Marbled Crayfish Procambarus Virginalis Research Articles

Lack of Genetic Variation in Low Heterozygosity and Clonal Animals Creates Lack of Physiological Variation

Data variability frequently complicates reproducibility and interpretation of experimental results. Such variability arises from numerous sources such as differences in procedures or not accounting for key biological factors (e.g. sex, biological rhythms, prandial state). Making the situation more problematic, variation in physiological performance is often viewed as highly labile, easily and rapidly influenced by environmental stressors, development, etc., making it diffcult to pin down a source for variation. Undeniably, however, unknown (or ignored) genetic variation among and within strains/lines can also be a significant source of data variability in published physiological measurements, though surprisingly this has not been extensively investigated as a specific source of physiological variation. We hypothesized that variation in physiological performance is correlated with the intrinsic degree of genetic variability of the subject animal. To test this hypothesis, we employed two animal models: 1) Inbred lines ( e.g., NHGRI-1) derived from wild type strains of the zebrafish ( Danio rerio), with an estimated 15% of the genetic heterozygosity of wild type AB zebrafish, and 2) the parthenogenetically reproducing marbled crayfish ( Procambarus virginalis), all specimens of which are genetically identical clones. For these two animal models, we measured both physiological variables (e.g. heart rate, stroke volume, cardiac output, oxygen consumption) and morphological variables (e.g. yolk-chorion ratio, body mass, embryo mass, total length, condition factor, specific growth rate) during development. We subjected the two animal models to environmental stress in the form of both temperature and hypoxia to stimulate physiological responses that could be compared and contrasted among populations. From these data we then calculated the resultant coeffcients of variation for measured variables for wild type and low/zero heterozygosity populations and/or species. In zebrafish, both the wildtype AB and NHRGI-1 lines showed similar developmental trajectories characterized by similar mean values for physiological and morphological variables. Additionally, similar mean values for physiological and morphological variables were recorded in the face of temperature and hypoxia challenge. Yet, importantly, the coeffcient of variation for each measured variable was significantly lower in NHGRI-1 than AB larvae for >90% of the assessed endpoints. In the clonal crayfish, genetically identical early stage marbled crayfish reared in different temperatures or oxygen levels show major acclimation responses, but generally showed less morphological and physiological variation about the mean than sexually-reproducing species crayfish with inherently much greater genetic variation, as evident from comparisons of calculated coeffcients of variation. A key question regarding the clonal crayfish is how can there be any morphological or physiological variation between individuals? We suggest that variability that persists may arise from microenvironmental differences during rearing (e.g. egg position during incubation on the mother’s pleon) and/or stochastic differences in gene expression (e.g. due to random epimutations) in this clonal species. In conclusion, genetic diversity clearly contributes to physiological variability. For future experiments, low heterozygosity lines and/or clonal species may be useful for decreasing inter-individual variation, thus aiding interpretation of results and enhancing reproducibility. In any event, scientific documentation of physiological studies should include as much information on (genetic) background of the experimental animals as possible. NSF IOS-2103499. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Assessing the invasive potential of parthenogenetic marbled crayfish Procambarus virginalis Lyko, 2017 (Decapoda, Astacidea) in the water bolies of the temperate zone of Europe

The experiment examined the effect of temperature on the parameters of reproduction and growth in female marbled crayfish. At temperatures close to 20 °C, females began to reproduce at 10–11 months with a body weight of 0.84–1.20 g, but up to 80 % of their egg clutches were nonviable. The duration of egg embryogenesis with an increase in temperature from 16–17 to 26–27 °C decreased from 66–69 days to 21–24 days with a lower temperature development threshold equal to 13.1 °C. A similar molting value that determined the growth rate of individuals in juveniles weighing up to 0.34 g was 13–14 °C, but in sexually mature females it decreased to 5 °C. In water bodies of the temperate zone with a short growing season, females were able to reach sexual maturity only in the third summer of life and produced no more than two clutches of eggs during their life cycle. Hence, the invasive potential of marbled crayfish in the temperate zone of Europe is very limited.

Stress conditions extend maternal care and delay juvenile development in crayfish

Abstract Maternal care in crayfish has been extensively studied, but little is known of its response to environmental factors. We studied the duration of maternal care and its association with the juvenile development of marbled crayfish Procambarus virginalis in adverse environmental conditions. We exposed females with developmental stage 3 juveniles to environments of low water volume (LW) with food provided, low water volume with no feed (starvation) (LWS), and low water volume without feeding plus an intruder (red swamp crayfish male) (LWSI). A control group with standard water level/feed conditions was included for comparison. Groups were monitored for up to 90 days. The LWS group showed significantly prolonged maternal care (~65 days) as indicated by an extended attachment phase, delayed moulting of mothers (~53 days), and retarded juvenile development. In the LWSI group, conflict precluded extended maternal care. Low use of shelter and feeding was evident under all stress conditions. The results showed that crayfish females modify maternal care in accordance with conditions, providing a longer period of safety for offspring under adverse circumstances. It is possible that the expression of maternal pheromones can manipulate the developmental rate in juveniles, a topic for future research.

Sustained ecological impacts of invasive crayfish following claw injury

The rapid acceleration of human-mediated translocation of species has led to the introduction of thousands of species outside their native range with severe consequences for global biodiversity. Freshwater crayfish are a particularly successful group of invasive species as exemplified by the increasingly widespread marbled crayfish Procambarus virginalis Lyko, 2017. A significant portion of crayfish populations has regenerating or missing claws. At the same time, claws play important roles in feeding and intraspecific interactions, altering crayfish ability to invade new areas and impact native communities. Here, we combined laboratory experiments and modeling to investigate whether the number of claws on marbled crayfish modulates its ecological impact (focusing on predation rate) using functional response analyses, as well as its intraspecific interactions via population dynamic modeling. We found that the number of claws did not affect the marbled crayfish's functional response type (hyperbolic type II), attack rates, or handling times when preying on chironomid larvae. Rates of partial prey consumption were overall small (< 2%), claw numbers had a significant effect on the partial consumption rate of prey, which tended to increase with the number of claws and prey density. The presence of multiple intraspecific predators influenced marbled crayfish non-trophic behavior, with antagonistic effects prevalent between crayfish pairs regardless of claw status. Moreover, the impact of multiple predators was prey density-dependent, with highest levels of antagonism shown at the lowest prey density across crayfish groups. Our findings indicate that the ecological influence of invasive crayfish remains unchanged by the number of claws, highlighting the escalating, context-independent threat these species pose to freshwater ecosystems

Temperature and hypoxia trigger developmental phenotypic plasticity of cardiorespiratory physiology and growth in the parthenogenetic marbled crayfish, Procambarus virginalis Lyko, 2017

Attempting to differentiate phenotypic variation caused by environmentally-induced alterations in gene expression from that caused by actual allelic differences can be experimentally difficult. Environmental variables must be carefully controlled and then interindividual genetic differences ruled out as sources of phenotypic variation. We investigated phenotypic variability of cardiorespiratory physiology as well as biometric traits in the parthenogenetically-reproducing marbled crayfish Procambarus virginalis Lyko, 2017, all offspring being genetically identical clones. Populations of P. virginalis were reared from eggs tank-bred at four different temperatures (16, 19, 22 and 25 °C) or two different oxygen levels (9.5 and 20 kPa). Then, at Stage 3 and 4 juvenile stages, physiological (heart rate, oxygen consumption) and morphological (carapace length, body mass) variables were measured. Heart rate and oxygen consumption measured at 23 °C showed only small effects of rearing temperature in Stage 3 juveniles, with larger effects evident in older, Stage 4 juveniles. Additionally, coefficients of variation were calculated to compare our data to previously published data on P. virginalis as well as sexually-reproducing crayfish. Comparison revealed that carapace length, body mass and heart rate (but not oxygen consumption) indeed showed lower, yet notable coefficients of variation in clonal crayfish. Yet, despite being genetically identical, significant variation in their morphology and physiology in response to different rearing conditions nonetheless occurred in marbled crayfish. This suggests that epigenetically induced phenotypic variation might play a significant role in asexual but also sexually reproducing species.

Temperature affects predation of schistosome-competent snails by a novel invader, the marbled crayfish Procambarus virginalis.

The human burden of environmentally transmitted infectious diseases can depend strongly on ecological factors, including the presence or absence of natural enemies. The marbled crayfish (Procambarus virginalis) is a novel invasive species that can tolerate a wide range of ecological conditions and colonize diverse habitats. Marbled crayfish first appeared in Madagascar in 2005 and quickly spread across the country, overlapping with the distribution of freshwater snails that serve as the intermediate host of schistosomiasis-a parasitic disease of poverty with human prevalence ranging up to 94% in Madagascar. It has been hypothesized that the marbled crayfish may serve as a predator of schistosome-competent snails in areas where native predators cannot and yet no systematic study to date has been conducted to estimate its predation rate on snails. Here, we experimentally assessed marbled crayfish consumption of uninfected and infected schistosome-competent snails (Biomphalaria glabrata and Bulinus truncatus) across a range of temperatures, reflective of the habitat range of the marbled crayfish in Madagascar. We found that the relationship between crayfish consumption and temperature is unimodal with a peak at ~27.5°C. Per-capita consumption increased with body size and was not affected either by snail species or their infectious status. We detected a possible satiation effect, i.e., a small but significant reduction in per-capita consumption rate over the 72-hour duration of the predation experiment. Our results suggest that ecological parameters, such as temperature and crayfish weight, influence rates of consumption and, in turn, the potential impact of the marbled crayfish invasion on snail host populations.

Effects of chemical cues and prior experience on predator avoidance in crayfish.

Multisensory stimuli provide organisms with information to assess the threat present in the surroundings. Olfactory cues show dominance over other sensory modalities in the aquatic environment. The impact of chemical predator cues combined with experiences gained (learning) in species without previous contact is not fully understood. We investigated the foraging and shelter-seeking behaviour of naïve and experienced marbled crayfish Procambarus virginalis juveniles in response to the chemical signals of pumpkinseed Lepomis gibbosus alone and in combination with alarm chemicals produced by preyed-upon conspecifics. Naïve and experienced (previously exposed to pumpkinseed predation) juveniles were stocked in an arena with shelter and feed and exposed (1) to water from a tank containing a predator actively feeding on conspecifics, (2) water from a tank with predator only and (3) water only as control. Crayfish exposed to the combined stimuli avoided the inlet zone and gravitated to shelter zone of the arena to a greater extent than did those exposed to predator-only cues and the control. Regardless of the treatment, experienced crayfish showed significantly reduced interest in feeding. Our findings imply that crayfish response to threat-associated odours with the greatest potency when visual or tactile cues are present, while previous encounters with predators may make them more cautious.

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.

Effect of psychoactive substances on cardiac and locomotory activity of juvenile marbled crayfish Procambarus virginalis

Pharmaceutically active compounds are common and increasing in the aquatic environment. Evidence suggests they have adverse effects on non-target organisms, and they are classified as emerging pollutants for a variety of aquatic organisms. To determine the effects of environmentally relevant levels of psychoactive compounds on non-target organisms, we analyzed cardiac and locomotory activity in early developmental stages of marbled crayfish Procambarus virginalis. Responses to sertraline, methamphetamine, and a mixture of citalopram, oxazepam, sertraline, tramadol, venlafaxine, and methamphetamine at a concentration of 1 µg L-1 of each compound were assessed. On day four of exposure, cardiac activity was recorded for 5 min, and on day eight, locomotory activity was recorded for 15 min. There was a significant increase (p < 0.01) in heart rate in methamphetamine-exposed and Mix-exposed juveniles compared to the unexposed control and there was significant difference (p < 0.01) in proportion of time (activity %) was observed with sertraline-exposed, whereas velocity, and distance moved did not significantly differ (p > 0.05) in exposed and control animals. These findings revealed that low concentrations of chemicals and their mixtures can modify the physiological state of aquatic animals without outward manifestations (activity, distance moved, and velocity). Aquatic animals can be impacted earlier than is visible, but effects can potentially lead to substantial changes in populations and in ecosystem processes. Additional research to investigate chemical combinations, exposure systems, and organism physiological and molecular responses may provide evidence of broad impact of environmental pharmaceuticals.

Distribution of Non-Indigenous Crayfish Species in Estonia and Their Impacts on Noble Crayfish (Astacus astacus L.) Populations

Invasive non-indigenous crayfish species (NICS) are a major threat to the existence of native crayfish populations in European freshwater ecosystems. The discovery of signal crayfish Pacifastacus leniusculus, marbled crayfish Procambarus virginalis, and spiny-cheek crayfish Faxonius limosus in Estonia has increased the risk of extinction of Estonia’s only native crayfish species, the noble crayfish Astacus astacus. The aim of this study was to give an overview of the status, distribution, and impacts of P. leniusculus, F. limosus, and Procambarus virginalis on A. astacus populations and assess the effect of trapping on NICS abundance. Annual monitoring of crayfish has been carried out since 2008 as part of A. astacus conservation and the NICS eradication plan. In this study, we present data from nine sampling locations monitored from 2010 to 2022. The spread of NICS continues to increase beyond their distribution areas, and in two sampling locations P. leniusculus and A. astacus live in sympatry. Our results suggest that trapping has a limited effect on population abundance, as NICS have already caused the extinction of two A. astacus populations. However, intensive trapping should continue simultaneously with sensitive molecular techniques to monitor the spread of NICS.

Comparative ultrastructure of the antennae and sensory hairs in six species of crayfish.

Antennae in crayfish are essential for gaining information about the local topography and localising food, chemicals, conspecifics or predator. There are still gaps in the research on the morphology of antennae in decapods compared to other arthropods. Biometrical and ultrastructural methods were applied using light and cryo-scanning electron microscopies to study the morphology of antennae in six different crayfish species, including marbled crayfish Procambarus virginalis, Mexican dwarf crayfish Cambarellus patzcuarensis, red swamp crayfish Procambarus clarkii, signal crayfish Pacifastacus leniusculus, common yabby Cherax destructor, and spiny-cheek crayfish Faxonius limosus to find their potential morphological differences. Significant differences in the antenna length, length and width of each segment to carapace length ratios, and the number of segments were found in the six crayfish species. The ultrastructure revealed differences in the distribution of sensory hairs on the antenna and the morphology of the antennal surface. The different morphology of antennae might reflect adaptation to the conditions of their specific habitats. In addition, results showed that a combination of differences in the morphological features and biometrical measurements of antennae could be used for the distinguishment of different studied crayfish species.

A voyage into the Levant: the first record of a marbled crayfish Procambarus virginalis (Lyko, 2017) population in Israel

A voyage into the Levant: the first record of a marbled crayfish Procambarus virginalis (Lyko, 2017) population in Israel

Hemocyte coagulation and phagocytic behavior in early stages of injury in crayfish (Arthropoda: Decapoda) affect their morphology

Crustacean hemocytes are important mediators of immune functions such as coagulation and phagocytosis. We employed an in situ approach to investigate the ultrastructural behavior of hemocytes during coagulation and phagocytosis in the early stages after injury caused by leg amputation, using transmission electron microscopy technique in marbled crayfish Procambarus virginalis. Hemocytes underwent drastic morphological changes during coagulation. The morphology of the cytoplasmic granules changed from electron-dense to electron-lucent forms in an expanding manner. The transformed granules containing amorphous electron-lucent material were observed to merge and discharge their contents into extracellular space for coagulation. We also observed that the contents of the nucleus participate in the process of coagulation. In addition, leg amputation induced extensive muscle degeneration and necrotic tissues were avidly taken up by the phagocytic hemocytes containing distinct phagosomes. Interestingly, we observed for the first time how the digested contents of phagocytized necrotic tissues are incorporated into granules and other cellular components that change the cell morphology by increasing the granularity of the hemocytes. Nevertheless, the degranulation of hemocytes during coagulation can also reduce their granularity. Given that morphological traits are important criteria for hemocyte classification, these morphological changes that occur during coagulation and phagocytosis must be taken into account.

Recurring infection by crayfish plague pathogen only marginally affects survival and growth of marbled crayfish

Invasive alien crayfish threaten the diversity of freshwater ecosystems and native crayfish fauna. In Europe, this is largely due to transmission of the crayfish plague to susceptible native crayfish. Many invasive species tolerate crayfish plague, but the infection still has the potential to reduce the fitness of a tolerant host due to energy trade-offs between immune response maintenance and life-history traits, such as growth and reproduction. In combination with other unfavourable conditions, such a response could alter further invasion success of an otherwise successful crayfish invader. We examined whether repeated infection with one of the most virulent haplogroups of crayfish plague agent (Aphanomyces astaci) affects growth or survival of the juvenile marbled crayfish (Procambarus virginalis). Juveniles were exposed to i) two levels of pathogen concentrations, and ii) two different feeding regimes under the higher pathogen concentration. In all performed trials, repeated infection reduced growth rates, while the combination of recurring infection and food limitation significantly increased mortality. The average energy cost of the immune response was estimated at 12.07 J/day for individuals weighing 0.3 grams. Since infections were frequent and pathogen concentrations high, results suggest that marbled crayfish is resistant to A. astaci pathogen and its survival is only affected by adding the stress of food limitation. The survival of almost half of the individuals exposed to high pathogen loads and extreme food limitation indicates that chronic infection by crayfish plague is unlikely to be an important factor impeding invasion success of the marbled crayfish, even under harsh conditions. Our results add to the growing body of evidence that marbled crayfish has potential to become one of the most successful freshwater invaders.

Marbled crayfish Procambarus virginalis invades a nature reserve: how to stop further introductions?

We hereby provide the first documented data on the occurrence of a viable Procambarus virginalis population in a nature reserve in Poland and the steps that were taken to prevent further introductions of the species in the country. To date, Poland represents the most north-eastward distribution area in Europe, where the species occurs in ecosystems with natural water temperature regimes. The ecological plasticity of P. virginalis and its obligate parthenogenetic reproduction make this crayfish an exceptional invader. The crayfish may have detrimental effects on the native invertebrates, amphibians, and fish, and alter the state of the entire ecosystem. Therefore, we investigated the presence of the species in the nature reserve of Pojezierze Łęczyńskie Landscape Park after a suspected P. virginalis individual was found by a local citizen. The nature reserve also includes an area designated to protect native amphibians and turtles. Our study revealed the presence of a thriving population of P. virginalis in the protected area and clear indications of its impact on native and invasive species, both in aquatic and terrestrial environments. If no action is taken, the species will likely expand to other water bodies across the country. An extensive sensibilization campaign allowed us to find additional invaded areas and significantly contribute to the effective ban of this and other invasive crayfish species from private and commercial online trade. Raising public awareness and banning invasive crayfish species trade is essential for successfully detecting and preventing further introductions.

Long-term changes in the prevalence of the crayfish plague pathogen and its genotyping in invasive crayfish species in Czechia

The widespread presence of North American alien crayfish in Europe is a major driver of native crayfish population declines, mainly because they are chronic carriers of the oomycete Aphanomyces astaci responsible for crayfish plague. Screening for the crayfish plague pathogen in host populations has become a common practice across Europe, but sampling usually covers spatial but not temporal variation. Our study focuses on the current situation in Czechia, where screening for A. astaci was first conducted in the mid-2000s. We provide data about the distribution and prevalence of this pathogen at almost 50 sites with three host crayfish: the spiny-cheek crayfish Faxonius limosus, signal crayfish Pacifastacus leniusculus, and marbled crayfish Procambarus virginalis. Among these sites were 20 localities that were resampled several years (usually more than a decade) after the original screening for A. astaci. We did not detect any A. astaci infection in two studied P. virginalis populations but documented several new hotspots of highly infected P. leniusculus in Czechia, and the first site with the coexistence of the latter with F. limosus. Our data suggest that despite some fluctuations, A. astaci prevalence in North American host populations generally does not tend to change significantly over time; we only observed two cases of a significant increase and one of a significant decrease. We no longer detected A. astaci in several originally weakly infected populations, but our data suggest it likely still persists in these areas and threatens native crayfish populations. At the single known site in the country where P. leniusculus and F. limosus coexist, we documented the presence of the same A. astaci genotype group in both crayfish species, likely due to interspecific transmission of the pathogen from the former host to the latter. However, genotyping of A. astaci in infected host individuals still supported the link between specific pathogen genotypes and crayfish hosts, suggesting that assessment of sources of mass mortalities from the pathogen genotyping is feasible in European regions where the mutual contact of different American crayfish species is uncommon.

Chronic Toxicity of Primary Metabolites of Chloroacetamide and Glyphosate to Early Life Stages of Marbled Crayfish Procambarus virginalis

Simple SummaryDue to the rising population, it is necessary to ensure sustainable agricultural management, especially in agricultural production. Therefore, using pesticides is the only way to reach a sufficient number of crops for the human population. However, using these agrochemicals has one big disadvantage—harmful effects on non-target species. Since aquatic ecosystems are essential for biota, fauna, flora, and humans, this study provides information about the toxicity of primary metabolites of commonly used glyphosate and acetochlor herbicides. Generally, it is known that pesticide degradation products may have lower, the same, or even higher toxicity than their parental compounds. Moreover, the developmental stages are more predisposed to be affected by pollution than adults, and consequently, in the worst case, it may affect the whole species population. Due to this reason, we studied the toxicity of these metabolites on embryolarval marbled crayfish—how they can affect their growth, ontogenetic development, behaviour, and gill morphology. Our study revealed that these two metabolites alone induce changes in behaviour, antioxidant enzymes, and gill morphology, even in combination. Nevertheless, there is a gap in the knowledge about pesticides’ metabolite toxicities, a small fraction of the hundreds with potential for entering the aquatic ecosystem. Therefore, chronic toxicity tests are suitable for evaluating the toxicity of aquatic pollution.Degradation products of herbicides, alone and in combination, may affect non-target aquatic organisms via leaching or runoff from the soil. The effects of 50-day exposure of primary metabolites of chloroacetamide herbicide, acetochlor ESA (AE; 4 µg/L), and glyphosate, aminomethylphosphonic acid (AMPA; 4 µg/L), and their combination (AMPA + AE; 4 + 4 µg/L) on mortality, growth, oxidative stress, antioxidant response, behaviour, and gill histology of early life stages of marbled crayfish (Procambarus virginalis) were investigated. While no treatment effects were observed on cumulative mortality or early ontogeny, growth was significantly lower in all exposed groups compared with the control group. Significant superoxide dismutase activity was observed in exposure groups, and significantly higher glutathione S-transferase activity only in the AMPA + AE group. The gill epithelium in AMPA + AE-exposed crayfish showed swelling as well as numerous unidentified fragments in interlamellar space. Velocity and distance moved in crayfish exposed to metabolites did not differ from controls, but increased activity was observed in the AMPA and AE groups. The study reveals the potential risks of glyphosate and acetochlor herbicide usage through their primary metabolites in the early life stages of marbled crayfish.

Chemical synthesis and functional evaluation of the crayfish insulin-like androgenic gland factor

Insulin-like androgenic gland factor (IAG) from the marbled crayfish Procambarus virginalis is an insulin-like heterodimeric peptide composed of A and B chains and has an Asn-linked glycan at the B chain. IAG is considered to be a male sex hormone inducing the sex differentiation to male in decapod crustacean, although there is no report on the function of IAG peptide in vivo. In order to characterize P. virginalis IAG, we chemically synthesized it and evaluated its biological function in vivo. A and B chains were prepared by the ordinary solid-phase peptide synthesis, and three disulfide bonds were formed regioselectively by dimethyl sulfoxide oxidation, pyridylsulfenyl-directed thiolysis and iodine oxidation reactions. An IAG disulfide isomer was also prepared by the same manner. Circular dichroism spectral analysis revealed that the disulfide bond arrangement affected the peptide conformation, which was similar to the other insulin-family peptides analyzed so far. On the other hand, the glycan moiety attached at the B chain had no effect on the peptide secondary structure. Injection of the synthetic IAG and its disulfide isomer to female crayfish did not induce male characteristics on the external morphology, but both peptides suppressed the oocyte maturation in vivo. These results suggest that IAG has a pivotal role on the suppression of female secondary sex characteristics.

Effect of Psychoactive Substances on Cardiac and Locomotory Activity of Juvenile Marbled Crayfish Procambarus Virginalis

Effect of Psychoactive Substances on Cardiac and Locomotory Activity of Juvenile Marbled Crayfish Procambarus Virginalis

Phylogeographic reconstruction of the marbled crayfish origin

The marbled crayfish (Procambarus virginalis) is a triploid and parthenogenetic freshwater crayfish species that has colonized diverse habitats around the world. Previous studies suggested that the clonal marbled crayfish population descended as recently as 25 years ago from a single specimen of P. fallax, the sexually reproducing parent species. However, the genetic, phylogeographic, and mechanistic origins of the species have remained enigmatic. We have now constructed a new genome assembly for P. virginalis to support a detailed phylogeographic analysis of the diploid parent species, Procambarus fallax. Our results strongly suggest that both parental haplotypes of P. virginalis were inherited from the Everglades subpopulation of P. fallax. Comprehensive whole-genome sequencing also detected triploid specimens in the same subpopulation, which either represent evolutionarily important intermediate genotypes or independent parthenogenetic lineages arising among the sexual parent population. Our findings thus clarify the geographic origin of the marbled crayfish and identify potential mechanisms of parthenogenetic speciation.