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Although pesticides are often discharged into surface waters in pulses as opposed to a sustained release, the effect of episodic pollution events on freshwater crayfish is largely unknown. We monitored change in heart rate and distance moved to assess the response of signal crayfish Pacifastacus leniusculus to short-term exposure to environmentally relevant concentrations of metazachlor (MTZ), terbuthylazine (TER), and thiacloprid (TCL). Crayfish exposed to 20 µg/L of MTZ exhibited a significant increase in mean heart rate and distance moved. Increased heart rate was detected at 118 ± 74 s post-exposure to MTZ. There were no significant differences in mean heart rate and distance moved in crayfish exposed to 6 µg/L of TCL and 4 µg/L of TER. A significant correlation between heart rate and distance moved was found in all exposed groups. These results suggest that pulse exposure to MTZ impact crayfish physiology and behavior during short-term period. With pulse exposure to TCL and TER, crayfish not exhibiting a locomotor response may continue to be exposed to lower, but potentially harmful, levels of pollutants. Evidence of the impacts of pesticide pulse at environmentally relevant concentrations on crayfish is scarce. Further study is required to determine the ecological effects of such events on freshwater crayfish.

Burrowing is a common trait among crayfish thought to help species deal with adverse environmental challenges. Here we used in-vivo experimental data and in-silico modelling of oxygen saturation in a virtual burrow inhabited by crayfish. Except for the entrance 200 mm region, the burrow microenvironment becomes anoxic, on average, within 8 hours, and 12-hour day-night multiple cycles were not sufficient for refreshing the burrow microenvironment even with temporary lack of crayfish. We asked whether the ecological category of crayfish burrowing activity is reflected in the physiological ability to cope with hypoxia and anoxia. As dissolved oxygen declined, respiration patterns of primary burrowers differed from those of secondary and tertiary burrowers, showing also the highest variability in anoxia tolerance. Secondary burrowers showed consistent tolerance with all species exhibiting a mean survival of > 3h anoxic conditions. Tertiary burrowers were variable, exhibiting moderate to zero tolerance of anoxia. The adaptive mechanisms to cope with hypoxia might be a basal legacy from the crayfish monophyletic ancestors – lobsters, traveller crustaceans often reaching deep depths in the ocean. These results challenge the current understanding of crayfish ecology, opening an evolutionary ecological perspective which might be relevant for the next generation of phylogenetical approaches.

Methamphetamine (METH), a central nervous system stimulant used as a recreational drug, is frequently found in surface waters at potentially harmful concentrations. To determine effects of long-term exposure to environmentally relevant levels on nontarget organisms, we analysed cardiac and locomotor responses of signal crayfish Pacifastacus leniusculus to acute stress during a 21-day exposure to METH at 1 &mu, g L&minus, 1 followed by 14 days depuration. Heart rate and locomotion were recorded over a period of 30 min before and 30 min after exposure to haemolymph of an injured conspecific four times during METH exposure and four times during the depuration phase. Methamphetamine-exposed crayfish showed a weaker cardiac response to stress than was observed in controls during both exposure and depuration phases. Similarly, methamphetamine-exposed crayfish, during METH exposure, showed lower locomotor reaction poststressor application in contrast to controls. Results indicate biological alterations in crayfish exposed to METH at low concentration level, potentially resulting in a shift in interactions among organisms in natural environment.

Methamphetamine (METH), a central nervous system stimulant used as a recreational drug, is frequently found in surface waters at potentially harmful concentrations. To determine effects of long-term exposure to environmentally relevant levels on nontarget organisms, we analysed cardiac and locomotor responses of signal crayfish Pacifastacus leniusculus to acute stress during a 21-day exposure to METH at 1 μg L−1 followed by 14 days depuration. Heart rate and locomotion were recorded over a period of 30 min before and 30 min after exposure to haemolymph of an injured conspecific four times during METH exposure and four times during the depuration phase. Methamphetamine-exposed crayfish showed a weaker cardiac response to stress than was observed in controls during both exposure and depuration phases. Similarly, methamphetamine-exposed crayfish, during METH exposure, showed lower locomotor reaction poststressor application in contrast to controls. Results indicate biological alterations in crayfish exposed to METH at low concentration level, potentially resulting in a shift in interactions among organisms in natural environment.

Intensive aquaculture is an important and fast-growing food production industry generating significant amounts of nutrient-rich sludge, which represents a potential environmental threat. Vermicomposting aquacultural sludge has been suggested, but remained poorly understood – only survival and growth of initial earthworm stocks have been assessed so far. The present study provides a comprehensive evaluation of the production system, examining vermicomposting of three types of sludge each at four inclusion levels and the possibility of further utilising end-products (vermicomposts and earthworms). Through an 18-week experiment, high survival of initial earthworm stocks, exceeding 90% among treatments up to week 6, was documented. Higher inclusion levels and sludge types richer in nutrients positively influenced individual weight of initial stocks and their reproduction indices (cocoon and juvenile production). The most progressive treatments sustained >300 juveniles in experimental incubators containing 200 g dw of initial substrates. Original sludge and final vermicomposts were found suitable for use in agriculture, complying with limits for heavy metals given in the most usually applied regulations. In relation to the heavy metals, earthworms were found to be a generally safe feed for fish. Only arsenic concentrations may occasionally exceed given limits. Still, observed concentrations are considered safe, presuming arsenic presence primarily in organic forms having largely reduced toxicity. Vermicomposting is recommended as a clean and sustainable technology transforming aquaculture sludge into highly valuable vermicompost and earthworm biomass.

In this study, cardiac and locomotor activities of signal crayfish Pacifastacus leniusculus were investigated under exposure to a range of natural (i.e., odors of conspecific crayfish, predatory fish, food, and injured conspecific) and one chemical (i.e., disinfectant chloramine-T) stimuli. Crayfish locomotion was simultaneously initiated with an increase in heart rate only when affected by chloramine-T, while locomotor response was delayed in all cases (or was not manifested at all by some specimens) when disturbed by the natural stressors. The heart rate differences measured before and during the stimulation were arranged as follows: odor of conspecific crayfish (9.2 ± 7.1%)

This study focuses on the use of crayfish as bioindicators in the water treatment process during operating conditions. The crayfish physiological responses to water disinfected with chlorine dioxide (ClO2) was evaluated. Monitoring was conducted at the private commercial enterprise Protiv&iacute, n Brewery in Czech Republic under standard operating conditions. This brewery has a water treatment facility, where ClO2 is used for water purification. A total of 25 adult signal crayfish (Pacifastacus leniusculus) were kept in separate flow-through aquaria receiving the purified water with ClO2 concentrations ranging from 0.01 to 0.29 mg L&minus, 1. Diurnal rhythms of 32% of crayfish was disturbed even at lower concentrations of ClO2 (0.01&ndash, 0.2 mg L&minus, 1), while higher concentrations (&gt, 1) affected all animals. A random decline and rise of heart rate was detected. In addition, the frequent occurrence of higher levels of ClO2 significantly increased mortality. On average, mortality of crayfish occurred three to four weeks after stocking into the experimental system. Crayfish mortality is estimated to occur at concentrations exceeding 0.2 mg L&minus, 1 of ClO2. Our results suggest that long-term exposure to ClO2 adversely affects crayfish physiology. In addition, the results of this study could contribute to the use of crayfish as bioindicators in long-term water quality monitoring under industrial conditions.

Evidence of the ecological and biological impact of pharmaceuticals in surface waters on aquatic organisms is increasing. Tramadol is a synthetic opioid analgesic used to treat chronic and acute pain. To investigate its long-term effects at environmentally relevant levels, we evaluated heart rate (HR) and locomotion of signal crayfish Pacifastacus leniusculus during a 21-day exposure to 1 μg L-1 tramadol followed by 14 days depuration. Locomotion and HR were recorded over a period 30 min before and 30 min after exposure to physiological fluids of an injured conspecific, a natural stressor, four times during the tramadol exposure and four times during depuration. A significant increase in HR following stress induction was found in the majority of tramadol-exposed and control crayfish, as well as significant group-specific HR changes between both groups. Locomotor activity during tramadol treatment differed from that during depuration, in general showing less time spent in locomotion and lower distance moved. The tramadol exposed crayfish exhibited higher velocity during depuration than during the exposure period. Results may suggest a potential shift in prey-predator relationships.

A crayfish is a pivotal aquatic organism that serves both as a practical biological model for behavioral and physiological studies of invertebrates and as a useful biological indicator of water quality. Even though crayfish cannot directly specify the substances that cause water quality deterioration, they can immediately (within a few seconds) warn humans of water quality deterioration via acute changes in their cardiac and behavioral activities. In this study, we present a noninvasive method that is simple enough to be implemented under various conditions due to a combination of simplicity and reliability in one model. This approach, in which the biological organisms are implemented into environmental evaluation processes, provides a reliable and timely alarm for warning of and preventing acute water deterioration in an ambient environment. Therefore, this noninvasive system based on crayfish physiological and ethological parameter recordings was investigated for the detection of changes in an aquatic environment. This system is now applied at a local brewery for controlling quality of the water used for beverage production, but it can be used at any water treatment and supply facility for continuous, real-time water quality evaluation and for regular laboratory investigations of crayfish cardiac physiology and behavior.

Environmental pollution by pharmaceutically active compounds, used in quantities similar to those of pesticides and other organic micropollutants, is increasingly recognized as a major threat to the aquatic environment. These compounds are only partly removed from wastewaters and, despite their low concentrations, directly and indirectly affect behaviour of freshwater organisms in natural habitats. The aim of this study was to behaviourally assess the effects of an opioid painkiller (tramadol) and antidepressant drug (citalopram) on behaviour patterns of a clonal model species, marbled crayfish. Animals exposed to environmentally relevant concentrations of both tested compounds (∼1 μg l−1) exhibited significantly lower velocity and shorter distance moved than controls. Crayfish exposed to tramadol spent more time in shelters. Results were obtained by a simple and rapid method recommended as suitable for assessment of behaviour in aquatic organisms exposed to single pollutants and combinations.

Crayfish cardiac activity monitoring and analysis are widely used during water pollution and ethological studies. A noninvasive crayfish cardiac activity monitoring (NICCAM) system discussed in the current study permits long-term, continuous monitoring of several crayfish simultaneously. The advantages of the system are low price, low number of required components and the possibility of cardiac signal shape monitoring. Calculation and analysis of parameters characterizing the shape of the double peak cardiac activity allows not only reducing the number of incorrect peak detections improving the system accuracy but also can provide additional information on crayfish state. The discussed preliminary experiments on the effect of food odor and chloramine-T on crayfish showed promising potential of signal shape analysis for studying of crayfish cardiac reaction to changes in the aquatic environment.

To evaluate the accumulation of aluminium, cadmium, chromium, copper, lead, mercury, nickel, and zinc in crayfish and fish organ tissues, specimens from three drinking water reservoirs (Boskovice, Landštejn, and Nová Říše) and one contaminated site (Darkovské moře) in the Czech Republic were examined. Crayfish hepatopancreas was confirmed to be the primary accumulating site for the majority of metals (Cu > Zn > Ni > Cd > Cr), while Hg and Cr were concentrated in abdominal muscle, and Al and Pb were concentrated in gill. Metals found in Nová Říše specimens included Cu > Zn > Ni and those found in Boskovice included Zn > Hg > Cr. Cd concentrations were observed only in Landštejn specimens, while contaminated Darkovské moře specimens showed the highest levels of accumulation (Cu > Al > Zn > Pb). The majority of evaluated metals were found in higher concentrations in crayfish: Cu > Al > Zn > Ni > Cr > Cd > Pb, with Hg being the only metal accumulating higher in fish. Due to accumulation similarities of Al in crayfish and fish gill, differences of Hg in muscle, and features noted for the remaining metals in examined tissues, biomonitoring should incorporate both crayfish and fish to produce more relevant water quality surveys.

Ultrastructure of spermatozoa of three crayfish genera including Orconectes limosus (Rafinesque, 1817), Procambarus clarkii (Girard, 1852), and Astacus leptodactylus (Eschscholtz, 1823) was studied using transmission electron microscopy. The length of the acrosome was significantly greater in A . leptodactylus (4.5 ± 0.65 μm) than O . limosus (1.7 ± 0.2 μm) and in O . limosus compared to P . clarkii (1.46 ± 0.16 μm). The width of the acrosome was significantly narrower in P . clarkii (2.45 ± 0.2 μm) than O . limosus (4.77 ± 0.51 μm) and in O. limosus compared to A. leptodactylus (8.23 ± 0.9 μm). Also, the length:width ratio was significantly greater in P . clarkii (0.6 ± 0.07) than A . leptodactylus (0.55 ± 0.08) and in A . leptodactylus compared to O . limosus (0.36 ± 0.05). The acrosome complex and nucleus are located at the anterior and posterior of the spermatozoon, respectively. The acrosome complex organelle is divided into two main parts: the main body of the acrosome that is a dense inverted cup-shaped structure and organized into three layers of differing electron densities and extended parallel filaments, and the sub-acrosome zone occupying the central part of the acrosome complex, which is divided into two electron dense areas. The spermatozoon of Orconectes limosus is described for the first time. In addition, an acrosome spike in the spermatozoon of Procambarus clarkii is described. Morphological and biometrical traits of spermatozoa may be used as tools for systematic studies in crayfish, as already reported for many other crustacean taxa.

Peracetic acid (PAA) is useful in treating a wide variety of serious fish diseases in aquaculture. As no information on PAA toxicity to crayfish is available, we conducted acute toxicity tests of Persteril 36, a commercial PAA-containing product, on three age/size classes of signal crayfish, Pacifastacus leniusculus. Results confirmed high tolerance of the target species to this product, expressed as a 96 h LC50 of 77.3 ± 1.0 mg L− 1 PAA in adults and low post-treatment mortality in 9 month old juveniles. As PAA concentrations successfully applied in aquaculture are generally 2.0 mg L− 1 or lower, PAA can be recommended for use in astaciculture. After necessary evaluations, uses might include limiting spread of crayfish plague, treating saprolegniosis on artificially incubated crayfish eggs, and avoiding translocations of further crayfish-related non-native species when introducing crayfish or stocking them in closed culture systems.

The crayfish play an essential role in the biomonitoring and may reflect ambient water quality through the biochemical, behavioural and physiological reactions. To assess whether narrow-clawed crayfish Astacus leptodactylus can respond by heart rate changes to presence in water of such biocide as chloramine-T, adult males were exposed to its low (2 and 5 mg L(-1)), moderate (10 mg L(-1), commonly used in industry and aquaculture) and exceeded (20 and 50 mg L(-1)) concentrations. In addition, a physical stress test evaluated energy expenditure following the chemical trials. Three key reactions (cardiac initial, first-hour and daily prolonged exposure) were discussed with particular focus on crayfish initial reaction as the most meaningful in on-line water quality biomonitoring. After short-term exposure to both chloramine-T concentrations, crayfish were found to respond rapidly, within 2-5 min. According to heart rate changes, the 1-h exposure did not adversely affect crayfish at either concentration, as well as during daily exposure to 10 mg L(-1). As assessed by the heart rate, the 24-h exposure to 50 mg L(-1) of chloramine-T was toxic for crayfish and led to substantial loss of energy that became apparent during subsequently conducted physical stress. The results supported a hypothesis that crayfish vital functions are connected with environment they inhabit closely enough to serve as biological monitors. Crayfish were tolerant to short-term chloramine-T exposure, while rapid crayfish reaction to an increased chemical level indicated their high sensitivity, an essential attribute of real-time environmental assessment.

Water quality monitoring using fish and crayfish as bio-indicators requires an understanding of the state of pollution of waters, choice of bio-indicators, physiological and behavioral endpoints of fish and crayfish, and principles of the methodology and their potential applications. Here, we discuss telemetry, acoustic monitoring, vision-based monitoring, measures of ventilatory activity, electrocardiography, and fiber-optic plethysmography. Assessment of water quality must be based, not only on physicochemical characteristics of the current environment as determined by chemical analyses, but also on observations of the physiology and behavior of its inhabitants. Real-time biomonitoring is suggested as the most reliable method, since it incorporates living organisms into the system to serve as biosensors. The potential application of the methods discussed includes use at water treatment plants and water supply stations for prevention of hazardous toxicological events, and, for aquaculture, in ponds, lakes, and aquariums for monitoring growth, population size, and behavior traits.

A non-invasive method of recording cardiac activity (heart rate – HR) and stress reaction (stress index – SI) was used to understand the immediate and ongoing stress reaction of crayfish to the chemical stimuli. This method detects changes in the shape and amplitude parameters of the response to the stress factors, which characterized the crayfish functional state. Experimental animals (Astacus leptodactylus) were divided to the two groups with (400 mg·L-1 Cl−) and without added chlorides and then exposed to a stepwise increased level of nitrite to the final (sublethal-lethal) concentration of 60 mg·L-1 N-NO\hbox{$_{2}^{-}$}−2 within 24 hours. The course of crayfish reaction was evident and provided information about their reaction to the sublethal-lethal concentration over time. As expected, a less prominent stress reaction was detected in the group with chlorides. The non-invasive method successfully evaluated the sensing of chemical stimuli in water through HR and SI changes.