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The behaviour of migratory eels,Anguilla rostrata, in response to current, salinity and lunar period
Springer Science and Business Media LLC - Tập 27 - Trang 211-233 - 1975
1. Behaviour of migratory silver eels and immature yellow eels,Anguilla rostrata, was studied in a choice-chamber apparatus. 2. Silver eels display a negative rheotaxis in both well water and natural stream water. 3. Silver eels reversed the sign of their response, to a positive rheotaxis, when salt water was introduced into the tank. 4. Rheotaxis and the salinity response are proposed as an effective orientation mechanism in the seaward migration of the silver eel. Responses are anticipatory in nature and are thought to be only part of a sequential arrangement of orientation behaviours. 5. Yellow eels showed no rheotactic response in August, but displayed a negative rheotaxis two months later into the fall. This seasonal difference in rheotactic responses of the yellow eels suggests periodic movement away from a home range in what might constitute a “dry run” for the eventual offshore migration. 6. Yellow and silver eels in heterogenous samples showed similar rheotactic responses in fresh water but were segregated by response in salt water. 7. The non-orientation of the yellow eels in the freshwater-saltwater choice suggests that it is the response to salinity which contains the yellow eel in its feeding habitat and later guides the silver eel away from it. 8. Perception of saltwater by silver eels is olfactory. 9. Locomotor activity of silver eels peaked to coincide with periods of naturally occurring darkness, between sunset and moonrise. The relationship between eel migration and lunar period is discussed in this respect. 10. Exogenous control over locomotor activity is indicated by experiments which induced activity during daylight hours. The presence of an endogenous factor is also suggested.
Physiological and biochemical changes during the larval development of a brachyuran crab reared under constant conditions in the laboratory
Springer Science and Business Media LLC - - 1989
Larvae of the spider crabHyas araneus were reared in the laboratory at constant conditions (12°C; 32‰S), and their feeding rate (F), oxygen consumption (R), nitrogen excretion (U), and growth were measured in regular intervals of time during development from hatching to metamorphosis. Growth was measured as dry weight (W), carbon (C), nitrogen (N), hydrogen (H) protein, and lipid. All these physiological and biochemical traits revealed significant changes both from instar to instar and during individual larval moult cycles. AverageF was low in the zoea I, reached a maximum in the zoea II, and decreased again in the megalopa. In the zoeal instars, it showed a bell-shaped pattern, with a maximum in the middle (zoea I) or during the first half of the moult cycle (zoea II). MaximumF in the megalopa was observed still earlier, during postmoult. Respiration (R) increased in the zoeal instars as a linear function of time, whereas it showed a sinusoidal pattern in the megalopa. These findings on variation inF andR during larval development confirm results obtained in previous studies onH. araneus and other decapod species. Excretion (U) was measured for the first time with a high temporal resolution in crab larvae. It showed in all three larval instars a bell-shaped variation pattern, with a maximum near the middle of the moult cycle, and significantly increasing average values from instar to instar. The atomicO/N ratio followed an inverse pattern, suggesting a maximum utilization of protein as a metabolic substrate during intermoult. Growth data from the present study and from a number of previous studies were compiled, showing consistency of growth patterns, but a considerable degree of variability between larvae from different hatches reared under identical conditions. The data show the following consistent tendencies: during the first part of each larval moult cycle (in postmoult, partly in intermoult), lipids are accumulated at a higher rate than protein, whereas an inverse growth patterns is typical of the later (premoult) stages. These two different growth phases are interpreted as periods dominated by reserve accumulation in the hepatopancreas, and epidermal growth and reconstruction (morphogenesis), respectively. Differences between individual larval instars in average biochemical composition and growth patterns may be related to different strategies: the zoeal instars and the early megalopa are pelagic feeding stages, accumulating energy reserves (principally lipids) necessary for the completion of larval development, whereas the later (premoult) megalopa is a semibenthic settling stage that converts a significant part of this energy to epidermal protein. The megalopa shifts in behaviour and energy partitioning from intense feeding activity and body growth to habitat selection and morphogenesis, preparing itself for metamorphosis, i.e. it shows an increasing degree of lecithotrophy. Data from numerous parallel elemental and biochemical analyses are compiled to show quantitative relationships betweenW, C, N, H, lipid, and protein. These regressions may be used as empirical conversion equations for estimates of single chemical components in larvalHyas araneus, and, possibly, other decapods.
Die Dynamik der Frühentwicklung vonSagitta setosa
Springer Science and Business Media LLC - Tập 12 - Trang 260-301 - 1965
1. Untersuchungsobjekt.Sagitta setosa
Joh. Müll. Vergleichsobjekt:Sagitta elegans arctica
Aurv. Methoden: Laufbild- und Teilbildanalyse von Mikrozeitrafferfilmen; kinematische Diagramme. 2. Unter Zeittransformation (Zeitraffung, Z.R.) wird eine Ausdehnung des Keimes während der Teilungsphase, gefolgt von einer Kontraktion in der Interphase, im Z.R.-Laufbild erkennbar. Dieser Rhythmus ist etwa vom 32-Blastomerenstadium bis zur neunten Teilung (256/512 Zellen) zu beobachten. Er kommt zustande durch die Summation der nach jeder Teilung einsetzenden aktiven Aneinanderpressung der jeweils entstandenen beiden neuen Blastomere. Dieser Vorgang ist bei den beiden untersuchten Sagitten-Arten besonders intensiv und führt in der Kontraktionsphase zur fast völligen Abkugelung des Keimes. 3. Die erste Andeutung des sehr kleinen Blastocoel wird bei der Aneinanderpressung der beiden ersten Blastomere in Gestalt eines in zwei Spitzen ausgezogenen Flüssigkeitstropfens wahrnehmbar. Die innerhalb der Berührungsfläche ausgepreßten kleineren Tropfen weisen zentripetale Ortsverlagerung auf und verschmelzen mit dem größeren „Blastocoel-Tropfen“. Der „Keimbahnkörper“ ist im Leben bis zum 16-Zellenstadium feststellbar. 4. Es folgt eine Wiederholung der Tropfenabsonderung nach jeder Teilung in der Pressungsphase bis zur neunten Teilung. Das Blastocoel vergrößert sich infolge der Flüssigkeitsaufnahme. 5. Kinematische Diagramme der ersten Teilungen, durch Teilbild-Analyse aus Z.R.-Aufnahmen gewonnen, beweisen, daß die stärkste Tropfenabsonderung jeweils mit der Phase intensiver Abkugelung zusammenfällt. 6. BeiSagitta elegans arctica
Aurv. ist die Tropfenabsonderung in der Interphase (Abrundungs-Pressungsphase) erheblich größer, die Abrundung geringer. 7. Die unbedeutende Vergrößerung des Blastocoel durch Flüssigkeitsaufnahme läßt keine direkte Entodermbildung durch Invagination zu. Der endgültigen Einstülpung gehen drei „Versuche“ voraus. 8. Die vom 32-Blastomerenstadium ab am vegetativen Pol teilweise herausragenden Urgeschlechtszellen weisen gegenüber den Somazellen Teilungsverzögerung auf. Bei der sechsten Teilung (32/64) zeigen die Urgeschlechtszellen unter Z.R. eine aktive zentripetale Bewegung; sie verschwinden am vegetativen Pol und drücken das Blastocoel mit ihren proximalen Enden ein: erster „Invaginationsversuch“. Zu Beginn der nächsten Teilung erfolgen rückläufige Bewegung und Wiedererscheinen am vegetativen Pol. Der zweite „Versuch“ findet bei der siebten Teilung statt (128 Blastomere), der dritte bei der achten Teilung (256 Zellen). Die Aktivität der nunmehr vier Urgeschlechtszellen ist unverkennbar. 9. Die sich zunächst nicht weiter teilenden vier Urgeschlechtszellen behalten etwa die Größe eines Blastomer des 64-Zellenstadium bei, während die Somazellen unterdessen wesentlich kleiner geworden sind. Gastrulation durch Invagination ist erst möglich, wenn das Größenverhältnis zwischen den beiden Zellgruppen eine Ortsverlagerung ektodermaler Zellen in das kleine Blastocoel dynamisch zuläßt. 10. Auffallend ist unter Z.R. die Fähigkeit der Blastomere zu aktiv-passiven Bewegungen, vor allem in der Region des Prostoma, in der „Umbiegungszone“ Ektoderm-Entoderm. 11. Nach Invagination des Entoderm, die vier Urgeschlechtszellen an der „Spitze“, liegt zunächst ein schmales Urdarmlumen vor. Das Entoderm zeigt während der Interphase wieder eine rückläufige Bewegung, die als „Restverhalten“ des vorausgegangenen Rhythmus aufzufassen ist. 12. Sobald die zentripetalen „Invaginations-Versuche“ der Urgeschlechtszellen — von der sechsten bis zur achten Teilung — einsetzen, dauern die Teilungsschritte länger als vorher; bis zur achten Teilung nimmt die Zeit erheblich zu; nach der neunten verlaufen die Teilungen nicht mehr synchron. 13. Die große Aktivität der vier Urgeschlechtszellen bleibt auch noch nach ihrer Einordnung in das Entoderm des Urdarmdaches erhalten, offenbar im Rhythmus der nunmehr lokalisierten Teilungen im Entoderm. 14. Nach Verlagerung der Urgeschlechtszellen in das Lumen des Archenteron, unter Beibehaltung des Kontaktes mit dem Entoderm, ist das Blastocoel bis auf den schmalen spaltartigen Raum zwischen Ekto- und Entoderm verdrängt. Das „Auswandern“ der vier Zellen erfolgt offenbar durch aktive, mit starker Metabolie verbundenen Bewegungen. Das Archenteron weist unter Z.R. rhythmische Erweiterungen und Verengungen auf. 15. Der Verschluß des Prostoma (Deuterostomia) verläuft synchron mit dem „Auswandern“ der Urgeschlechtszellen.
The rough tingleOcenebra erinacea (Neogastropoda: muricidae): An exhibitor of imposex in comparison toNucella lapillus
Springer Science and Business Media LLC - Tập 46 - Trang 311-328 - 1992
The muricid gastropodOcenebra erinacea exhibits imposex (occurrence of male parts in addition to the female genital duct), a phenomenon which is caused by tributyltin (TBT)-compounds leached from ships’ antifouling paints. Five stages of imposex development (1–5) with two different types at stage 1 can be distinguished and are documented with SEM-photographs for the first time. Four additional alterations of the genital tract are shown. Close to harbours and marinas,O. erinacea females exhibit malformations of the pallial oviduct, which seem to inhibit copulation and capsule formation resulting in sterilization. The TBT accumulation in the whole body and the accumulation pattern in single tissues are described; contrary to other prosobranchs no sexrelated differences were found. The VDS, uncubed RPS and average female penis length of a population were analysed regarding their quality as parameters for TBT biomonitoring. On the background of the ecology of this species the VDS is chosen as the best index. Only in highly polluted areas should the uncubed RPS be used as a secondary parameter. A statistical study, based on the analysis of natural populations ofNucella lapillus andO. erinacea, allows a comparison of the specific TBT sensitivity of the two bioindicators. Dogwhelks exhibit a greater TBT sensitivity, namely at slightly polluted sites, nevertheless even here rough tingles develop obvious imposex characteristics.
Extended hatching periods in the subantarctic lithodid crabs Lithodes santolla and Paralomis granulosa (Crustacea: Decapoda: Lithodidae)
Springer Science and Business Media LLC - Tập 57 - Trang 110-113 - 2003
Temporal pattern of hatching was studied in the subantarctic lithodid crabs Lithodes santolla (Molina) and Paralomis granulosa (Jaquinot) from the Argentine Beagle Channel. In both species, larval hatching occurred in low daily numbers over an extended period of up to several weeks, depending on hatch size. Low daily hatching activity and low oxygen-consumption rates in freshly hatched P. granulosa larvae are discussed as life history adaptations to, and/or physiological constraints by, the environmental conditions of high latitudes.
Guest research facilities at the Biologische Anstalt Helgoland: Past and present
Springer Science and Business Media LLC - Tập 49 - Trang 243-254 - 1995
The Biologische Anstalt Helgoland (BAH) offers unique possibilities for research and education in marine sciences in the southern part of the North Sea. Besides its own research duties, the Institute provides research facilities and technical assistance for guest scientists, assists in the teaching and education of university student groups, and conducts its own courses. The Institute further supplies universities and research institutions on the mainland with marine organisms. The marine station on Helgoland has 14 laboratories, with a total of 32 working places available for guest scientists. The Wadden Sea Institute in List on the island of Sylt offers 6 laboratories with a total of 18 working places. Furthermore, laboratory classrooms are located on Helgoland and in List for 50 and 20 participants, respectively. For the convenience of the guest researchers staying at the BAH, guest-houses are run on Helgoland (Arthur-Hagmeier-Haus, Wilhelm-Mielk-Haus) und in List (Adolf-Bückmann-Haus). Guest researchers have been welcome since the founding of the Institute in 1892. Heincke gave a brief report on the activities of the first visitors from 1892 to 1897. Only sporadic reports are available for the first 60 years of this century. Guest scientists and their activities have only been recorded in detail in the annual reports of the BAH since 1962. The number of researchers and the length of their visits have increased continuously since 1962. The research facilities on Helgoland, in List and Hamburg have been modernized during the last 20 years. In 1971, four modern laboratories for guest researchers could be opened on Helgoland with financial support of the German Research Foundation (DFG). The number, of guest researchers in List and Hamburg increased after the completion of new buildings in 1979 and 1982. The recent increase in research activities by guest scientists is due to numerous students, from many different universities, using the superb research facilities to do their Masters thesis, or Ph.D. Guest researchers and students either perform their own research or cooperate with scientists of the BAH.
Beitrag zur quantitativen Verteilung mariner und „terrestrischer“ Bakterien im Wasser und in Sedimenten der Deutschen Bucht
Springer Science and Business Media LLC - Tập 15 - Trang 226-242 - 1967
1. Mit Hilfe von drei verschiedenen Kulturmedien wurden die Dichten heterotropher Bakterien im Wasser und in der oberen Schicht der Bodensedimente auf acht Stationen in der südlichen Nordsee bestimmt. 2. Mit Meerwassermedium wurden im freien Wasser 150 bis 15 000 Bakterien/ml, in den Sedimenten 6000 bis 6 500 000 entwicklungsfähige Bakterien/cm3 ermittelt. Die geringste Bakteriendichte in den Sedimenten wurde im Sand, die höchste im Schlick ausgewiesen. 3. Meerwassermedium, das reduzierende SH-Gruppen enthielt, erbrachte aus einem Teil der Wasser- und Sedimentproben höhere Keimzahlen. In einigen Bodenproben stehen die mit Thioglykolat-Meerwassermedium ermittelten Bakteriendichten im Widerspruch zu den physiko-chemischen Bedingungen der Sedimente. 4. Mit Süßwasseragar wurden im allgemeinen nur Bruchteile der mit Meerwasseragar gewonnenen Bakterienzahlen erfaßt. Mit einer Ausnahme lagen diese Anteile in den Sedimenten unter 10%. In wenigen Proben bodennahen Wassers wurden mit diesem Medium höhere Bakterienzahlen ausgewiesen als mit Meerwasseragar. Die prozentualen Anteile dieser „terrestrischen“ Bakterien waren in den Sedimentproben nicht höher als in den Wasserproben. Mit fortschreitender Entfernung von der Küste verringerten sich die Anteile dieser Formen an der Bakterienpopulation der Sedimente nicht. Deshalb wird angenommen, daß sie ein normaler Bestandteil der Bakterienpopulation der Nordsee sind. Im Sediment einer ca. 50 km von der Küste entfernten Station wurden noch 50 000 Bakterien/cm3 mit Süßwassermedium nachgewiesen. Entgegen unseren Erwartungen war der Anteil dieser Bakterien in einem Sandsediment sehr hoch, in einem Schlicksediment sehr klein. 5. Im Bereich der untersuchten Stationen war keine Abhängigkeit der Bakteriendichten im Wasser und im Sediment von der Entfernung der Stationen von der Küste erkennbar. 6. Vergleichsuntersuchungen, in denen Bakterien mariner und limnischer Herkunft in Abhängigkeit von der Zelldichte in natürlichem, durch Filtration entkeimten Meerwasser kultiviert wurden, wiesen ein unterschiedliches Entwicklungsvermögen der Mikroorganismen aus. Im Gegensatz zu den marinen Arten scheint die Vermehrung limnischer Bakterien besonders stark gehemmt zu werden, wenn diese Bakterienarten in sehr geringer Zelldichte im Meerwasser vorliegen.
Effect of the surfactant Corexit 7664 on uptake of cadmium by organisms and biological matter in a closed circulated brackish-water system
Springer Science and Business Media LLC - Tập 35 - Trang 1-12 - 1982
Juvenile flounder and common mussel from the Baltic Sea were kept in Corexit 7664 (50 µg/l) and cadmium (5 µg/l)-contaminated, recirculated, sea-water systems for 200 days at 15 °C and 20 ‰ S. Accumulation of cadmium with exposure time was measured in several fish tissues and in mussel. There were no differences in the cadmium accumulation by tissues with or without the addition of Corexit 7664. No acute effects of the contaminants on the experimental animals could be noted. Final cadmium concentrations, reached for all biological matter analysed, were 4 times higher than in full-strength sea water.
Shedding light on the larval genus Eretmocaris: morphological larval features of two closely related trans-isthmian Lysmata species (Decapoda: Caridea: Hippolytidae) described on the basis of laboratory cultured material
Springer Science and Business Media LLC - Tập 66 - Trang 97-115 - 2011
Complete larval series are known for only three of the 39 valid species worldwide in the genus Lysmata. The present work deals with the larval development of two closely related trans-isthmian species of Lysmata, L. galapagensis (eastern Pacific Ocean), and L. moorei (southwestern Atlantic Ocean), using laboratory cultured material. The morphological features of the first four zoeal stages of both species, the fifth to seventh stages of L. galapagensis, and the last stage of L. moorei are described and compared with the larval descriptions currently available for the genus. Larvae of both species hatch with a similar form to L. seticaudata, with their first and fifth pereiopods as buds, and show a very steady development of their morphological characters. The zoeal characters match the phylogenetic results currently available for the genus Lysmata and L. galapagensis, L. moorei and L. seticaudata belong to the same monophyletic clade. We hypothesize that the larvae of all species within this clade will hatch with the first and fifth pereiopods as buds and will present a maximum of nine zoeal stages. The relationships between the studied material and the composite larval genus Eretmocaris are discussed, with emphasis on Eretmocaris corniger which has an extremely long rostrum and a spine on the dorsal surface of the third pleomere, characters also recorded in L. galapagensis. The larval forms earlier described as the tropical eastern Pacific E. corniger are matched to a known Lysmata species, L. galapagensis. The identity of E. corniger larvae recorded one century ago from the tropical eastern Atlantic is also discussed.
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