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.     

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.     

Cardiac activity of freshwater crayfish at wakefulness, rest, and “animal hypnosis”

In laboratory experiments, simultaneous continuous recording of the circadian cycle of behavioral reactions and cardiac activity of freshwater crayfish Astacus astacus and Procambarus clarkii was carried out. A non-invasive fiber-optic method of recording of the heart rate (HR) was used. The obtained data were analyzed by the method of variational pulsometry (VP). It was revealed that certain values of HR and characteristics of VP corresponded to the physiological states of active wakefulness and rest. It was found that during long immobilization of crayfish it is possible to identify the states of operative rest and sleep by the animal behavioral reactions and parameters of cardiac activity. Crayfish were studied in the state of artificially evoked immobilization (“animal hypnosis”). During this state, a high HR level, an increase of indexes of tension and autonomic equilibrium, and changes of other VP characteristics were observed. It is suggested that the different level of cardiac activity in different physiological states of crayfish (active wakefulness, operative rest, sleep, and “animal hypnosis”) is regulated by nervous influences analogous to sympathetic and parasympathetic influences in vertebrates. It was concluded that freshwater crayfish as a representative of the highly organized invertebrates can serve an effective model for studying mechanisms of sleep-like states and “animal hypnosis” in animals.     

Compensatory possibilities of the crayfish cardiovascular system under conditions of progressing hypoxia

Under laboratory conditions, the rate of oxygen consumption and changes of inotropic and chronotropic parameters of work of the crayfish heart were studied under conditions of hypoxia and anoxia. In all studied crayfishes regardless of species and sex there exists regulation of the rate of oxygen consumption until its concentration in water about 1 mg/l at room temperature, the rate of standard metabolism being independent of oxygen concentration above 24% from saturation; below this level the rate of oxygen consumption amounts to 54% of its standard consumption. The ability to regulate metabolism in hypoxia is also presents in small crayfishes; however, their respiration rate is several times higher than in adult animals. Under conditions of severe hypoxia the cardiovascular system (CVS) of crayfish functions in economic regime with use of dependent regimes of initiation of inotropic and chronotropic heart parameters; with increase of severity of the hypoxic factor, a tendency is observed for a decrease of the heart rate (HR) and for an increase of amplitude parameters. Under anoxic conditions the crayfish demonstrated the heart contractile activity for almost 10 h; analysis of the HR by the method of variation pulsometry has shown deterioration of the crayfish functional state, which was due to desynchronization of regulatory processes in the central and peripheral chains of control of CVS.     

Evaluation of functional state of crayfish <Emphasis Type="Italic">Pontastacus leptodactylus</Emphasis> 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.     

Heart and ventilatory measures in crayfish during environmental disturbances and social interactions

Most animals assess the environment in which they live and alter their behavior according to various stimuli. When the animal does not make significant behavioral changes, as measured by bodily movements, the animal may be characterized as unresponsive to a given stimulus. This study demonstrates that when behavioral movements of crayfish cannot be observed, physiological measures of heart rate (HR) and ventilatory rate (VR) show dramatic changes in response to defined sensory stimuli. In the majority of cases, upon anticipation of a social interaction with another crayfish both HR and VR will increase. During an agonistic encounter between two crayfish, the level of HR and VR correlate with the intensity of the interaction. Such rapid responses in cardiac and respiratory systems to environmental disturbances and anticipation of a social interaction suggest an autonomic-like regulation associated with fear, flight or fight. Since behavioral observations do not allow an internal status to be readily assessed, we suggest that HR and VR may serve as a useful bioindex in crustaceans to their internal drive or possibly an awareness level to environmental cues.     

Entrainment analysis of the circadian locomotor activity rhythm in specimens of the crayfish, Faxonella clypeata, having activity peaks at different times of the solar day.

Locomotor activity rhythms in the crayfish, Faxonella clypeata, were recorded under conditions of controlled light and temperature. In LD 12:12, dark active rhythms with a major activity onset at lights-off, and bimodally active rhythms with onsets at both lights-on and lights-off were recorded. In DD, most of the LD dark active rhythms retained the lights-off activity onset. However, among the majority of the LD bimodally active crayfish, only the lights-on activity peak persisted in DD. A small number of the LD bimodal rhythms remained bimodal in DD. DD records revealed free-running period lengths both greater and less than 24 hrs. An hypothesis stating that the two recorded LD rhythms represent two basically different rhythmic types is presented. The dark active crayfish appear to entrain to the lights-off position, but the bimodally rhythmic crayfish appear to entrain to the lights-on position.     

In situ studies on heart rate and locomotor activity in the freshwater crayfish, Astacus astacus (L.) in relation to natural fluctuations in temperature and light intensity

1. By the aid of a computer technique, the in situ variations in heart rate and locomotor activity were recorded continuously for 7 days in sixteen individuals of the crayfish, Astacus astacus (Linnaeus 1758), in association with natural changes in water temperature and light intensity.
2. All sixteen crayfish investigated were found to express circadian rhythmicity in heart rate with a periodicity of ≈ 24 h. For 88% of the animals investigated, rhythmicity was significant ( P < 0.05). Ninety‐three per cent of the crayfish showed circadian rhythmicity in locomotor activity with a 24 ± 2 h periodicity and, for 67% of the animals, this rhythmicity was significant ( P < 0.05). In general, the expression of circadian rhythms was associated with nocturnal behaviour, heart rates and locomotor activity levels being higher at night than by day.
3. A positive correlation was observed between heart rate and locomotor activity. Temperature and light intensity exerted positive and negative influences on heart rate in A. astacus , respectively.
4. In the first experiment, 84% of the variation in heart rate could be explained by the changes in locomotor activity, temperature and light intensity. In the second experiment 35% of the variation in the heart rate was explained using these parameters.     

Novelty stress and reproductive state alters responsiveness to sensory stimuli and 5-HT neuromodulation in crayfish

Sensory stimuli can produce varied responses depending on the physiological state of an animal. Stressors and reproductive stage can result in altered biochemical status that changes the responsiveness of an animal to hormones and neuromodulators, which affects whole animal behavior in relation to sensory stimuli. Crayfish serve as a model for examining the effects of neuromodulators at the neuromuscular junctions (NMJs) and for alterations in stereotypic behaviors for particular stimuli. Thus, we used crayfish to examine the effect of novelty stressors in males and the effect of being gravid in female crayfish to exogenous application of serotonin (5-HT). The responsiveness of neuromuscular junctions to 5-HT revealed that stressed as well as gravid crayfish have a reduced response to 5-HT at NMJs. The stressed crayfish were not fatigued since the basal synaptic responses are large and still showed a pronounced response to 5-HT. Using intact animals to examine a tail flip behavior, we showed that the rate of habituation in tail flipping to a strong repetitive stimulus on the telson is reduced in stressed males. Gravid females show no tail flipping behavior upon telson stimulation.     

Renal dopamine receptors are involved in the development of cardiac hypertrophy

The present study examined the effect of fenoldopam, a known dopamine-1 receptor (DA1) agonist in order to understand its involvement in the cardiac hypertrophic process. Male Sprague-Dawley rats underwent abdominal aortic constriction (AB) with placement of a suprarenal ligature while sham operated animals served as controls. The AB groupsshowed an increase in their heart wt, left ventricular (LV) wt, heart wt/body wt and LV wt/body wt ratio. Furthermore, the length of these hearts, as measured from the auriculoventricular border to the apex, LV wall and interventricular (IV) septal thickness were increased from control levels. Treatment with SCH 23390, a DA1 antagonist, on the other hand, was able to partially regress the cardiac hypertrophic changes. All these parameters were also increased in control animals treated with fenoldopam (F). Such changes were more striking in the F+AB group which showed a significant acceleration of the cardiac hypertrophic process on super-imposing the two treatments. Plasma dopamine and renin activity were increased in all the groups as compared to control. These results indicate that dopamine receptors are implicated in the development of cardiac hypertrophy.     

Heart Rate Variability as an Indicator of Chronic Stress Caused by Lameness in Dairy Cows

Most experimental studies on animal stress physiology have focused on acute stress, while chronic stress, which is also encountered in intensive dairy cattle farming–e.g. in case of lameness–, has received little attention. We investigated heart rate (HR) and heart rate variability (HRV) as indicators of the autonomic nervous system activity and fecal glucocorticoid concentrations as the indicator of the hypothalamic–pituitary–adrenal axis activity in lame (with locomotion scores 4 and 5; n = 51) and non-lame (with locomotion scores 1 and 2; n = 52) Holstein-Friesian cows. Data recorded during the periods of undisturbed lying–representing baseline cardiac activity–were involved in the analysis. Besides linear analysis methods of the cardiac inter-beat interval (time-domain geometric, frequency domain and Poincaré analyses) non-linear HRV parameters were also evaluated. With the exception of standard deviation 1 (SD1), all HRV indices were affected by lameness. Heart rate was lower in lame cows than in non-lame ones. Vagal tone parameters were higher in lame cows than in non-lame animals, while indices of the sympathovagal balance reflected on a decreased sympathetic activity in lame cows. All geometric and non-linear HRV measures were lower in lame cows compared to non-lame ones suggesting that chronic stress influenced linear and non-linear characteristics of cardiac function. Lameness had no effect on fecal glucocorticoid concentrations. Our results demonstrate that HRV analysis is a reliable method in the assessment of chronic stress, however, it requires further studies to fully understand the elevated parasympathetic and decreased sympathetic tone in lame animals.     

Erg circadian rhythm in the course of ontogeny in crayfish

• 1.1. The objective of the present work was to study the ontogeny of the ERG circadian rhythm in crayfish.
• 2.2. Long-term recordings of ERG and shielding retinal pigments position measured from the instar, the second instar, the third instar and the adult crayfish were obtained.
• 3.3. In the youngest animals (1–8 days old) an ultradian rhythm (15min-4hr periods) in the ERG amplitude was detected.
• 4.4. Older animals showed a progressive increment in the period length before they exhibited a circadian pattern. This last appeared, the first time, in 30-day-old animals and showed noticeable differences in the adult crayfish. At the same time, the crayfish began to show photomotor reflex. Later on (140-day-old crayfish) the circadian rhythm attained its final parameters.
• 5.5. The SD was used as a measure of lability in periods. The 4 hr ultradian rhythm and the 22.4 hr circadian rhythm showed the lowest SD indicating that they are the most precise period values.
• 6.6. Our results support the idea that the ERG circadian rhythm results from the coupling among high frequency (ultradian) oscillators, particularly those of 4 hr periods and that the coupling depends on the action of neurosecretions released from the sinus gland.

     

Heart rate measures in blind cave crayfish during environmental disturbances and social interactions

Most animals continually assess the environment in which they live and alter their behavior according to various stimuli. As an observer, one looks for changes in a behavior indicating that an animal responded to a particular event. When the animal does not make significant behavioral changes as measured by bodily movements, the animal may be characterized as unresponsive to a given stimulus. This study demonstrates that when behavioral body movements can not be observed an internal physiological measure of heart rate (HR) shows dramatic changes following presentation of defined stimuli. This study used the blind cave crayfish and examined their responsiveness to the following stimuli: light (infrared, dim red, and white), water-borne vibrations, removal of water, olfactory cues, and social interaction with partners. This study demonstrates that there is substantial individual variation of HR at basal levels and with the intensity of an social interaction. We find HR is a reasonable measure of the responsiveness of blind cave crayfish to given stimuli even in the absence of observable behavioral changes. This enables the observer to determine if an individual is responsive to and making an assessment of particular cues.     

Changes in heart rate and circadian cardiac rhythm as physiological biomarkers for estimation of functional state of crayfish <Emphasis Type="Italic">Pontastacus leptodactylus</Emphasis> Esch. upon acidification of the environment

The changes in heart rate and circadian cardiac rhythm of crayfish Pontastacus leptodactylus Esch. kept in a lightning regime that is close to natural under optimal or low pH values were studied. The heart rate was registered in real time using an original noninvasive fiberoptic method. Upon acidification, disorders in circadian cardiac rhythm and organism reaction (by heart rate) in the suspension test were detected. The characteristics of cardiac activity are considered criteria for estimating the crayfish’s functional state at normal and stress conditions caused by the changes in the quality of the environment.     

Djungarian hamsters: a species with a labile circadian pacemaker? Arrhythmicity under a light-dark cycle induced by short light pulses

In most cases, phase-shifting effects of light pulses are studied in animals kept in constant darkness (DD) or in animals released into DD following the stimulus. In this study, the authors exposed Djungarian hamsters (Phodopus sungorus) to short light pulses during the dark phase of a 16:8 light-dark (LD) cycle and thus obtained a type VI phase response curve. Light pulses early in the night caused phase delays of the activity onset as well as phase advances of the activity offset, whereas light pulses later in the night resulted in phase advances of the activity offset only. A combination of two 15-min light pulses-the first one given late in the scotophase and the second given early in the dark phase of the following night-led to a strong compression of the activity phase alpha. In 75% of all animals, daily rhythms were no longer visible after complete alpha compression, and long-term arrhythmicity (up to 145 days) persisted despite continued exposure to an LD cycle. Because three independent output rhythms of the clock (i.e., activity, body temperature, and melatonin rhythms) were equally affected, the authors conclude that overt arrhythmicity was due not merely to disrupted output pathways but to an altered state of the central pacemaker. The authors suggest a qualitative two-oscillator model to explain this phenomenon. Their hypothesis assumes that, due to loose coupling, the pacemaker of Djungarian hamsters can be driven to a state of zero phase difference between the two oscillators, with zero amplitude of their outputs.     

Effects of pulsed magnetic stimulation on isolated crayfish heart

ABSTRACT

Cardiac muscular contraction of the neurogenic heart that could be excited by pulsed magnetic stimulation (PMS) was investigated using preparation of the isolated crayfish heart. When a figure-eight magnetic coil was set over the isolated heart, cardiac contraction induced by a single PMS was not observed. Cardiac arrest occurred immediately after repetitive PMS and persisted for dozens of seconds depending on the number of stimuli. We concluded that PMS caused neuronal modulation in the neuronal network in the cardiac ganglion.     

Acceleratory nervous regulation of juvenile myogenic hearts in the isopod crustacean Ligia exotica

We examined regulation of the myogenic heart by two identified cardioacceleratory neurons (CA1, CA2) in early juveniles of the isopod Ligia exotica. Repetitive stimulation of either the CA1 or CA2 axon increased the frequency and plateau amplitude of the action potential and decreased the maximum hyperpolarization of the cardiac muscle. These effects were larger with increasing stimulus frequency. The rate of increase in the frequency caused by CA1 stimulation was significantly larger than that by CA2. No impulse activity of the cardiac ganglion was induced by acceleratory nerve stimulation. The frequency of the muscle activity was decreased by injection of a hyperpolarizing current into the muscle during stimulation of the acceleratory nerve. In a quiescent heart, acceleratory nerve stimulation caused an overall depolarization in the muscle membrane and the amplitude of the depolarization induced by CA1 stimulation was significantly larger than that by CA2. These results suggest that CA1 and CA2 neurons regulate the myogenic heart affecting directly the cardiac muscle; the CA1 neuron produces more potent effects than does the CA2 neuron.     

Alterations in habituation of the tail flip response in epigean and troglobitic crayfish

We demonstrate that the probability of the crayfish, P. clarkii, to tail flip in response to a touch on the dorsal tail fan is dependent on both the size and the behavioral state of the animal. Alterations in the animal's internal physical state, such as when the animal autotomizes its chelipeds, will cause larger-sized animals to tail flip; if they were not autotomized, then no tail flip response would occur. Altering the external environment by removal of water causes small crayfish, which normally habituate slowly, to rapidly habituate. Observation of large adult crayfish in a species, O. australis packardi, one that evolved to live in total cave darkness, revealed that they are more likely to tail flip than are the sighted, adult P. clarkii. Results indicate that the behavioral state of the crayfish can result in rapid and long-term alterations in the tail flip response and in habituation rates to repetitive stimuli. This ability to show plasticity in gain setting may be regulated by neuromodulators and can occur in large adults of the sighted crayfish. Differences between the two species indicate that size may not be the sole contributing factor to account for tail flip behaviors. J. Exp. Zool. 290:163-176, 2001.     

In vitro study of functional parameters and cardiac arrhythmia in localized ischemia followed by reperfusion in two rat strains (Sprague Dawley and Wistar)

The cardiac parameters of two rat strains [Wistar (W) and Sprague Dawley (SD)] were compared during Langendorff perfusion. The values of coronary flow, heart rate, amplitude of contraction and the incidence of arrhythmias were studied during three 10 minutes periods: perfusion, ischemia by coronary artery occlusion and reperfusion. The values of heart rate and coronary flow of SD hearts are always higher than those of W hearts whatever the potassium (K+) concentration of perfusate (5.9 or 3 mM). Furthermore, with a high K+ perfusate (5.9 mM) and during ischemia. W rat hearts showed ventricular tachycardia periods which are never observed in SD rat hearts. It is concluded that W rat hearts present a higher sensitivity to the development of dysfunction than SD rat hearts.     

Allometric relationship of postmolt net ion uptake, ventilation, and circulation in the freshwater crayfish Procambarus clarkii: intraspecific scaling

There are few intraspecific studies relating physiological parameters to body mass. This study relates scaling of ionic regulation and respiratory parameters with body mass in crayfish (Procambarus clarkii). These animals were chosen because of their direct development, spanning four orders of magnitude in body mass. Usually, these animals are hyperregulators and must maintain hemolymph electrolyte levels above those in the ambient freshwater. This is especially important in the postmolt, when ion imbalance can occur. Maintaining hemolymph ion levels above ambient involves active processes that are independently related to metabolic rate, ventilation, and circulation. Therefore, this study investigates relationships among size and ionic regulation, heart rate, and ventilation in crayfish, spanning a size range of 0.003-24 g. Postmolt net ion uptake of Ca, titratable base, Na, Cl, and NH4 increase with body mass (positive allometry) with slopes of 0.92, 0.79, 0.90, 0.84, and 0.87, respectively. Between 72% and 97% of variation in ionic regulation was related to body mass. The slopes differed from each other for Ca and titratable base but not for Na, Cl, and NH4. For heart rate and ventilation rate, different relationships were derived for animals smaller and larger than 0.01 g (between first and third instar). Animals larger than 0.01 g show a negative allometric relationship between heart rate and body size ([body mass](0.15)), while smaller animals show positive allometry with body size, but only 29% of variation in heart rate is explained by body size alone. For ventilation rates, the negative allometry with body size for animals larger than 0.01 g is present, but less than 15% of variation in ventilation rate is explained by size, while for smaller animals the size dependency disappears. Based on these results, predictions of physiological parameters such as ionic regulation based on body size are useful in crayfish, but estimates of respiratory parameters and body size should be used with caution.