Partial desiccation induced by sub-zero temperatures as a component of the survival strategy of the Arctic collembolan Onychiurus arcticus (Tullberg)

The mechanism by which the freeze susceptible Arctic collembolan Onychiurus arcticus survives winter temperatures of −25°C in the field is not fully understood but exposure to sub-zero temperatures (e.g. −2.5°C) is known to induce dehydration and lower the supercooling point (SCP). In this study, changes in the water status and certain biochemical parameters (measured in individual Collembola) during a 3-week exposure to decreasing temperatures from 0 to −5.5°C were studied. Osmotically active and inactive body water contents were measured by differential scanning calorimetry (DSC), water soluble carbohydrates by high performances liquid chromatography (HPLC) and glycogen by enzymatic assays. The activity of trehalase and trehalose 6-phosphate synthase were also measured. During the experiment, total water content decreased from 70 to 40% of fresh weight, mostly by the loss of osmotically active water with only a small reduction in the osmotically inactive component. The SCP decreased from −7 to −17°C. Analysis of the results shows that if O. arcticus is exposed to −7°C in the presence of ice, all osmotically active water would be lost due to the vapour pressure gradient between the animals supercooled body fluids and the ice. Under these conditions the estimated SCP would reach a minimum of c. −27°C, but the Collembola may never freeze as all the osmotically active water has been lost, the animal becoming almost anhydrobiotic. Trehalose concentration increased from 0.9 to 94.7 μg mg−1 fw while glycogen reserves declined from 160 to 7.7 nmol glucose equivalents mg−1 protein. Trehalase activity declined as the temperature was reduced, while trehalose 6-phosphate activity peaked at 0°C. By adopting a strategy of near anhydrobiosis induced by sub-zero temperatures, O. arcticus, which was previously thought to be poorly adapted to survive severe winter temperatures, is able to colonise high Arctic habitats

Antioxidant defense in mitochondria during diapause and postdiapause development of European corn borer (Ostrinia nubilalis, Hubn.)

Antioxidant enzymes (CAT, catalase; GPx, selenium nondependent glutathione peroxidase; GST, glutathione-S-transferase; GR, glutathione reductase; DHAR, dehydroascorbate reductase) were determined in the mitochondria of diapausing and non-diapausing larvae and pupae of both diapausing and non-diapausing larvae of the European corn borer (Ostrinia nubilalis, Hubn., Lepidoptera: Pyralidae). CAT, GST, and DHAR activity in mitochondria of diapausing larvae were reduced compared to non-diapausing larvae. Pupae of diapaused-larvae possessed lower GST, but higher DHAR activities compared to pupae of non-diapaused individuals. Comparison between larvae and pupae revealed lower GPx activity in the mitochondria of pupae. CAT activity in the mitochondria of pupae was higher compared to diapausing larvae, but lower than in non-diapausing ones. Correlation and canonical discriminant analyses revealed different antioxidant enzyme compositions for a particular stage and developmental pattern. Our results show that antioxidant enzymes have a similar role in the regulation of energetics in mitochondria as that in diapause and metamorphosis

Effect of cold acclimation on the antioxidant defense system of two larval lepidoptera (noctuidae)

Activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR), glutathione-S-transferase (GST), as well as total glutathione (tGSH) concentration were analyzed in the hemolymph and fat body of the European corn borer Ostrinia nubilalis Hubn. and the Mediterranean borer Sesamia cretica Led. (Lepidoptera, Noctuidae). Controls were maintained at 8°C while experimental groups of larvae were exposed to –3°C for ten days and then to –12°C for 23 days (only for Ostrinia). Cold exposure significantly increased fat body SOD, GR, and GST activities of Ostrinia larvae. Only GST activity and tGSH levels increased significantly in Ostrinia larval hemolymph on cold exposure. In Sesamia larvae after cold exposure, hemolymph CAT activity was significantly lower, while fat body tGSH increased. The antioxidant defense systems of these two species show differences, probably influenced by their respective cold-hardiness metabolism. According to its antioxidant profile, the response of Ostrinia suggests a significant physiological alteration in its metabolism during cold exposure, indicating a compensatory mechanism. By contrast this is not evident in Sesamia.Arch. Insect Biochem. Physiol. 36:1–10, 199

Water Quality Assessment in Lakes of Vojvodina

ABSTRACT:This study focused on use of bacterial extracellular enzyme activities as biochemical parameters, along with the microbiological and physicochemical characteristics, in a comprehensive assessment of water quality of four lake ecosystems in the Province of Vojvodina (northern Serbia): Provala, Ludas, Zobnatica and Palic. Water samples were collected in June and October, 2008. For assessment of microbiological water quality, heterotrophic plate count, total and fecal coliform count, as well as total bacterial count was determined. Based on microbiological parameters, the water ecosystems were appropriately classified. The following extracellular enzyme activities were determined: alkaline phosphatase, β-D-glucosidase and acetate esterase using fluorogenic 4-methylumbelliferone labeled substrates. The results showed that Provala Lake had the best water quality taking in consideration all of the parameters, followed by Zobnatica, while Ludas and Palic had a significant level of organic water pollution both in June and October. The results indicate that further similar studies should include both microbiological and biochemical analyses, in order to obtain more relevant data on water quality