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The fossil record of neritopsid opercula and shells shows thatthe shell shape typical for Neritopsidae and Neritidae appearedin the Triassic. The ancestors of Neritimorpha were most probablyforms similar to Naticopsis. The operculum of Recent Neritopsisis composed of two calcitic parts secreted from inside and anaragonitic callus deposited from outside. Similar neritopsidopercula were already present in the Late Triassic. The firstopercula with asymmetrically situated muscle scars, possiblyancestral for neritids, also appeared at that time. (Received 27 May 2004; accepted 8 December 2004)  相似文献   

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A systematic revision of the species of Benthobrookula Clarke,1961 from the Southwestern Atlantic Ocean was carried out. Theglobose protoconch, sculptured with a reticulate pattern, isrecognized as a diagnostic character for the genus. Benthobrookulaexquisita Clarke, 1961 and B. powelli Clarke, 1961 are redescribedand Cyclostrema calypso Melvill & Standen, 1912, Brookulapfefferi Powell, 1951 and Brookula strebeli Powell, 1951 areredescribed and allocated to Benthobrookula. Benthobrookulastrebeli is validated on the basis of the study of topotypicalspecimens. Two new species are described: Benthobrookula argentinafrom South Georgia and Benthobrookula paranaensis from off Brazil.A new allocation of Scalaria brevis d'Orbigny, 1840 to Benthobrookulais proposed. (Received 14 October 2004; accepted 20 May 2005)  相似文献   

5.
There is controversy about the phylogenetic relationships betweenIberus gualtieranus and I. alonensis. Some authors considerthem as valid species or subspecies while others believe thatthe flattened shell of I. gualtieranus is an ecotypic adaptationto dry karstic environments. Two fragments of the mitochondrialDNA (partial COI and 16S rRNA) were sequenced and used in maximumparsimony, maximum likelihood and neighbour-joining analyses.Iberus alonensis show two distinct lineages, one from Almeríaand the other one from Granada and Jaén-Córdobaregions. Iberus gualtieranus populations are recovered as aterminal node within the I. alonensis group from Almería.The I. gualtieranus clade shows a polytomy and there are nodifferences between the populations of the three isolated localitieswhere I. gualtieranus is currently distributed. This indicatesthat the geographical isolation of these populations has notresulted in genetic diversification. The results indicate thatthe population of I. gualtieranus from Sierra de Gádorin Almería is the only autochthonous one, while the othertwo populations originated by historical introductions. On thebasis of the differences in shell morphology, together withthe presence of a hybrid zone connecting both taxa in nature,and the possibility of obtaining fertile hybrids under laboratoryconditions, we conclude that these two taxa represent two subspecies:Iberus gualtieranus gualtieranus and I. gualtieranus alonensis. (Received 27 September 2004; accepted 10 March 2005)  相似文献   

6.
l-Carnitine (vitamin BT) plays a vital role in the transportation of long-chain fatty acids into mitochondrial matrix in mammals. l-Carnitine has a wide range of applications in pharmaceuticals, food products, and feed additives. Due to the increasing demand for l-carnitine in food and pharmaceutical applications, production of this compound has become prominent. However, very little has been reported on the production of l-carnitine. This review discusses the microbial and the enzymatic production of l-carnitine from different starting materials (substrates).  相似文献   

7.
The genus Tambja previously included 24 described species. Fournew species, T. tentaculata n. sp., T. gabrielae n. sp., T.zulu n. sp. and Tambja victoriae n. sp., from the Indo-Pacificare described. Tambja tentaculata n. sp., from Guam, is theonly known species in the genus with well developed, dorsolaterallygrooved, oral tentacles. Its inner lateral teeth have a bifidinner cusp with two long, sharp denticles. The oral tentaclesof T. tentaculata are more typical of Roboastra species, whilethe shape of the inner lateral teeth is more typical of Tambja.Nevertheless, the arrangement of the two cusps of the innerlateral teeth and the presence of a rachidian tooth withoutdenticles and with a central notch at the anterior edge, typicalof the species of the genus Tambja, suggest the placement withinthis genus. Tambja gabrielae n. sp., from Indonesia and PapuaNew Guinea, has dark green to dark brown ground colour withbright yellow patches scattered on the body. Tambja zulu n.sp. from Durban, South Africa, is characterized by a black groundcolour with slender yellow longitudinal lines. Tambja victoriaen. sp. is a new species from Papua New Guinea and Australiathat has frequently been misidentified as Roboastra arika, characterizedby its blue body colour and yellow lines. The four species aredistinguishable based on differences in body coloration, ofcharacters of the radula and of the reproductive system. Anoverview on distinguishing features of all known Indo-PacificTambja species is presented. (Received 21 June 2004; accepted 20 January 2005)  相似文献   

8.
The gland of Leiblein of the muricid Nucella lapillus and thenassariid Hinia reticulata has been examined by scanning andtransmission electron microscopy. The origin and functionalsignificance of its complex organization and its relationshipwith the rest of the mid-oesophagus in Nucella are discussed.It is absorptive as well as secretory, and a mechanism is proposedby which solute-rich fluids may enter the gland. Its epitheliumis composed of occasional mucous cells and two major cell types:ciliated cells engaged in protein metabolism and unciliatedcells responsible for uptake and storage of lipids and carbohydrates,both of which show evidence of pinocytotic uptake of solutesand intracellular digestion in lysosomes. Some enzyme activitypersists in the residual bodies they shed by apocrine secretion,but they remain intact in a mucous string until they reach thestomach. Preliminary ultrastructural examination indicates thatthe gland absorbs cadmium not only from the blood but also directlyfrom its lumen and that it may have the capacity to sequestera wide range of toxins. The same types of cell occur in Hiniain which their cyclical activity has been correlated with feeding.Similar cells have been identified in the oesophageal glandsof other prosobranchs. The foregut glands of carnivorous caenogastropodsare compared with the gland of Leiblein. There is an inversecorrelation between the role of the mid-oesophagus in digestionand absorption and the complexity of the stomach. (Received 16 August 2004; accepted 24 January 2005)  相似文献   

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The functional morphology of the Thraciidae is poorly understood.Although some morphological aspects of several members havebeen described, only Trigonothracia jinxingae from Chinese watersis known in detail. Thracia meridionalis is the only representativeof the family in Antarctic waters, and is common in AdmiraltyBay, King George Island, where it inhabits muddy sediments.Thracia meridionalis shares many features with Tr. jinxingaethat are typical of most Anomalodesmata, i.e. a secondary ‘ligament’of thickened periostracum, extensively fused mantle margins,ctenidia of type E, a ctenidial-labial palp junction of categoryIII, a stomach of type IV and simultaneous hermaphroditism.Thracia meridionalis is, however, strikingly different fromTr. jinxingae in a number of ways, such as the presence of afourth pallial aperture, statocysts of type B3, heterorhabdicctenidia, direct communication between the mantle chambers,a deep-burrowing habit (individuals lying on the left shellvalve), siphons that retract into mucus-lined burrows, a stomachwith extensive sorting areas, a rectum which passes over thekidneys and separate male and female gonadial apertures. Thereis, therefore, a greater range of morphological diversity withinthe Thraciidae than previously suspected. (Received 27 April 2004; accepted 30 November 2004)  相似文献   

11.
Among several other factors, body size has been found to influenceegg production in several species of hermaphroditic snail. Wetested whether this relationship between body size and egg productionexists in Helisoma trivolvis, a freshwater hermaphroditic species.We isolated 50 H. trivolvis from a laboratory population, measuredshell diameter, and monitored egg production for seven weeks.We found a positive relationship between body size and totalnumber of eggs produced, as well as body size and number ofeggs per egg mass. When body size and egg production are linked,it should be adaptive for larger individuals to act as femalesand smaller individuals as males. Since body size is relatedto female fecundity in this species, the relative size of snailsshould determine, at least in part, which individual acts asmale and which as female during copulation. However, the relationshipbetween body size and egg production is not nearly as strongas it is in other snail genera. Other factors such as age, genotypeand previous experience may be important in determining egg-layingcapacity and therefore gender choice in this species. In addition,we found a negative relationship between growth during thisperiod and egg production. This relationship has been foundin other pulmonates, and is evidence of resource allocationtradeoffs. (Received 3 August 2004; accepted 2 August 2005)  相似文献   

12.
The mitochondrial genome of grape (Vitis vinifera), the largestorganelle genome sequenced so far, is presented. The genomeis 773,279 nt long and has the highest coding capacity amongknown angiosperm mitochondrial DNAs (mtDNAs). The proportionof promiscuous DNA of plastid origin in the genome is also thelargest ever reported for an angiosperm mtDNA, both in absoluteand relative terms. In all, 42.4% of chloroplast genome of Vitishas been incorporated into its mitochondrial genome. In orderto test if horizontal gene transfer (HGT) has also contributedto the gene content of the grape mtDNA, we built phylogenetictrees with the coding sequences of mitochondrial genes of grapeand their homologs from plant mitochondrial genomes. Many incongruentgene tree topologies were obtained. However, the extent of incongruencebetween these gene trees is not significantly greater than thatobserved among optimal trees for chloroplast genes, the commonancestry of which has never been in doubt. In both cases, weattribute this incongruence to artifacts of tree reconstruction,insufficient numbers of characters, and gene paralogy. Thisfinding leads us to question the recent phylogenetic interpretationof Bergthorsson et al. (2003, 2004) and Richardson and Palmer(2007) that rampant HGT into the mtDNA of Amborella best explainsphylogenetic incongruence between mitochondrial gene trees forangiosperms. The only evidence for HGT into the Vitis mtDNAfound involves fragments of two coding sequences stemming fromtwo closteroviruses that cause the leaf roll disease of thisplant. We also report that analysis of sequences shared by bothchloroplast and mitochondrial genomes provides evidence fora previously unknown gene transfer route from the mitochondrionto the chloroplast.  相似文献   

13.
Naticid gastropods leave a record of predation in the form ofcharacteristic countersunk circular boreholes. We fed bivalveprey to naticids to test whether the ratio between the innerand outer borehole diameter differed among three Recent naticidspecies: Euspira heros, E. lewisii and Neverita duplicata. Fossilshells from a Miocene-aged assemblage, containing naticids previouslyidentified as E. heros and N. duplicata, were also includedin our analyses. Ratios of the inner to outer diameters of naticidboreholes in bivalve shells showed that there were significantdifferences in borehole shape between E. heros and the two otherRecent species. We found no significant differences betweenthe ratios of E. lewisii and N. duplicata; however, a principalcomponent analysis showed that boreholes distinctly clusteraccording to species. The Miocene boreholes were also distinctfrom the Recent, indicating that the Miocene naticids may bea separate species from E. heros and N. duplicata. We have shownthat there is a species-specific component to borehole geometry.This may have important implications for palaeobiological studies,because the index of borehole functionality, previously describedas an inner to outer borehole ratio of 0.5 for all naticids,may differ between species. (Received 23 March 2004; accepted 10 January 2005)  相似文献   

14.
A recent paper (Leclerc et al. 2004) described limited variationin dinucleotide microsatellites from Plasmodium vivax, suggestingvery recent bottlenecks or genome-wide selective events. Wedescribe patterns of variation in 11 dinucleotide microsatellitesin P. vivax populations from Colombia, India, and Thailand.We find abundant variation with heterozygosity of 0.64, 0.76,and 0.77, respectively, in the three countries. The discrepancybetween these two studies results is simply explained by thedifferences in the size of repeat arrays. The microsatellitesstudied by Leclerc et al. (2004) have very few repeats (median5.5, range 4–13) and so would not be expected to be variable.Plasmodium vivax microsatellites show comparable levels of variationto those in Plasmodium falciparum when repeat array length istaken into account and provide no support for recent bottlenecksor widespread selective purging  相似文献   

15.
An in-depth understanding of the biology of animals will requirethe generation of genomics resources from organisms from allphyla in the metazoan phylogenetic tree. Such resources willideally include complete genome sequences and comprehensiveEST (expressed sequence tag) datasets for each species of interest.Of particular interest in this regard are animals in the earlydiverging non-bilaterian phyla Porifera, Placozoa, Cnidaria,and Ctenophora. Publications describing the results from theuse of genomics approaches in these phyla have only recentlybegun to appear (Kortschak et al., 2003; Yang et al., 2003;Steele et al., 2004). Issues to be considered here include choosingthe basal metazoan species to examine with genomics approaches,the relative advantages and disadvantages of genome sequencingversus EST projects, and the resources and infrastructure requiredto carry out such projects successfully.  相似文献   

16.
A new species of pomatiopsid gastropod, Robertsiella silvicola,is described from Perak, peninsular Malaysia. The encapsulationof the ducts of the bursa copulatrix complex, short (wide) spermathecalduct and penial stylet indicate that this is a species of Robertsiella.Robertsiella silvicola is distinguished from other Robertsiellaby its small size, the lack of pronounced spiral macrosculptureon the shell, and the nature of the stylet. Robertsiella silvicolais found in water bodies ranging from small, spring-fed, first-orderstreams to tiny trickles of water draining off forested hillsides.This species appears restricted to limestone areas in the foothillsof the mountain chains of Kedah and Perak States, West Malaysia.It appears to be a highly compatible intermediate host for theparasitic blood fluke Schistosoma malayensis Greer, Ow-Yang& Yong, 1980 that infects humans and other mammals in Malaysia. (Received 15 September 2004; accepted 21 March 2005)  相似文献   

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Sclerotium-forming filamentous fungi are of great agriculturaland biological interest because they can be viewed as modelsof simple metamorphosis. They differentiate by asexually producingsclerotia but the processes involved in sclerotial metamorphosiswere poorly understood. In 1997, it was shown for the firsttime that the sclerotial differentiation state in Sclerotiumrolfsii concurred with increasing levels of lipid peroxides.This finding prompted the development of a theory supportingthat sclerotial metamorphosis is induced by oxidative stress.Growth factors that reduce or increase oxidative stress areexpected to inhibit or promote sclerotium metamorphosis, respectively.This theory has been verified by a series of published dataon the effect of certain hydroxyl radical scavengers on sclerotialmetamorphosis, on the identification and quantification of certainendogenous antioxidants (such as ascorbic acid, ß-carotene)in relation to the fungal undifferentiated and differentiatedstates, and on their inhibiting effect on sclerotial metamorphosisas growth nutrients. In 2004–2005, we developed assaysfor the measurement of certain redox markers of oxidative stress,such as the thiol redox state, the small-sized fragmented DNA,and the superoxide radical. These new advances allowed us toinitiate studies on the exact role of glutathione, hydrogenperoxide, and superoxide radical on sclerotial metamorphosis.The emerging data, combined with similar data from other better-studiedfungi, allowed us to make some preliminary postulations on theROS-dependent biochemical signal transduction pathways in sclerotiogenicfilamentous fungi.  相似文献   

19.
Patelloida pygmaea (Dunker) and its closely allied species,P. heroldi (Dunker) and P. conulus (Dunker) have caused nomenclaturalconfusion because of their variable shell morphology and distinctivehabitats. According to current nomenclature, these species ofPatelloida have been synonymized and treated as one specieswith two ecological forms. Patelloida pygmaea lives on the shellof Crassostrea gigas (Ostreidae), P. pygmaea form heroldi occurson intertidal rocks on sheltered shores and P. pygmaea formconulus is found on the shell of Batillaria multiformis (Batillariidae).Their taxonomic relationships and possible species status are,however, unclear. Using two mitochondrial genes (fragments ofCOI and 16S ribosomal RNA; total 1192 sites), we analysed 88specimens of P. pygmaea, P. pygmaea form heroldi and P. pygmaeaform conulus from 37 localities in East Asia. In the resultingmolecular phylogenetic trees, the specimens of Patelloida fallinto four clades with high bootstrap probabilities; these cladescorrespond taxonomically to P. pygmaea, P. conulus, P. heroldiand a fourth previously unrecognized taxon, Patelloida ryukyuensisn. sp., described here. A minimum-spanning network for 29 uniquemitochondrial COI haplotypes obtained from 45 specimens in thesame bay in central Japan form three distinct clusters, consistingof P. pygmaea, P. conulus and P. heroldi, respectively. Thissuggests that reproductive isolation has been established betweeneach group. A detailed examination of radular and shell morphologiesof the four taxa clarifies the morphological distinction betweenthese species. The four species form a rather young clade inthe genus Patelloida that diverged during the Pliocene. Theyprovide an example of habitat segregation in a restricted marineenvironment. (Received 21 December 2004; accepted 11 March 2005)  相似文献   

20.
Xeropicta derbentina (Krynicki, 1836), a native of Eastern MediterraneanEurope, was introduced to southeastern France during the 1940sand is now widely spread across Provence. In summer it aggregateson plants, making its populations clearly visible. However,its life cycle within the Mediterranean basin is poorly documented.While X. derbentina in its native area exhibits an annual lifecycle, this species has been found in Provence to have a bienniallife cycle. Moreover, in southeastern France, field studieswithin a restricted area show variations in demographic structure.In consequence, the life cycle of X. derbentina and the demographicpatterns observed require clarification. Five populations withvarious demographic structures were studied over 1 year in thesame location, i.e. under the same climatic conditions. Thefield study was complemented by laboratory observations on mating,egg-laying and hatching. Xeropicta derbentina appears to bea semelparous species, with an annual life cycle being foundon four plots. The reproductive period begins at the end ofsummer and lasts until the beginning of winter. First egg-layingoccurs within 1 week after mating and lasts up to 30 days. Hatchingtakes place 15–20 days after egg-laying. Xeropicta derbentinapossesses multiple mating and egg-laying sessions, involvingsuccessive hatching. Populations are mainly characterized bytwo growth stages, the first in spring when newly-hatched snailsevolve into juveniles, and the second in late summer when theyreach maturity. However, on the highest density plot, a bienniallife cycle is observed for some newly-hatched snails that showan interrupted growth during summer and evolve into juvenilesonly in the second autumn. Moreover, this life cycle not onlyvaries among plots but also at a 1-year interval within plots.Hence, the life span of X. derbentina is between 12 and 20 months,but can be extended up to 30 months according to whether hatchingoccurs early or late and whether they survive the first andsecond winters. Xeropicta derbentina is thus able to have variousgrowth speeds and life spans, and appears to switch from anannual life cycle to a biennial cycle in response to populationdensity or climatic conditions. (Received 8 October 2004; accepted 15 December 2004)  相似文献   

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