Zur überwindung der biologischen Grenze Meer—Land durch Mollusken

Zusammenfassung Je höher marine Gastropoden ins Supralitoral vordringen, umso größer wird ihre Salinitätstoleranz. Das äußert sich im Überleben auf extremen Salinitäten, in der Waschstumsgeschwindigkeit und in der Fortpflanzungsrate.Die toleranz wird bei den drei großen Gastropodengruppen—Opisthobranchier (Limapontia depressa)—Prosobranchier (Assiminea grayana)—Pulmonaten (Ovatella myosotis)—im niedrigsalzigen Bereich durch Entwicklung einer Hypertonieregulation und bei hoher Salinität durch Poikilosmotie ermöglicht. Während adulte Schnecken des Supralitorals große Schwankungen im Salzgehalt ertragen, sind die Eier dagegen sehr empfindlich; Embryonen entwickeln sich bevorzugt bei Salinitäten, bei denen die Gelege von den Adulten produziet wurden.

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The emigration of Gastropods from the seaII. Studies on Limatpontia capitata, L. depressa und Assiminea grayana

Summary The higher marine Gastropods live on the shore the more their salinity tolerance increases. This is expressed in the animals' survival, their growth rate, and their reproduction rate on extreme salinity concentrations. In all the three gastropod groups—Opisthobranchia (Limapontia depressa), Prosobranchia (Assiminea grayana), Pulmonata (Ovatella myosotis)—a more or less effective hyperosmotic regulation has evolved which enables the animals to live with low salinity concentrations in their surrounding. In high salinities they are poikilosmotic. Adult supralittoral Gastopods can stand considerable salinity changes. The eggs are more delicate: The embryos develop best when the eggs stay on the salinity where they were produced even if the concentrations are extremely high or low.

     

Zur Überwindung der biologischen Grenze Meer—Land durch Mollusken

Zusammenfassung Die Überwindung der biologischen Grenze zwischen Meer und Land durch Mollusken ist bisher nur wenig im Hinblick auf physiologische Umstellungen untersucht worden. Unter diesem Aspekt wurden Experimente durchgeführt an Alderia modesta, einem amphibisch lebenden Opisthobranchier des unteren Supralitorals, und an Ovatella myosotis, einer Pulmonate, die im oberen Supralitoral vorkommt. Alderia zeigt eine relativ enge Salinitätstoleranz. Zu hohe und zu niedrige Salzgehalte hemmen die Entwicklung, führen zu Mißbildungen bei der Embryonalentwicklung und lassen adulte tiere rasch eingehen. In Beziehung zu der Salinität der angrenzenden Gewässer (Brackwasser der Ostsee und der Ästuare, Meerwasser der Nordsee) existieren verschiedene Biotypen, die auf Aussüßung und hohe Salzkonzentration unterschiedlich reagieren.Die weiter ins Supralitoral vorgedrungene Ovatella myositis hat eine wesentlich breitere Salinitätstoleranz. Schädigungen der Adulten treten auf Süßwasser nicht, auf Salzwasser erst oberhalb von 55 auf. Durch schrittweise Adaptation können höhere Konzentrationen ertragen werden. Der Toleranzunterschied zwischen den untersuchten Populationen ist genetisch bedingt. Eiablage, Embryonalentwicklung und Wachstum erfolgen im Bereich zwischen 5 und mindestens 50 Substratsalinität.Physiologisch wird diese große Salinitätstoleranz durch ein fast durchgehendes poikilosmotisches Verhalten ermöglicht. Auf sehr ausgesüßtem Substrat sind die Schnecken stark hypertonisch (auf Süßwasser hat das Binnenmedium auf 7), im ganzen übrigen Bereich weniger stark (3–4 über der Substratsalinität). Im oberen Extrembereich vermögen die Tiere diese Hypertonie offenbar nur schwer aufrechtzuerhalten (vgl. S. 149).Die Veränderungen von Gastropoden auf dem Wege vom Meer über das Supralitoral zum Land werden diskutiert; im Gebiet der Salzwiesen läßt sich ein günstigeres Schema zu dieser Frage aufstellen als bei den bisher meist zitierten Littorinen.

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On the emigration of gastropodes from the sea: Studies on Alderia modesta and Ovatella myosotis

Summary Up to now little attention has been paid to the phylogenetic emigration of gastropods from the sea: almost nothing is known about the physiological changes which enable snails to live in terrestrial habitats. To help solve this question, experiments were carried out on Alderia modesta, an opisthobranch slug of the lower supralittoral, and Ovatella myositis, a primitive pulmonate snail of the upper supralittoral. In each case two subspecies were studied.North Sea Alderias differ from their Baltic counterparts in size and salinitytolerance. The difference in size between Ovatella of the Mediterranean and of the Baltic is very slight. There is a marked difference, however, in the salinity-tolerance. Alderia modesta survives in a comparatively narrow range of different salinities. The optimum is between 10 and 20 for Baltic specimens and between 15 and 35 for those of the North Sea. The results are the same in and out of water. Ovatella can live on a freshwater substratum as well as on 55. Specimens of the Mediterranean can even become adapted to 90. Flooded with water of differrent salinities the tolerated range becomes markedly smaller. Eggs are produced between 5 and 50 (Baltic specimens) or 5 and 65 (Mediterranean specimens). All eggs develop without being damaged between 5 and 40 and 10 and 45 respectively. The optimal salinity-concentration for growth and egg-production is 10. Salinity-concentrations below and above these marks disturb the development. In one spawn-mass some eggs cleave normally, others become deformed, and again others do not cleave at all. This heterogeneous reaction points to the existence of something like a physiological polymorphism in regard to salinity-tolerance. The salinity-concentration of the blood of Ovatella was measured after a long-term acclimatisation. Ovatella is poikilosmotic and slightly hypertonic (3–4) throughout almost the whole range of salinities it tolerates. On extremely low concentrations it becomes more hypertonie; on extremely high concentrations it becomes nearly isotonic.

     

Indirekte Regelmechanismen der Stoffwechselgröße von Fischen

Metabolic rate does not strictly follow changes of influencing parameters. O₂-consumption by fish is ordinarily said to be independent from O₂-pressure throughout a wide range. This constancy is probably the result of a regulation. The metabolic rate itself or an auxiliary mechanism “before” or “after” metabolism may be regulated. On the basis of vanDam's paper (1938) and our own experiments, the problem whether or not O₂-pressure in blood serves as a regulated auxiliary mechanism in order to maintain a certain metabolic constancy is discussed. The disadvantage of such a regulation would be the energy demand of increased ventilation and circulation as compensating mechanisms. In accordance with this assumption we have found a rise in O₂-consumption at a somewhat reduced O₂-pressure. Locomotory behaviour supports the constancy of metabolic rate; thus a contrary shift of the temperature preferendum after application of substances which influence metabolism has been found.     

Production of doubled haploid lines in frequencies sufficient for barley breeding programs

Winter barley (Hordeum vulgare L.) anthers were cultured on different liquid and on starch-solidified media. The optimal embryo and callus formation with different F₁-lines and the cv. Igri was obtained on a liquid medium with 20% Ficoll, 20 g/l maltose and barley starch. But the influence of the growth conditions of the donor plants and the genotypical differences are still enormous. The procedure has been optimized to such an extent that it can be used economically.     

Heat Shock RNA Levels in Brain and Other Tissues After Hyperthermia and Transient Ischemia

A number of studies have demonstrated increased synthesis of heat shock proteins in brain following hyperthermia or transient ischemia. In the present experiments we have characterized the time course of heat shock RNA induction in gerbil brain after ischemia, and in several mouse tissues after hyperthermia, using probes for RNAs of the 70-kilodalton heat shock protein (hsp70) family, as well as ubiquitin. A synthetic oligonucleotide selective for inducible hsp70 sequences proved to be the most sensitive indicator of the stress response whereas a related rat cDNA detected both induced RNAs and constitutively expressed sequences that were not strongly inducible in brain. Considerable polymorphism of ubiquitin sequences was evident in the outbred mouse and gerbil strains used in these studies when probed with a chicken ubiquitin cDNA. Brief hyperthermic exposure resulted in striking induction of hsp70 and several-fold increases in ubiquitin RNAs in mouse liver and kidney peaking 3 h after return to room temperature. The oligonucleotide selective for hsp70 showed equivalent induction in brain that was more rapid and transient than observed in liver, whereas minimal induction was seen with the ubiquitin and hsp70-related cDNA probes. Transient ischemia resulted in 5- to 10-fold increases in hsp70 sequences in gerbil brain which peaked at 6 h recirculation and remained above control levels at 24 h, whereas a modest 70% increase in ubiquitin sequences was noted at 6 h. These results demonstrate significant temporal and quantitative differences in heat shock RNA expression between brain and other tissues following hyperthermia in vivo, and indicate that hsp70 provides a more sensitive index of the stress response in brain than does ubiquitin after both hyperthermia and ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)     

In Vivo Labeling of Serotonin Uptake Sites with [3H]Paroxetine

Previous work has shown that [3H]paroxetine is a potent and selective in vitro label for serotonin uptake sites in the mammalian brain. In the present study, [3H]paroxetine was tested in mice as an in vivo label for serotonin uptake sites. Maximum tritium concentration in the whole brain (1.4% of the intravenous dose) was reached 1 h after injection into a tail vein. Distribution of the tracer at 3 h after injection followed the distribution of serotonin uptake sites known from previous in vitro binding studies (r = 0.85). The areas of highest [3H]paroxetine concentration, in decreasing order, were: hypothalamus greater than frontal cortex greater than olfactory tubercles greater than thalamus greater than upper colliculi greater than brainstem greater than hippocampus greater than striatum greater than cerebellum. Preinjection of carrier paroxetine (1 mg/kg) significantly decreased [3H]paroxetine concentration in all areas except in the cerebellum, which is known to contain a relatively low number of specific binding sites. Kinetic studies showed highest specific [3H]paroxetine binding (tissue minus cerebellum) at 2 h after injection and slow clearance of activity thereafter (half-time of dissociation from the hypothalamus, 215 min). The specificity of in vivo [3H]paroxetine binding was studied by preinjecting monoamine uptake blockers or receptor antagonists 5 min before administration of [3H]paroxetine. Serotonergic or muscarinic cholinergic receptor antagonists and dopamine or norepinephrine uptake blockers did not reduce the in vivo binding of [3H]paroxetine. In contrast, there was an excellent correlation (r = 0.99) between the in vivo inhibitory potencies of serotonin uptake blockers in this study and previously published in vitro data on inhibition of [3H] serotonin uptake in brain synaptosomes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cell multiplication and ultrastructure ofMicrasterias denticulata (Desmidiaceae) grown under salt stress

Cells ofMicrasterias denticulata Bréb. were kept in nutrient solution of high osmolality (salt stress) for four weeks. In a special cell multiplication test it was established that cell division is gradually inhibited at increasing salt concentrations and totally arrested at the highest concentration (26 mosm/kg). Recovery studies proved that even cells from the highest concentration range start dividing immediately after being placed in aqua bidest. thus indicating the full reversibility of the inhibiting effect. — Cells of the highest concentration range show marked ultrastructural changes. Besides an enormous accumulation of starch and oil bodies and a condensed appearance of the ground plasma, a reduction of mitochondria, ER and the Golgi-system is found. The most striking effect occurs on the vacuolar system which appears extremely reduced and condensed. The cell wall is thickened by the formation of an additional cell wall layer with a spongy electron microscopical appearance. Through the cell wall many droplets of a probably fat-like substance are excreted. — In summary, salt stress induces growth-inhibited akinete cells in the sense ofFritsch; these can be reactivated by decreasing the salt concentration. The salt-induced akinete state seems to be an ecological adaption to unfavourable conditions rather than a degeneration of the cells.Dedicated to Prof. DrLothar Geitler on the occasion of his 90th birthday.23. 12. 1988     

On the ultrastructure and the supposed function of the mineralizing matrix coat of sea urchins (Echinodermata,Echinoida)

Summary Echinoderm ossicles are part of the mesenchyme. Their formation and growth, with respect to the underlying tissues, is studied using echinoid spines and teeth and applying different methods of fixation. The calcification process in echinoderms is strictly intracellular and needs (1) syncytial sclerocytes which completely enclose (2) a vacuolar cavity which in turn contains (3) an organic matrix coat. Strictly speaking, each ossicle is nothing but the calcified vacuolar space of a single syncytium of sclerocytes. In fully grown parts, however, the continuous sheath may split open and the matrix-coated mineral may come into contact with the extracellular space. According to biochemical analyses the matrix consists of insoluble components, but most (95%) of its constituents are soluble in EDTA or weak acids. If routine transmission electron microscope methods are used the soluble components are lost and the matrix at best looks electron light. If tannic acid is added to the fixative the soluble matrix components are preserved and reveal further ultrastructural details of the biomineralization process in echinoderms. The matrix coat looks extremely electron dense. Further soluble material is to be found within the vacuolar space or attached to the vacuolar surface of the cytoplasmic sheath. The results lead to the opinion that the matrix coat consists of a hydrophobic framework of insoluble components that contains soluble components which guide the Ca through pores in the hydrophobic layers into the interior of the matrix-coated space. It is only within this space that the mineral is deposited.