Wirbellose Meerestiere als Parasiten,Kommensalen oder Symbionten in oder an Scyphomedusen

Zusammenfassung 1. Das Vorkommen wirbelloser Tiere als Parasiten, Kommensalen oder Symbionten in Scyphomedusen, das zwar in zahlreichen Schriften über diese Medusen erwähnt, aber nicht in größere Fachwerke aufgenommen und daher wenig bekannt ist, wird an Hand der Literatur der Scyphomedusen zusammenfassend dargestellt.2. In Tabellen sind einerseits die Medusen mit den an ihnen beobachteten Wirbellosen zusammengestellt und andererseits die einzelnen Arten der Wirbellosen mit den Medusen, in denen sie gefunden sind, nach ihren systematischen Gruppen aufgeführt.3. Es ergibt sich daraus, daß 51 Arten aus 28 Gattungen der Scyphomedusen Wirbellose als Parasiten, Kommensalen oder Symbionten enthalten, die den Actiniariae, Turbellariae, Trematoda, Cestoda, Nematoda und verschiedenen Gruppen niederer und höherer Crustaceen sowie sogar den Echinodermen und Cephalopoden angehören können, wobei allerdings Crustaceen bei weitem am häufigsten sind und in ein und derselben Meduse mehrere verschiedene Wirbellose, z. T. gleichzeitig, vorkommen können.4. Die Frage, welcher Art diese Vergesellschaftung der Wirbellosen mit den Medusen ist, d. h. ob Parasitismus, Kommensalismus oder Symbiose vorliegt, wird für die einzelnen Fälle erörtert; vielfach mußte diese ungeklärt bleiben.5. Beweise für eine der drei möglichen Beziehungen fanden sich bei den Crustaceen nur für Parasitismus. Bei den Coelenteraten, Turbellarien, Trematoden, Cestoden und Nematoden kann meist das Verhältnis mit Sicherheit als Parasitismus, verbunden mit einem Generationswechsel, angesehen werden, wobei die Medusen die Zwischenwirte für die Entwicklungsstadien darstellen, deren Adulte in Fischen leben, welche die Medusen fressen. Als Putzsymbiose kann das Zusammenleben der RhizostomeeRhopilema hispidum mit dem OphiuridenOphiocnemis marmoratus betrachtet werden.6. Die Umwandlung von Metacercarien des TrematodenNeopechona pyriforme ausDactylometra quinquecirrha in dem FischStenostoma zu dem Adultus, die experimentell nachvollzogen worden ist, wird beschrieben.7. Die überraschenden Funde eines RiesenisopodenAnuropus spec. von 7 cm Länge in der neu aufgefundenen TiefseemeduseDeepstaria enigmatica (bis zu 70 cm Durchmesser) sowie des ParasitenOuwensia catostyli in der MeduseCatostylus ouwensi werden näher beschrieben und diskutiert.8. Das Reiten von zwei Arten des Papiernautilus,Argonauta boettgeri undA. hians, auf den MedusenCrambionella orsini undPelagia noctiluca wird als ein Ausruhen auf dem Substrat verstanden.

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Marine invertebrates as parasites, commensales or symbionts associated with Scyphomedusae

Observations on invertebrates living in or on Scyphomedusae are compiled from literature. 51 species of 28 genera are listed as hosts for different taxa (Actiniariae, Turbellaria, Trematoda, Cestoda, Nematoda, Crustacea, Echinodermata and Cephalopoda). The relation of these invertebrates to their hosts is discussed and characterized as parasitism, commensalism or symbiosis. Trematodes and cestodes may be regarded as true parasites, with medusae as intermediate hosts and fishes as final hosts. The feeding on detritus from the mouth-frills may be interpreted as a cleaning symbiosis. The accociations of the recently discovered deepsea medusaDeepstaria enigmatica with the giant isopodAnuropus sp. and the rhizostomeCatostylus ouwensi with the parasiticOuwensia catostyli (the taxonomic position of which is still unclear) are described and discussed in detail.

     

The quantitative separation of meiofauna

Summary 1. This paper presents the results of a meeting on the evaluation of quantitative procedures for the separation of meiofauna, held at the Marine Station of the Biologische Anstalt Helgoland, in May 1972. Close co-operation on the part of the participants (p. 194) has allowed assessment of advantages and disadvantages of the separation methods applied. The time needed for preserved methods can be reduced by changing to scanning rather than picking out for sorting and counting.2. Sorting without concentrations: This method is suitable for very fine-grained sediments, oozes; it is generally applied for preserved samples; adequate for hard fauna; insufficient for soft fauna; very time consuming.3. Decantation: Suitable for sandy sediments; generally applied for preserved samples; adequate for hard fauna; insufficient for soft fauna; time consuming.4. Elutriation: Suitable for sandy sediments; for unpreserved samples only with anaesthetization, more effective with preserved samples; limited for total live fauna. With preserved samples, adequate for hard fauna; insufficient for soft fauna; quick method.5. Warm-water elutriation: Suitable for sandy sediments; designed for live hard fauna (especially nematodes, ostracods); quick method.6. Sea-water ice treatment: Suitable for sandy sediments with microporal structure; only for live extraction; limited for hard fauna; well suited for soft fauna (including ciliates and flagellates); time consuming.

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Die quantitative Isolierung der Meiofauna. Ein Methodenvergleich

Kurzfassung Im Mai 1972 fand an der Meeresstation der Biologischen Anstalt Helgoland ein Arbeitstreffen mit dem Ziel statt, die verschiedenen Methoden zur quantitativen Isolierung der Meiofauna aus dem Sediment in ihrer Effektivität miteinander zu vergleichen. Die Verfahren zur Anreicherung der Meiofauna in der Probe, des Sortierens und Auszählens werden beschrieben und die durch die Teilnehmer am Arbeitstreffen gemeinsam erzielten Ergebnisse diskutiert. Die Wertung der einzelnen Methoden zur Erfassung der Gesamtfauna, der harten und der weichen Meiofauna, von konservierten und nichtkonservierten Organismen sowie die Anwendung der Methoden auf verschiedenen Sedimenttypen werden durch statistische Analysen abgesichert. Eine Zusammenfassung der Arbeitsverfahren sowie deren Charakterisierung und Leistungsfähigkeit beschließt die Darstellung.

     

Dynamics of chloride and potassium currents during the action potential in Chara studied with action potential clamp

TheCl^– and K⁺ currents underlying the action potential (AP) in the giant alga Chara were directly recorded with the action potential clamp method. An electrically triggered action potential was recorded and repetitively replayed as command voltage to the same cell under voltage clamp. The resulting clamp current was close to zero. Only the initial rectangular current used for stimulation was approximately reproduced by the clamp circuit. Inhibition of Cl^– channels with niflumic acid or ethacrynic acid and of K⁺ channels with Ba²⁺ evoked characteristic compensation currents because the amplifier had to add the selectively inhibited currents. Integration of the compensation currents revealed a mean flux through Cl^– and K⁺ channels of 3.3 10^–6 and 2.1 10^–6 mole M^–2 AP^–1 respectively. The dynamics of CI^– and K⁺ channel activation/inactivation were obtained by converting the relevant clamp currents to ionic permeabilities using the Goldman-Hodgkin-Katz current equation. During the AP the Cl^– permeability reaches a peak 370 ms, on average, after termination of the stimulating pulse. The following inactivation proceeds 3.6 times slower than the activation. The increase in K⁺ permeability lags behind the rise in Cl^– permeability, reaching a peak approximately 2 s after the latter.     

Identification and characterization of a 3C-like protease from rabbit hemorrhagic disease virus, a calicivirus.

Expression studies conducted in vitro and in Escherichia coli led to the identification of a protease from rabbit hemorrhagic disease virus (RHDV). The gene coding for this protease was found to be located in the central part of the genome preceding the putative RNA polymerase gene. It was demonstrated that the protease specifically cuts RHDV polyprotein substrates both in cis and in trans. Site-directed mutagenesis experiments revealed that the RHDV protease closely resembles the 3C proteases of picornaviruses with respect to the amino acids directly involved in the catalytic activity as well as to the role played by histidine as part of the substrate binding pocket.     

Early origin of foraminifera suggested by SSU rRNA gene sequences

Foraminifera are one of the largest groups of unicellular eukaryotes with probably the best known fossil record. However, the origin of foraminifera and their phylogenetic relationships with other eukaryotes are not well established. In particular, two recent reports, based on ribosomal RNA gene sequences, have reached strikingly different conclusions about foraminifera's evolutionary position within eukaryotes. Here, we present the complete small subunit (SSU) rRNA gene sequences of three species of foraminifera. Phylogenetic analysis of these sequences indicates that they branch very deeply in the eukaryotic evolutionary tree: later than those of the amitochondrial Archezoa, but earlier than those of the Euglenozoa and other mitochondria-bearing phyla. Foraminifera are clearly among the earliest eukaryotes with mitochondria, but because of the peculiar nature of their SSU genes we cannot be certain that they diverged first, as our data suggest.      

Recovery of cytopathogenic and noncytopathogenic bovine viral diarrhea viruses from cDNA constructs.

After cDNA cloning of the genome of bovine viral diarrhea virus (BVDV) isolate CP7, a full-length cDNA clone was constructed. RNA transcribed in vitro from this construct was shown to direct the generation of infectious BVDV upon transfection into bovine cells. To confirm the de novo generation of infectious BVDV from cloned cDNA a genetically tagged virus was constructed. In comparison with parental BVDV, the recombinant virus was slightly retarded in growth. The NS2 coding region of the CP7 genome contains a duplication of 27 nucleotides which is not present in the genome of its noncytopathogenic counterpart, NCP7. Exchange of a small fragment harboring this insertion against the corresponding part of the NCP7 sequence led to recovery of noncytopathogenic BVDV. Alteration of the construct by introduction of a fragment derived from a cytopathogenic BVDV defective interfering particle resulted in a chimeric defective interfering particle which exhibits a cytopathogenic phenotype. These findings confirm the hypothesis that the recombination-induced alterations in the genomes of cytopathogenic BVDV are responsible for the induction of cell lysis.     

Cytopathogenicity of border disease virus is correlated with integration of cellular sequences into the viral genome.

Two border disease virus (BDV) pairs each consisting of cytopathogenic (cp) and non-cp viruses have been analyzed at the molecular level. Within the NS2-3 (p125) encoding region of both cp viruses, insertions of cellular sequences were identified which were absent in the corresponding non-cp isolates. A comparative sequence analysis revealed that within each pair the cp and non-cp viruses are almost identical. This strongly suggests that the cp BDV isolates developed from the non-cp viruses by RNA recombination between the viral genome and cellular sequences. Nonstructural protein NS3 (p80) was demonstrated after infection with both cp BDV strains. In addition, fusion proteins composed of cellular and viral sequences were identified. In contrast, expression of NS3 and the fusion proteins was not found after infection with the respective non-cp counterparts.     

Identification and characterization of the virus causing rabbit hemorrhagic disease.

Liver tissue from animals that died of rabbit hemorrhagic disease (RHD) was used to identify the causative agent. After extraction of liver homogenates and sucrose density gradient ultracentrifugation, distinct bands were obtained. The respective gradient fractions reacted positively in an enzyme-linked immunosorbent assay as well as in hemagglutination assays and were infective for rabbits. These fractions contained virions which had a diameter of 40 nm and resembled morphologically those of the family Caliciviridae. By immunoblotting, a major structural protein with a molecular weight of 60,000 was identified. Highly pure RNA of about 8 kilobases was isolated from virions. Labeled cDNA synthesized from virion RNA detected two RNAs of 8 and 2 kilobases in Northern (RNA) blots of liver RNA from animals infected with RHD virus. Finally, isolated virion RNA injected into the liver of rabbits produced a disease with clinical symptoms and pathological findings typical of RHD. We conclude that a calicivirus represents the causative agent of RHD.