S. V. Kholodkevich

Study of contractile activity of the crayfish heart with the aid of a new non-invasive technique

The dynamics of the numbers of the decapod crustacean populations depends essentially on the anthropogenous load on inner reservoirs. This process affects the most substantially the crayfish speciesAstacus astacus L. that is aboriginal for the North-West of Russia. The sensitivity of these crayfish to changes of the water quality in the ecosystems has been noted by many authors [1, 11, 15]. For an ecophysiological monitoring of the reservoirs as well as for a nature-protective and aquacultural activity necessary, is necessary to have methods and means of determination of quantitative parameters of responses of animal life-providing systems, for example, the cardiovascular system. In the present work, a new non-invasive technique is proposed for recording parameters of the crayfish heart activity. The method is based on measurement of the laser emission of the near-infrared diapason, which is scattered in the reverse direction. This paper describes the instrumental part of the complex and exposes some preliminary data obtained with the aid of the used method of recording the crayfish heart activity. This method is shown to permit not only recording the crayfish heart rate under conditions of free behavior, without any harm to the animals, but also tracing changes of the shape and amplitude parameters of the response, which characterize the animal state.

Total protein in hemolymph of crawfish Pontastacus leptodactylus as a parameter of the functional state of animals and a biomarker of quality of habitat

Analysis of total protein in hemolymph was performed by Lowry method on sexually mature crawfish Pontastacus leptodactylus. The total protein content in the crawfish hemolymph was studied for one year. The protein concentration varied widely, amounted to from 12 to 95 mg/ml, and depended on season and the molting cycle phase. There are presented histograms for distribution of animals for the protein level during different seasons and their character is analyzed. In summer the amount of protein is maximal prior to molt and decreases by 40% at once after it. There is studied the diapason of total protein concentrations in hemolymph, in which survival of crawfish at unfavorable changes in habitat is maximal. The adaptive possibilities of crawfish with the low protein content are attenuated. The crawfish with the protein concentration in hemolymph lower than the «critical» one were submitted for different time by action of hydroquinone (1 g/l) used as a model toxicant. A brief action did not affect the protein content in hemolymph. At a long toxic action the protein level in hemolymph fell, on average, by 40%, which preceded death of the animals. Possible mechanisms of positive correlation of the protein concentration in the crawfish hemolymph and of their survival at deterioration of quality of the water medium are discussed.

Evaluation of functional state of crayfish Pontastacus leptodactylus in normal and toxic environment by characteristics of their cardiac activity and hemolymph biochemical parameters

The work deals with study of basic characteristics of cardiac activity (heart rate—HR and stress-index—SI) and hemolymph protein parameters in the crayfish Pontastacus leptodactylus. The main criteria of the crayfish selection are developed for formation of the animal reference groups available for subsequent toxicological experiments. The action of a model toxicant, hydroquinone (often present in waste water), at a concentration of 1 g/l on parameters of the crayfish cardiac activity at various exposition time, its effect on circadian cardioactivity and on the hemolymph total protein were studied. At its short-term action, hydroquinone produced a temporary increase of HR and stress-index, but had no marked effect on total protein parameters in hemolymph. At long action (for one day), hydroquinone led to a considerable tachycardia, disturbance of the circadian cardioactivity and to a decrease by 40% of the hemolymph total protein. In 50% of cases the toxicant caused death of the animals either in the course of its short-term action or at period of washout from the toxicant. Mechanisms of the toxic action of hydroquinone at various levels of organization are discussed.

Peculiarities of Cardiac Activity in the Crayfish Astacus astacus in Different Functional States

Analyzed are changes of temporal and amplitude characteristics of the cycles in animals in different functional states, using a non-invasive method of recording of cardiac activity in the adult noble crayfish Astacus astacus L. under laboratory conditions. It has been shown that the state of excitation in the crayfish after action of an intense stimulus lasts for a long time (more than 1 h) and can have no manifestations in some observed behavioral responses. Based only on the cardiac response (the heart rate), the real physiological state of the animal could be evaluated. Characteristic of the excited animal is a short-term response to the stimulus. In a high excitement of the animal (a high heart rate), significant transformations of the heart activity in response to other current stimuli may be barely noticeable. For the quiet animal, the response to a stimulus is longer than for the excited animal at the same stimulus intensity; for a comparative search for significant readjustments of the animal state, based on the heart activity parameters, the cardiograms typical of the quiet animal should be used. In the quiet animals, the cardiogram parameters change to a greater extent than in the excited ones. The quiet animals have longer diastole duration (DD) than the systole duration (SD). The diastole amplitude (DA) is higher than the systole amplitude (SA), and DA changes more markedly than SA. The healthy animals are characterized by equal values of DD and SD, sometimes by longer SD than DD, but, on the background of a continuing action, their values and the values of DA and SA become equal. There were noted a negative correlation between the systolic and diastolic phases by temporal parameters for healthy animals and an increase of the correlation significance in transition of the animal into the excited state. Based on the cardiovascular system response, the chief features of a shift of the functional crayfish state to pathological direction seem to include a stable heart rate reduction, a decrease of the heart contraction amplitude, a more frequent predominance of SD over DD, an increase of the means and the standard deviations of the parameters, especially of the cycle amplitudes. Changes of the sign and significance of correlation relations between inotropic and chronotropic parameters of cardiac activity in sick animals appear to indicate a disturbed mechanism of central coordination of the cardiovascular system work with its autonomic mechanisms. The results are discussed on the basis of known mechanisms of the heart activity control in Decapoda. The records of cardiac activity, such as laser light cardiograms (LLC), in testaceous invertebrates may be useful and interesting in studies on mechanisms and processes of internal control and management of the cardiovascular system activity of the animals.

Heart Activity in the Crayfish Astacus astacus during Early Ontogenesis

Using a non-invasive method of recording of heart activity in crayfish Astacus astacus in early ontogenesis (1–9 months) and analysis of parameters of cycles of laser light cardiogram, it is shown that cardiac contraction rate (CCR) decreases with increases of weight and size of the animals. The range of changes of CCR parameters in air and in water is wider in larger crayfish of the same age, than in crayfish retarding from them in size and weight. This seems to allows the larger crayfish to be better adapt to environmental changes. It is shown that in crayfish, at change of environmental conditions, inotropic parameters of the cardiogram, amplitude of diastole and systole (DA and SA), change more, than chronotropic parameters, duration of diastole and systole (DD and SD). This may indicate that systems of regulation of inotropic parameters of the cardiac activity are the first to become mature in ontogenesis of the crayfish cardiovascular system; later, maturation of system of regulation of chronotropic parameters of the heart activity occurs. This is confirmed by results of experiments on adult crayfish. Analysis of correlations between parameters of cardiogram cycles in crayfish has shown that regardless of crayfish weight, higher correlation coefficient values are revealed between inotropic parameters of the heart activity cycles, than between chronotropic parameters. In larger crayfish, DD values are higher, than SD, whereas in stress, SD is longer than DD. During stress, the highest negative values of the correlation coefficient are revealed between CCR and DA, CCR and SA regardless of in which medium (air, water) the crayfish is placed.

Osphradial chemosensory organ as a probable trigger of the cardiac system adaptive reaction to the effect of heavy metals in aquatic molluscs

The responses of the osphradium in the freshwater mollusc Viviparus sp. and single osphradial neurons in the pond snail Lymnaea stagnalis to L-glutamine and L-asparagine as well as the changes in these responses under the effect of heavy metals (Cu, Cd) were recorded electrophysiologically. The functional connections of the osphradium with the identified neurons of the central pattern generator of respiratory movements and cardiac activity as well as the modification of these connections under the effect of short-term application of HgCl2 solution onto the snail osphradium were investigated. The heart rate (HR) in the mollusc Littorina littorea under the effect of Cu ions was registered non-invasively in long-term experiments. The dose-dependent short-term effects of heavy metals injected into the mantle cavity on cardiac activity in intact molluscs and the absence of CR changes after osphradium damage were revealed. The implication of osphradium in adaptive reactions of the cardiac system in aquatic molluscs to the environmental heavy metal pollution is suggested. The dependence of HR on the degree of accumulation of copper ions in the mollusc tissues was detected. The results obtained are essential for unraveling neural mechanisms and pathways allowing heavy metals to affect the functional state of hydrobionts, particularly, the cardiac activity frequency characteristics of which are widely used as informative biomarkers to assess physiological condition of aquatic invertebrates.