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1.
Nathan W. Riser 《Hydrobiologia》1993,266(1-3):141-157
A majority of the nemertine species from the western North Atlantic were originally described from life in the nineteenth century. Many of these were established by A. E. Verrill who had ‘an eye for species’ no matter which phylum he was working with, and thus when living nemertines which he described are encountered, they can usually be recognized. The morphology of most of these species has never been reported; some may prove to be species described earlier from the eastern North Atlantic. Morphological observations on the nemertine species from the North East coast of the Pacific are inadequate and have prevented satisfactory comparison with species from Japan and eastern Russia. The morphology of some species collected in the Gulf of Maine and from Cape Cod, as well as a re-examination of some of the slides of type specimens of species from the west coast of North America, indicates that their generic placement must be re-examined. The architectonic plan of the heteronemertines postulated over 100 years ago can not be substantiated and is redescribed. Three new heteronemertean genera are described: Tenuilineus gen.n. Parvicirrus gen.n., Tarrhomyos gen.n.  相似文献
2.
Major characters and enoplan systematics   总被引:5,自引:5,他引:0  
Frank B. Crandall 《Hydrobiologia》1993,266(1-3):115-140
The history of enoplan systematics is briefly reviewed. Various taxonomic characters significant at the generic level and above are discussed, with comments on their application to traditional classifications and to recently propounded theories and new approaches to enoplan classification schemes. Several new characters are introduced and their potential significance examined. Finally, a revised classification scheme is presented which leaves open some of the phylogenetic questions about which there is presently much debate but, at the same time, provides secure higher taxa to contain the many forms and groups currently undergoing revision.  相似文献
3.
Three new species of monostiliferous hoplonemerteans from the Great Barrier Reef province of Australia are described and illustrated. These are, with their families indicated in parentheses, Poseidonemertes bothwellae sp. nov. (Amphiporidae), Nemertes hermaphroditicus sp. nov. (Emplectonematidae) and Pantinonemertes mooreae sp. nov. (Prosorhochmidae).  相似文献
4.
Nemerteans of the Great Barrier Reef 3. Anopla Heteronemertea (Lineidae)   总被引:3,自引:0,他引:3  
Nine species of lineid heteronemerteans are recorded from the Great Barrier Reef province of Australia. Six of these are new species, including four new genera, and are fully described and illustrated. These are Aetheorhynchus actites gen. et sp. nov. , Bennettiainsularis gen. et sp. nov., Cerebratulus magnetkus sp. nov., Colemania albulus gen. et sp. nov., Mkrura tridacnae sp. nov. and Quasilineus pulcherrimus gen. ct sp. nov. Lineus tricuspidatus (Quoy & Gaimard) is re-established, illustrated and described. Gorgonorhynchus repens Dakin & Fordham and Parborlasia hutchingsi Gibson have been fully described elsewhere, but a full list of known locations is provided.  相似文献
5.
The water chemistry, structure of sediment grain size, algal biomass, and patterns of nine bacteria physiological groups were studied monthly from May to October 1991 in an adjacent stream, ecotone, and reservoir zones (southern Poland). The distribution of five particulate organic carbon fractions was significantly different among the zones. Biomass of benthic algae demonstrated a maximum in the ecotone (22.74 g C m–2). Most of the bacterial groups were more numerous in the stream sediments where aerobic heterotrophs prevailed (1.2–6.5 × 1011 cells m–2). The significant differences in density were found for anaerobic heterotrophs, anaerobic nitrogen fixing, amylolytic, and cellulolytic bacteria among the zones. The small density of bacteria in the ecotone was probably an effect of the rapid water fluctuations, accompanied by movement of fine sediments or/and an inhibitory effect of compounds secreted by the periphyton. The principal component analysis showed that the ecotone zone was more similar to the reservoir open water than to the stream.  相似文献
6.
Two new genera and species of reptantic polystiliferous hoplonemerteans from the Great Barrier Reef province of Australia are described and illustrated. Urichonemertes pilorhynchus gen. et sp. nov. and Xenonemertes rhamphocephalus gen. et sp. nov. are both placed in the family Drepanophoridae (Polystilifera: Eureptantia: Aequifurcata).  相似文献
7.
Phylogeny,natural groups and nemertean classification   总被引:2,自引:2,他引:0  
Per Sundberg 《Hydrobiologia》1993,266(1-3):103-113
Contemporary practice in the classification of nemerteans (phylum Nemertea) is critically discussed. It is argued that basing higher taxa on the existence of a unique combination of characters in a species (or genus) is unlikely to lead to monophyletic taxa, and that this approach should be abandoned in favour of a classification based on explicit hypotheses of phylogeny. These hypotheses should be based on all available characters and characters should not be excluded before the analysis. The classification should be based on a reconstruction of the phylogeny and reflect this phylogeny in an unambiquous way.  相似文献
8.
A new genus and species of monostiliferoidean enoplan nemertean from Alaska is described and illustrated. The nemertean, Alaxinus oclairi gen. et sp. nov. , was found on the egg mass of a red king crab, Paralithodes camtschatica .  相似文献
9.
Biogeographic patterns and the evolution of eureptantic nemerteans   总被引:1,自引:0,他引:1  
The origin and evolution of the eureptantic nemerteans is discussed from a biogeographic point of view. It is most likely that East Indian Ocean was part of the ancestral distribution of the Eureptantia. The area cladogram estimated by Brooks parsimony analysis (BPA) is to a high degree congruent with a vicariance explanation of the evolution of the Eureptantia and suggests an ancestral distribution concordant with the Tethys Sea. A general area cladogram based on a combined BPA analysis of eureptantic nemerteans and acanthuroid fishes is reconstructed and suggested as a hypothesis of the relationships between east Indian Ocean, west Indian Ocean, west Pacific Ocean, east Adantic Ocean, west Atlantic Ocean, and the Mediterranean. This tree is compared with cladograms from the same areas based on other taxa.  相似文献
10.
Phylogenetic position of Nemertea derived from phylogenomic data   总被引:1,自引:0,他引:1  
Nemertea and Platyhelminthes have traditionally been grouped together because they possess a so-called acoelomate organization, but lateral vessels and rhynchocoel of nemerteans have been regarded as coelomic cavities. Additionally, both taxa show spiral cleavage patterns prompting the placement of Nemertea as sister to coelomate Protostomia, that is, either to Neotrochozoa (Mollusca and Annelida) or to Teloblastica (Neotrochozoa plus Arthropoda). Some workers maintain a sister group relationship of Nemertea and Platyhelminthes as Parenchymia because of an assumed homology of G?tte's and Müller's larvae of polyclad Platyhelminthes and the pilidium larvae of heteronemerteans. So far, molecular data were only able to significantly reject a sister group relationship to Teloblastica. Although phylogenomic data are available for Platyhelminthes, Annelida, Mollusca, and Arthropoda, they are lacking for Nemertea. Herein, we present the first analysis specifically addressing nemertean phylogenetic position using phylogenomic data. More specifically, we collected expressed sequence tag data from Lineus viridis (O.F. Müller, 1774) and combined it with available data to produce a data set of 9,377 amino acid positions from 60 ribosomal proteins. Maximum likelihood analyses and Bayesian inferences place Nemertea in a clade together with Annelida and Mollusca. Furthermore, hypothesis testing significantly rejected a sister group relationship to either Platyhelminthes or Teloblastica. The Coelomata hypothesis, which groups coelomate taxa together to the exclusion of acoelomate and pseudocoelomate taxa, is not congruent with our results. Thus, the supposed acoelomate organization evolved independently in Nemertea and Platyhelminthes. In Nemertea, evolution of acoely is most likely due to a secondary reduction of the coelom as it is found in certain species of Mollusca and Annelida. Though looking very similar, the G?tte's and Müller's larvae of polyclad Platyhelminthes are not homologous to the pilidium larvae of heteronemerteans. Finally, the convergent evolution of segmentation in Annelida and Arthropoda is further substantiated.  相似文献
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