渐尖毛蕨和齿牙毛蕨的配子体发育研究

采用混合土培养渐尖毛蕨和齿牙毛蕨的孢子,显微镜下观察记录了它们的孢子萌发及配子体发育过程.结果表明:两者的孢子均为深褐色,极面观为椭圆形,赤道面观为半圆形,单裂缝;渐尖毛蕨的孢子萌发所需时间较渐尖毛蕨短,但两者萌发类型均为书带蕨型;丝状体阶段均发达;原叶体边缘均可产生少量毛状体;成熟原叶体均呈心脏形;由原叶体发育成幼孢...     

Condition factor and diet of Chrysichthys nigrodigitatus and Chrysichthys auratus (Siluriformes: Bagridae) from Aiba Reservoir, Iwo, Nigeria

Chrysichthys nigrodigitatus and C. auratus are important, highly valued and threatened freshwater species. To contribute with their ecological knowledge, the condition factor and diet of these two congeneric species were studied between April 2005 and April 2006. Food items of fish were evaluated by occurrence and numerical abundance methods, and the possible changes among sexes, seasons and sizes were considered. Results showed that generally C. nigrodigitatus were better conditioned than C. auratus. The males of C. nigrodigitatus and females of C. auratus were in better condition than their respective opposite sex throughout the year, and during the wet season compared to the dry. The food items of C. nigrodigitatus and C. auratus were similar and comprised twelve species belonging to five groups: Insecta (three species), Crustacea (five species), Arachnida (one species), Rotifera (one species) and Mollusca (two species). Other food items included fish scales, unidentified green eggs, plant parts, detritus and sand. Insecta and Crustacea dominated the food items in both species. For C. nigrodigitatus, insect consumption increased with fish size, while Crustacea items decreased (from 89.59% for 8.1cm - 12.0cm size class to 1.58% for 20.1cm - 26.0cm size class). However, while C. auratus smaller sized fish preferred Crustacea (98.72% for 8.1cm -12.0 cm size class), larger sized fish had both groups in relatively similar amounts. Schoener Overlap Index for both species and between seasons is 1.00. Diet breadth ranged from 0.00-1.47 for C. nigrodigitatus and 0.00-1.32 for C. auratus. Food Richness ranged from 0.00-1.44 for both species. Gut Repletion Index for C. nigrodigitatus and C. auratus are 76.39% and 76.27% respectively. Although, there is considerable similarity and overlap in the utilization of food resource for both coexisting species, condition factor and feeding behavior suggest strategies to reduce intra- and interspecific competition.     

Six New Species of Dobsonflies from Venezuela (Megaloptera: Corydalidae: Corydalinae)

Six new species of dobsonflies (Megaloptera: Corydalidae: Corydalinae) from Venezuela are described and illustrated, two in the Neotropical genus Chloronia and four within the New World genus Corydalus. Chloronia contains 15 previously described species. The new species Chloronia gaianii and C. marthae, each from the southern tepui and Andean regions, appear to be most closely related to C. hieroglyphica (Rambur) and C. mirifica Navás, respectively. Corydalus contains 30 previously described species. The new species Corydalus clavijoi, of Andean affinity, appears most closely related to C. tesselatus Stitz; C. crossi, from Auyán-tepuí, might be closely related to C. nubilus Erichson; and both C. hayashii and C. mayri, from westernmost Guayana Shield area and Aracamuni tepuis, respectively, clearly belong in the distinct and monophyletic C. arpi Navás species group. Keys for identification of the Venezuelan species of both genera are provided.     

Biochemical, genetic and physiological characterization of venom components from two species of scorpions: Centruroides exilicauda Wood and Centruroides sculpturatus Ewing

Current literature concerning the taxonomic names of two possibly distinct species of scorpions from the genus Centruroides (sculpturatus and/or exilicauda) is controversial. This communication reports the results of biochemical, genetic and electrophysiological experiments conducted with C. exilicauda Wood of Baja California (Mexico) and C. sculpturatus Ewing of Arizona (USA). The chromatographic profile fractionation of the soluble venom from both species of scorpions is different. The N-terminal amino acid sequence for nine toxins of C. exilicauda was determined and compared with those from C. sculpturatus. Lethality tests conducted in mice support the idea that C. exilicauda venom should be expected to be medically less important than C. sculpturatus. Thirteen genes from the venomous glands of the scorpion C. exilicauda were obtained and compared with previously published sequences from genes of the species C. sculpturatus. Genes coding for cytochrome oxidase I and II of both species were also sequenced. A phylogenetic tree was generated with this information showing important differences between them. Additionally, the results of electrophysiological assays conducted with the venom from both species on the Ca(2+)-dependent K(+)-channels, showed significant differences. These results strongly support the conclusion that C. exilicauda and C. sculpturatus are in fact two distinct species of scorpions.     

Cytotaxonomic studies of six Indian species of Chlorophytum

Taxonomy of six species of Chlorophytum (Liliaceae) from India has been reassessed in the light of their morphological and cytological characters. C. tuberosum (Roxb.) Baker (2 n = 16), a wide-spread species, is morphologically well defined but C. bharuchae Ansari, Raghavan & Hemadri (2 n = 16) has been confused with C. glaucum Dalz. and C. glaucoides Blatter (both 2 n = 42) by earlier workers. C. malabaricum Baker (2 n = 42) is a delicate species and occurs in the Nilgiris and the Western ghats. Two closely allied species, C. nepalense (Lindley) Baker and C. khasianum Hooker fil. (both 2 n = 56) are distributed in Eastern India. The first two species, with 2 n = 16, have been considered as at the diploid level with base number 8 while the rest of them appear to be autoallopolyploids with base number 7.     

Congruence of electrical properties in two Antarctic and two middle-latitude marine species of Euplotes (Ciliata, Hypotrichida)

Electric membrane properties and motor behaviour of two Antarctic and two middle-latitude species of Euplotes were compared. Membrane potential fluctuations and whole-cell currents were measured using the whole cell clamp. The electrical properties of both of the Antarctic species between themselves and of both of the middle-latitude species are nearly identical. Furthermore, after warming up to 22°C, the Antarctic species grown at 4°C show the same pattern of spontaneous potential fluctuations, induced potential oscillations and membrane currents as the middle-latitude species grown and measured at 22°C. After cooling down to 4°C, the middle-latitude species grown at 22°C show the same electrical properties as the Antarctic species grown and measured at 4°C. The congruence of the temperature-dependent electrical properties in Euplotes species from completely different habitats is presumably based on a universal mechanism of temperature dependence of ionic conductances, indicating the close physiological relationship among the species. Received: 29 October 1997 / Accepted: 20 April 1998     

The taxonomic distribution of C4 photosynthesis in Amaranthaceae sensu stricto

C(4) photosynthesis evolved multiple times in the Amaranthaceae s.s., but the C(4) evolutionary lineages are unclear because the photosynthetic pathway is unknown for most species of the family. To clarify the distribution of C(4) photosynthesis in the Amaranthaceae, we determined carbon isotope ratios of 607 species and mapped these onto a phylogeny determined from matK/trnK sequences. Approximately 28% of the Amaranthaceae species use the C(4) pathway. C(4) species occur in 10 genera-Aerva, Amaranthus, Blutaparon, Alternanthera, Froelichia, Lithophila, Guilleminea, Gomphrena, Gossypianthus, and Tidestromia. Aerva, Alternanthera, and Gomphrena contain both C(3) and C(4) species. In Aerva, 25% of the sampled species are C(4). In Alternanthera, 19.5% are C(4), while 89% of the Gomphrena species are C(4). Integration of isotope and matK/trnK data indicated C(4) photosynthesis evolved five times in the Amaranthaceae, specifically in Aerva, Alternanthera, Amaranthus, Tidestromia, and a lineage containing Froelichia, Blutaparon, Guilleminea, Gomphrena pro parte, and Lithophila. Aerva and Gomphrena are both polyphyletic with C(3) and C(4) species belonging to distinct clades. Alternanthera appears to be monophyletic with C(4) photosynthesis originating in a terminal sublineage of procumbent herbs. Alpine C(4) species were also identified in Alternanthera, Amaranthus, and Gomphrena, including one species (Gomphrena meyeniana) from 4600 m a.s.l.     

A comparative study of byssogenesis on zebra and quagga mussels: the effects of water temperature, salinity and light-dark cycle

The quagga mussel (Dreissena rostriformis bugensis) and zebra mussel (Dreissena polymorpha) are invasive freshwater bivalves in Europe and North America. The distribution range of both Dreissena species is still expanding and both species cause major biofouling and ecological effects, in particular when they invade new areas. In order to assess the effect of temperature, salinity and light on the initial byssogenesis of both species, 24 h re-attachment experiments in standing water were conducted. At a water temperature of 25°C and a salinity of 0.2 psu, the rate of byssogenesis of D. polymorpha was significantly higher than that of D. rostriformis bugensis. In addition, byssal thread production by the latter levelled out between 15°C and 25°C. The rate of byssogenesis at temperatures<25°C was similar for both species. Neither species produced any byssal threads at salinities of 4 psu or higher. At a salinity of 1 psu and a water temperature of 15°C, D. polymorpha produced significantly more byssal threads than D. rostriformis bugensis. There was no significant effect of the length of illumination on the byssogenesis of either species. Overall, D. polymorpha produced slightly more byssal threads than D. rostriformis bugensis at almost all experimental conditions in 24 h re-attachment experiments, but both species had essentially similar initial re-attachment abilities. The data imply that D. rostriformis bugensis causes biofouling problems identical to those of D. polymorpha.     

Host utilization of field-caged native and introduced thistle species by Rhinocyllus conicus

Rhinocyllus conicus Fr?elich was introduced from Europe into North America as a biological control agent of the exotic weed Carduus nutans L. Concern exists over the feeding of this weevil on at least 25 species of native Cirsium thistles. Beginning in 2008, cage studies isolating adults of R. conicus on buds and flower heads of all eight thistle species (native and introduced) recorded from Tennessee were conducted to test if R. conicus could use these species for reproduction and what impacts larval feeding of R. conicus may have on seed production. Larvae of R. conicus completed development in heads of the native species C. carolinianum (Walter) Fernald and Schubert. and C. horridulum Michaux, and significant reductions in seed numbers of both species occurred during 2008. Rhinocyllus conicus oviposited on both C. carolinianum and C. horridulum at significantly greater levels than the introduced species C. arvense (L.) Scopoli and C. vulgare (Savi) Tenore. Infested heads of C. carolinianum contained numbers of R. conicus per centimeter of plant head width similar to Ca. nutans in 2008, and both native species contained numbers of R. conicus per centimeter of plant head width similar to C. arvense and C. vulgare in 2009. Body length was similar between R. conicus reared on native thistles and its target host Ca. nutans. This report is the first documentation of R. conicus feeding and reproducing on C. carolinianum and C. horridulum. Although R. conicus has been observed only on introduced thistles in naturally occurring populations in this region, the utilization of C. carolinianum and C. horridulum as host species in controlled conditions warrants continued monitoring of field populations and further investigation into factors that may influence nontarget feeding in the future.     

Identification of species of the genus Candida by analysis of the 5.8S rRNA gene and the two ribosomal internal transcribed spacers

The PCR amplification and subsequent restriction analysis of the ribosomal region spanning the internal transcribed spacers (ITS1 and ITS2) and the 5.8S rRNA gene is applied to the identification of yeasts belonging to the genus Candida. This methodology has previously been used for the identification of some species of this genus, but in the present work this application has been applied to the identification and characterisation of a greater number of species of the genus Candida, with a special survey of species of clinical and biotechnological interest. Among the species of the genus Candida, the high variability observed, both in the length of the amplified region (ranging between 390 and 900 bp) and in their restriction patterns, allows the unequivocal identification to the species level, with the exception of the group of species that comprises C. membranifaciens, C. conglobata, C. atlantica, C. atmosphaerica, and C. oleophila, that required the sequencing of the D1/D2 domain of the 26S rRNA gene or the 5.8S-ITS region for their proper differentiation. The 5.8S-ITS restriction analysis also failed in the differentiation of species within the pairs C.aaseri/C.butyri,C.fructus/C.musae,C.santamariae var. santamariae / C. beechii and C. zeylanoides / C. krissii. In this case, the high sequence similarities obtained for their 26S D1/D2 domain and the 5.8S-ITS region indicate that each pair of species should be considered as a single species. The main purpose of this work is to generate a database for a high number of yeast species, of both biotechnological and clinical interest, and to facilitate their easy, fast, and reliable identification. The present work improves the database available online at the IATA web page (http://motor.edinfo.es/iata/) with the patterns of 75 species belonging to the genus Candida.     

The taxonomy and biology of two sympatric sibling species of Culex, C. pipiens and C. torrentium (Diptera, Culicidae)

The mosquito Culex torrentium Martini is a sibling species of C. pipiens L. and was first discovered in Britain in 1951. However, it is now evident that it was present in this country from at least 1900. Collections from a few southern localities in England indicate that the size of its population is about a third that of C. pipiens.
A comparative taxonomic study showed that neither the eggs nor larvae can be separated from those of C. pipiens , and that only in certain instances can the pupae of the two species be distinguished. Males are readily separated on the structure of the terminalia. Previously it was considered that C. torrentium could be distinguished by the presence of a pre-alar patch of scales, but it is shown that in a few specimens they are absent and in others they may become easily detached.
Larvae of both species frequently occur together in the same habitats, and no differences were observed in the biology of their immature stages. Serological tests showed that adults of both species feed on birds. Adult females of both species hibernate during the autumn, but whereas those of C. pipiens are common in man-made shelters, C. torrentium is absent.     

C-banding and FISH in chromosomes of the blow flies Chrysomya megacephala and Chrysomya putoria (Diptera, Calliphoridae)

The blow flies Chrysomya putoria and C. megacephala have 2n=12 chromosomes, five metacentric pairs of autosomes and an XX/XY sex chromosome pair. There are no substantial differences in the karyotype morphology of these two species, except for the X chromosome which is subtelocentric in C. megacephala and metacentric in C. putoria and is about 1.4 times longer in C. putoria. All autosomes were characterized by the presence of a C band in the pericentromeric region; C. putoria also has an interstitial band in pair III. The sex chromosomes of both species were heterochromatic, except for a small region at the end of the long arm of the X chromosome. Ribosomal genes were detected in meiotic chromosomes by FISH and in both species the NOR was located on the sex chromosomes. These results confirm that C. putoria was the species introduced into Brazil in 1970s, and not C. chloropyga as formerly described.     

Reproduction of two species of congeneric fruit bats (Cynopterus) in Brunei, Borneo

In summary, the reproductive cycles of C. minutas and C. brachyotis are shown in Fig. 12. Reproduction of both species is seasonal and continuous bimodal polyoestry, however, reproduction of neither species is linked to rains nor the general season of flowering/fruiting of trees.
Adult females of both species produce 2 litters/yr, 1 neonate/birth. Within each species, the females are in reproductive synchrony, with young born in two distinct seasons (3–4 months each) of parturition 5–7 months apart, centring about the two seasons of less rain, which may correspond to the fruiting of certain species of trees (e.g. mangoes for C. brachyotis ). Each parturition is followed by postpartum oestrus. Gestation spans about 5–6 months, with embryonic development delayed or arrested in early stages. Both sexes of C. minutas (and probably also C. brachyotis ) attain sexual maturity at about 7 months, with females giving birth the first time at about 12 months.     

Molecular characterization of Cryptosporidium isolates from humans and animals in Iran

Isolates of Cryptosporidium spp. from human and animal hosts in Iran were characterized on the basis of both the 18S rRNA gene and the Laxer locus. Three Cryptosporidium species, C. hominis, C. parvum, and C. meleagridis, were recognized, and zoonotically transmitted C. parvum was the predominant species found in humans.     

Assimilatory sulfate reduction in C(3), C(3)-C(4), and C(4) species of Flaveria

The activity of the enzymes catalyzing the first two steps of sulfate assimilation, ATP sulfurylase and adenosine 5'-phosphosulfate reductase (APR), are confined to bundle sheath cells in several C(4) monocot species. With the aim to analyze the molecular basis of this distribution and to determine whether it was a prerequisite or a consequence of the C(4) photosynthetic mechanism, we compared the intercellular distribution of the activity and the mRNA of APR in C(3), C(3)-C(4), C(4)-like, and C(4) species of the dicot genus Flaveria. Measurements of APR activity, mRNA level, and protein accumulation in six Flaveria species revealed that APR activity, cysteine, and glutathione levels were significantly higher in C(4)-like and C(4) species than in C(3) and C(3)-C(4) species. ATP sulfurylase and APR mRNA were present at comparable levels in both mesophyll and bundle sheath cells of C(4) species Flaveria trinervia. Immunogold electron microscopy demonstrated the presence of APR protein in chloroplasts of both cell types. These findings, taken together with results from the literature, show that the localization of assimilatory sulfate reduction in the bundle sheath cells is not ubiquitous among C(4) plants and therefore is neither a prerequisite nor a consequence of C(4) photosynthesis.     

Photosynthetic phosphoenolpyruvate carboxylases: characteristics of alloenzymes from leaves of c(3) and c(1) plants

A detailed comparison of green leaf phosphoenolpyruvate carboxylases from the C(4)-species Atriplex spongiosa and the C(3)-species Atriplex hastata revealed significant physical and kinetic differences. The two alloenzymes can be separated by anion exchange chromatography but have comparable molecular weights (350,000). Maximal velocity estimates were 38.0 and 1.48 micromoles per minute per milligram of chlorophyll for the carboxylases of A. spongiosa and A. hastata, respectively. Km phosphoenolpyruvate estimates were 0.49 and 0.08 mm for the C(4)A. spongiosa and C(3)A. hastata and the Km Mg estimates were 0.33 mm for the C(4) species and 0.017 mm for the C(3) species. The activity of the phosphoenolpyruvate carboxylase of A. spongiosa is more sensitive to chloride and phosphate than the phosphoenolpyruvate carboxylase of A. hastata, but both are equally sensitive to Mg chelating substances such as ATP, ADP, and citrate if assayed at their respective Km Mg values. A survey of the phosphoenolpyruvate carboxylases from 18 C(4) and C(3) species resulted in mean maximal velocity estimates of 29.0 +/- 13.2 and 1.50 +/- 0.57 micromoles per minute per milligram of chlorophyll for the C(4) species and C(3) species, respectively. Km phosphoenolpyruvate estimates were 0.59 +/- 0.35 mm and 0.14 +/- 0.07 mm for the C(4) and C(3), and Km Mg estimates were 0.50 +/- 0.30 and 0.097 +/- 0.057 mm for C(4) and C(3). All differences between means were significant at the 0.01 confidence level, supporting our hypothesis that the phosphoenolpyruvate carboxylase alloenzymes of C(4) and C(3) plants are functionally different and are associated with different photosynthetic roles. Both function in the photosynthetic production of C(4) acids, the phosphoenolpyruvate carboxylase of C(4) species largely producing malate or aspartate (or both) as a photosynthetic intermediate and the phosphoenolpyruvate carboxylase of C(3) species producing malate or aspartate (or both) as a photosynthetic product.     

Biochemical and stress responses of rohu Labeo rohita and mrigal Cirrhinus mrigala in relation to acclimation temperatures

The biochemical and stress responses of two Indian major carps, rohu Labeo rohita and mrigal Cirrhinus mrigala were studied after acclimating them to four preset temperatures (26, 31, 33 and 36° C) for 30 days. The blood glucose and liver glycogen levels showed an inverse trend in both the species and were significantly different in L. rohita at higher temperatures. The decrease in the liver glycogen level of C. mrigala , however, was not significant. Plasma cortisol levels increased significantly whereas the ascorbic acid content in the brain and kidney of both the species decreased significantly with increasing temperatures. Total lipid content in the liver of both the species decreased significantly with increasing acclimation temperatures. The phospholipid concentration decreased in L. rohita with increasing acclimation temperatures, and in C. mrigala the values decreased up to 33° C and increased at 36° C. In C. mrigala , the cholesterol level decreased up to 33° C and then increased at 36° C, but the absolute value was lower in comparison to L. rohita . The cholesterol levels, however, were not significantly different in L. rohita . Triglycerides and free fatty acids concentrations decreased significantly with increasing acclimation temperatures in both the species. The present study indicates species-specific metabolic responses of L. rohita and C. mrigala to thermal acclimation.     

Species pattern of phosphatidylinositol from lung surfactant and a comparison of the species pattern of phosphatidylinositol and phosphatidylglycerol synthesized de novo in lung microsomal fractions.

1. Phosphatidylinositol (PI) is a minor component of lung surfactant which may be able to replace the functionally important phosphatidylglycerol (PG) [Beppu, Clements & Goerke (1983) J. Appl. Physiol. 55, 496-502] without disturbing lung function. The dipalmitoyl species is one of the main species for both PI (14.4%) and PG (16.9%). Besides the C16:0--C16:0 species, the C16:0--C18:0, C16:0--C18:1, C16:0--C18:2 and C18:0--C18:1 species showed comparable proportions in the PG and PI fractions. These similarities of the species patterns and the acidic character of both phospholipids could explain why surfactant PG may be replaced by PI. 2. PI and PG were radiolabelled by incubation of microsomal fractions with [14C]glycerol 3-phosphate (Gro3P). For 11 out of 14 molecular species of PI and PG we measured comparable proportions of radioactivity. The radioactivity of these 11 species accounted together for more than 80% of the total. The addition of inositol to the incubation system decreased the incorporation in vitro of Gro3P into PG and CDP-DG (diacylglycerol) of lung microsomes (microsomal fractions), but did not change the distribution of radioactivity among the molecular species of PG. These results supported the idea that both acidic surfactant phospholipids may be synthesized de novo from a common CDP-DG pool in lung microsomes.     

Evolution of codon usage patterns: the extent and nature of divergence between Candida albicans and Saccharomyces cerevisiae.

Codon usage in a sample of 28 genes from the pathogenic yeast Candida albicans has been analysed using multivariate statistical analysis. A major trend among genes, correlated with gene expression level, was identified. We have focussed on the extent and nature of divergence between C.albicans and the closely related yeast Saccharomyces cerevisiae. It was recently suggested that significant differences exist between the subsets of preferred codons in these two species [Brown et al. (1991) Nucleic Acids Res. 19, 4293]. Overall, the genes of C.albicans are more A + T-rich, reflecting the lower genomic G + C content of that species, and presumably resulting from a different pattern of mutational bias. However, in both species highly expressed genes preferentially use the same subset of 'optimal' codons. A suggestion that the low frequency of NCG codons in both yeast species results from selection against the presence of codons that are potentially highly mutable is discounted. Codon usage in C.albicans, as in other unicellular species, can be interpreted as the result of a balance between the processes of mutational bias and translational selection. Codon usage in two related Candida species, C.maltosa and C.tropicalis, is briefly discussed.     

Trans-atlantic distribution of a mangrove oyster species revealed by 16S mtDNA and karyological analyses

Three species of mangrove oysters, Crassostrea rhizophorae, C. brasiliana, and C. gasar, have been described along the Atlantic shores of South America and Africa. Because the distribution of these molluscs is of great biological and commercial interest, their taxonomy and distribution deserve further clarification. Therefore, 15 populations were sampled from both continents. Their 16S mitochondrial polymorphism was studied by sequencing and PCR-RFLP analysis. Two haplotypes were identified. Haplotype a was the only one observed in Africa, but it was also observed in South America together with haplotype b. Because C. gasar is the only mangrove oyster identified on the west coast of Africa, haplotype a was attributed to this species, which has thus been shown to occur in South America. Haplotype b is attributed to C. rhizophorae. The karyotypes of specimens of C. gasar, from Africa and from South America, were very similar, and both species were observed at the same location in Brazil. The occurrence of C. gasar in South America adds a third species-in addition to C. rhizophorae and C. brasiliana-to the list of species present along these coasts. The predominant surface circulation patterns in this part of the Atlantic Ocean favor the hypothesis that C. gasar was transported from Africa to America. Finally, a phylogenetic tree built with seven 16S sequences from Crassostrea and Saccostrea species showed that C. gasar is intermediate between the American Crassostrea species (C. virginica and C. rhizophorae) and the Asian species (C. gigas and C. ariakensis).