Low temperature tolerance and osmotic regulation in the amphipod Gammarus oceanicus from Spitsbergen waters

The amphipod Gammarus oceanicus can survive being frozen into solid sea ice at a temperature of –6 to 7C- The animals appear to be supercooled at this temperature. No thermal hysteresis agents were present the haemolymph, and the prevention of internal freezing in the animals thus requires a body surface with a low Permeability to water and ice. Gammarus oceanicus is a euryhaline species. Below 700 mOsm seawater, it displays a very efficient osmoregulation, whereas it is an osmoconformer at seawater osmolalities above this value. At +5°C the amphipods die whenever their body fluid osmolality exceeds about 1000 mOsm. When the animals are trapped in freezing seawater, the osmolality of the brine may exceed this value considerably. The tolerance of the animals to hyperosmotic stress thus seems to be higher at subzero temperatures than at +5°C

Synergistic effects of an oil dispersant and low temperature on the freezing tolerance and solute concentrations of the blue mussel (Mytilus edulis L.)

Exposure of blue mussels (Mytilus edulis L.) to an oil dispersant in increasing concentrations caused increased degree of injury in the mussels. The oil dispersant seemed to affect mechanisms responsible for the distribution of inorganic ions (Na+, K+, Cl-) and free amino acids across the cell membranes. The dispersant caused a marked reduction in the ability of the mussels to survive freezing at -10°C. Freezing also caused more pronounced alterations in the transmembrane ionic distributions observed following exposure to the dispersant. This may indicate that the injuries caused by freezing are qualitatively the same as those caused by exposure to the dispersant alone, but brought into more extreme conditions. Thus, freezing appears to potentiate the effect of environmental pollutions by concentrating them in the fluid fraction of the frozen body fluids

The effects of oil and oil dispersants on the amphipod Gammarus oceanicus from Arctic waters

Amphipods of the species Gammarus oceanicus were exposed to water soluble fractions and water emulsions crude oil, the dispersants Finasol OSR-5 and Finasol OSR-12, and combinations of the oil and dispersants. Adding Finasol OSR-12 to the crude oil caused a reduction in the mortality of the amphipods compared with amphipods exposed to the water soluble fraction and the water emulsion of crude oil alone, probably due to a reduced mole fraction of toxic oil components in the mixture of oil and dispersant. Exposure to sublethal concentrations of water soluble fractions increased the respiratory rates of the amphipods in the majority of the exposed groups. The water soluble fractions slightly increased the concentrations of sodium in the haemolymph and in the whole organism. Some exposures gave a significant increase in the relative water content of the amphipods. The water soluble fractions probably increase the membrane permeability to water and ions, leading to an increased influx of water and sodium from the medium. The increased respiratory rates are likely to be due to a compensatory extrusion of sodium. Exposure to sublethal concentrations of water emulsions reduced the respiratory rates of the amphipods, probably due to oil droplets adhering to the gill membranes and thus causing a reduced rate of oxygen diffusion into the organisms. The majority of the exposures to water emulsions increased concentrations of sodium in the haemolymph as well as in whole organisms. Thus, sodium probably accumulates in the intracellular compartments because the sodium pumps are restricted by the reduced energy available. This is likely to lead to an osmotic swelling of cells. Reduced total free amino acid concentrations in these amphipods is ascribed to volume regulation of the swollen cells, and a reduced co-transport of sodium and free amino acids from the haemolymph to the intracellular compartments

Notes on the ecology and physiology of the Antarctic oribatid mite Maudheimia wilsoni

The oribatid mite Maudheimia wilsoni Dalenius was found to be numerous on the underside of stones at Jutulsessen (72°S, 3?E) in Dronning Maud Land, Antarctica. Daily temperature fluctuations of the microhabitat from as high as 19°C and to as low as – 17°C were observed during the austral summer. Optimal activity of the mites occurred at 10°C. Even in January the mean supercooling point of adult mites was as low as -30.8±4.7°C. Haemolymph osmolality ranged from 500 to 800mOsmol and thermal hystersis freezing points from ?4.7 to ?6.1°C. Adult mites had a mean water content of 43.6% and a water loss rate of 0.12 ?gh?1 at 15°C and 10% relative humidity

Ecophysiological studies on arthropods from Spitsbergen

The cold-hardiness, high temperature tolerance and metabolic activity of summer specimens of staphylinid beetles (Atheta graminicola), collembolans (Onichiurus groenlandicw), spiders (Erigone arcrica), and prostigmatid mites (Molgus linoralb) from Spitsbergen were investigated. The animals displayed coldhardiness and haemolymph melting points within the normal ranges for summer insects from temperate regions, but were less tolerant to high temperatures. Haemolymph from spiders and from one species of collembolans (lsoroma sp.) was found to contain thermal hysteresis factors. The beetles. collembolans. and mites were found to have oxygen consumption rates above the values of their relatives in other climatic zones, whereas the spiders had values within the range of temperate arachnoids. The study supports the view that polar arthropods have activation energy values lower than those of temperate animals

Physiological adaptations in Coleoptera on Spitsbergen

Metabolic rates and Qlo values were determined for three species of Spitsbergen Coleoptera, Amara quenseli, Simplocaria metallica and Rhynchaenw flagellum. The beetles had metabolic rates which were elevated compared to values of Coleoptera from other regions. This is interpreted as an adaptation to the prevailing low temperatures and short activity period on Spitsbergen. A. quenseli had rates of water loss comparable to values of beetles in temperate and tropical xeric habitats, indicating that the habitat of the beetles on Spitsbergen at least occasionally is xeric. Determination of cold-hardiness parameters such as supercooling point and haemolymph melting point of A. quenseli beetles revealed that the beetles had values corresponding to those of active insects in the temperate and tropical region. They had no thermal hysteresis factors. Thus, during summer they show no physiological adaptations to cold

Thermal hysteresis antifreeze agents in fishes from Spitsbergen waters

The occurrence of macromolecular antifreeze agents (so-called Thermal Hysteresis Factors) in blood plasma of fishes from Spitsbergen waters was investigated in August 1983, October 1984, and January 1986. Thermal hysteresis was found in the plasma of three species of Spitsbergen fishes: shorthorn sculpin (Myoxocephalw scorpiw), polar cod (Boreogadw saidu), and sea snail (Lipuris lipuris). This is the first time thermal hysteresis is reported from the sea snail. Seasonal changes in the amount of thermal hysteresis were observed in blood plasma of the shorthorn sculpin and the sea snail. With the exception of the polar cod, blood plasma of deep water fishes displays no thermal hysteresis. The reason for this is probably that the polar cod also occurs in shallow ice laden sea water, where an 'antifreeze' would be needed to protect against inoculative freezing. No thermal hysteresis was observed in blood plasma of the saithe (Pollachim virens), despite the fact that the saithe was observed swimming in ice laden sea water at a temperature of -1 to -1.5"C under natural conditions, and was rapidly killed when it came into contact with ice in the laboratory. It is not known how the saithe survives in ice laden water under natural conditions