostomata, supra-ord. nov.  相似文献   

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Since 1989, effects of biotic interactions including predation and herbivory have been examined in a replicated experimental study in a north‐central Chilean semiarid thorn scrub community. Strong responses of small mammals and plants to El Niño Southern Oscillations (ENSO) have also been documented suggesting that “bottom‐up” factors related to high rainfall are important. To simulate increased primary productivity effects on small mammals, ad lib rabbit pellet additions were initiated in mid‐1997 on unfenced grids near the experimental complex. Following the 1997 El Niño event with three times normal precipitation, numbers of small mammals during pre‐addition months and the first treatment year were similar on control and food addition grids. During the second year (1998–1999), a period of severe drought, food additions had significant positive effects on numbers of two predominantly herbivorous “core” (resident) species, Octodon degus and Phyllotis darwini, and an omnivorous “quasi‐core” (resident but highly fluctuating) species, Akodon olivaceus; however, all three species declined towards the end of the second treatment year. Two “opportunistic” (temporarily resident) species, Abrothrix longipilis (an insectivore) and Oligoryzomys longicaudatus (a granivore), showed no responses to food additions. An insectivorous marsupial, Thylamys elegans (also a “core species”), had significantly lower numbers on food addition grids. Changes in body weight distributions and proportions of reproductive individuals particularly in O. degus indicate in situ responses. Whereas no differences in residency, numbers of stations visited, and trappability were observed, energy compensation ratios greater than one suggest significant immigration in the second year. Thus, food additions elicited strong responses by herbivorous/omnivorous “core” and “quasi‐core species” whereas they had no effects on “opportunistic species”. These results reinforce the view that “bottom‐up” factors influencing food availability exert prevailing control on numerically important small mammal species by temporarily increasing carrying capacity, and that “top‐down” factors (i.e., biotic interactions) become important when small mammal numbers are at or near their carrying capacity. Spatial dynamics may be important in explaining declines of species populations exhibiting initially positive responses to food additions.  相似文献   

7.
Extracellular polysaccharides (EPS) produced by Pseudomonas syringae pv. phaseolicola are obviously composed of two main components: the long known levan consisting of fructose, and a mannuronan consisting mainly of mannuronic acid (manA), thus resembling alginic acid (alginate). The identification of manA was established by TLC utilizing different developing systems, and by cellulose acetate electrophoresis in different buffers. References were authentic uronic acids and hydrolyzed authentic alginate. A rough quantification of the “alginate” present in crude EPS was achieved with a selective colour reaction which largely excluded compounds other than uronic acids. Levan was only synthesized with sucrose as primary carbon source. When grown on several other sugars and related compounds “alginate” was the predominant component of the EPS. Additionally, rhamnose, fucose, glucose and amino sugars were found in some instances in hydrolysates of crude EPS, suggesting the release of lipopolysaccharides (LPS) from the bacterial cell walls during culture. Growth on carbon sources not related to sugars resulted in these “LPS” as the main constituent of EPS. After cultivation with sucrose, the “alginate” was restricted to the “slime” fraction of the EPS. In the “capsular” fraction, levan was predominating. A screening program revealed the capacity to synthesize the “alginate” in six additional P. syringae pathovars: pisi, lachrymans, aptata, tomato, syringae, and glycinea. All of the strains tested so far produced levan from sucrose, however, the “alginate” was formed not by all of them. There was a tendency that fresh isolates produced more “alginate” than strains subcultured for an extended time in vitro. This was also true for the total amount of EPS.  相似文献   

8.
Kleinodendron, a new genus of Euphorbiaceae, was assigned by Smith and Downs to the tribe Cluytieae. A xylem anatomical survey indicates that there are no objections to this placement. Woods of Cluytieae are diverse but may be characterized generally by having pores which average less than 80 μ in diameter and which are well divided between solitary and radial multiple distributions in the same species; simple vessel perforations; alternate intervascular pitting; fiber-tracheids and libriform wood fibers; exclusively uniseriate, or uniseriate and biseriate heterocellular vascular rays in the same species; uniseriate “bridges” linking superposed biseriate ray segments; diffuse, diffuse-in-aggregates, and scanty vasicentric axial parenchyma, sometimes in the same species; and crystal rhomboids. That Microdesmis and Pogonophora diverge sharply from these generalizations in having scalariform vessel perforations and broad vascular rays, is an indication that they may not be closely related to other genera in Cluytieae.  相似文献   

9.
Tetrahymena mitochondrial cox1 barcodes and nuclear SSUrRNA sequences are particularly effective at distinguishing among its many cryptic species. In a project to learn more about Tetrahymena natural history, the majority of >1,000 Tetrahymena‐like fresh water isolates were assigned to established Tetrahymena species with the remaining assigned to 37 new species of Tetrahymena, nine new species of Dexiostoma and 12 new species of Glaucoma. Phylogenetically, all but three Tetrahymena species belong to the well‐established “australis” or “borealis” clades; the minority forms a divergent “paravorax” clade. Most Tetrahymena species are micronucleate, but others are exclusively amicronucleate. The self‐splicing intron of the LSUrRNA precursor is absent in Dexiostoma and Glaucoma and was likely acquired subsequent to the “australis/borealis” split; in some instances, its sequence is diagnostic of species. Tetrahymena americanis, T. elliotti, T. gruchyi n. sp., and T. borealis, together accounted for >50% of isolates, consistent with previous findings for established species. The biogeographic range of species found previously in Austria, China, and Pakistan was extended to the Nearctic; some species show evidence of population structure consistent with endemism. Most species were most frequently collected from ponds or lakes, while others, particularly Dexiostoma species, were collected most often from streams or rivers. The results suggest that perhaps hundreds of species remain to be discovered, particularly if collecting is global and includes hosts of parasitic forms.  相似文献   

10.
Comparison of a “smooth” and a “rough” isolate of Pseudomonas syringae pv. phaseolicola The “smooth” (S) wild strain of Pseudomonas syringae pv. phaseolicola was compared with a “rough” (R) variant of low virulence. Both strains grew nearly equally well on a sucrose containing medium with yeast extract and casamino acids, and the strains did not differ markedly in the quantity of produced EPS (= extracellular polysaccharides). Principally the same results were obtained for high and medium concentrations of sucrose, or when sucrose was replaced by glucose or fructose. However, on glucose and fructose considerably lower quantities of EPS were produced. The biological activity of S-EPS was higher than that of R-EPS. This difference between the EPS preparations was not as marked as leaf inoculation with both bacterial isolates. After prolonged bacterial culture the EPS-production increased further, so that the differences between both strains decreased. A different EPS type was produced on the glycerol containing medium of KING B. Variations in the composition of this medium resulted in different morphology of the agar grown cultures, and the relative differences between S and R bacteria changed. When 62 different physiological tests for both bacterial strains were compared, the “rough” bacteria revealed a lowered range of positive reactions, with a few exceptions. However, it appeared unlikely that the reduced virulence of the “rough” bacteria was due to these differences. Obviously, defects in the extracellular products, but not in levan, were responsible for the reduction of virulence.  相似文献   

11.
Bacillus larvae, the causative agent of American foulbrood in honey bees completes its life cycle of germination, outgrowth and sporulation in young honey bee larvae by killing them and often bringing about the destruction of the entire hive. While B. larvae germinates and outgrows on complex organic media in vitro, the literature suggests, for reasons that are not at all clear, that a relatively large number of spores of B. larvae are required to yield each visible colony (colony forming units, CFU) on media. Various researchers have reported that from 16 to 3,000 or more spores of B. larvae are required to yield a single colony on an agar plate. HANSEN in Denmark designed a useful method of spreading approximately 80 mg of honey directly on the surface of a PETRI plate containing “J” agar medium to determine if B. larvae spores are present in the honey. In the present study, selected media were tested for the ability to recover B. larvae spores in honeys in the form of visible colonies (CFU) using HANSEN's strek method. A modification of a medium (TMYGP) developed by DINGMAN and STAHLY, (T-HCL-YGP agar), recovered considerably more viable B. larvae spores in the form of visible colonies (CFU) than HANSEN's “J” medium. When “J” medium was fortified with 0.1% sodium pyruvate, it was comparable to modified T-HCL-YGP medium in its recovery of B. larvae spores. Brain heart infusion agar (BHIA) with the addition of thiamine recovered more spores in the form of viable colonies than did “J” medium but it was not as efficient as T-HCL-YGP medium. Serial dilution from 100 to 10,000 times of weighed samples of honey with deionized water led to higher spore counts (CFU per g honey) than that indicated by undiluted honeys plated at 80 mg levels directly onto the surface of media by the HANSEN procedure.  相似文献   

12.
Small-sized vegetative cells were found to co-occur with normal-sized cells in populations of the European bloom-forming dinoflagellate Gymnodinium cf. nagasakiense Takayama et Adachi, currently known as Gyrodinium aureolum Hulburt, but not in populations of the closely related Japanese species Gymnodiniumn agasakiense. We examined how cell size differentiation may influence growth and cell cycle progression under a 12:12-h light: dark cycle in the European taxon, as compared to the Japanese one. Cell number and volume and chlorophyll red fluorescence in both species varied widely during the photocycle. These variations generally appeared to be related lo the division period, which occurred at night, as indicated by the variations of the fraction of binucleated cells (mitotic index) as well as the distribution of cellular DNA content. “Small” cells of G. cf. nagasakiense divided mainly during the first part of the dark period, although a second minor peak of dividing cells could occur shortly before light onset. In contrast, “large” cells displayed a sharp division peak that occurred 9 h after the beginning of the dark period. The lower degree of synchrony of “small” cells could be a consequence of their faster growth. Alternatively, these data may suggest that cell division is lightly controlled by an endogenous clock in “large” cells and much more loosely controlled in “small” cells. Cells of the Japanese species, which were morphologically similar to “large” cells of the European taxon, displayed an intermediate growth pattern between the two cell types of G. cf. nagasakiense, with a division period that extended to most of the dark period.  相似文献   

13.
Alston , R. E. (U. Texas, Austin), and H. S. Irwin . The comparative extent of variation of free amino acids and certain “secondary” substances among Cassia species. Amer. Jour. Bot. 48(1): 35–39. Illus. 1961.—Five species of Cassia, selected to include 4 sections of the genus, were examined by chromatographic methods for free amino acids and for substances visible in ultraviolet light, visible light and after spraying with a general reagent for phenols. The latter, representing a heterogeneous group, are referred to as “secondary” substances (implying that they are not intimately involved in basic energy transfer or assimilative activity of all tissues). Among the species examined there was definite but only moderate variation in the free amino acids present, and differences were predominantly quantitative. In contrast, a minimum of 25 “secondary” substances appeared on the chromatograms when viewed in ultraviolet light and ammonia vapor, with no more than 9 of the spots present in a single species. While free amino acid patterns may be useful in themselves, it seems that patterns of variation of “secondary” substances offer a greater potential in taxonomic work.  相似文献   

14.
One specimen (300 mm in standard length) of Saloptia powelli, belonging to the family Serranidae, was newly collected in a local fish market in Manado, North Sulawesi, constituting a new record for the species in the Indonesian archipelago. This species was diagnosed by the following morphological traits: dorsal rays VIII—11, anal rays III—8, well-defined opercular spines, pelvic fins below pectoral fins, caudal fin emarginate, mouth moderate in size, supplemental maxillary present, fine teeth in irregular rows on vomer and palatines. Head, body, and fins yellow in color. We suggest “kerapu emas”, a translation of its existing common name “golden grouper”, for the Indonesian species names.  相似文献   

15.
Optical activity of aromatic chromophores. I. O, m, and p-tyrosine   总被引:1,自引:0,他引:1  
T M Hooker  J A Schellman 《Biopolymers》1970,9(11):1319-1348
The optical activity and the conformational energy of the amino acids tyrosine, o-tyrosine, and m-tyrosine have been calculated as a function of molecular conformation. A new graphic technique, rotatory strength–conformational energy maps, was developed for the presentation of these calculations. Experimental circular dichroism spectra were determined by utilization of a new experimental technique that involves complete computer control of a Cary spectropolarimeter. This permitted repetitive scanning with signal averaging over extended time periods and resulted in a greatly enhanced signal to noise ratio. On the basis of these calculations, it, was concluded that the Kirkwood “coupled oscillator” mechanism is capable of explaining the observed optical activity of the aromatic chromophores of the molecules that were investigated.  相似文献   

16.
Two subpopulations differing essentially by their mean cell size were observed regularly in cultures and natural samples of the naked dinoflagellate Gymnodinium cf. nagasakiense Takayama et Adachi (currently known as Gyrodinium aureolum Hulburt), a species which frequently forms red tides in North European seas. “Large” cells represented the typical forms; they were morphologically similar to cells of the closely related Japanese species G. nagasakiense, which did not form any subpopulation of reduced size. “Small” and “large” cells of G. cf. nagasakiense had the same DNA content, but the nucleus of the former appeared to be much more condensed during interphase. Each cell type was able to divide and had its own growth dynamics; therefore, any intermediary between pure populations of “small” and of “large” cells were observed in culture. The “large” form generated a “small” cell by an atypical budding-like division, whereas the “small” form gave back a “large” form, once it ceased to divide, by simple enlargement of its cell body. Factory inducing cell size differentiation are yet unclear. Neither nitrogen nor phosphorus starvation induced a significant increase in the relative proportion of “small” and budding cells. Although cell size differentiation is associated with the formation of gametes in a variety of dinoflagellates, we demonstrated that “small” cells of G. cf. nagasakiense are able to divide asexually, in contrast to gametes of most other species. The high proliferative power of “small” cells as compared with normal cells suggests that they could play a significant role during red tides of G. cf. nagasakiense; in contrast, cells of the Japanese species G. Nagasakiense could sustain high growth rates with larger cell size because this species generally blooms in waters much warmer than those found in northern Europe.  相似文献   

17.
A survey of protozoa polluting bottled mineral water in Mexico was carried out using samples obtained from the three best-selling brands of bottled mineral water in the country. The organisms were concentrated through filtration procedures and subsequently cultured in sterile media. The cultures were observed over four weeks, with identification to the level of genus and species. Most commonly found were the amoebae Naegleria gruberi, Acanthamoeba astronyxis, and Vahlkampfia vahlkampfi (trophic as well as cystic stages) plus one flagellate, Bodomorpha minima. No ciliates were detected. The public health importance of the findings is obvious, since some strains of Naegleria and Acanthamoeba have the potential to cause human disease that may lead to death.  相似文献   

18.
The size and shape of the basicranium (seen in norma basilaris) in Homo, Gorilla, Pan, Pongo, and Australopithecus have been studied by recording the relative disposition of midline and bilateral bony landmarks. Fifteen linear measurements and two angles were used to relate the landmarks. The relatively longer and narrower cranial base of Gorilla, Pan, and Pongo is clearly contrasted with the wider, shorter cranial base in Homo sapiens. When the same observations were made on two “robust” and two “gracile” australopithecine crania, marked differences were found between the taxa. In the two “robust” specimens, the foramen magnum is located relatively further forward, and the axis of the petrous temporal bone is aligned more nearly with the coronal plane than in the two “gracile” crania. The implications of this apparent parallelism in basicranial morphology between Homo sapiens and the “robust” australopithecines are discussed.  相似文献   

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Eighteen populations of Bemisia tabaci, collected from different geographic locations (North & Central America, the Caribbean, Africa, the Middle East, Asia and Europe), were studied to identify and compare biological and genetic characteristics that can be used to differentiate biotypes. The morphology of the fourth instar/pupal stage and compound eye structures of adults were investigated using scanning electron microscopy and found to be typical of the species among all biotypes and populations studied. Setae and spines of B. tabaci larval scales from the same colony were highly variable depending on the host plant species or leaf surface characteristics. The location and the morphology of caudal setae, characteristic of all B. tabaci studied to date, were present in all colonies. However, differences in adult body lengths and in the ability to induce phy to toxic disorders in certain plant species were found between biotypes or populations. The recently identified “B” biotype, characterised by a diagnostic esterase banding pattern and by its ability to induce phytotoxic responses in squash, honeysuckle and nightshade was readily distinguished from non-“B” biotype populations. None of the non-“B” biotypes studied, were found to induce phytotoxic responses. Nine populations examined showed typical “B” biotype characteristics, regardless of country of origin. All tested populations, determined as “B” or “B”-like biotypes successfully mated with other “B” biotype colonies from different geographic areas. Non-“B” biotype colonies did not interbreed with other biotypes. The B. tabaci populations were tested for their ability to transmit 15 whitefly-transmitted geminiviruses (WTGs) from different geographic areas with a wide range of symptom types. All WTGs were transmitted by the “B” biotype colonies and by most non-“B” biotype colonies, with the exception of three viruses found in ornamental plants which were non-transmissible by any colony. Some non-“B” biotypes would not transmit certain geminiviruses and some geminiviruses were more efficiently transmitted than were others.  相似文献   

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