[Individual Growth of the Great Ramshorn Snail Planorbarius corneus (Gastropoda, Planorbidae) Embryos].

Individual growth of the great ramshorn snail Planorbarius corneus has been studied by intravital video imaging. As has been observed, the types of growth change over the embryogenesis. The linear dimensions slightly but in a statistically significant manner decrease during the stages of cleavage to blastula. Starting from the stage of blastula to trochophore, the embryo diameter remains constant to commence increasing at the stage of middle trochophore. During the larval stages (trochophore and veliger), the growth is synchronous (in Dettlaffs, biological time units) for the embryos in both the same clutch and different clutches. The growth at that time is exponential but later desynchronizes in individual clutches. The embryos in eight clutches grew and developed slower and hatched later as compared with the remaining five egg clutches. An accelerated growth follows an asymptomatic pattern according to the von Bertalanffy equation. A retarded growth is describable with a linear equation. The observed differences are likely to be associated with the number of embryos in a clutch. All types of changes in the linear dimensions observed in the great ramshorn snail embryogenesis can be described with the same united equation.

Irregularity of the Linear Growth of the Margaritifera margaritifera (Bivalvia: Margaritiferidae) Population of the Nemina River, Karelia.

The dependence of shell growth in length and height during ontogeny has been studied in the pearl mussel Margaritifera margaritifera inhabiting the Nemina River (basin of Lake Onega, Karelia). It has been shown that the population is heterogenous based on the height-to-length ratio. It has been found that during ontogeny M. margaritifera from the studied population undergoes a constant change in the relative growth of the shell leading to either lengthening or rounding of the shell.

[Specific Features of Linear Growth Influencing Morphometric Parameters of the Shell in Margaritifera margaritifera (Bivalvia: Margaritiferidae)].

Interdependence of parameters of shell growth in length and height during ontogeny has been studied in the freshwater pearl mussel M. margaritifera. It has been shown that the results of determining the height-to-length ratio depend on at least two factors: shell corrosion in the apical (umbo) zone and regular, rhythmic deviation of this ratio from values expected from linear regression equation. The first factor may be taken into account by applying an individual correction for each specimen, thereby making the ratio of linear dimensions independent of mussel age and size. The calculation error caused by biological rhythms may be reduced by measuring the greatest possible number of annual rings (> or = 18). Factors accounting for alternation between periods of prevalent shell growth in length or in height are discussed.

[Effect of an altered magnetic field on the development of great ramshorn Planorbarius corneus (Gastropoda, Planorbidae)].

Effects of a 100-300-fold attenuated geomagnetic field on the embryonic development of great ramshorn Planorbarius corneus and water oxidation-reduction properties were studied in a hypomagnetic chamber. The hypomagnetic field was largely favorable to the P. corneus development. Specifically, teratogenic effects were less massive, i.e. embryos that had known no other environment but hypomagnetism were characterized by low death rate. The agility index grew in embryos on the stages of late veliger and post-metamorphosis. A sharp increase of the magnetic field to the normal strength resulted in rapid death of embryos and juvenile mollusks (virtually, their growth was arrested). Type of induction was dependent on adaptation of juvenile P. corneus to a magnetic field. Mollusks grown in the normal geomagnetic field would prefer the conditions with maximal induction, whereas mollusks developed in the hypomagnetic chamber, on the contrary, chose the conditions with minimal induction. The oxidation-reduction potential of water increased as magnetic induction attenuated pointing to a natural decline in internal energy of water molecules due, as we see it, to inhibition of the mollusk embryonic development.

[Endogenous biorhythms of the specific growth rate in individual development of Lymnaea stagnalis (Lymnaeidae, Gastropoda)].

On the basis of data on the growth of freshwater gastropods Lymnaea stagnalis, the dependence of the specific growth rate on age in the late postlarval ontogeny is calculated. The presence of two endogenous biorhythms of the specific growth rate with periods of 10.3 weeks and 6.5 weeks was revealed using singular spectrum analysis. Local maxima of both biorhythms in different individuals fall on the same age, and their periods are approximately the same in all animals studied and remain unchanged during individual postlarval development. The biorhythm with a period of 10.3 weeks is decaying, its amplitude is reduced from 3.2 year(-1) (at the age of 10 weeks) to 0.8 year(-1) (at the time of death of the shellfish). The biorhythm with a period of 6.5 weeks is non-decaying and has an average amplitude of 0.8 year(-1).

[Endogenous biorhythms of the oxygen consumption rate in individual development of Lymnaea stagnalis (Lymnaeidae, Gastropoda)].

Two endogenous biorhythms of the oxygen consumption rate with periods of 10.3 and 7.2 weeks have been revealed in the late postlarval ontogenesis of freshwater gastropods Lymnaea stagnalis by singular spectrum analysis. It has been determined that local maxima of both biorhythms in different individuals occur at the same age; in addition to that, the periods of biorhythms are approximately the same in all studied animals and remain unchanged during the whole individual development. It has been noted that the biorhythm with a period of 10.3 weeks is damped (its amplitude decreases from 8 µL O2/(h x g) at the age of 20 weeks to 3 µL O2/(h x g) at the time of death), and the biorhythm with the period of 7.2 weeks is sustained (its average amplitude is 2.4 ± 0.4 µL O2(h x g).

[Specific features in realization of the principle of minimum energy dissipation during individual development].

Realization of the principle of minimum energy dissipation (Prigogine's theorem) during individual development has been analyzed. This analysis has suggested the following reformulation of this principle for living objects: when environmental conditions are constant, the living system evolves to a current steady state in such a way that the difference between entropy production and entropy flow (psi(u) function) is positive and constantly decreases near the steady state, approaching zero. In turn, the current steady state tends to a final steady state in such a way that the difference between the specific entropy productions in an organism and its environment tends to be minimal. In general, individual development completely agrees with the law of entropy increase (second law of thermodynamics).

[Dependence of size of the great ramshorn (Planorbarius corneus L., Gastropoda, Pulmonata) on population density].

The dependence of the mean mass (M) of great ramshorn (Planorbarius corneus) individuals on the number of individuals (N) that reached 82-days age in culture with constant conditions--water volume 50 ml, temperature 25 degrees C, and redundant food (dandelion leaves)--has been studied. The relationship between these parameters has been shown to be approximated by the equation M = 139/N mg. Consequently, at least in these conditions the total biomass of same-aged ramshorn individuals in the culture is relatively constant and does not depend on the number of individuals in the population.

[Energetic metabolism during individual development of Lymnaea stagnalis (Lymnaeidae, Gastropoda): III. Late postlarval ontogeny].

Changes in the rate and intensity of oxygen consumption during individual ontogeny of 14 specimens of Lymnaea stagnalis in the period from the 10th week after emergence until death was investigated in aquaculture. It was demonstrated that the rate of oxygen consumption increased and the intensity of this process decreased during the whole period of observations. Alterations of these parameters were accompanied with permanent oscillations of their meanings. The correlation between intensity of oxygen consumption (q) and age (t) can be described with the equation q = q(st)(1-exp(-k(g)(t+t0))). The values of coefficients of this equation do not differ significantly between individuals and, on average, comprise k(g) = 0.0696 +/- 0.0072 weeks(-1); q(st) = 60.42 +/- 2.6 mcl O2/(hour(g)); t0 = -3.0 +/- 0.7 weeks. The dependence of the rate of oxygen consumption (Q, microl O2/h) on body weight (M, g) for all data is significantly described with the allometric equation Q = 0.369M(0.779).

[The growth and energy metabolism of Lymnaea stagnalis (Lymnaeidae, Gastropoda): I. Early postlarval period].

The growth and the oxygen uptake rate of Lymnaea stagnalis were studied during the first ten days after hatching. It is shown that these processes are atypical during early ontogenesis in comparison with adult mollusks. The obtained data on linear (height of shell) and weight growth can be equally well approximated with the von Bertalanffy equation or exponential and polynomial equations. Both linear and weight growth are characterized by an approximately constant specific rate associated with synchronous oscillations of a two-week period. The oscillations were observed also for the oxygen uptake rate, but of another period (about 2.6 weeks). On average the metabolic rate after the initial triple increase during the first three days remains stable. The polynomial coefficient of the allometric dependence of the total weight on the shell height is less reliable than that of the adult.

[Patterns of individual growth in the field slug Deroceras agreste (Gastropoda, Agriolimacidae)].

The growth of individual Deroceras agreste slugs from the date of sampling to the end of life has been studied under laboratory conditions. Seven out of 37 mollusks (approximately 19%) have shown a finite growth pattern, with their body weight reaching a maximum and decreasing thereafter. The data on these mollusks are well approximated by the finite growth equation. Other mollusks have not reached the maximum weight. In many cases, periods of a sharp decrease in body weight with subsequent return to the initial growth curve (compensatory growth) have been observed. In three animals, the growth curve has changed after such a decrease. A comparison of growth parameters in different individuals with the aid of the Ford-Wallford equation has shown that differences between them lack statistical significance. In generally, the slug D. agreste appears to belong to animals with the finite growth pattern.

[Individual growth of Lymnaea stagnalis (Lymnaeidae, Gastropoda): II. Late postlarval ontogeny].

Our investigation on the growth of 14 individuals of the great pond snail Lymnaea stagnalis was performed in an aquatic culture at 18 degrees C beginning from the 10th week after hatching until death. It has been demonstrated that the increase in the mollusk mass follows an S-like curve during the whole studied period. Linear growth (conch height) follows a parabolic (convex) curve until the age of 39 weeks. Both weight and linear growth during studied period significantly approximate to the Bertalanffy equation, while the interrelation between mass and conch height corresponds to the allometric equation. The meanings of the coefficients of these equations do not differ significantly in different individuals. At the age of 38 to 39 weeks, all mollusks demonstrate breakage in the curve of linear growth, then followed with abrupt slowing of growth until stopping or even decreasing in size in some cases. Neither the Bertalanffy equation nor the allometric relation describe the linear growth of individuals with ages exceeding 39 weeks.

[Patterns of individual growth of gray garden slug Deroceras reticulatum].

Individual growth of gray garden slug Deroceras reticulatum was studied under laboratory conditions in the period from collection to death. The studied population demonstrated different patterns of growth. Three groups of slugs were recognized: (1) slugs that reached the maximum weight after 4 months of raring, after which their weight rapidly decreased (the life span in culture was 6-7 months); (2) slugs that have not reached the maximum weight until death (the life span was 6-7 months); (3) slugs that reached the maximum weight after 7-8 months, after which their weight oscillated with a trend to decrease (the life span was about 10 months). The obtained data were approximated by the equation of finite growth.

[Retrospective analysis of influence of environmental conditions on growth parameters of White Sea edible mussels Mytilus edulis].

Retrospective analysis of influence of environmental conditions on growth parameters of White Sea edible mussels Mytilus edulis has been done by measurements of successive annual rings on shell surface. Analysis by non-linear criterion and Bertalanffy's growth equation allows to deduce that the best environmental condition for edible mussels growth was in 1999 (population from Kastyan island region) and in 2001 (population of Malaya Pir-guba region). The worst one was in 1998 for both populations.

[Equations describing changing of mass and intensity of oxygen consumption during post-embryonal animal development].

Equations fitting changing of mass and mass specific rate of oxygen consumption during post-embryonal animal development are deduced from formulae of thermodynamics of linear irreversible processes. Requirements of applicability of the equations as well as requirements allowing to reduce the growth equation to Bertalanffi's equation and changing of mass specific rate of oxygen consumption with body mass to allometric dependence are described.

[The rate of oxygen consumption during embryogenesis of Lymnaea stagnalis (Gastropoda)].

We studied the rate of oxygen consumption by the Lymnaea stagnalis embryos. The rate of oxygen consumption increased consistently during embryogenesis. The volume specific rate of oxygen consumption increased initially from the early cleavage stages until the gastrula stage and then decreased gradually to the eclosion of snails. There are three periods in embryogenesis of L. stagnalis, which differ in the coefficients of allometric dependence between the rate of oxygen consumption and volume of embryos: (1) early embryogenesis, when the increase in the rate of oxygen consumption is not accompanied by the growth of volume of the embryos; (2) larval period (trochophore and veliger stages; exponential coefficient k = 0.514), and (3) postlarval period (exponential coefficient k = 0.206).

[Comparative analysis of growth of edible mussel Mytilus edulis from different White Sea regions].

Growth properties were studied in edible mussel Mytilus edulis from different biotopes of the Kandalaksha Bay in the White Sea. Growth curves of the mussel shell were approximated by the von Bertalanffy equation. The highest growth rate, primarily dependent on hydrological conditions, was observed in mussels from the Chupa Bay (Levin Navolok fishery), while the lowest rate was observed in mussels from the Umba region (Turn Cape, Murmansk Region). Allometric relationships of the mussel shell were determined. Analysis of the relationship between the maximum width/convexity and their length demonstrated that this relationship is described by a single allometric equation for mussels from the Umba region, which indicates the homogeneity of this population. For mussels from the Chupa Bay, this relationship cannot be described by a single equation, which points to the population heterogeneity. For 90% mussels from this region, the shell width/convexity ratio ranged from 0.5 to 0.9; while for the remaining 10%, it ranged from 0.9 to 1.15.

[Age-related changes in oxygen consumption in the common mussel Mytilus edulis from the White Sea]. / Vozrastnye izmeneniia porebleniia kisloroda midiei obyknovennoi Mytilus edulis Belogo moria.

We determined the rate of oxygen consumption in the White Sea mussel Mytilus edulis of different ages. The rate of oxygen consumption proved to decrease with mussel age according to the equation: qO2 = 40.1/(1 - e(-0.194t)), where qO2 is respiration rate and t is age. Allometric coefficients of the oxygen consumption rate-soft tissue weight relationship were also determined.

[Thermal compensation of respiration in pulmonate snails (Pulmonata) of Arion and Deroceras genera living in polar and temperate climatic zone]. / Temperaturnaia kompensatsiia dykhaniia u legochnykh molliuskov (Pulmonata) rodov Arion and Deroseras, obitaiushchikh v Zapoliar'e i v umerennoi klimaticheskoi zone.

Comparison of respiration rate in pulmonate snails living in various climatic zones demonstrated higher constant a in representatives of Arion genus (A. subfucus and A. fasciatus) from Polar Area (Murmansk Region) as compared to inhabitants of temperate latitudes (Moscow Region). The snails of Deroceras genus (D. reticulatum) from these two climatic zones were indistinguishable by relative standard metabolism. Different effects of climatic thermal conditions on respiration rates in representatives of these two snail genera can be due to their specific biology. Representatives of Deroceras genus are short-cycle synanthropic species, while the snails of Arion genus are long-cycle species living mostly in the forest zone.

[Respiration rate and species-specific lifespan in fresh water bivalves of Margaritiferidae and Unionidae families]. / Intensivnost' dykhaniia i vidovaia prodolzhitel'nost' zhizni presnovodnykh dvustvorchatykh molliuskov semeistv Margaritiferidae i Unionidae.

We studied changes in the respiration rate in five species of freshwater bivalves as a function of animal age and size. The species-specific lifespan was calculated on the basis of the obtained data: Rubner's constant (Ru) and lifespan at standard temperature 20 degrees C (T20). The longest and shortest lifespan among the studied mollusks was specific for the pearl mussel Margaritifera margaritifera (Ru = 37 kJ and T20 = 36 years) and the freshwater mussel Anodonta anatina (Ru = 8 kJ and T20 = 8 years), respectively.