Ist eine intrazelluläre Eisbildung bei Tieren tödlich? Versuche mit Polypen der Gattung Laomedea

Many authors are of the opinion that intracellular freezing causes death of cells. Observations on organisms tolerating intracellular freezing have been regarded not convincing or exceptional. In this investigation, experiments dealing with polyps of the cnidarians Laomedea flexuosa and L. loveni are described. A special experimental procedure made it possible to induce, selectively, extra- and intracellular freezing or extra-cellular freezing alone. Ice crystals could not be observed directly, but darkening of the test individuals is indicative of ice formation in the cell; this darkening (flashing or black-out) always follows ice formation in the surroundings. Intracellular ice formation is endured for a short period of time (Fig. 1). Small differences in freezing temperature exert great influence on survival rates (Fig. 2). These depend also on the duration of exposure to freezing conditions. Freezing resistance is lower after intracellular ice formation; the difference, however, appears to involve quantitative rather than qualitative aspects, although intracellular ice formation could possible destroy protoplasmic structures.     

Correction to: Geochemical contamination in the Densu Estuary,Gulf of Guinea,Ghana

Environmental Science and Pollution Research - The correct equations are presented below.     

Occurrence of a cold-water coral along natural pH gradients (Patagonia, Chile)

Increasing dissolution of anthropogenic-released carbon dioxide into the world’s oceans is causing ocean acidification (OA). OA is thought to negatively affect most marine-calcifying organisms, notably cold-water corals (CWC), which may be especially sensitive due to the deep and cold waters they normally thrive in. However, the impact of OA on CWC is difficult to predict. Recorded distributions of CWC are rarely linked to in situ water chemistry, and the boundaries of their distributions are not clearly defined. The fjord Comau in Chilean Patagonia features pronounced pH gradients, and up to 0.5 pH units have been recorded both vertically (at some sites within 50 m depth) and less distinct horizontally (from head to mouth). The cosmopolite coral Desmophyllum dianthus grows along the course of the fjord and of the entire pH range. It occurs in shallow depths (below 12 m, pH 8.1) as part of a deep-water emergence community, but also in 225 m depth at a pH of 7.4. Based on pH and total alkalinity, data calculations of the associated carbonate chemistry revealed that this CWC thrives commonly close the aragonite (the orthogonal crystal form of calcium carbonate, the mineral structure of coral skeletons) saturation horizon and even below. This suggests a high adaptation potential of D. dianthus to adjust its calcification performance to conditions thermodynamically unfavourable for the precipitation of aragonite.     

Large-scale diversity and biogeography of benthic copepods in European waters

A large-scale database concerning benthic copepods from the Arctic, Baltic Sea, North Sea, British Isles, Adriatic Sea and Crete was compiled to assess species richness, biodiversity, communities, ecological range size and biogeographical patterns. The Adriatic showed the highest evenness and the most species-rich communities. Assemblages from the North Sea, British Isles, Baltic and Crete had a lower evenness. The British Isles were characterised by impoverished communities. The ecological specificity of copepod species showed two diverging trends: higher specificity of species in more diverse assemblages was observed in the Adriatic, North Sea and Baltic. A uniformly high species specificity disregarding sample diversity was found on Crete and in the British Isles. Benthic copepod communities showed distinct patterns that clearly fit the predefined geographical regions. Communities were distinguishable and β-diversity was found to be high around Europe, indicating a high species turnover on the scale of this investigation. The British Isles and the North Sea were found to be faunistic links to the Baltic and the Arctic.     

Der einfluß von temperaturänderungen anf enzyme der fischmuskulatur. Versuche mit Rhodeus amarus

The enzyme activities estimated in the muscles of Rhodeus amarus (Bloch) may vary according to the kind of muscle, age and sex of the test individuals, as well as with the time of day, and the season. Oxygen consumption of individuals acclimated to different temperatures was tested at 22°C. At low adaptation temperatures no adaptation was found; at high adaptation temperatures, however, compensation could be ascertained. In view of the considerable fluctuation of the enzyme activities, estimated from individuals adapted to different temperatures, a relation to certain adaptation types, established by Precht (1961b, 1968), is hardly possible. During the first days following sudden or slow changes of adaptation temperature (increase or decrease) more or less marked fluctuations of enzyme activities were obtained. Later, however, in accordance with the proceeding adaptation, a new, labile balance was established. Temperature changes represent a physiological stress even within normal temperature ranges. This fact requires general attention in studies on biological processes. Disturbance of a newly established balance of enzyme activities can be obtained, when test fishes are exposed to high temperatures. This finding may be of importance in regard to the heat resistance of the animals.     

Der einfluß von temperaturänderungen auf enzyme der fischmuskulatur. Versuche mit goldorfen Idus idus

Succinate respiration and various enzyme activities were measured in the white dorsal muscles of golden orfs (goldcoloured race of Idus idus L.) adapted to different temperatures. Some of the values obtained on enzyme activities measured on successive days revealed significant differences in fish adapted to the same temperature. These differences could not be attributed to variations between experimental groups, nor to disturbances caused by the removal of some fish (Figs. 2 and 3). In adaptation experiments, attention must be paid to diurnal fluctuations in enzyme activity; such fluctuations were especially apparent with isocitrate-dehydrogenase. Season can also influence the level of enzyme activity, possibly through changes in day-length. Succinate respiration of golden orfs adapted to 5°C is about 10% higher than in individuals adapted to 20°C (experimental temperature 25°C). Following reverse adaptation from 20° to 5°C (at the rate of 5C^o/h), the values approach, after fluctuations, those of 5°C individuals. After raising or lowering the adaptation temperature at the rate of 5 or 2 C^o/h), fluctuations in several enzymes appeared initially, as in the abrupt transfers reported by Lehmann (1970a); even if significant, these were, however, not always reproducible. Change in temperature causes a limited phase of increased functional lability.     

Diet and seasonal prey capture rates in the Mediterranean red coral (Corallium rubrum L.)

Gorgonians are passive suspension feeders, contributing significantly to the energy flow of littoral ecosystems. More than in active suspension feeders (such as bivalves, ascidians and sponges) their prey capture is affected by spatial and temporal prey distribution and water movement. Corallium rubrum is a characteristic gorgonian of Mediterranean sublittoral hard bottom communities. This study found a high variability in the annual cycle of prey capture rate, prey size and ingested biomass, compared to other Mediterranean gorgonians. Detrital particulate organic matter (POM) was found throughout the year in the polyp guts and constituted the main proportion of the diet (25–44%). Crustacean fragments and copepods (14–46%) accounted for the second major proportion, while invertebrate eggs (9–15%) and phytoplankton (8–11%) constituted the smallest part of the diet. To verify the importance of detrital POM in the energy input of this precious octocoral species, in situ experiments were carried out during the winter–spring period. The results confirm the importance of detrital POM as the main source of food for C. rubrum [0.13±0.04 μg C polyp⁻¹ h⁻¹ (mean±SD)]. This study also compares the prey capture rates of two colony size classes and two depth strata: Within the same patch, small colonies (<6 cm height) captured significantly more prey per polyp (0.038±0.09 prey polyp⁻¹ h⁻¹) than larger colonies (>10 cm high) (0.026±0.097 prey polyp⁻¹ h⁻¹) and showed a higher proportion of polyps containing prey (17% compared to 10%). Comparing colonies of similar size (<6 cm height) revealed that the colonies situated at 40 m depth captured significantly more prey (0.038±0.09 prey polyp⁻¹ h⁻¹) than the ones at 20 m (0.025±0.11 prey polyp⁻¹ h⁻¹). One pulse of copepods was recorded that constituted 16% of all captured prey during the 15-month period studied in one of the sampled populations. The data suggest that the variability of hydrodynamic processes may have a higher influence on the feeding rate than seasonal changes in the seston composition. The carbon ingestion combined with data on the density of the exploited population results in 0.4–9.6 mg C m⁻² day⁻¹. The grazing impact of current, heavily exploited and small-sized populations is comparable to that of larger Mediterranean gorgonians, suggesting that unexploited red coral populations may have a high impact compared with other passive suspension feeders.     

Geochemical contamination in the Densu Estuary,Gulf of Guinea,Ghana

Environmental Science and Pollution Research - Chemical contaminants are released from mining, domestic and industrial effluents into an aquatic environment. Sediments (n?=?10) were...