V. Ya. Berger

The participation of electrolytes in adaptation mechanisms of intertidal molluscs' cells to altered salinity

Abstract 1. 1. The water content, volume of inulin space, Na, K, Mg content and protein synthesis in the adductor of bivalve molluscs Mytilus edulis L. and in the foot muscle of the snails (Gastropoda) Littorina littorea (L.) were investigated at different environmental salinity. 2. 2. The reaction of mollusc cells to the decreasing of salinity appears to be automatic and independent of nervous or humoral influences. 3. 3. There is an effective mechanism of retaining potassium in the molluscs, the amount of this ion not decreasing even in the first steps of hypotony when there is a great loss of sodium and magnesium ions. The retaining of intracellular K in a wide range of environmental salinity changes enables the cell to maintain the transmembrane gradient K i K o independent of other ions by varying the cell volume. 4. 4. The stabilization of cell volume is achieved by passive influx of Na and apparently Cl into the cell at high salinities and by active removal of these ions at hypotony. 5. 5. The data acquired by means of inhibitors suggest that there exists an independent transport of Na linked to the accompanying anion (Cl, apparently) in the mollusc cells in addition to Na/K-ion exchanging mechanism, providing osmo- and volume regulation of the cell. 6. 6. Concentration of intracellular Na serves as one of the signals regulating the activity of protein synthesis of the molluscs cells in water of different salinities.

The changes of ionic composition and cell volume during adaptation of molluscs (Littorina) to lowered salinity

Abstract 1. 1. The changes of water content, volume of inulin space and Na, K and Mg content in the foot muscle and hepatopancreas of gastropod molluscs Littorina littorea , L. saxatilis and L. obtusata acclimated to lowered salinity (14–16‰) were investigated. 2. 2. The molluscs have an inability to completely regulate cell volume, the hydration level of which increases sharply at the first period of hypotony and partly re-establishes itself during prolonged acclimation to dilute seawater. 3. 3. During adaptation of L. littorea to lowered salinity the role of ions (especially potassium) in the cell osmoregulation increases. There is an effective mechanism of retaining potassium in the cells of these molluscs, the ionic quantity not decreasing even in the first steps of hypotony, when there is a great loss of sodium and magnesium ions.

Assessment of primary production in the White Sea

The literature and original data on the primary production of phytoplankton in the White Sea are analyzed. By this parameter, the White Sea is significantly inferior only to the Chukchi Sea; it is similar to the Barents Sea, and exceeds other Russian Arctic seas by two to three times (the Kara Sea, Laptev Sea, and East Siberian Sea).

Floating seaweeds and associated fauna in the White Sea

Floating seaweeds and associated fauna in Kandalaksha, Onega, and Dvina bays and in the Gorlo of the White Sea were studied. The bulk of the drifting objects were composed of various algae of the Fucus, Chorda, and Chordaria genera. In these drifting communities, 82 different animal and plant species were encountered. The drifting objects were most abundant in Kandalaksha and Onega bays. The minimal abundances were detected in the Gorlo and in Dvina Bay. The total abundance and biomass of the drifting seaweeds and animals were estimated as 25.5 million individuals and 24.2 thousand tons, respectively. The role of the phenomenon considered in the distribution of the animals and seaweeds and in the balance of matter and energy in the White Sea is discussed.

Tolerance and Resistance in Gastropod Mollusks Hydrobia ulvaeand H. ventrosafrom the White Sea to Abiotic Environmental Factors

Tolerance to salinity changes and resistance to desiccation, fresh water, and freezing were studied in two hydrobiid species from the White Sea, Hydrobia ulvae(Pennant) and H. ventrosaMontagu. It was shown that H. ventrosahas a greater tolerance to low salinities in the range of 6–10‰ but is less tolerant to high salinities (35–45‰). The interspecies differences in low salinity tolerance persisted after the acclimation of snails to 20, 16, and 12‰. A comparison of survival in fresh water and under desiccation conditions suggests that H. ulvaeis more resistant to these factors. In fresh water, LT50was 30 and 60 days for H. ventrosaand H. ulvae, respectively. Under desiccation conditions, LT50was 6 and 25 days for H. ventrosaand H. ulvae, respectively. At subzero temperatures, H. ventrosawas shown to be a superior survivor. Within the same species of mud snail, the detrimental effect of freezing depended on the salinity: survival decreased with decreasing salinity. These data suggest significant differences in the mechanisms of resistance and tolerance to abiotic environmental factors between the two species. Despite the partial overlapping of their ecological niches, the interspecies differences may play an important role in the distribution and spatial structure dynamics of coexisting populations of these species in the White Sea region.

Production of planktonic crustaceans in the White Sea

This paper analyzes different methods for assessment of the production of marine organisms. The estimated values of annual production and ration of planktonic copepods of the White Sea are 5.0 × 1012 and 2.2 × 1013 kcal, respectively. Comparison of the planktonic copepod ration with phytoplankton production shows that the energy demands of the copepod community are met by consumption of phytoplankton and, probably, also bacterioplankton and detritus.

Production of fucoid brown algae Ascophyllum nodosum and Fucus vesiculosus in the White Sea

Year-round studies of photosynthesis and respiration in the fucoid brown algae Ascophyllum nodosum and Fucus vesiculosus in the White Sea were performed. The annual specific production of the macrophytes was determined to be 1314 and 1642 cal/g of wet weight for A. nodosum and F. vesiculosus, respectively. The total annual production of fucoids (4.88 × 1011 kcal) comprised about 0.8% of the phytoplankton production in the White Sea.

Cations in molluscan tissues at sharply different hemolymph osmolality

Experiments on different bivalve and gastropod species living in fresh, brackish, and sea water of different salinity demonstrated a direct correlation between the osmolality of the hemolymph and interstitial fluid and the concentration of sodium ions in it. A direct correlation between the osmolality of the interstitial fluid and the content of potassium and magnesium ions in the tissues (adductor and foot) was revealed. The significance of physicochemical indices of the environment and formation of eukaryotic cells at the initial stages of animal evolution are discussed.

The effect of environmental salinity on the level of heat shock proteins in gill epithelium of Mytilus edilis L. mussel

The composition and the level of heat shock proteins in the gill epithelium cells of mussels Mytilus edulis L. from the White Sea under different levels of environmental salinity were studied by the method of immunoblotting. In mussels maintained under normal salinity (26%), constitutive Hsp70 and protein of about 40 kDa were revealed. After long-term (11–14 days) acclimation to 14 and 35‰ of the level Hsp70 in gill epithelium cells increased. Hsp70 induction was also observed in cells of isolated gills after salinity shock at 14% for 3 and 24 h.

Production of the eel grass Zostera marina Linnaeus, 1753 in the White Sea

The results of year-round studies of the photosynthesis and respiration rates of the eel grass Zostera marina L. in the White Sea are presented. The annual production of eel grass is estimated to be 9.86 × 1011 kcal. It is concluded that the total annual production of the eel grass constitutes about 3% of the annual phytoplankton production (3 × 1013 kcal; according to the data of Bobrov et al., 1995) in the White Sea.