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.
The number of species of caridean, brachyuran and anomuran decapods increases from high to low latitudes in both hemispheres. This is shown to be due mainly to changes in the abundance of small species. Possible explanations for these variations in abundance are discussed. The other infraorders of decapods are confined to mid and low latitudes.  相似文献   

2.
    
Remains of two large sarcopterygians are described from Famennian deposits in Belgium. One of them is referred to Eusthenodon wängsjöi Jarvik; it is the first occurrence of this genus in Belgium. The other, much larger one, appears to be a tristichopterid. It has a postspiracular; size and shape of the mandible similar to those of Platycephalichthys skuenicus and P. bischoffi ; snout and cheek patterns close to those of Eusthenodon ; unusual shape of the supratemporal resembling that of Hyneria , Mandageria and Platycephalichthys skuenicus ; and tooth histology quite similar to that of Eusthenodon and Platycephalichthys .  相似文献   

3.
    
Abstract:  Additional material of a large specimen of tristichopterid fish from the Upper Famennian Evieux Formation of Belgium is described. This large fish was previously assigned to Tristichopteridae gen. et sp. indet. due to the lack of diagnostic anatomical data. New available material consists of the internal surface of the parietal shield, vomers and anterior part of the parasphenoid, subopercular and submandibulo-branchiostegal bones, and an internal view of the anterior part of the mandible. A possible autapomorphy of the new form from Belgium, Langlieria socqueti gen. nov. et sp. nov., is the absence of marginal teeth on the vomer except on its most lateral part. Apart from these features, it only differs from the genus Mandageria from Australia in the absence of marginal teeth between the dentary fang and the mandibular symphysis, in the presence of a raised marginal crest lateral to the anterior coronoid fang, and in the presence of numerous small marginal teeth on the premaxilla. It differs from the cosmopolitan genus Eusthenodon in a number of respects: the supratemporal, tabular, and postparietal bones are superficially fused, as are the intertemporal and parietal bones, the dermal ornament is proportionally very fine, and the denticulated field of the parasphenoid stands proud rather than being recessed into the body of the bone.  相似文献   

4.
  相似文献   

5.
    
Invasion of the land has been a considerable challenge for aquatic organismal lineages, primarily because of desiccation and lack of physical support in air. Gastropod molluscs are among the most successful animals in this habitat shift because of their hard exoskeleton, whereas land slugs, regarded as descendants of land snails, gradually lost their shells in sheltered, moist environments. We present solid evidence of terrestrial invasion by a lineage of sea slugs; this invasion is represented by a newly discovered species, Aiteng marefugitus (Panpulmonata: Acochlidia), from a humid tropical rainforest on a small island in the Republic of Palau, western Pacific. The slug lineage seems to have invaded the forest habitat directly from the upper littoral zone in the Cenozoic.  相似文献   

6.
Abdennour  C.  Smith  B. D.  Boulakoud  M. S.  Samraoui  B.  Rainbow  P. S. 《Hydrobiologia》2000,432(1-3):217-227
The concentrations of the trace metals Zn, Cu, Fe, Cd and Pb were measured in four caridean decapods; Atyaephyra desmaresti, Palaemonetes varians, Parapenaeus longirostris and Aristeus antennatus, from freshwater , estuarine and marine habitats in northeast Algeria variably affected by anthropogenic metal contamination. The two coastal species (P. longirostris and A. antennatus) are a food source for the local population. Accumulated metal concentrations varied interspecifically, and intraspecifically between sites and between seasons, except in the case of Aristeus antennatus. The fresh and brackish water species (Atyaephyra desmaresti and Palaemonetes varians) accumulated more Cd and Pb than their marine counterparts. Results are discussed with respect to anthropogenic inputs and the environmental conditions of the regions studied.  相似文献   

7.
    
A new basal land plant, Teruelia diezii gen. et sp. nov., is described from the shallow‐water marine deposits of the Lower Devonian (Lochkovian–Pragian) Nogueras Formation of the Iberian Peninsula (north Gondwana palaeocontinent). Teruelia is preserved as a compression fossil and consists of isotomously branched, robust stems terminated in large, fusiform, twisted sporangia. This morphology suggests that Teruelia is very probably equivalent to Aglaophyton, a permineralized early polysporangiophyte known up to now only from the Lower Devonian (early Pragian to ?earliest Emsian) Rhynie Chert in Scotland (Laurussia palaeocontinent), which represents an early terrestrial hot‐spring ecosystem. Accepted phylogenies identify Aglaophyton as sister to vascular plants. Our phylogeny‐based results identify the Aglaophyton/Teruelia biological entity (i.e. Aglaophyton anatomical characters plus Teruelia external morphology) as the most direct vascular plant precursor. It shows that at least one Rhynie Chert type plant had a much wider distribution than previously known and suggests that Aglaophyton was not restricted to hydrothermal environments, unlike other Rhynie Chert plants.  相似文献   

8.
    
Summary

In the last few years, (bio)chemical and molecular biological studies have shown that several members of the hyperglycemic hormone family are present in different molecular forms. In vivo and in vitro bioassays revealed that some of these isoforms also play a role in the control of reproduction in decapod crustaceans. This communication gives a review of the cytological aspects of the eyestalk X-organ sinus gland complex, responsible for the synthesis, storage and release of these neuropeptides, and the molecular and functional aspects of those members involved in the control of reproduction. Finally, the role of the hyperglycemic hormone family in the regulation of reproduction in the female lobster is described as an example of the (possible) interactions of the members of the hyperglycemic hormone family with other (neuro)endocrine factors in the reproductive process of crustaceans.  相似文献   

9.
    
Metabolic rates provide an estimate of the cost of living for different organisms that can readily be compared across species to provide an estimate of their relative requirements for survival. As such, metabolic rates have been measured for decades on a wide range of organisms. Here, we review published estimates of metabolic rates for brachyuran crabs, a ubiquitous and ecologically and economically important group of consumers. Consistent with ecological theory and results in many other groups of animals, and after controlling for phylogenetic relationships, crab metabolic rates scale with body mass with a scaling exponent of 0.65. Similarly, as with other groups of poikilotherms, crab metabolic rates increase strongly with temperature, with a Q10 of 1.26. Additionally, we found that metabolic rates were correlated with ecological niche, varying with both the diet strategy and the habitat occupied. These results help clarify the relative risk to crabs from environmental changes that impose metabolic stress, including climate change and the proliferation of hypoxic zones.  相似文献   

10.
5-羟色胺(5-HT)和多巴胺(DA)是两种神经递质,可与众多不同类型的受体结合发挥多种重要的生理功能.现已证明其广泛分布于多种动物的不同组织中,在动物的打斗行为活动中起着重要的调节作用.目前,在虾蟹中已被报道的5-HT受体主要有5种,分别是5-HT1A、5-HT1B、5HT2A、5HT2B和5-HT7;DA受体主要为DA1A、DA1B、DA2和DA4.5-HT和DA及其受体分布存在明显的种属和组织特异性.5-HT和DA参于了虾蟹打斗行为的调节过程并有不同的调节机理.5-HT可以调节环磷酸腺苷(cAMP)或高血糖激素(CHH)的释放,促进或抑制虾蟹打斗行为;而DA同样能够通过调节cAMP及COMT等物质的释放来调节虾蟹打斗行为.  相似文献   

11.
    
Protonympha is an enigmatic fossil represented by two species from the Middle Devonian (Protonympha transversa) and Late Devonian (Protonympha salicifolia) of New York. Although interpreted in the past as a polychaete worm or starfish arm, Protonympha is not found with marine fossils, but with fossil plants. This fossil plant community was a swamp woodland of Lepidosigillaria whitei, with ground cover of Haskinsia colophylla, fringing brackish to freshwater coastal lagoons of the Catskill Delta. Protonympha shares with Ediacaran Vendobionta a quilted body of unskeletonized biopolymer that is unusually resistant to burial compaction. In overall form, Protonympha is most like the Ediacaran genus Spriggina. Protonympha has branching and tapering tubular structures radiating from the bottom. These rhizine‐like structures, thallus stratification and internal chambers revealed by petrographic thin sections suggest affinities with lichenized fungi. As for Cambrian Swartpuntia and Ordovician–Silurian Rutgersella, Protonympha may have been a post‐Ediacaran vendobiont.  相似文献   

12.
    
The Zosterophyllopsida were major contributors to the diversification of early land plants. We present the first detailed analysis of the diversity dynamics of these plants from an updated database of all currently recognized zosterophyllopsid species. A set of quantitative methods classically used in palaeodiversity studies was applied to two data sets. The first one, ‘Zosterophyllopsida sensu stricto’, corresponds to the clade identified by Hao & Xue (The Early Devonian Posongchong Flora of Yunnan. (2013), Science Press). In the second, called ‘Zosterophyllopsida sensu lato’, barinophytalean‐type plants and taxa for which zosterophyllopsid affinities are suspected are added. The number of localities is used to explore sampling bias. Results show that sampling effect is minimal for the Early Devonian. For this time interval, both data sets record consistent patterns of changes suggesting that, whatever their affinities, all taxa included in the Zosterophyllopsida sensu lato show similar evolutionary trends. The diversity dynamics of zosterophyllopsids are characterized by a radiation during the Lochkovian, maximal values in the Pragian and a decline starting in the Emsian. The proportion of zosterophyllalean taxa with terminal sporangia is high until the Late Lochkovian when gosslingialean taxa without terminal sporangia evolved. During the Middle and Late Devonian, when diversity patterns are strongly affected by sampling, zosterophyllopsid diversity is low and characterized by a high proportion of barinophytacean and gosslingialean taxa, the latter becoming extinct in the Early Frasnian.  相似文献   

13.
    
Land plants comprise the bryophytes and the polysporangiophytes. All extant polysporangiophytes are vascular plants (tracheophytes), but to date, some basalmost polysporangiophytes (also called protracheophytes) are considered non‐vascular. Protracheophytes include the Horneophytopsida and Aglaophyton/Teruelia. They are most generally considered phylogenetically intermediate between bryophytes and vascular plants and are therefore essential to elucidate the origins of current vascular floras. Here, we propose an alternative evolutionary framework for the earliest tracheophytes. The supporting evidence comes from the study of the Rhynie chert historical slides from the Natural History Museum of Lille (France). From this, we emphasize that Horneophyton has a particular type of tracheid characterized by narrow, irregular, annular and/or, possibly spiral wall thickenings of putative secondary origin, and hence that it cannot be considered non‐vascular anymore. Accordingly, our phylogenetic analysis resolves Horneophyton and allies (i.e. Horneophytopsida) within tracheophytes, but as sister to eutracheophytes (i.e. extant vascular plants). Together, horneophytes and eutracheophytes form a new clade called herein supereutracheophytes. The thin, irregular, annular to helical thickenings of Horneophyton clearly point to a sequential acquisition of the characters of water‐conducting cells. Because of their simple conducting cells and morphology, the horneophytophytes may be seen as the precursors of all extant vascular plant biodiversity.  相似文献   

14.
    
Drought affects more people than any other natural disaster but there is little understanding of how ecosystems react to droughts. This study jointly analyzed spatio‐temporal changes of drought patterns with vegetation phenology and productivity changes between 1999 and 2010 in major European bioclimatic zones. The Standardized Precipitation and Evapotranspiration Index (SPEI) was used as drought indicator whereas changes in growing season length and vegetation productivity were assessed using remote sensing time‐series of Normalized Difference Vegetation Index (NDVI). Drought spatio‐temporal variability was analyzed using a Principal Component Analysis, leading to the identification of four major drought events between 1999 and 2010 in Europe. Correspondence Analysis showed that at the continental scale the productivity and phenology reacted differently to the identified drought events depending on ecosystem and land cover. Northern and Mediterranean ecosystems proved to be more resilient to droughts in terms of vegetation phenology and productivity developments. Western Atlantic regions and Eastern Europe showed strong agglomerations of decreased productivity and shorter vegetation growing season length, indicating that these ecosystems did not buffer the effects of drought well. In a climate change perspective, increase in drought frequency or intensity may result in larger impacts over these ecosystems, thus management and adaptation strategies should be strengthened in these areas of concerns.  相似文献   

15.
Decapod crustaceans are relatively widespread in Jurassic deposits of Europe and a small number have been collected from the north-east of France. A new fossil of a macrurous decapod assigned to Eryma burgundiaca sp. nov., an erymid lobster, is described from this area and comparisons are made with closely allied species from Europe. Probable pagurid anomurous decapods are represented by Orhomalus magnificus sp. nov., Palaeopagurus acutus sp. nov. and Palaeopagurus neraudeaui sp. nov. No brachyurous decapods are presently known from the fauna. Based on the associated ammonites, the material is considered to be Callovian in age.  相似文献   

16.
    
Spectroscopy information (functional groups and semiquantitative data) by Fourier transform infrared (FTIR) spectroscopy of Spongiophyton Kräusel emend. Chaloner et al. is reported for the first time, in an attempt to identify spectroscopic patterns that would differentiate species of these taxa. A total of 33 specimens identified as S. lenticularis, S. nanum and S. minutissimum and preserved as compressions were analysed. They come from the same fossiliferous horizon of one outcrop situated in the uppermost Middle Devonian São Domingos Formation of the Paraná Basin in southern Brazil. The results reveal that functional groups in the 3000–2800 and 1800–700 cm?1 wavenumber regions are present in all specimens. Infrared‐derived ratios (CH2/CH3, Al/Ox, Ox1/Ox2, C=O cont., C=C cont., Al2 and Ar/Al) and types of kerogen led to a comparison of the morphological characteristics of the studied material and indicate that compressions of S. lenticularis, S. nanum and S. minutissimum contain different organic compounds. S. nanum and S. minutissimum show higher oxidation and lower aromaticity of its organic matter than S. lenticularis. Additionally, S. lenticularis shows low A‐factor values, suggesting a composition similar to type III kerogen, while S. nanum and S. minutissimum showed intermediate to high A‐factor values, suggesting a composition similar to type II kerogen. In conclusion, the chemical‐analytical techniques and statistical analysis (using PCA technique) reveal a closer taxonomic relationship between S. nanum and S. minutissimum than either has with S. lenticularis, supporting their taxonomic separation, previously proposed in the literature on the basis of morphological features. Lastly, the chemical signatures support the hypothesis that links these enigmatic fossils to a type of lichen or other early inland plant.  相似文献   

17.
    
Since its introduction in 2003, DNA barcoding has proven to be a promising method for the identification of many taxa, including mosquitoes (Diptera: Culicidae). Many mosquito species are potential vectors of pathogens, and correct identification in all life stages is essential for effective mosquito monitoring and control. To use DNA barcoding for species identification, a reliable and comprehensive reference database of verified DNA sequences is required. Hence, DNA sequence diversity of mosquitoes in Belgium was assessed using a 658 bp fragment of the mitochondrial cytochrome oxidase I (COI) gene, and a reference data set was established. Most species appeared as well‐supported clusters. Intraspecific Kimura 2‐parameter (K2P) distances averaged 0.7%, and the maximum observed K2P distance was 6.2% for Aedes koreicus. A small overlap between intra‐ and interspecific K2P distances for congeneric sequences was observed. Overall, the identification success using best match and the best close match criteria were high, that is above 98%. No clear genetic division was found between the closely related species Aedes annulipes and Aedes cantans, which can be confused using morphological identification only. The members of the Anopheles maculipennis complex, that is Anopheles maculipennis s.s. and An. messeae, were weakly supported as monophyletic taxa. This study showed that DNA barcoding offers a reliable framework for mosquito species identification in Belgium except for some closely related species.  相似文献   

18.
    
Abstract: All known etyid crabs (Crustacea, Decapoda) from the upper Albian – lower Cenomanian Aldoirar coralgal‐dominated patch reef (Albeniz Unit, Eguino Formation), as exposed at the disused Koskobilo quarry in Navarra, northern Spain, are described, discussed and illustrated. A new species, Xanthosia koskobiloensis, the first member of the genus on record from southern Europe, is erected, and a variety that appears closely related to this, Xanthosia cf. X. koskobiloensis, is recognised. This new taxon could be a forerunner of the early Palaeocene (Danian) Xanthosia gracilis from Fakse (Sjælland, eastern Denmark), with which it shares a morphologically closely similar carapace. On the basis of a revised overview here of all species assigned to it, the genus Xanthosia may have evolved in an environment dominated by deposition of siliciclastics, rather than chalks. In addition, Etyxanthosia fossa has been collected at Koskobilo, and as the distribution of all known specimens demonstrates, E. fossa inhabited various environments. Another new species, Caloxanthus paraornatus, is closely similar as well to a species from Fakse, Caloxanthus ornatus, and constitutes the first record of the genus for southern Europe.  相似文献   

19.
    
A study of nematodes associated with the large larch bark beetle Ips cembrae (Heer 1836) was carried out at three locations in the Czech Republic. The proportion of beetles infested by endoparasitic nematodes (representatives of genera Contortylenchus, Parasitylenchus, Cryptaphelenchus and Parasitorhabditis) ranged from 29.9 to 50.9%. Significant differences were determined in nematode infestation levels among locations, generations and sampling methods. No differences were found in infestation rates between males and females. The percentage of bark beetles with phoretic nematodes ranged from 18 to 42.9%. Phoretic nematodes directly found under elytra, on wings and between body segments of the bark beetles belong to the genus Micoletzkya. However, adults and juveniles of other two phoretic species Laimaphelenchus penardi and Bursaphelenchus sp. were found in the gallery frass of I. cembrae. Infestation by phoretic nematodes positively correlated with the presence of mites under elytra.  相似文献   

20.
    
It has recently been unveiled that a wide variety of microbial eukaryotes (protists) occur in chemosynthetic ecosystems, such as hydrothermal vents and methane seeps. However, there is little knowledge regarding protists associated with endemic animals inhabiting these environments. In the present study, utilizing PCR techniques, we detected fragments of the small subunit ribosomal RNA gene (SSU rRNA gene) from a particular protist from gill tissues of a significant fraction of the vesicomyid clams Calyptogena soyoae and C. okutanii complex and of the mussel Bathymodiolus platifrons and B. japonicus, all of which harbor chemosynthetic endosymbiont bacteria and dominate methane seeps in Sagami Bay, Japan. Based on the phylogeny of SSU rRNA gene, the organism in question was shown to belong to Alveolata. It is noteworthy that this protist did not affiliate with any known alveolate group, although being deeply branched within the lineage of Syndiniales, for which the monophyly was constantly recovered, but not robustly supported. In addition, the protist detected using PCR followed by sequencing was localized within gill epithelial cells of B. platifrons with whole‐mount fluorescence in situ hybridization. This protist may be an endoparasite or an endocommensal of Calyptogena spp. and Bathymodiolus spp., and possibly have physiological and ecological impacts on these bivalves.  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