As the ecologically important recipient channels for riverine ecosystems, tributaries provide unique microhabitats for microorganisms, among which zooplankton constitutes the most important heterotrophic organisms. In...As the ecologically important recipient channels for riverine ecosystems, tributaries provide unique microhabitats for microorganisms, among which zooplankton constitutes the most important heterotrophic organisms. In particular, the reduced water velocity caused by dams is more favorable for zooplankton development;therefore, dammed rivers are expected to support extremely diverse and abundant zooplankton communities and notably different spatiotemporal distribution patterns. So far,however, only very few molecular studies support these assumptions. Using high-throughput sequencing, a high number of 350 operational taxonomic units(OTUs;97% cutoff) were retrieved from 30 samples collected in the Xiangxi River, the nearest large tributary upstream of the Three Gorges Dam. Zooplankton did not show significant spatial distribution in the channel. Instead,the community structures varied significantly over sampling dates, corroborating the seasonal patterns found in lakes and ponds in the subtropical zone. As expected, the community compositions were deterministically governed by environmental filtering processes(phylogenetic clustering), in which water velocity appeared to be much less important than other investigated environmental factors. Moreover, most of the detected phylotypes(OTUs) had a relatively high(>90%) sequence similarity to previously deposited sequences, suggesting a mediocre degree of genetic novelty within the zooplankton communities in the Xiangxi River.展开更多
The ultrastructure of ciliates carries important cytological,taxonomical,and evolutionary signals for these single-celled eukaryotic organisms.However,little ultrastructural data have been accumulated for most ciliate...The ultrastructure of ciliates carries important cytological,taxonomical,and evolutionary signals for these single-celled eukaryotic organisms.However,little ultrastructural data have been accumulated for most ciliate groups with systematic problems.In the present work,a well-known marine uronychiid,Diophrys appendiculata,was investigated using electron microscopy and a comparison with,and a discussion considering,phylogenetic analyses were made.The new findings primarily show that:(i)this species lacks the typical alveolar plate,bears cortical ampule-like extrusomes,and has microtubular triads in the dorsal pellicle,and thus exhibits some ultrastructural features in common with most of its previously studied congeners;(ii)each adoral membranelle before the level of frontal cirrus II/2 contains three rows of kinetosomes and each membranelle after the level of frontal cirrus II/2 contains four rows,which might be related with morphogenesis and could be considered as a distinctive character of Diophrys;(iii)some structural details of the buccal field,such as the extra-pellicular fibrils,pellicle,pharyngeal disks and microtubular sheet,were documented.In addition,based on the ultrastructural comparison of representatives,we discuss the differentiation between the subfamilies Diophryinae and Uronychiinae.A hypothetical systematic relationship of members in the order Euplotida based on a wide range of data is also provided.展开更多
The ciliate genus Protocruzia belongs to one of the most ambiguous taxa considering its systematic position,possibly as a member of the classes Heterotrichea,Spirotrichea or Karyorelictea,which is tentatively placed i...The ciliate genus Protocruzia belongs to one of the most ambiguous taxa considering its systematic position,possibly as a member of the classes Heterotrichea,Spirotrichea or Karyorelictea,which is tentatively placed into Spirotrichea in Lynn’s 2008 system.To test these hypotheses,multigene trees(Bayesian inference,evolutionary distance,maximum parsimony,and maximum likelihood) were constructed using the small subunit rRNA(SSU rRNA) gene,internal transcribed spacer 2(ITS2) and a protein coding gene(histone H4).All analyses agree that:(1) four morphotypes of Protocruzia from different geographical origins group together and form a monophyletic clade,which cannot be assigned to any of the eleven described ciliate classes;(2) it is invariably positioned on an isolated branch separated from the class Spirotrichea suggesting that this clade should be clearly removed from Spirotrichea;(3) this leads us to hypothesize that this taxon may indeed represent a lineage on a class rank.Based on the fact that it is,both morphologically and in molecular features,closely related to the heterotrichs,Colpodea and Oligohymenophorea,Protocruziida might be an ancestral form for the subphylum Intramacronucleata in the evolutionary line from the class Heterotrichea(subphylum Postciliodesmatophora) to higher taxa.展开更多
基金supported by the National Natural Science Foundation of China (31772433, 31801984)Biodiversity survey of aquatic organisms in Three Gorges Reservoir area and the illustrated handbook compilation (2014FY120200)
文摘As the ecologically important recipient channels for riverine ecosystems, tributaries provide unique microhabitats for microorganisms, among which zooplankton constitutes the most important heterotrophic organisms. In particular, the reduced water velocity caused by dams is more favorable for zooplankton development;therefore, dammed rivers are expected to support extremely diverse and abundant zooplankton communities and notably different spatiotemporal distribution patterns. So far,however, only very few molecular studies support these assumptions. Using high-throughput sequencing, a high number of 350 operational taxonomic units(OTUs;97% cutoff) were retrieved from 30 samples collected in the Xiangxi River, the nearest large tributary upstream of the Three Gorges Dam. Zooplankton did not show significant spatial distribution in the channel. Instead,the community structures varied significantly over sampling dates, corroborating the seasonal patterns found in lakes and ponds in the subtropical zone. As expected, the community compositions were deterministically governed by environmental filtering processes(phylogenetic clustering), in which water velocity appeared to be much less important than other investigated environmental factors. Moreover, most of the detected phylotypes(OTUs) had a relatively high(>90%) sequence similarity to previously deposited sequences, suggesting a mediocre degree of genetic novelty within the zooplankton communities in the Xiangxi River.
基金supported by the National Natural Science Foundation of China(32170446,32030015,31961123002)the National Natural Science Foundation of Shanghai(21ZR1419000).
文摘The ultrastructure of ciliates carries important cytological,taxonomical,and evolutionary signals for these single-celled eukaryotic organisms.However,little ultrastructural data have been accumulated for most ciliate groups with systematic problems.In the present work,a well-known marine uronychiid,Diophrys appendiculata,was investigated using electron microscopy and a comparison with,and a discussion considering,phylogenetic analyses were made.The new findings primarily show that:(i)this species lacks the typical alveolar plate,bears cortical ampule-like extrusomes,and has microtubular triads in the dorsal pellicle,and thus exhibits some ultrastructural features in common with most of its previously studied congeners;(ii)each adoral membranelle before the level of frontal cirrus II/2 contains three rows of kinetosomes and each membranelle after the level of frontal cirrus II/2 contains four rows,which might be related with morphogenesis and could be considered as a distinctive character of Diophrys;(iii)some structural details of the buccal field,such as the extra-pellicular fibrils,pellicle,pharyngeal disks and microtubular sheet,were documented.In addition,based on the ultrastructural comparison of representatives,we discuss the differentiation between the subfamilies Diophryinae and Uronychiinae.A hypothetical systematic relationship of members in the order Euplotida based on a wide range of data is also provided.
基金supported by the “Natural Science Foundation of China” (Grant No 30870264)the Deutsche Forschungsgemeinschaft (DFG) STO414/2-4supported by the Center of Excellence in Biodiversity Research and the DNA Research Chair, King Saud University
文摘The ciliate genus Protocruzia belongs to one of the most ambiguous taxa considering its systematic position,possibly as a member of the classes Heterotrichea,Spirotrichea or Karyorelictea,which is tentatively placed into Spirotrichea in Lynn’s 2008 system.To test these hypotheses,multigene trees(Bayesian inference,evolutionary distance,maximum parsimony,and maximum likelihood) were constructed using the small subunit rRNA(SSU rRNA) gene,internal transcribed spacer 2(ITS2) and a protein coding gene(histone H4).All analyses agree that:(1) four morphotypes of Protocruzia from different geographical origins group together and form a monophyletic clade,which cannot be assigned to any of the eleven described ciliate classes;(2) it is invariably positioned on an isolated branch separated from the class Spirotrichea suggesting that this clade should be clearly removed from Spirotrichea;(3) this leads us to hypothesize that this taxon may indeed represent a lineage on a class rank.Based on the fact that it is,both morphologically and in molecular features,closely related to the heterotrichs,Colpodea and Oligohymenophorea,Protocruziida might be an ancestral form for the subphylum Intramacronucleata in the evolutionary line from the class Heterotrichea(subphylum Postciliodesmatophora) to higher taxa.
