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Aspects of the life cycle of marine nematodes 总被引:1,自引:0,他引:1
Summary 1. Life cycles of approximately one month are recorded for laboratory maintained cultures of chromadorid, monhysterid and oncholaimid nematodes.2. Amphimictic and parthenogenetic reproduction occurs in the species investigated. Reproduction inMonhystera parelegantula is by parthenogenesis.3. The chromadoridChromadorina epidemos and the oncholaimidViscosia macramphida are able to reproduce by either amphimixis or parthenogenesis.4.Acanthonchus cobbi, Chromadora macrolaimoides andEuchromadora gaulica are amphimitically reproducing species.
Aspekte des Lebenszyklus mariner Nematoden
Kurzfassung Bei einigen marinen Nematoden, die in Biscayne Bay (Florida) gesammelt und im Labor gezüchtet worden sind, vollzieht sich der gesamte Lebenszyklus ungefähr innerhalb eines Monats. BeiAcanthonchus cobbi, Chromadora macrolaimoides undEuchromadora gaulica ist zweigeschlechtliche Fortpflanzung festgestellt worden.Monohystera parelegantula vermehrt sich parthenogenetisch. Ein möglicherweise durch Umwelteinflüsse bedingter Wechsel von bisexueller und parthenogenetischer Fortpflanzung tritt beiChromadora epidemos undViscosia macramphida auf.相似文献
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Summary 1. Studies of the broad-leafed turtle grass,Thalassia testudinum
König, have revealed a diverse range of fungal infestation different in generic composition and dynamics of attack from that found on submerged wood. Certain of the fungi, notably the AscomyceteLindra thalassiae, initiate considerable degradation of leaf tissue and show a developmental cycle in nature related to the physiological state of the host plant.2. Use of fungal-cellulose mats as a trapping substrate has been extremely effective for discernment of ecologically significant shifts in nematode concentrations, especially those of the omnivorous species,Metoncholaimus scissus.3. Patterns of activity ofM. scissus, as well as those of various foliicolous nematodes, suggest that loci of organic material, such as fungal infested leaves and decaying plant tissue, significantly affect biological activity of these animals.4. Laboratory analysis of degraded cotton cellulose filters show a striking incidence of fungal reproduction of the ascomycetous fungusLulworthia, along with development of a considerable associated nematode fauna, especially species ofViscosia (V. macramphida) andLeptolaimus (L. plectoides). Successional patterns in nematode development are noted with continued degradation of the cotton cellulose matrix.
Contribution No. 768 from the Institute of Marine Science, University of Miami, Miami, Florida, and from the Canada Department of Agriculture, Ottawa, Canada. This work was supported at the IMS by grant GM 12842 from the National Institutes of Health, USA. 相似文献
Studien über marine Pilz-Nematoden-Assoziationen und Pflanzendegradation
Kurzfassung Untersuchungen am SeegrasThalassia testudinum König haben ergeben, daß sich hier Pilzinfektionen hinsichtlich der Komposition der beteiligten Gattungen und der Dynamik des Befalls von den am untergetauchten Holz festgestellten Infektionen unterscheiden. Bestimmte Pilze, insbesondere der AscomycetLindra thalassiae, leiten eine erhebliche Degradation des Blattgewebes ein und zeigen einen Entwicklungszyklus, welcher in Beziehung steht zum physiologischen Zustand der Wirtspflanze. Die Anwendung von Pilz-Zellulose-Matten als Einfangsubstrat war außerordentlich erfolgreich für das Erkennen ökologisch signifikanter Verschiebungen in den Nematodenkonzentrationen, insbesondere bei der omnivoren ArtMetoncholaimus scissus. Die Aktivitätsmuster vonM. scissus — ebenso wie die verschiedener foliicolöser Nematoden — deuten darauf hin, daß pilzinfizierte und zerfallende Pflanzenteile in entscheidendem Maße die biologische Aktivität dieser Tiere beeinflussen. Laboratoriumsanalysen degradierter Wollzellulosefilter lassen eine überraschend starke Vermehrung des AscomycetenLulworthia erkennen und gleichzeitig die Entwicklung einer beachtlichen Fauna assoziierter Nematodenarten, insbesondere vonViscosia macramphida undLeptolaimus plectoides. Im Verlaufe der weiteren Degradation der Wollzellulosematrix kommt es bei der Nematodenfauna zu entsprechenden Sukzessionen.
Contribution No. 768 from the Institute of Marine Science, University of Miami, Miami, Florida, and from the Canada Department of Agriculture, Ottawa, Canada. This work was supported at the IMS by grant GM 12842 from the National Institutes of Health, USA. 相似文献
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Chromosome numbers for 26 different species of the generaPiper, Peperomia andPothomorphe (Piperaceae) are reported. The basic chromosome numbers are 2n = 26, x = 13 (Piper, Pothomorphe) and 2n = 22, x = 11 (Peperomia), polyploid series are characteristic forPiper andPeperomia. Piper has the smallest chromosomes and prochromosomal interphase nuclei,Peperomia the largest ones and mostly reticulate to euchromatic nuclei.Pothomorphe is intermediate in both characters. The karyomorphological differences betweenPothomorphe andPiper underline their generic separation. Interspecific size variation of chromosomes occurs inPiper andPeperomia. Infraspecific polyploidy was observed inPiper betle. C-banding reveals different patterns of heterochromatin (hc) distribution between the genera investigated. The genome evolution is discussed. 相似文献
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The extremely thermophilic, obligately aerobic bacterium Sulfolobus solfataricus forms the tetrapyrrole precursor, -aminolevulinic acid (ALA), from glutamate by the tRNA-dependent five-carbon pathway. This pathway has been previously shown to occur in plants, algae, and most prokaryotes with the exception of the -group of proteobacteria (purple bacteria). An alternative mode of ALA formation by condensation of glycine and succinyl-CoA occurs in animals, yeasts, fungi, and the -proteobacteria. Sulfolobus and several other thermophilic, sulfur-dependent bacteria, have been variously placed within a subgroup of archaea (archaebacteria) named crenarchaeotes, or have been proposed to comprise a distinct prokaryotic group designated eocytes. On the basis of ribosomal structure and certain other criteria, eocytes have been proposed as predecessors of the nuclear-cytoplasmic descent line of eukaryotes. Because aplastidic eukaryotes differ from most prokaryotes in their mode of ALA formation, and in view of the proposed affiliation of eocytes to eukaryotes, it was of interest to determine how eocytes form ALA. Sulfolobus extracts were able to incorporate label from [1-14C]glutamate, but not from [2-14C]glycine, into ALA. Glutamate incorporation was abolished by preincubation of the extract with RNase. Sulfolobus extracts contained glutamate-1-semialdehyde aminotransferase activity, which is indicative of the five-carbon pathway. Growth of Sulfolobus was inhibited by gabaculine, a mechanism-based inhibitor of glutamate-1-semialdehyde aminotransferase, an enzyme of the five-carbon ALA biosynthetic pathway. These results indicate that Sulfolobus uses the five-carbon pathway for ALA formation.Abbreviations AHA
4-amino-5-hexynoic acid
- ALA
-aminolevulinic acid, Gabaculine, 3-amino-2,3-dihydrobenzoic acid
- GSA
glutamate 1-semialdehyde 相似文献
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Labidocera aestiva and L. scotti were found in the Tamiahua Lagoon, Veracruz, Mexico. Fleminger (1957) found that the populations of these species may overlap geographically, although L. aestiva has affinity to the Carolinian province and L. scotti to the Caribbean province. This study describes the seasonal behavior and succession of this species in the Tamiahua Lagoon, a brackish water system with a high marine influence. A qualitative and quantitative analysis of samples was made in March, July, and September 1985 and January 1986. L. aestiva was found in temperatures below 26 °C in a wide salinity range. At temperatures above 26 °C and up to 32 °C, L. aestiva was present also with euryhaline character. In the Tamiahua Lagoon these two species did not overlap during this study. Both species are considered temporary inhabitants of this estuarine system in the Western Gulf of Mexico. 相似文献