Papierchromatographische Untersuchung von Thyroxin und anderen Jodthyroninen

The Science of Nature -     

Effects of mercury exposure on ionic regulation in the crayfish Orconectes propinquus

Hemolymph sodium, potassium and calcium concentrations were determined in crayfish (Orconectes propinquus) exposed to (203)HgCl(2) mixed with food to a concentration of 1 microg Hg g(-1). Dummy-fed animals were exposed to Hg-dosed food wrapped in dialysis tubing to control for mercury reaching the animals via leaching from food to water. Hemolymph analyses were made following 14-day Hg exposures and again after a further 21-day 'depuration' period during which all animals were fed Hg-free food. After 14 days, the mercury reached a concentration of 0.175 microg g(-1) in the hepatopancreas and approximately half this level in the gills of Hg-fed animals. No depuration occurred from the hepatopancreas although the gills lost approximately two-thirds of their labelled mercury during the depuration period. Hemolymph sodium concentrations in Hg-exposed crayfish, both fed and dummy-fed, after 14 days were significantly lower than in Hg-free controls and remained low following the 21-day depuration period. Hemolymph calcium concentrations were lower in Hg-fed animals than in dummy-fed and control animals after 14 days although calcium levels rose in all treatments after 35 days. This may have been due to the incidence of pre-molt animals in all experimental groups, although the relationship between this and mercury exposure was not established unequivocally. Hemolymph potassium levels showed no differences between treatments.     

Changes in the digestive gland of Euphausia superba during short-term starvation: lipid class,fatty acid and sterol content and composition

During a period of short-term (19 d) starvation, total lipid in the digestive gland of Euphausia superba Dana decreased from 21 to 9% dry weight. Total lipid per digestive gland decreased significantly during starvation compared to Day 0 individuals, falling from 1960 (±172) to 385 (±81) g. Polar lipid was the major lipid class utilised during starvation, falling from 1510 (±225) to 177 (±46) g per digestive gland (76 to 45%). Absolute levels of triacylglycerol fell from 300 (±41) to 76 (±5) g; however, relative levels remained unchanged. The relative level of free fatty acid increased significantly with starvation (4 to 39%) with absolute levels ranging from 79 (±1) to 156 (±20) g per digestive gland. Absolute levels of all fatty acids per digestive gland declined continually until the end of the starvation period. The long-chain polyunsaturated acids eicosapentaenoic (20:53) and docosahexaenoic (22:63), decreased with starvation from 37 to 26% and 15 to 10%, respectively whereas the saturated fatty acid, palmitic acid (16:0), increased from 15 to 20%. Cholesterol, the major sterol in this organ, increased from 17 (±20) to 44 (±13) g per digestive gland by Day 3, and by Day 19 had returned to levels found in the digestive gland of Day 0 individuals. Desmosterol followed a similar pattern to cholesterol, increasing from 3 (±1) g per digestive gland on Day 0 to 11 (±4) g on Day 3, and falling to 2 (±1) g on Day 19. Other sterols in the digestive gland, predominantly of algal origin, fell from the levels found in Day 0 individuals to near zero amounts by Day 6. The digestive gland of E. superba plays a dynamic role during shortterm starvation in terms of lipid content and composition. The relative levels of polar lipids, free fatty acids and cholesterol in the digestive gland may provide reliable indices of the nutritional condition of E. superba in the field. Sterols in the digestive gland are indicative of recent dietary composition of krill, and may also be used to quantify dietary input from individual phytoplanktonic species.