首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Heterodera longicolla n. sp., a member of the H. goettingiana group, is described and illustrated from roots of buffalo-grass, Buchloë dactyloides (Nutt.) Engelm., in Manhattan, Kansas. This new abullate species, having second-stage larvae with only three lines in the lateral field, is most closely related to H. cyperi Golden, Rau & Cobb, 1962, but differs particularly in having a shorter stylet in larvae, males and females; in possessing only three annules on the head of larvae and males; in having a shorter tail in larvae; and by the presence on cysts of a small anus without a circum-anal pattern.  相似文献   

6.
7.
《Aquatic Botany》1986,24(4):321-334
The oogonium in Turbinaria conoides (J. Agardh) Kürzing at the time of release is 8-nucleate and consists of 3 wall layers namely exochiton, mesochiton and endochiton. The exochiton contains alginic acid. The mesochiton a mixture of alginic acid and sulphated polysaccharides. The endochiton that is evident in the unreleased 8-nucleate oogonium, stains for sulphated polysaccharides, but is PAS negative. In a released oogonium, the endochiton is Alcian blue and PAS positive and consists of both alginic acid and sulphated polysaccharides.Polysaccharide granules are secreted near the perinuclear region and in thecytoplasmic vacuoles during the initiation of mesochiton. Furthermore, at the distal end the mesochiton froms a pad that fuses with the exochiton. The pad consists of alternate thick and thin bands. The exochiton opens at one side due to the swelling of the oogonium and accumulation of sulphated polysaccharides between exochiton and mesochiton followed by formation and elongation of a mesochiton stalk. The 8-nucleate oogonium is, thus, extruded from the conceptacle, but remains attached to the exochiton by means of a long mesochiton stalk. The secretory paraphyses, at the time of oogonial release, produce copious amounts of polysaccharides. The oogonium is, thus, extruded through the ostiole by the combined efforts of the 3 wall layers that are histochemically and histologically different, in combination with secretion produced by secretory paraphyses.  相似文献   

8.
9.
10.
11.
12.
The authors describe a new species in the genus Schilbetrematoides Kritsky & Kulo, 1992 from the gills of Schilbe mandibularis (Günther, 1867) (Schilbeidae) caught in the rivers Bia and Agneby in Ivory Coast. S. manizani n. sp. differs from S. pseudodactylogyrus Kritsky & Kulo, 1992, a parasite of Schilbe intermedius Rüppell, 1832 by having morphologically distinct gripi.  相似文献   

13.
Protistan parasites of the genus Marteilia, phylum Paramyxea, cause the molluscs disease named Marteiliosis. Histological observations and transmission electron microscopy revealed the presence of life cycle stages of a Marteilia sp. in the bivalve mollusc Solen marginatus (Solenidae). Parasites occurred in epithelial cells of the digestive ducts and tubules. Early stages (primary cells) presented one or several nuclei while advances stages formed a complex of cells-within-cells (secondary and tertiary cells) culminating in spores. Refringent bodies were present inside the presporangia. This is the first report of a Marteilia sp. in S. marginatus.  相似文献   

14.
15.
The aim of this study is to supply detailed information about oak (Quercus sp.) pollen seasons in Poznań, Poland, based on a 16-year aerobiological data series (1996–2011). The pollen data were collected using a volumetric spore trap of the Hirst design located in Poznań city center. The limits of the pollen seasons were calculated using the 95 % method. The influence of meteorological parameters on temporal variations in airborne pollen was examined using correlation analysis. Start and end dates of oak pollen seasons in Poznań varied markedly from year-to-year (14 and 17 days, respectively). Most of the pollen grains (around 75 % of the seasonal pollen index) were recorded within the first 2 weeks of the pollen season. The tenfold variation was observed between the least and the most intensive pollen seasons. These fluctuations were significantly related to the variation in the sum of rain during the period second fortnight of March to first fortnight of April the year before pollination (r = 0.799; p < 0.001). During the analyzing period, a significant advance in oak pollen season start dates was observed (?0.55 day/year; p = 0.021), which was linked with an increase in the mean temperature during the second half of March and first half of April (+0.2 °C; p = 0.014). Daily average oak pollen counts correlated positively with mean and maximum daily temperatures, and negatively with daily rainfall and daily mean relative humidity.  相似文献   

16.
17.
Anna Bothár 《Hydrobiologia》1986,140(2):97-104
Analysis of the population dynamics of Bosmina longirostris (O. F. Müller) was carried out in the River Danube in the years 1981 and 1982. An estimation method of secondary production elaborated far standing waters was adapted to river conditions. In the River Danube, compared to lakes, standing crop and production values were smaller, while fecundity, P/B values were larger and turnover time was shorter. Possible reasons for this are discussed.  相似文献   

18.
Male meiosis was studied in a population of Acanonicus hahni (Stål), and nine of the sixteen individuals analyzed showed desynapsis. The frequency of univalents varied from one to seven percent in eight of them, while in the ninth the percentage of cells with univalents was higher (12%). The univalents auto-orientate at metaphase I in the center of the ring formed by autosomal bivalents and divide equationally at anaphase I; at metaphase II they show touch-and-go pairing, and lie in the center of the ring of autosomes.A desynaptic origin of the univalents is proposed, and the arrangement of the chromosomes in the first and second metaphase plate in the normal and desynaptic individuals is compared and discussed. The meiotic characteristics of these desynaptic individuals are also compared with those described in other insects with holocentric and monocentric chromosomes. It is suggested that any achiasmatic chromosome, whether a univalent, m or sex chromosome, will induce the formation of a ring and with some or all of them lying in its centre.  相似文献   

19.
Koref-Santibanez  S.  Günther  R. 《Genetica》1984,52(1):195-207
The karyotypes of the three water frog forms: Rana lessonae, R. ridibunda and R. esculenta were analysed from bone marrow cell preparations of animals captured in several localities of the GDR. In the three forms chromosome morphology was similar (5 large and 8 small pairs), although differences in the relative length of most elements were found; R. esculenta chromosomes were always intermediate.One of the small pairs (Chr. 12) was found to be metacentric in R. lessonae and submetacentric in R. ridibunda. Most R. esculenta individuals examined had one meta-and one submetacentric 12th element, indicating the hybrid nature of this form. However 16.6% esculenta proved to be homozygous for either the metacentric or the submetacentric chromosome 12, while 13% lessonae individuals and 7.7% ridibunda were heterozygous for this element.By starch gel electrophoresis an analysis was undertaken of serum proteins from water frogs coming from regions in which the forms occur together (sympatric populations) and from zones in which only one of them lives (allopatric populations).In Rana lessonae, where only one allele had been previously described, two different alleles were found in animals coming from the GDR.If genetic polymorphism is excluded, between 6.1% and 9.1% individuals from sympatric lessonae and ridibunda populations showed introgression of an albumin allele. No gene introgression was found in allopatric lessonae populations from the Leningrad region or in ridibunda from Alma Ata and southern Bulgaria.  相似文献   

20.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号