In aquarium experiment, the effect of nickel on the activity of lysosomal glycosidases in the soft tissues of one of the most common mollusks in the littoral was studied. Mussels collected from collectors for their cultivation were acclimated for two weeks to laboratory conditions at different salinities (25‰ and 15 ‰). Then the shellfish were kept for 1, 3 and 10 days in water with different concentrations of nickel cations (10, 100 and 500 μg/l). The activity of four lysosomal glycosidases (ɑ-glucosidase, β-glucosidase, β-galactosidase and β-glucuronidase) was determined in the hepatopancreas and gills of mussels. It was shown that both factors (desalination and ecotoxicant), individually and in combination caused a significant change in the activity of the studied enzymes. An increase in the activity of almost all glycosidases in the organs of mussels at a salinity reduced to 15 ‰ indicates the use of glycogen as the main energy source in adaptive reactions, as well as their possible participation in the biosynthesis of substances necessary at this time, that regulate metabolism. At normal salinity (25 ‰), the effect of nickel was manifested by both a decrease and an increase in the activity of ɑ- and β-glucosidases, depending on the concentration and time of exposure to the metal. The activity of glucuronidase in most cases increased under the influence of nickel, which indicates the participation of this enzyme in detoxification and elimination of toxicants from the body. A multidirectional reaction of the lysosomal apparatus of the hepatopancreas and gills to the presence of this metal in the environment was revealed. The phase nature of adaptive metabolic changes in mussels under environmental stress conditions is discussed.

The effect of the toxicant on the activity of lysosomal hydrolases in organs of the White Sea mussels Mytilus edulis (Linnaeus 1758) was studied in aquatic experiments simulating a crude oil spill in the tidal zone. The mollusks were exposed for 1, 5 and 10 days to three pollutant concentrations (0.05; 0.25, and 2.50 ml/l). The impact of oil pollution was studied in combination with salinity normal for White Sea surface water (25 ‰) and low (15 ‰), which corresponds to reality during oil spills on the coast and in estuaries. We determined the activity of six lysosomal enzymes (acid phosphatase, RNase, DNase, β-glucosidase, β-galactosidase, and β-glucuronidase) in the gills and hepatopancreas. Both factors (sea water desalination and oil impact) had a significant effect on the activity of acid hydrolases. The most pronounced lysosomal reaction to oil appeared in the gills under normal salinity at 0.25 ml/l concentration and exposure for 10 days, as evidenced by a several-fold increase in the activity of acid phosphatase, DNase, β-galactosidase, and β-glucuronidase compared to the control. In the hepatopancreas, the same dependence in enzyme activity was noted, but to a lesser extent. Seawater desalination to 15 ‰ in the control caused a slight increase in the activity of DNase, β-galactosidase, and β-glucuronidase in the gills, while the effect for the hepatopancreas was insignificant. The combined effect of desalination and oil pollution somewhat reduced the protective functions of the lysosomal apparatus in mussels organs, which was especially noticeable at high oil concentrations and prolonged exposure of mollusks to experimental conditions. Thus, the results of the study demonstrate active participation of the lysosomal apparatus of the gills and hepatopancreas of mollusks in the adaptive responses to the combined effects of oil pollution and low water salinity. Compensatory changes in the activity of the enzyme complex of lysosomes are aimed at the utilization, transformation and excretion of oil components from the body, elimination of the structures and macromolecules damaged by the toxicant, as well as maintaining the vital activity of the organism under adverse conditions.

The activity of lysosomal enzymes in juveniles of the three-spined stickleback Gasterosteus aculeatus L. from three biotopes of the Kandalaksha Gulf of the White Sea (Seldyanaya Inlet, Kolyushkovaya Lagoon, Sukhaya Salma Strait), differing in temperature regime, salinity, water exchange rate, density of aquatic vegetation, and other parameters, was studied. Fry for research was caught twice during the summer period: at the end of July and in August. In the samples, the activity of six acid hydrolases (acid phosphatase, RNase, DNase, β-glucuronidase, cathepsin B and cathepsin D) was determined. Some differences were revealed in the activity of the studied enzymes in the tissues of developing stickleback fry from different biotopes and depending on the time of sampling. The acid phosphatase activity in fry from all water areas practically did not depend on the sampling time. At the same time, the level was significantly higher in the samples from Kolyushkovaya Lagoon taken in August. The RNase activity was the highest in fry from all three biotopes captured in August compared to those taken in July, which indirectly indicates the intensive biosynthesis processes in growing juveniles of fish during this period. A noticeable increase in DNase activity in the group of juveniles from Sukhaya Salma caught in August suggests that they include more long-term mechanisms of adaptive metabolic rearrangements that affect the genome. Judging by the size-mass characteristics, this group is represented by fry of a later generation compared to groups from other biotopes, and they have recently completed morphogenetic transformatios associated with the transition to the juvenile period of development, in which lysosomal enzymes are involved. Compared to those from other biotopes, juveniles from Kolyushkovaya Lagoon have a relatively higher activity of β-glucuronidase and cathepsin B. Both of these enzymes are involved in the synthesis of components that regulate metabolism. It can be assumed that the main factor causing the need to adjust the metabolism of juvenile fish by August in the Kolyushkovaya Lagoon is the diversity and abundance of food components in this biotope. Thus, the active participation of lysosomal hydrolases in the adaptive metabolic rearrangements of stickleback fry under the influence of abiotic (temperature, salinity, tidal cycles) and biotic (feeding patterns) environmental factors has been shown.

The results of studies on the activity of lysosomal enzymes in different organs (liver, gills, muscles, gonads) of mature threespine stickleback Gasterosteus aculeatus L. at the beginning and in the end of the spawning period are reported. Fish were captured from three spawning grounds in the Gulf of Kandalaksha, White Sea, which differed in temperature, salinity, retention time, aquatic vegetation and other parameters. The samples were analyzed for the activity of five acid hydrolases (acid phosphatase, RNase, DNase, β-galactosidase, β-glucuronidase). During the spawning period, fish were shown to be in a state of high metabolic stress, as evidenced by an increase in acid phosphatase and glycosidase activity in the liver and especially a significant increase in the level of almost all the studied enzymes in the skeletal muscles of stickleback males and females from all habitats by the end of spawning. We are thus driven to the conclusion about a powerful effect of endogenous factors (sex steroid and other hormones) on fish metabolism. As they hydrolyze intracellular reserves and the components which are less necessary at the moment, lysosomal enzymes provide the body with important energetic and constructive materials. Lysosomal enzymes take part in the transport of substances from internal organs to gonads to promote their maturation in the fish arriving at spawning grounds later, and help compensate the lack of exogenous nutrients, especially in stickleback males who care for the offspring in the end of the spawning period. The elevated activity of acid hydrolases in gonads of females is apparently associated with the resorption of unspawned eggs and regeneration of gonad tissues. Gills, unlike other organs, featured an inhibition of the activity of glycosidases and activation of RNase by the end of the spawning period even in the spawning ground with the most favorable conditions (Seldyanaya Bay), which is most likely due to a sharp change in salinity in this area over the spawning period. In general, the response of lysosomal hydrolases to environmental fluctuations in different habitats was less pronounced compared with the effect of endogenous factors associated with spawning.

Criteria for quantitatively describing the state and state variation of a living organism in various conditions are proposed using a set of its measurable characteristics (indicators, properties). The measurable indicators (of diff erent origin and dimensionality) of an organism converted into a dimensionless form relative to their control values are combined into a single integral indicator showing relative deviation averaged over all the indicators. This integral indicator is useful to compare the results of diff erent experiments. If the range of normal variability (reference range) is known for each indicator involved, the second integral indicator is proposed to be calculated as the normalized relative deviation from the middle of all reference ranges (in percentage) averaged over all the indicators. The calculation is performed in such a way that the range 0–100 % of this deviation of an indicator corresponds to the normal variability (where 0 corresponds to the middle of the reference range, 100 % – to its lower or upper limit), while the values over > 100 % represent a pathological response. The normalized relative deviation from the middle of all reference ranges (in percentage) averaged over all the indicators is an assessment of the state of a living organism (based on the given set of indicators) relative to the range of normal variability. The application of the suggested approach is illustrated by an example of a toxicological experiment.

The results on the activity of lysosomal hydrolases (proteases (cathepsins) and nucleases) in salmon (Salmo salar L.) underyearlings (0+), 1+ and 2+ parr, and smolts (2+, 3+)from the Indera River (White Sea drainage basin) are reported, testifying their possible involvement in the processes accompanying the growth and development of juveniles.The highest levels of the enzymes’ activity found in 0+ fish were probably related to the demand for “building blocks” for the biosynthetic processes of protein accumulation necessaryfor the subsequent structural changes in growing juveniles switching from endogenous nutrition to a mixed diet. Further on, in 1+ & 2+ parr and 2+ & 3+ smolts, the activityof cathepsin D (lysosomal proteolytic enzyme with a catabolic function) decreased somewhat in the liver and was virtually undetectable in skeletal muscles. These changes in the activity of cathepsin D are consistent with the indeterminacy of growth processes in fish, which is based on the prevalence of synthetic processes over catabolic ones. The relatively high activity of cathepsin B (lysosomal cysteine protease with a regulatory function) and nucleases (RNase and DNase) in older salmon smolts (3+) most likely reflects the role of these enzymes in forming the smolts’ fitness for foraging migration to the sea.The revealed changed in the activity of lysosomal hydrolases in salmon juveniles indicates there is a correlation between the activity of the enzymes and the fish age, showing thatlysosomal enzymes are involved in protein metabolism rearrangements accompanying the processes of growth and development in salmonids.

At present time, due to the deterioration of environment, the pollution of rivers by industrial and domestic wastewater, as well as unsustainable fishing resulted in decrease of Atlantic salmon reserves all over the world. In the north-west part of Russia, the one of few rivers where the natural reproduction of this the most valuable commercial species is preserved, is Varzuga River (Murmansk region). To develop strategies for sustainable conservation of salmon populations the monitoring should be conducted in order to maintain stable living conditions in the river ecosystem. It is known that the enzymes involved in the protein, energy and carbohydrate metabolism are quite informative indicators of fish growth, development and adaptation to environmental changes. Along with parameters mentioned above, lysosomal hydrolyses, including acid nucleases involved in compensatory reconstructions of nucleic acid and the closely related protein metabolism are used to assess the status of aquatic ecosystems. The activity of lysosomal nucleases (RNAse, DNAse) in muscles of different age groups (0+, 1+, 2+) of juvenile Atlantic salmon Salmo salar L. from Varzuga River (Sobachiy porog) was investigated in the present study. It was shown that the activity of enzymes studied and the protein content in skeletal muscles increased linearly and were maximal in two-years-old salmon. The absolute values of lysosomal RNAse activity were slightly higher than DNAse activity. The data obtained indicate that the active participation of lysosomal nucleases in adaptive reactions of juvenile salmon on the early stages of post-embryonic development. First of all, it results in the intensification of biosynthetic processes of protein. To conclude the living conditions in Varzuga River are favorable for the growth and development of juvenile Atlantic salmon.

The effect of various concentrations (1.9-38.8 mg/l) of oil products (diesel fuel) on the activity of lysosomal deoxyribonuclease in White Sea mussels Mytilus edulis L. were studied in aquarium experiments. The most significant changes in the activity and range of DNase isoforms occurred in soft tissues under the impact of low (1.9 mg/l) and medium (8.4 & 17.4 mg/l) doses of diesel fuel. When the concentrations of petroleum hydrocarbons were high (38.8 mg/l) differences in the nuclease activity and the fractional composition of the enzyme between the treatment and the control were minor. We discuss the potential mechanisms behind the high resistance of the mussels to oil pollution, and the role of nucleases in the selected biochemical adaptation strategies, which differ in the involvement of the genome in the compensatory adjustments of the metabolism in response to different doses of the pollutant.