首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   14篇
  2002年   3篇
  1997年   4篇
  1995年   5篇
  1991年   1篇
  1967年   1篇
排序方式: 共有14条查询结果,搜索用时 93 毫秒
1.
While developing a data base for phylogenetic analysis of the New World streptocephalids we compaired them with species from Africa, Europe, and India. In doing this, we found that the morphology of the peduncle of the distal antennal outgrowth and the biramous ovaries developed in seven North American species can contribute to the systematics of the genus. Thus, our investigation consisted of (1) a review of the external morphology of the antenna, (2) biometry of selected parts of the antenna to obtain informative ratios, (3) a review of the presence or absence of genetal linguiform outgrowths, extension of the non-retractile parts of the penes, and general morphology of the cercopods, (4) a study of the location of the ovaries, and extension of the brood-pouch. On the basis of the results we classifyStreptocephalus into nine species groups. Five subgroups are identified within two of the species groups Several implications of the present approach are discussed.  相似文献
2.
New penis characters to distinguish between two American Artemia species   总被引:3,自引:1,他引:2  
Biofilms are an ensemble of autotrophs and heterotrophs, which are highly efficient in removing inorganic and organic compounds, as well as other chemicals, from river water. They are, therefore, key elements in the self-purification processes which occur in rivers. Biofilm function is related to several environmental factors that govern river ecosystems: physical (light, temperature, water current), chemical (nutrient availability, toxicant effects), but also biological. Among the biological factors, community composition (algae, bacteria and fungi), biofilm structure (layer arrangement and biomass accumulation), and the presence of grazers determine variations in the efficiency of the self-depuration function of biofilms in rivers. Algae and bacteria show specific abilities for nutrients and other organic and inorganic compounds, but biofilm thickness may affect these abilities, both through a decrease in diffusion and by enhancing recycling within the biofilm. Nutrient uptake and consequently the capacity of biofilm to ameliorate water quality decreases with biomass. Moreover, biofilm thickness determines the effect of toxicants, since biomass prevents their diffusion through the biofilm. Grazing interferes in the relative efficiency of biofilms, by simplifying the composition of the biofilm community and by decreasing the amount of sorption and uptake of the biofilm. Closer attention should be paid to these aspects, since they unambiguously interfere with the performance of biofilms in the amelioration of the quality of river water.  相似文献
3.
Supplement to "Checklist of the Anostraca"   总被引:3,自引:3,他引:0  
Denton Belk  Ján Brtek 《Hydrobiologia》1997,359(1-3):243-245
Our 1995 "Checklist of the Anostraca" covered all species described through 31 December 1993 along with those described in the volume from the Second International Large Branchiopod Symposium (Hydrobiologia 298). This supplement includes new species (14) described through 31 December 1996, one change in rank and one new species discussed in this symposium volume, anew synonym, and correction of errors discovered in the original. We do not update new range extensions. With these additions and changes, we number the named anostracan fauna of the world at 273 species and six subspecies organized in 23 genera. The need for more study of anostracan zoogeography is again demonstrated by the fact that seven of the 16 species added to the checklist are know only from their type localities. Until we have more complete information on the distributions of the species, it will not be possible to make an accurate evaluation of the status of anostracan biodiversity. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献
4.
We present an updated diagnosis of 13Streptocephalus species of North America. Three new species are included. A key to the species is provided.The phylogeny of the group is discussed on the basis of (1) a systematic approach (Maeda-Martinezet al., 1995; this volume), which considers the entire distal antennal outgrowth, the frontal appendage, and the morphology of the ovaries as essential in defining different genetic lineages or species-groups, and (2) a cladistic analysis. We suggest that of nine monophyletic groups, three are represented in both the Old and New World. Thus, contrary to former disparsalist hypotheses, we argue that the New World species represent relict forms of ancestral groups fragmented by continental drift (vicariance model).  相似文献
5.
Anostraca of the Indian Subcontinent   总被引:2,自引:2,他引:0  
There are 15 species of Anostraca belonging to 6 genera on the Indian Subcontinent. These are:Artemia sp. (reportedly a bisexual form of undetermined species);Artemia parthenogenetica Bowen & Sterling, 1978;Branchinecta orientalis Sars, 1901;Branchinella hardingi (Qadri & Baqai, 1956);Branchinella kugenumaensis (Ishikawa, 1895);Branchinella ornata Daday, 1910;Branchipodopsis acanthopenes (Malhotra & Duda, 1970);Branchipodopsis affinis Sars, 1901;Branchipus schaefferi Fischer, 1834;Chirocephalus priscus (Daday, 1910);Streptocephalus dichotomus Baird, 1860;Streptocephalus echinus Bond, 1934;Streptocephalus longimanus Bond, 1934;Streptocephalus simplex Gurney, 1906;Streptocephalus spinifer Gurney, 1906.Comparing numbers of species for southern India with other reasonably well studied areas, demonstrated that anostracan species richness is higher in the climatically more varied temperate regions than it is in the more uniform tropics. Tropical South India has six species compared to 13 in Arizona (USA), 19 in California (USA), 10 in Morocco, and 14 in Italy.  相似文献
6.
This paper reviews and extends the knowledge of anostracan penile morphology and its taxonomic significance. Since Linder‘s pioneering classification(based partly on male genital characters), the morphology of both basal and distal penile parts has been applied repeatedly to reorganize or establish higher anostracan taxa, or to extend their diagnoses. In general, the configuration of both basal and distal penile structures follows a constant pattern in well-defined genera. Size and shape of processes and spinulation on the basal (in Linderiella and Chirocephalidae) and the distal parts (in Parartemia), however, may show inter-specific differences. Variability in penile structures in the current genus Brachinella indicates the need for a taxonomic revision of this genus. Similar intra-generic penis morphology may contribute to hybridizability of congeners and validate Dubois‘genus concept for use in anostracans. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献
7.
SYNOPSIS. Field observations and experiments in a tropical forest revealed that Paramecium multimicronucleatum and other small aquatic organisms are transported between Heliconia flowers by terrestrial snails of the genus Caracolus . It is probable that dispersal is readily accomplished in tropical forests, and that the presence or absence of Paramecium in a given area therefore is determined by biological interactions.  相似文献
8.
9.
A survey of more than 60 ephemeral pools during March 1989 resulted in finding three large branchiopods not previously known to occur on the Caribbean Island of Aruba. These were two Anostraca, Dendrocephalus spartaenovae Margalef, 1967 and Thamnocephalus venezuelensis Belk & Pereira, 1982, and one Spinicaudata, Leptestheria venezuelica Daday, 1923. The notostracan previously reported from Aruba, Triops longicaudatus (LeConte, 1846), was also collected from several pools. All of these species occur also in Venezuela, which is separated from Aruba by an ocean gap of about 25 km. Comparison of Leptestheria venezuelica with Leptestheria compleximanus (Packard, 1877) demonstrated that cephalic morphology provides useful taxonomic features including length of rostrum, depth of occipital notch, shape of the occipital region, and protrusion of the eye capsule. These features may prove useful in studying other species of Leptestheria.  相似文献
10.
Anostracans were found living in ephemeral pools in the dark sections of three caves on the As Summan Plateau in Saudi Arabia. Branchipus schaefferi Fischer, 1834 occurred alone in one while it cohabited with Streptocephalus torvicornisbucheti Daday, 1910 in a second cave; fairy shrimps were observed but not collected from the third. None of the specimens demonstrated any of the types of morphological changes typically associated with cave adapted species. This is likely due to continuing colonization of the pools during flooding events. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献
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