Behavior Of Crayfish Research Articles

Boosting crayfish algorithm based on halton adaptive quadratic interpolation and piecewise neighborhood for complex optimization problems

The Crayfish Optimization Algorithm (CFish) is an innovative meta-heuristic approach that draws inspiration from the movements and behaviors of crayfish. CFish exhibits strong performance across many test sets and optimization issues, but it faces challenges with sluggish convergence, an uneven distribution between exploration and exploitation, and inadequate accuracy due to high-dimensional tasks. To tackle these concerns, this study presents an evolved version named QICFish, which integrates multiple sophisticated strategies to optimize performance. The CFish algorithm improves its population initialization by using the Halton sequence, resulting in a substantial enhancement of the exploration phase and an increase in population variety. Furthermore, the implementation of the adaptive quadratic interpolation approach enhances the algorithm's capacity to exploit its surroundings by eliminating individuals of worse quality and expediting the creation of solutions of superior quality. Furthermore, an adaptive mutation method is employed to improve the process of exploration and effectively locate more favorable areas inside the search space. Finally, the adaptive piecewise neighborhood strategy, enhances the pace of convergence and maintains a balanced transition between exploration and exploitation. Then, QICFish outperforms other cutting-edge algorithms across several dimensions of the CEC’17 and CEC’20 test sets, as shown by experimental comparisons. Furthermore, the efficacy and feasibility of the solution are confirmed by successfully addressing six intricate engineering problems and two truss topology optimization problems. The simulation findings demonstrate that QICFish exhibits robust competitive capabilities and shows great potential for engineering optimization challenges. Therefore, QICFish is a very efficient meta-heuristic approach for solving engineering optimization problems.

Novel Hybrid Crayfish Optimization Algorithm and Self-Adaptive Differential Evolution for Solving Complex Optimization Problems

This study presents the Hybrid COASaDE Optimizer, a novel combination of the Crayfish Optimization Algorithm (COA) and Self-adaptive Differential Evolution (SaDE), designed to address complex optimization challenges and solve engineering design problems. The hybrid approach leverages COA’s efficient exploration mechanisms, inspired by crayfish behaviour, with the symmetry of SaDE’s adaptive exploitation capabilities, characterized by its dynamic parameter adjustment. The balance between these two phases represents a symmetrical relationship wherein both components contribute equally and complementary to the algorithm’s overall performance. This symmetry in design enables the Hybrid COASaDE to maintain consistent and robust performance across a diverse range of optimization problems. Experimental evaluations were conducted using CEC2022 and CEC2017 benchmark functions, demonstrating COASaDE’s superior performance compared to state-of-the-art optimization algorithms. The results and statistical analyses confirm the robustness and efficiency of the Hybrid COASaDE in finding optimal solutions. Furthermore, the applicability of the Hybrid COASaDE was validated through several engineering design problems, where COASaDE outperformed other optimizers in achieving the optimal solution.

Using crayfish behavior assay as a simple and sensitive model to evaluate potential adverse effects of water pollution: Emphasis on antidepressants

The freshwater crayfish, Procambarus clarkii is an excellent aquatic animal model that is highly adaptable and tolerant. P. clarkii is widely used as a toxicity model to study various pharmaceutical exposure. This animal model has complex behavioral traits and is considered sensitive to environmental changes, making it an excellent candidate to study psychoactive drugs based on a behavioral approach. However, up to now, most behavioral studies on crayfish use manual observation and scoring that require panelists. In this study, we aim to develop an automation pipeline to analyze crayfish behavior automatically. We use a deep-learning approach to label body parts in multiple crayfish, and based on the trajectory results, the intra- or inter-individual crayfish were calculated. Reliable and fast results of several behavior endpoints in multiple crayfish were retrieved. We then validated the detection performance of numerous crayfish in specific gender groups (male-male and female-female). Based on the result, the male crayfish displayed significantly higher aggression than females. We also tested the antidepressant exposure on this animal model to evaluate the psychoactive effects of this drug. As male crayfish display more distinct agonistic behavior than females, we exposed them to sertraline (SRT) 1 ppb for 7 and 14 days. It was revealed that sertraline was able to alter several behavioral endpoints in crayfish. Significant increases in extend claw ratio, total distance moved, average speed, and rapid movement were displayed in sertraline-exposed crayfish but decreased interaction time and longest interaction time. In addition, SRT 14 days exposure could atler the aggressiveness and bold behavior In the present method, DeepLabCut (DLC) has been utilized to analyze the locomotion behavior of multiple crayfish. This established method provides rapid and accurate ecotoxicity measurements using freshwater crayfish, which beneficient and applicable for environmental research.

Feeding in predator naïve crayfish is influenced by cues from a fish predator

In this study, we experimentally evaluated how the feeding behaviour of marbled crayfish Procambarus virginalis is influenced by cues from conspecifics and the round goby Neogobius melanostomus, a fish predator, in tanks that permitted chemical communication but not visual recognition. We used four experimental groups with different combinations in two sub-tanks. The first sub-tank always contained a crayfish and prey (40 individuals of the water louse Asellus aquaticus). The other sub-tanks were set up as follows: (i) empty, serving as a control (C); (ii) with a conspecific crayfish (Cr); (iii) with a round goby (G) to simulate predator-only odour; and (iv) a round goby and three small conspecific crayfish (G + Cr) to simulate the presence of a predator and/or the alarm odour. Two sub-treatments were defined for the fourth group, categorised as ‘injured’ or ‘not injured’ depending on whether prey crayfish were visibly injured or not, respectively. We observed a significant decline in the consumption of water lice in the G and G + Cr treatments compared to the C and Cr treatments (up to 47% on average). There were no significant differences in consumption between the G and G + Cr treatments, or C and Cr treatments. No significant differences in food consumption parameters were detected between sub-treatments with ‘injured’ and ‘not injured’ conspecific crayfish. Knowledge of modifications in the feeding behaviour of marbled crayfish in the presence of round goby (and fish predators in general) is essential for ecologists attempting to understand the changes and impacts occurring in invaded freshwater ecosystems.

The Effects of Cannabidiol and Serotonin on Anxiety-Like Behavior in Crayfish

Cannabidiol (CBD) is a cannabinoid that is being used as a new treatment for many mental and physical medical conditions, including anxiety. Serotonin (5-HT) is a neurotransmitter that has been shown to have many roles, including stabilizing mood. Crayfish are invertebrate animals that have been used as a model system to study human diseases. Crayfish are well suited to study the effect of CBD on anxiety due to their documented endocannabinoid system and anxiety-like behavioral traits. In this study, the effects of CBD on anxiety-like behavior in crayfish were investigated using a Light-Dark maze as a behavioral analysis tool. At the doses used, CBD did not independently show any influence on either the Light-Dark preference or the total position moves made by crayfish. 5-HT showed quite variable results compared to the saline solution. 5-HT injection significantly decreased time spent in the dark for crayfish injected with 2µg/g of CBD and significantly decreased movement for crayfish injected with 4µg/g of CBD. The dichotomous behavior of the 5-HT injected crayfish requires more study to determine if underlying factors can explain the varying responses. The concentrations of CBD may also need to be increased to properly examine its role in reducing anxiety.

Flow discharge impacts competition for food and shelter between two overlapping species of crayfish

Competition between aquatic organisms is heavily influenced by abiotic factors in the environment, specifically flow regime in aquatic systems. Flow regime has been shown to significantly affect the way in which a species uses the environmental resources and alterations in flow can exasperate competitive advantages by congenerics. However, little work has concentrated on the competitive outcome between native and invasive organisms as a function of flow regime. Here, we sought to uncover how competition between two crayfish species (the native virile crayfish [Faxonius virilis] and invasive rusty crayfish [Faxonius rusticus]) was affected by varying flow rates. To do this, we size-matched crayfish and quantified three separate behaviors (food use, shelter use, and fights) of crayfish in four different discharge levels (no discharge—0 cm3/s; low discharge—116 cm3/s; intermediate discharge—345 cm3/s; high discharge—450 cm3/s). We found that the number of foraging bouts was significantly (p < 0.001) influenced by discharge levels for both species, where rusty crayfish foraged more often in no and discharge. The number of times crayfish sheltered also varied between species and was significantly (p < 0.001) altered by discharge level, where rusty crayfish sheltered more often in no discharge and virile crayfish sheltered more in low and intermediate discharge levels. Similarly, the number of fights that crayfish engaged in also significantly (p < 0.001) depended upon species and discharge levels. Rusty crayfish engaged in more agonistic activities in no and high discharge levels while virile crayfish participated most often in low and intermediate discharge levels.

Limiting burrowing activity and overland dispersal of the invasive alien red swamp crayfish Procambarus clarkii by sophisticated design of watercourses

Invasive alien crayfish species pose major ecological and hydrological risks globally. The red swamp crayfish (Procambarus clarkii) is one of the most widespread crayfish species worldwide. Its impacts arise from burrowing activities and lead to mobilization of soil nutrients, water safety risks by instability of dikes and erosion of banks. Increased sediment load demands additional dredging of drainage ditches and canals to ensure their water discharge capacity. Sustainable methods for limiting burrowing in banks and dispersal behaviour of crayfish were not yet available. Therefore, a field study was performed to determine whether the number of burrows and overland movement of crayfish were related to a particular bank type. Burrows were counted in three watercourses during a water-level decline. The number of burrows was significantly lower in natural banks than in non-natural and semi-natural banks. The construction of natural-like banks along watercourses may significantly reduce sediment load, erosion and the collapse of banks by burrowing activities of crayfish. An inclination experiment mimicking various types of terrestrial dispersal barriers elucidated that steepness, soil type and vegetation structure of small embankments near watercourses were significant factors for manipulating overland movement of crayfish. Crayfish were taken out of the water for this purpose and placed on small experimental embankments varying in slope and types of vegetation. The lowest frequencies of upward movement were recorded at inclinations of 20° and 30° on bare sandy soil and short and species-poor grassland substrates. This implies that crayfish crawling out of the water will return to the watercourse when encountering such a dispersal barrier. Therefore, a sophisticated design of embankments along watercourses can be a tool to reduce colonization risk of nearby located, hydrologically isolated water bodies with high nature values.

Portland's Keystone Crustacean: Signal Crayfish Behavior, Health, &amp; Habitat in the Tryon Creek Watershed

<span id="docs-internal-guid-259fb444-7fff-fc81-16a7-d1010f100e2e" style="font-size: 12pt; font-family: Garamond,serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">In the Portland Metro Area, the signal crayfish (</span><span style="font-size: 12pt; font-family: Garamond,serif; color: #000000; background-color: transparent; font-weight: 400; font-style: italic; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Pacifastacus leniusculus</span><span style="font-size: 12pt; font-family: Garamond,serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">) is a keystone species. Signal crayfish consume inaccessible plant matter and detritus, feed various game fish, engineer riverbeds, and are even harvested commercially for human consumption. Recognizing signal crayfishes’ multifaceted ecological and social significance, the purpose of this study was to assess the habitat factors that impact signal crayfish health and behavior in the Tryon Creek Watershed. Data collection revealed that overall, Tryon Creek crayfish were disproportionately likely to be observed in locations with high infrastructure presence levels; substrates composed of silt/sand or a combination of boulders and cobbles; culverts, runs, and pools; and water depths between 10 and 39 cm. Meanwhile, juvenile crayfish were disproportionately likely to be observed in locations with low human impact levels, substrates composed of silt/sand and a combination of cobbles and gravel, and water depths between 0 and 19 cm. Similarly, unhealthy crayfish — specimens that were deceased, immobile, or struggling, or that consisted of severed appendages — were disproportionately likely to be observed in locations with culverts and riffles and water depths between 0 and 19 cm. The study found no evidence for an established population of invasive crayfish in Tryon Creek, although further monitoring (particularly in Tryon Cove) are necessary to ensure the watershed’s continued protection. The analysis also suggested that human-caused ecosystem disruptions can seriously decrease the health and wellness of signal crayfish populations, pointing to a need for better waterway designs that can benefit fish and crustaceans alike.</span>

Serotonergic modulation of appetitive and ingestive behavior in crayfish.

Serotonin is an important modulator of feeding behavior across animal species. In invertebrates, much is known about the regulation of feeding in several model organisms, but comparative data are limited. We examined the modulation of feeding behavior in crayfish by administering serotonin and two serotonin receptor ligands, mianserin and 5-carboxamidotryptamine. We found that, compared to control injections, exogenous serotonin significantly reduced appetitive behaviors in response to a chemical food stimulant and reduced consumption when food was present. The two ligands also significantly reduced the amount of food consumed. However, they had no significant effects on appetitive feeding movements, suggesting that appetitive and consummatory feeding phases may be regulated by different serotonergic mechanisms. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Combining Old and New Tricks: The Study of Genes, Neurons, and Behavior in Crayfish.

For over a century the nervous system of decapod crustaceans has been a workhorse for the neurobiology community. Many fundamental discoveries including the identification of electrical and inhibitory synapses, lateral and pre-synaptic inhibition, and the Na+/K+-pump were made using lobsters, crabs, or crayfish. Key among many advantages of crustaceans for neurobiological research is the unique access to large, accessible, and identifiable neurons, and the many distinct and complex behaviors that can be observed in lab settings. Despite these advantages, recent decades have seen work on crustaceans hindered by the lack of molecular and genetic tools required for unveiling the cellular processes contributing to neurophysiology and behavior. In this perspective paper, we argue that the recently sequenced marbled crayfish, Procambarus virginalis, is suited to become a genetic model system for crustacean neuroscience. P. virginalis are parthenogenetic and produce genetically identical offspring, suggesting that germline transformation creates transgenic animal strains that are easy to maintain across generations. Like other decapod crustaceans, marbled crayfish possess large neurons in well-studied circuits such as the giant tail flip neurons and central pattern generating neurons in the stomatogastric ganglion. We provide initial data demonstrating that marbled crayfish neurons are accessible through standard physiological and molecular techniques, including single-cell electrophysiology, gene expression measurements, and RNA-interference. We discuss progress in CRISPR-mediated manipulations of the germline to knock-out target genes using the ‘Receptor-mediated ovary transduction of cargo’ (ReMOT) method. Finally, we consider the impact these approaches will have for neurophysiology research in decapod crustaceans and more broadly across invertebrates.

Sustained Anxiety-Like Behavior in Crayfish Exposed to Thermal Burn

Both invertebrates and vertebrates make immediate simple reactions to noxious stimuli; a tail flip to escape is a typical example in crayfish. More complex sustained emotional responses, such as anxiety or fear, can be demonstrated in many vertebrates but until recently have not been seen in crustaceans. Several recent studies have found sustained anxiety-like behavior (ALB) in crayfish in response to electric shock and social bullying, and this behavior can be suppressed by anti-anxiety medications. In this study, crayfish were subjected to a thermal burn stress, and then observed for ALB in an established model (light-dark maze). Stressed animals spent almost all of their time in the dark zone, in contrast to unstressed crayfish, who demonstrated normal crayfish exploratory behavior. In this model, crayfish clearly demonstrated ALB in response to stressful burn. This research has implications for humane treatment of crustaceans.&#x0D;

Zn contamination stimulate agonistic behavior and oxidative stress of crayfishes (Procambarus clarkii)

BackgroundAs a result of the global industrial revolution, contamination of the ecosystem by heavy metals has given rise to one of the most important ecological and organismic problems. The current study aimed to evaluate the effect of Zn contamination on agonistic behavior and oxidative damage of crayfish. MethodsCrayfishes of the field study group were collected from a polluted area (Rosetta branch), where the highest concentration for heavy metals in water was zinc (Zn). Besides the field study group, other crayfishes were exposed to different doses of ZnSO4 (0, 203, and 406 mg L−1), which corresponding to Zn concentration (0, 46.03, and 92.06 mg L−1) respectively in aquariums for consecutive four days. Agonistic behavior is quantified by decreasing fast retreat, slowly back away and no response, increasing initial claw use, active claw use, approach with the threat, approach without threat, and unrestrained behavior. ResultsThe result revealed that agonistic behavior increases significantly with the increase of water Zn concentration. Malondialdehyde and catalase levels increased, while glutathione concentration reduced with the increase of Zn concentration. ConclusionOur current study reveals that zinc exposure is capable of inducing an increase in the social status (agonistics behavior) and oxidative stress parameters in Procambarus clarkii. The increase in aggressive behavior may have major population-level consequences given the high mortality experienced by this crayfish.

Opposing effects of dopamine on agonistic behaviour in crayfish.

The effects of dopamine on the agonistic behaviour of crayfish were analysed. When dopamine concentrations of 1 μmoll-1 were injected into large crayfish, individuals were beaten by smaller opponents, despite their physical advantage. Injection of 10 μmoll-1 dopamine into small animals increased their rate of winning against larger opponents. Injection of a D1 receptor antagonist prohibited the onset of a 'loser' effect in subordinate animals, suggesting that the inhibitory effect of dopamine on larger animals is mediated by D1 receptors. Similarly, injection of a D2 receptor antagonist prohibited the onset of a 'winner' effect in dominant animals, suggesting that the facilitating effect of dopamine on small animals is mediated by D2 receptors. Since the inhibitory effect of 1 μmoll-1 dopamine was similar to that seen with 1 μmoll-1 octopamine and the facilitating effect of 10 μmoll-1 dopamine was similar to that of 1 μmoll-1 serotonin, functional interactions among dopamine, octopamine and serotonin were analyzed by co-injection of amines with their receptor antagonists in various combinations. The inhibitory effect of 1 μmoll-1 dopamine disappeared when administered with D1 receptor antagonist, but remained when combined with octopamine receptor antagonist. Octopamine effects disappeared when administered with either D1 receptor antagonist or octopamine receptor antagonist, suggesting that the dopamine system is downstream of octopamine. The facilitating effect of 10 μmoll-1 dopamine disappeared when combined with serotonin 5HT1 receptor antagonist or D2 receptor antagonist. Serotonin effects also disappeared when combined with D2 receptor antagonist, suggesting that dopamine and serotonin activate each other through parallel pathways.

Exposure to a common antidepressant alters crayfish behavior and has potential subsequent ecosystem impacts

AbstractPharmaceuticals are ubiquitous in aquatic environments, yet little is known regarding their impacts on ecological processes. Selective serotonin reuptake inhibitors (SSRIs) are frequently prescribed human antidepressants and have been shown to alter crayfish behavior. These behavioral alterations are particularly relevant as crayfish play a central role in freshwater ecosystems and often reach high biomass in anthropogenically influenced environments commonly exposed to pharmaceutical contamination. Using a 14‐d artificial stream experiment, we exposed spinycheek crayfish (Faxonius limosus) to citalopram, a common SSRI, at an environmentally realistic concentration (0.5 µg/L). We used a Y‐shaped flume to quantify the effects of SSRI exposure on crayfish behavior and food/conspecific preference. We also tested the interacting effects of citalopram and crayfish on habitat‐specific and whole‐stream ecosystem functions and biomass. Crayfish exposed to SSRIs exhibited increased boldness (time to emerge from shelters; P &lt; 0.05) and spent more time orienting to food resources than nonexposed crayfish. Crayfish increased water column chlorophyll a (P &lt; 0.01) and benthic organic matter (P = 0.03). Furthermore, crayfish potentially increased water column respiration (P = 0.09) and potentially decreased nitrate uptake (P = 0.05). SSRI exposure exhibited a potential effect of decreasing benthic chlorophyll a (P = 0.07), but there were no significant CRAY+SSRI interactions. Neither crayfish nor SSRI treatments affected whole‐stream metabolism. These results suggest that citalopram has the potential to affect algal biomass but did not affect ecosystem functioning. However, alterations to crayfish behavior driven by SSRI exposure could lead to subsequent ecosystem‐level effects as crayfish did affect various response metrics. We were unable to detect the effects of altered crayfish behavior at the ecosystem scale during our study, likely due to the short time frame (2 weeks) of our experiment. Further work is needed to quantify longer‐term ecosystem consequences of sublethal effects of pharmaceuticals, but these results show that ecological responses to pharmaceuticals should consider the entire ecosystem.

Motion‐triggered laser photography reveals fine‐scale activity patterns for burrowing crayfish

Abstract Burrowing crayfish represent 15% of total crayfish species and 32% of imperilled species. Few life history studies exist for these species and more information is needed regarding their ecology, population status, distribution, and biogeography for effective conservation efforts. Challenges to gaining such information include sampling difficulty and small sample sizes. Collection efforts may be more efficient if activity patterns can be identified for species of interest. The goal of our study was to assess specific environmental indicators of burrowing crayfish activity patterns. We evaluated activity patterns of two primary burrowing crayfish species, Lacunicambarus erythrodactylus (Simon &amp; Morris, Proc. Biol. Soc. Wash., 127, 2014, 572) and Procambarus holifieldi (Schuster, Taylor, &amp; Adams, Zootaxa, 4021, 2015, 1) using laser‐triggered digital photography for one‐year periods in the Bogue Chitto Creek floodplain, Dallas County, Alabama, U.S.A. We predicted that activity would be related to time of day, season, groundwater depth, and precipitation. Activity by L. erythrodactylus covaried significantly with time of day, daylength, groundwater temperature, and relative air temperature, while activity by P. holifieldi covaried with time of day, season, groundwater temperature, and relative air temperature. Additionally, burrow chimney construction by P. holifieldi covaried with daylength, groundwater temperature, relative air temperature, and precipitation. Out‐of‐burrow activity for both species was greatest at night and during periods of relatively cool groundwater temperatures and relatively warm air temperatures, which may be linked to thermal regulation behaviour. The probability of chimney construction by P. holifieldi increased with increasing daylength and decreasing precipitation and was highest during periods of cool groundwater temperatures and air temperatures. A distinct lull in activity from October through March for both species was likely to be the result of reproductive behaviours such as period of egg production and incubation within burrows. Identifying peak out‐of‐burrow activity periods for burrowing crayfish will allow collection efforts to be focused on periods of greatest activity, thereby facilitating the study of burrowing crayfish behaviour.

Outcomes of agonistic interactions alter sheltering behavior in crayfish

‘Winner’ and ‘loser’ effects have been demonstrated in a broad range of species, but such investigations are often limited to the effects of prior contest outcomes on future agonistic interactions. Much less is known about the impacts of winning or losing contests on other aspects of individual behavior, like courtship interactions and sheltering behavior. In this investigation, I examined the effect of prior contest outcomes on sheltering behavior in the crayfish Faxonius virilis. I predicted that winners of contests would spend less time inside shelters and more time exploring, while losers of contests would spend more time inside shelters and less time exploring. I compared individual sheltering behavior before and after staged dyadic encounters between competitively mismatched individuals. This experiment revealed strong effects on the behavior of contest losers, which showed significant increases in the amount of time spent inside the shelter immediately after the contest. However, there was no significant change in the sheltering behavior of contest winners. These results reinforce the idea that contest outcomes can affect individual behaviors other than agonistic behavior, and suggest that losing a contest may motivate individual crayfish to engage in less-risky behavior, at least for a brief period after the contest.

Fine‐tuned responses to chemical landscapes: crayfish use predator odors to assess threats based on relative size ratios

AbstractThe threat‐sensitive predator avoidance hypothesis suggests that prey animals should minimize the costs of antipredator behaviors by only responding to predators that pose a potentially lethal threat. Thus, prey must use risk assessment strategies to determine which predators present a great enough threat to merit a response. A rich literature demonstrates that chemical signals can communicate information about predator identity, diet, and size. However, the relationship between predator size and prey size has been largely overlooked. What remains unknown is how prey respond to odors from predators along a continuum of relative size. Here, we tested the responses of crayfish (prey) to odor cues from two species of predatory fish along a gradient of relative size relationships. Crayfish and fish were paired according to crayfish carapace width and the fish’s gape width to represent different relative size pairings. Foraging and shelter use video assays were used to evaluate changes in crayfish behavior under the different levels of threat presented. The analysis revealed significant increases in macrophyte consumption, foraging effort, and overall activity among crayfish that were small relative to their predators, independent of the absolute size of fish or crayfish size. Crayfish that were small relative to predator size showed significantly less shelter use than crayfish that were large relative to predator gape size. The results demonstrate that the crayfish are assessing threat based on their size relative to the predator gape size solely using chemical signals. As a result of this assessment, crayfish are changing their resource use to potentially grow larger to limit future predatory threats. Overall, this research supports the threat‐sensitive predator avoidance hypothesis and provides an opportunity to refine the landscape of fear concept to accommodate more detailed risk assessments by prey.

A transcription factor glial cell missing (Gcm) in the freshwater crayfish Pacifastacus leniusculus

The transcription factor glial cell missing, Gcm, is known to be an important protein in the determination of glial cell fate as well as embryonic plasmatocyte differentiation in Drosophila melanogaster. So far, no function for Gcm in crustaceans has been reported. In this study, we show the cDNA sequence of a Gcm homologue in the freshwater crayfish Pacifastacus leniusculus. The P. leniusculus Gcm transcript is expressed exclusively in brain and nervous tissue, and by in situ hybridization we show that the expression is restricted to a small number of large cells with morphology similar to neurosecretory cells. Furthermore, we show that the expression of Gcm coincides with the expression of a Repo homologue, that is induced in expression by Gcm in Drosophila. Moreover, the Gcm transcript is increased shortly and transiently after injection of cystamine, a substance that inhibits transglutaminase and also strongly affects the movement behavior of crayfish. This finding of Gcm transcripts in a subpopulation of brain cells in very low numbers may enable more detailed studies about Gcm in adult crustaceans.

Effects of chloridazon on early life stages of marbled crayfish

The effects of chloridazon exposure at concentrations of 2.7 μg/L (maximal real environmental concentration in the Czech Republic), 27 μg/L, 135 μg/L and 270 μg/L on early life stages of marbled crayfish (Procambarus virginalis) were evaluated. Significantly higher glutathione S-transferase activity and reduced glutathione level was observed at all tested concentrations of chloridazon compared with the control. Chloridazon in concentrations 27, 135 and 270 μg/L caused delay ontogenetic development and slower growth. Histopathological changes in hepathopancreas were found in two highest tested concentrations (135 μg/L and 270 μg/L). Crayfish behaviour was not altered in control vs. exposed animals, while the activity parameters tend to decline with increasing chloridazon concentrations.

Discrete modulation of anti-predatory and agonistic behaviors by sensory communication signals in juvenile crayfish.

We investigated how the exchange of sensory signals modulates the individual behaviors of juvenile crayfish in an anti-predatory context as well as during intraspecific agonistic encounters. We first compared crayfish housed in total sensory isolation or in pairs with access to chemical and visual cues. After 1 week of housing, we analysed their individual responses to a visual danger signal while they were foraging. We found that crayfish previously housed in pairs with exchange of sensory signals responded to a simulated predator attack predominantly with freezing behavior, whereas animals deprived of all sensory communication mostly responded by performing escape tail-flips. Next, we used the same housing conditions in between repeated fights in pairs of crayfish. Aggressive and submissive behaviors increased in subsequent fights both after total isolation and after exchange of olfactory and visual signals. Thus, unlike responses to simulated predator attacks, intraspecific agonistic behavior was not modulated by exposure to the same sensory signals. However, when we tested the effects of olfactory or visual communication independently, aggression increased dramatically after the exchange of olfactory signals, which also led to a high number of rank reversals in second fights, suggesting a destabilization of the original dominance relationship. Exposure to visual cues during the 1-week separation, however, produced the opposite effect, reducing agonistic behaviors and rank reversals. These findings demonstrate that exchange of sensory signals modulates future anti-predatory decision-making and intraspecific agonistic behaviors discretely, suggesting that the effect of these signals on shared neural circuitry is context dependent.