Random patterns in fish schooling enhance alertness: a hydrodynamic perspective

One of the most highly debated questions in the field of animal swarming and social behaviour, is the collective random patterns and chaotic behaviour formed by some animal species, in particular if there is a danger. Is such a behaviour beneficial or unfavourable for survival? Here we report on one of the most remarkable forms of animal swarming and social behaviour - fish schooling - from a hydrodynamic point of view. We found that some fish species do not have preferred orientation and they swarm in a random pattern mode, despite the excess of energy consumed. Our analyses, which includes calculations of the hydrodynamic forces between slender bodies, show that such a behaviour enhances the transfer of hydrodynamic information, and thus enhances the survivability of the school. These findings support the general hypothesis that a disordered and non-trivial collective behaviour of individuals within a nonlinear dynamical system is essential for optimising transfer of information - an optimisation that might be crucial for survival.Comment: 12 pages, 5 figures, 1 tabl

Schwamm drüber! - Vom Hygieneartikel zum Arzneilieferant aus dem Meer

Jeder kennt ihn, viele besitzen ihn: den Badeschwamm. Doch Schwämme sind von weit höherem Nutzen: Sie produzieren eine Vielzahl bioaktiver Substanzen von großem pharmazeutischen Wert. Im Meer schützen sich die festgewachsenen Schwämme dadurch vor dem Gefressen- und Überwachsenwerden. Aber auch beim Kampf um neuen Lebensraum, zum Beispiel im dichtbesiedelten Korallenriff, werden die chemischen „Kampfstoffe“ eingesetzt (Abb. 1,2). Diese Substanzen können bisher jedoch nicht in großem Maßstab gewonnen und genutzt werden. Abhilfe können neue Methoden zur Kultivierung von Schwämmen im Meer und in Aquarien sowie zur Züchtung von Schwammzellen in der Petrischale oder im Bioreaktor leisten. Erstmals wird in einem bundesweiten Projekt die nachhaltige Nutzung mariner Schwämme in Zusammenarbeit mit internationalen Gruppen fokussiert. Durch die Bündelung und Vernetzung der Kompetenzen sollen die ersten Erfolge der am Forschungsvorhaben BIOTECmarin beteiligten Gruppen weiterentwickelt werden, Extrakte hinsichtlich der pharmazeutischen Produkte untersucht und biotechnologische Verfahren zur Produktion erarbeitet werden

The freshwater jellyfish Craspedacusta sowerbii Lankester, 1880 (Limnomedusa: Olindiidae) in Germany, with a brief note on its nomenclature

The freshwater jellyfish Craspedacusta sowerbii Lankester is distributed worldwide in temperate, freshwater habitats. However, such a successful, worldwide dispersion of the medusa and its minute, less obvious polyp is unique among the freshwater jellyfish species (Limnomedusae, Olinidiae). Although numerous reports were given shortly after its discovery, the interest did not cease over the years. In cooperation with the German Underwater Federation (Verband Deutscher Sporttaucher e. V.) additional data of freshwater jellyfish occurrences could be obtained. In combination with previously published discovery reports, these data provide an area- wide observation of the distribution of freshwater jellyfish within the Federal Republic of Germany, adding 21 to the previously known C. sowerbii locations. Indications are that there is a far more wide spread distribution of the medusa than thought and the potentially even wider distribution of the often times overlooked polyp

Closing and opening of gap junction pores between two- and threedimensionally cultured tumor cells

Intercellular signal transfer via gap junction pores in cultured multicell spheroids of BICR/M1R-K cells decreases with increasing spheroid age. In two days old spheroids the pores allow passage of Lucifer yellow molecules. Two days later, this fluorescent dye is retained in the injected cell even though the cells are still electrically coupled. Gap junction plaques of considerable size are still found in 9 days old spheroids, when the cells are completely uncoupled. The same cells growing as monolayer cultures do not exhibit such a gradual closing of their gap junction pores: Their coupling is established at first cell contact, probably by a gradual opening of the pores, which remain open even up to 9 days in culture

Intrazelluläre Bakterien – Freunde oder Feinde?

Legionärskrankheit aus Klimaanlagen? Augeninfektionen durch Kontaktlinsen? Bergen Protozoen und Niedere Tiere neue Krankheitserreger? Lange bevor es Tiere und Pflanzen gab, wurden die Zellen der einzelligen Lebewesen (Protozoen) von Bakterien befallen. Wir wissen somit, Infektionskrankheiten sind viel älter als die Menschheit. Und manche dieser garstigen Krankheitserreger haben sich gewissermaßen in den Menschen verirrt, da sie sonst in Protozoen, beispielsweise in Amöben, leben. Aber auch heute finden wir in jedem Tümpel, im Meer oder im Boden Protozoen und kleine Tiere, die von Mikroorganismen besiedelt werden. Den intensiven Kontakt mit solchen infizierten Kleinstlebewesen sollten wir meiden, aus ihrem Studium können wir jedoch eine Menge lernen

Diversity and abundance of photosynthetic sponges in temperate Western Australia

<p>Abstract</p> <p>Background</p> <p>Photosynthetic sponges are important components of reef ecosystems around the world, but are poorly understood. It is often assumed that temperate regions have low diversity and abundance of photosynthetic sponges, but to date no studies have investigated this question. The aim of this study was to compare the percentages of photosynthetic sponges in temperate Western Australia (WA) with previously published data on tropical regions, and to determine the abundance and diversity of these associations in a range of temperate environments.</p> <p>Results</p> <p>We sampled sponges on 5 m belt transects to determine the percentage of photosynthetic sponges and identified at least one representative of each group of symbionts using 16S rDNA sequencing together with microscopy techniques. Our results demonstrate that photosynthetic sponges are abundant in temperate WA, with an average of 63% of sponge individuals hosting high levels of photosynthetic symbionts and 11% with low to medium levels. These percentages of photosynthetic sponges are comparable to those found on tropical reefs and may have important implications for ecosystem function on temperate reefs in other areas of the world. A diverse range of symbionts sometimes occurred within a small geographic area, including the three "big" cyanobacterial clades, <it>Oscillatoria spongeliae</it>, "<it>Candidatus </it>Synechococcus spongiarum" and <it>Synechocystis </it>species, and it appears that these clades all occur in a wide range of sponges. Additionally, spongin-permeating red algae occurred in at least 7 sponge species. This study provides the first investigation of the molecular phylogeny of rhodophyte symbionts in sponges.</p> <p>Conclusion</p> <p>Photosynthetic sponges are abundant and diverse in temperate WA, with comparable percentages of photosynthetic to non-photosynthetic sponges to tropical zones. It appears that there are three common generalist clades of cyanobacterial symbionts of sponges which occur in a wide range of sponges in a wide range of environmental conditions.</p

A million cells in search for contact : multicell spheroids not only for cancer research

Three-dimensional, spherical aggregates of cells - so-called multicell spheroids - have many practical applications. In cancer research, for example, they contribute to a drastic reduction in the number of experiments with animals. The authors of the following article were awarded a special DM 10,000 prize under the Felix-Wankel-Tierschutz-Forschungspreis in November 1986 for their work on intercellular communication in multicell spheroids

Standardisierte in-vitro-Modelle zur Charakterisierung von Stoßwellen

Zum jetzigen Zeitpunkt ist die physikalische Vermessung von Stoßwellen allerdings noch nicht problemlos möglich. Außerdem ist unbekannt, welche Stoßwellenparameter (wie Anstiegszeit und Dauer der Über- und Unterdruckamplitude) für die Steinzertrümmerung und die biologischen Nebenwirkungen bedeutsam sind. Wir haben deshalb vier in vitro-Modelle standardisiert, mit denen sich Wirkungen von Variationen der Behandlungsparameter schnell und zuverlässig aufzeigen lassen. Weiterhin kann die Stoßwellenwirkung auf Zellen, Gewebe und Steine in Lithotriptem mit unterschiedlichen Stoßwellenquellen getestet und verglichen werden

Histopathology of shock wave treated tumor cell suspensions and multicell tumor spheroids

L1210 mouse leukemia cell suspensions exposed to 500 shock waves (SW) in an experimental lithotripter (XLI, Dornier) revealed severe cellular damage. Apart from cell fragments and cellular debris, cells exhibited alterations of shape, vacuolisation of the cytoplasm, perinuclear cisternae, swelling of mitochondria or rupture of the mitochondrial fine structure, and permeabilization of the cell membrane. Treatment of multicell tumor spheroids of both HeLa and EMT6/Ro cells in suspension with 500 SW resulted either in loss of peripheral cells and serious cellular damage in the outer regions or in a fragmentation of the spheroids. Many of the geometrically intact cells exhibited the same histopathological alterations as the suspended L1210 cells. Immobilization of the spheroids in agar or gelatine, however, prevented spheroids from being agitated and accelerated during SW-exposure. After treatment with 500 SW, spheroids immobilized in gelatine were not different from control cultures, as investigated with light- and electronmicroscopy. From our results we conclude that spheroids in suspension are subject to cavitation and liquid jet formation, causing not only acceleration and shearing forces but also collisions which account for the observed cell damage

Cavitation-generated free radicals during shock wave exposure: investigations with cell-free solutions and suspended cells

Extracorporeally generated shock waves as used in lithotripsy of urinary and biliary stones exhibit side effects in vivo. Furthermore, these shock waves destroy eukaryotic cells during in vitro treatment in suspension. A possible cause of these damaging effects might be cavitation, the growth and collapse of bubbles in liquids exposed to tensile stresses. During the collapse, temperature inside these cavitation bubbles rises up to several thousand K, leading to the formation of free radicals. We demonstrated the occurrence of cavitation-generated free radicals by direct reaction with fluorescent dyes in solution after shock wave treatment and investigated the resulting cell killing by variation of the cellular antioxidative defense status. We present evidence for the generation of intracellular free radicals during shock wave treatment of suspended cells