Pontastacus Leptodactylus Research Articles

Dietary supplementation of Chlorella vulgaris improved growth performance, immunity, intestinal microbiota and stress resistance of juvenile narrow clawed crayfish, Pontastacus leptodactylus Eschscholtz, 1823

A 63- day feeding trial was conducted to study the effect of fishmeal substitution levels with Chlorella vulgaris meal (25, 50, 75 and 100%) on the growth performance, nutrient digestibility, immune responses and the stress resistance of juvenile narrow clawed crayfish, Pontastacus leptodactylus (6.19 ± 0.13 g). The highest values of final weight (25.52 g), specific growth rate (2.24% body weight day−1), protein efficiency ratio (3.24), the protein productive value (54.67%), in vivo ADCOM (88.40%) and in vivo ADCCP (93.50%) and the lowest feed conversion ratio (1.49) were observed in the juvenile crayfish fed the diet containing 75% fishmeal substituted level with chlorella meal (p < 0.05). With an increment in the dietary inclusion level of chlorella meal, the activities of alkaline protease (r2 = 0.97), lipase (r2 = 0.98), amylase (r2 = 0.97), phenoloxidase (r2 = 0.98), superoxide dismutase (r2 = 0.99), lysozyme (r2 = 0.96) and nitric oxide synthase (r2 = 0.98) were promoted as a third-order polynomial regression model (p < 0.05). There was an increasing trend in Lactobacillus count (r2 = 0.99) and a decreasing trend in Escherichia coli count (r2 = 0.97) with an increase in the fishmeal substitution level with chlorella meal. Based on the broken line regression model, the dietary fishmeal substitution level (%) with chlorella meal for maximum growth (SGR) and weight gain values and minimum FCR value of crayfish were estimated to be 85.49%, 78.14% and 78.13%, respectively.

New codend designs to improve the size selectivity of fyke net for narrow-clawed crayfish (Pontastacus leptodactylus)

The narrow-clawed crayfish (Pontastacus leptodactylus) is one of the most ecologically and economically important freshwater species in Turkey. However, the harvest of this species has declined from 7937 t in 1984 to 696 t in 2019. One of primary reasons for this decrease in stock is the use of fishing gears with poor size selectivity. In this study, new codend designs were investigated to improve the size selectivity of fyke nets forP. leptodactylus. Seven codends of three different designs were tested: (1) a commercially used standard codend with 34 mm mesh size (Com34); (2) sorting grids with 20 (SG20), 25 (SG25) and 30 mm (SG30) bar spacing attached to the last circle of the net; and (3) a stiff rigged net, the last part of the fyke nets (codend) with 34 (SRN34), 42 (SRN42) and 50 mm (SRN50) mesh size. The average length at 50% retention probability (L50) and selection range (SR) (L75–L25) values ofCom34were 9.4 cm and 3.1 cm, respectively. For theSG20,SG25andSG30grids, theL50values were 11.3 cm, 11.6 cm and 12.0 cm, while theSRvalues were 1.4 cm, 1.3 cm and 0.6 cm, respectively. For theSRN34,SRN42andSRN50codends, theL50values were 10.9 cm, 11.6 cm and 11.6 cm, while theSRvalues were 2.1 cm, 2.1cm and 1.1 cm, respectively. Overall, the commercial codend resulted in lowerL50values when the minimum conservation reference length of 10 cm was considered. However, all tested new codend designs showed improved selectivity compared with the standard, with optimum results obtained withSG20.SG20grid decreased discarding by 15.7% compared to the classic commercial fyke net; thus, this is a very important result for the sustainability of naturalP. leptodactylusstocks.

Effects of methyl farnesoate injection on spermatozoa number and reproductive indices in the narrow-clawed crayfish Pontastacus leptodactylus

In this study, the effect of methyl farnesoate (MF) injection on haemolymph MF levels, spermatozoa production and the reproductive indices of gonadosomatic index (GSI), testicular index (TI) and vasosomatic index (VSI) were investigated in males of Pontastacus leptodactylus (Escholtz, 1823). Sixty male P. leptodactylus were used for the study. They were housed in a total of twelve tanks in their normal reproductive season in 2018 and were fed ad libitum with a pelleted food. Animals were injected once a week for five consecutive weeks, at doses of 250 (G2), 500 (G3) and 1000 (G4) ng MF g-1 of body weight. The doses of the injections, the durations used, and the frequency of administration were determined according to the literature. An increase was observed in gonadosomatic index and spermatozoal number of crayfish injected with 1000 ng of MF g-1 of body weight when compared to control (G1, no MF injection applied) and other experimental groups. In addition, the present study indicated that G4 crayfish had a higher GSI, TI and VSI than control crayfish. There was no difference in the level of hemolymph MF between control and MF injected crayfish. In conclusion, MF injection is effective for inducing increased gonadasomatic index and spermatozoal number in P. leptodactylus.

Effect of feed supplementation with effective microorganisms (em) bokashi onhepatopancreas and gut histology, growth performance, and survival rate of freshwatercrayfish Pontastacus leptodactylus (Eschscholtz, 1823)

A sixty-day feeding trial was conducted to investigate the effect of dietary effective microorganisms (EM) Bokashi on organ histology, growth performance, and survival rate of freshwater crayfish Pontastacus leptodactylus (Eschscholtz, 1823). Bokashi serum and powder consisted of two major microorganisms as Bacillus amyloliquefaciens spp. plantarum and Lactobacillus plantarum. Four treatment groups were established in control (without bokashi), bokashi powder 1% and 5% supplemented to diets. Bokashi serum was added at a ratio of 0.01% (v/v) of the total volume of the tank water once a week into which there was a constant flow of fresh water at a flow rate of 1.2 L min$^{-1}$. The crayfish were fed ad libitum with treatment diets for 60 days. The results showed that there was no significant difference in growth performance among the groups, but survival rates were significantly different between groups (p < 0.05). As a result of the microscopic examination of the intestine, pathological changes such as inflammatory cell infiltrations in the interstitial tissue, and lack of B, F, and R epithelial cells were found in the groups that were supplemented with bokashi while the control group exhibited normal tissue histology. As a result of this study, the addition of nonindustrial bokashi to crayfish diets had no effect on growth. In addition, nonindustrial bokashi products supplementation to crayfish diets caused severe pathological findings in hepatopancreas and

English

Abstract The invasive spiny-cheek crayfish (Faxonius limosus) has been able to colonize many European waterbodies since its first introduction into Europe, threatening the indigenous crayfish fauna. The remarkable reproductive plasticity of this species has been suggested as an important factor contributing to the alarming invasiveness of this species. In this study, we compared the reproductive strategies of an invasive (F. limosus) and a sympatric indigenous crayfish (Pontastacus leptodactylus). We questioned if the reproductive abilities, namely parthenogenesis and multiple paternity, may contribute to an ongoing invasion process in the Lower Danube. Using microsatellites, we genotyped the mothers and their offspring from 11 clutches of F. limosus and 18 clutches of P. leptodactylus. While no parthenogenesis has been found in F. limosus populations, multiple paternity has been detected for the first time in both species, with comparable incidence. The results of the study indicate that multiple paternity does not play a dominant role in the successful colonization of F. limosus in the Danube. However, the presented results have to be regarded as a pilot study, with a limited number of samples and loci investigated. Given the relevance of mating system knowledge for management measures, future studies with larger sample number could provide valuable contributions to ongoing conservation actions.

English

AbstractWe examined gills (podobranchs, arthrobranchs and pleurobranchs) from five European Astacidae (Austropotamobius pallipes, Austropotamobius torrentium, Astacus astacus, Pontastacus leptodactylus and Pontastacus pachypus) to assess the relationships between their phylogeny and gill morphology and formulae. In addition, we checked for the presence or absence of pleurocoxal lappets. The morphology of the gills and associated structures was similar in all examined European astacid species except for three rudimentary pleurobranchs found in P. pachypus. In European Astacidae and Cambaroididae, the pleurocoxal lappets are absent but are present in the American Astacidae, Cambaridae and Parastacidae. The number of pleurobranchs decreases from the most primitive Parastacidae to the most advanced Cambaridae. Nevertheless, although the most primitive parastacid crayfish and the most advanced Cambaridae all have pleurocoxal lappets, they are absent in European Astacidae and Cambaroididae, which suggests that a reversible gill morphology has occurred in crayfish evolution.

Disturbance in invasion? Idiopathic necrotizing hepatopancreatitis in the signal crayfish Pacifastacus leniusculus (Dana, 1852) in Croatia.

As the most successful crayfish invader and possible vector for infectious agents, signal crayfish Pacifastacus leniusculus is among the major drivers of the native crayfish species decline in Europe. We describe histopathological manifestation and frequency of newly detected idiopathic necrotizing hepatopancreatitis along the invasion range of the signal crayfish in the Korana River in Croatia. Our results show extremely high prevalence of necrotizing hepatopancreatitis (97.3%), with 58.9% of individuals displaying mild and 31.5% moderate histopathological changes in the hepatopancreas, also reflected in the lower hepatosomatic index of analysed animals. Recorded histopathological changes were more frequent in the invasion core where population density is higher. Our preliminary screening of co-occurring native narrow-clawed crayfish Pontastacus leptodactylus showed lower incidence (33.3%) and only mild hepatopancreatic lesions, but potentially highlighted the susceptibility of native crayfish populations to this disease. Pilot analyses of dissolved trace and macro elements in water, sediment fractions and crayfish hepatopancreas do not highlight alarming or unusually high concentrations of analysed elements. Hepatopancreas microbiome analysis, using 16S rRNA gene amplicon sequencing, identified taxonomic groups that should be further investigated, along with impacts of the disease on health and viability of both invasive and native crayfish populations.

Effects of serotonin (5‐HT) on juvenile culture of narrow‐clawed crayfish Pontastacus leptodactylus (Eschscholtz, 1823)

Serotonin was used for the first time in this study as a feed additive in juvenile freshwater crayfish Pontastacus leptodactylus, (stage II-V) to investigate its effects on growth performance, survival and immune response based on total haemocyte count (THC). Serotonin was included in diets at levels of 0 (control), 5, 10, 20 and 40 mg kg−1. When the results were examined, a significant quadratic increase was observed in the values of final total length: FTL and final body weight: FBW, weight gain (WG), length gain (LG) and specific growth rate (SGR) with dietary serotonin amounts (Plinear and Pquadratic <0.05). The survival rates of crayfish showed a significant linear increase with doses of serotonin (Plinear = 0.001). THC values, on the other hand, were not affected by serotonin amounts in experimental diets. The broken line models estimated optimum dietary serotonin inclusions based on FBW and FTL as 20.03 and 20.44 mg kg−1, respectively. In conclusion, dietary serotonin can be used in growing juvenile P. leptodactylus during the developmental stages of II-V.

Role of river crayfish Pontastacus leptodactylus (Esch.) in maintaining the stability of freshwater bodies in Eurasia

The role of the long-toed crayfish (Pontastacus leptodactylus leptodactylus) in the hydrocenosis of a water body in the floodplain of the Rutka River, one of the tributaries of the Middle Volga, was studied in order to determine an ecologically grounded catch rate. During the study period, the population of P. l. leptodactylus had a high productivity and occupied the dominant status in the biocenosis among the components of animal origin. The amount of plant biomass consumption in summer by juveniles and sexually mature crayfish was calculated. Zoobenthos is consumed in relatively small quantities by all age groups of the crayfish population; zooplankton – by underyearlings. The consumption of aquatic vegetation by crayfish determines the importance of their role in restraining its growth and in limiting the eutrophication of the water body. The biomass of the P. l. leptodactylus population was calculated. It must always be present in the water body to maintain the stability of its biocenosis, which is possible if the annual catch of crayfish is limited to 10-15% of their commercial stock.

Effect of Melatonin on Development, Survival Rate and Immune Response in the Juveniles of Freshwater Crayfish (Pontastacus leptodactylus Eschscholtz, 1823)

Bu çalışmanın amacı melatoninin, Pontastacus leptodactylus yavrularının (II-IV. dönem) gelişim, hayatta kalma oranı ve bağışıklık yanıtı (total hemosit sayısı) üzerindeki etkilerini araştırmaktır. Melatonin dozları 0, 0,5, 1, 2, 4 mg / kg oranında deneme yemine ilave edilerek 4 tekerrürlü 5 ayrı grup şeklinde deneme grupları oluşturulmuştur. Denemeler, II. Dönem P. leptodactylus yavruları ile kurulmuş ve 60 gün süre ile besleme yapılmıştır. Deneme süresince günde bir kez %50 oranında su değişimi ve sürekli bir havalandırma sağlanmıştır. Stok yoğunluğu her deneme tekerrürü için 20 yavru olarak belirlenmiştir. Yavrular, günde bir kez canlı ağırlıklarının %5’i oranında beslenmiştir. Yavruların başlangıç ortalama ağırlık ve total boyları 34 ± 4 mg ve 11,6 ± 0,4 mm olarak belirlenmiştir. Deneme sonunda en yüksek ortalama total boy 22,0 ± 3,6 mm olarak 2 mg/kg melatonin içeren grupta, en iyi ortalama canlı ağırlık 216 ± 116 mg olarak 4 mg/kg melatonin grubunda, en iyi yaşama oranı %44,4 ± 13,9 olarak 2 mg / kg melatonin doz grubunda ve en yüksek ortalama total hemosit miktarı ise 2,27 ± 0,49 x 106 hücre/ml olarak yine 2 mg/kg melatonin doz grubunda elde edilmiştir. Bununla birlikte gruplar arasındaki farklar istatistiki açıdan önemli bulunmamıştır (p &amp;gt; 0,05). Sonuç olarak, bu çalışmada P. leptodactylus yavrularının gelişim, hayatta kalma oranı ve bağışıklık yanıtı üzerinde melatonin katkılı yemler ile beslemenin önemli bir etkisinin olmadığı belirlenmiştir.

Soil-Related Predictors for Distribution Modelling of Four European Crayfish Species

One of the most critical challenges in species distribution modelling is testing and validating various digitally derived environmental predictors (e.g., remote-sensing variables, topographic variables) by field data. Therefore, here we aimed to explore the value of soil properties in the spatial distribution of four European indigenous crayfish species. A database with 473 presence and absence locations in Romania for Austropotamobius bihariensis, A. torrentium, Astacus astacus and Pontastacus leptodactylus was used in relation to eight digitalised soil properties. Using random forest modelling, we found a preference for dense soils with lower coarse fragments content together with deeper sediment cover and higher clay values for A. astacus and P. leptodactylus. These descriptors trigger the need for cohesive soil river banks as the microenvironment for building their burrows. Conversely, species that can use banks with higher coarse fragments content, the highland species A. bihariensis and A. torrentium, prefer soils with slightly thinner sediment cover and lower density while not influenced by clay/sand content. Of all species, A. astacus was found related with higher erosive soils. The value of these soil-related digital descriptors may reside in the improvement of approaches in crayfish species distribution modelling to gain adequate conservation measures.

English

Abstract Eroded swimmeret syndrome (ESS) was first described in 2014 from Swedish signal crayfish (Pacifastacus leniusculus (Dana)), and later also from Finland, with gross symptoms and disease agent candidates identified and described by 2015. The ESS was first discovered affecting alien signal crayfish in Fennoscandia. The ESS is caused by a multiple infection involving Aphanomyces astaci (Schikora) and Fusarium species complex (SC). The ESS symptoms include first melanised spots in swimmerets, then partial swimmeret erosion and finally loss of a swimmeret. There could be a total loss of all swimmerets in the most severe cases. Both females and males can be affected by the ESS. In females, the ESS lowers reproductive success while in males the ESS often causes erosion of the gonopods and thus possible partial failure in mating. The ESS is more frequent among mature females that have reproduced once compared to immature females or those that are mature but have not yet reproduced. The proportion of females with ESS has ranged from 10 to 50% among Lake Saimaa signal crayfish in Finland and in a wider survey from Sweden the range was from 0 to 38%. Among Lake Saimaa male signal crayfish, the ESS proportion has been less than 10%, while it was only 0.6% in the Swedish data. The ESS has also been observed among alien signal crayfish in Switzerland. There are recent observations of ESS affecting narrow-clawed crayfish, Pontastacus leptodactylus (Eschscholtz), in Croatia and Romania (i.e., among native European crayfish stocks). Here, we summarise current knowledge about the ESS and speculate on a few potentially crucial impacts of this syndrome.

Evaluation of mealworms (Tenebrio molitor) meal as an alternative protein source for narrow‐clawed crayfish (Pontastacus leptodactylus) juveniles

An eighty-day feeding study was performed to investigate the effects of mealworm meal (Tenebrio molitor) on the growth, survival and moulting frequency of juvenile Narrow-clawed crayfish (Pontastacus leptodactylus). Three dietary treatment groups with triplicate were fed with a fish meal-based without MW (control diet: MW0), two diets with 50% (MW50) and 100% (Mw100) of fish meal substitution with MW respectively. P. leptodactylus juveniles (11.0 ± 0.05 mm, mean ±SE and 0.011 ± 0.002 g, mean ±SE) were randomly stocked into nine flow-through tanks with a density of 30 crayfish per tank and reared for 80 days. Crayfish fed with MW50 mealworm meal showed positive effects on weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER), apparent net protein utilization (ANPU), moulting frequency (MF) and feed conservation ratio (FCR), but lower survival rate (SR) as compared to the other diet groups. Protein and lipid contents of the whole body of the crayfish fed with replacement diet (MW50) were found to be higher than those of the other two diet groups (p<0.05). However, the MW100 diet slightly increased the moisture and ash contents of the crayfish. Our observation indicated that the addition of a 50% mealworm meal in the diet of P. leptodactylus juveniles improved the growth performance of the crayfish without causing any adverse effects. Therefore, T. molitor meal can be considered as an alternative animal source of protein for the narrow-clawed crayfish juveniles.

Düğümlü ağdan donanmış geleneksel kerevit pinteri ile alternatif olarak düğümsüz ağdan donanmış pinterlerin CPUE karşılaştırması

In this study, it is aimed to compare the yield and strength of the crayfish fyke rigged with knotless net with 210d/12 rope thickness with those of the traditional net material rigged with 210d/6 knotted net which is widely used in Turkey in fishing crayfish (Pontastacus leptodactylus, Eschscholtz, 1823). The study was carried out on a monthly basis between June 2017 and May 2018. In the study, a total of 300 fyke nets, equipped with 150 classical and 150 alternative nets, were used. The caught crayfishes were measured and weighted according to the fyke net they were caught in. A total of 3509 crayfish were caught, 1465 of which were caught with alternative fyke net and 2044 with traditional fyke net. Average CPUE value ranged from 10.93 (g/fyke net/day) to 281.14 (g/fyke net/day) for per fishing operation. Average CPUE value of the traditional gear was found to be 98.34 (g/fyke net/day) , while that of the alternative gear was determined as 79.46 (g/fyke net/day), and no statistically significant difference was found between average CPUE values (p&gt;0.05). Average strength value of the traditional fyke net was determined as (± SE) 10.43 ± 0.27 kg, while that value in 210d / 12 knotless net was identified as 14.50 ± 0.91 kg (p&lt;0.05). Although it has high strength, since the CPUE value of the alternative fyke net is lower by 19.20% compared to the traditional gear, it is believed that its use in crayfish fishing will not be profitable.

Molecular identification of burn spot disease syndrome agent Fusarium avenaceum in Turkish crayfish Pontastacus leptodactylus populations.

In this study, we aimed to isolate and identify the causative agent of burn spot disease syndrome from crayfish populations within Turkish water bodies. Crayfish Pontastacus leptodactylus samples were captured from Bayramşah Reservoir, Karaidemir Reservoir and Keban Reservoir (Turkey). Fungi samples were taken from symptomatic crayfish and cultured in potato dextrose agar, and DNAs were extracted. Species-specific PCR primers (FAF1 and FAR) were used in order to amplify the internal transcribed spacer (ITS) region of fungal DNA. Sequences obtained from the amplified regions were analyzed using GenBank and identified. As a result, a molecular diagnosis of the fungi samples was made, and the pathogen was identified as Fusarium avenaceum. In addition, a challenge test with healthy crayfish was conducted to evaluate the pathogenicity of the fungi. F. avenaceum was reisolated from experimentally infested individuals, and thusly we confirmed the disease. It was concluded that F. avenaceum causes burn spot disease syndrome in P. leptodactylus.

Detection of fish pathogen Saprolegnia parasitica in environmental DNA samples by droplet digital PCR

Oomycetes are fungal-like microorganisms parasitic towards a large number of plant and animal species. Genera from order Saprolegniales, such as Saprolegnia and Aphanomyces, cause devastating infections of freshwater animals. Saprolegnia parasitica is a widely distributed oomycete pathogen that causes saprolegniosis, a disease responsible for significant economic losses in aquaculture, as well as declines of natural populations of fish and other freshwater organisms. Despite its negative impact, no monitoring protocol for S. parasitica has been established to date. Thus, we aimed to develop a droplet digital PCR (ddPCR) assay for the detection and quantification of S. parasitica in environmental DNA samples. Saprolegnia parasitica-specific primers were designed to target internal transcribed spacer region 2 (ITS 2), based on the alignment of ITS sequences of S. parasitica and a range of Saprolegnia spp., as well as other oomycetes. The specificity of primers was tested using genomic DNA of S. parasitica (as positive control) and DNA of non–S. parasitica oomycete isolates, as well as trout/crayfish DNA (as negative control). The primers specifically amplified a segment of the ITS region of oomycete pathogen S. parasitica, while no amplification (i.e. no positive droplets) was obtained for closely related Saprolegnia spp. (e.g. Saprolegnia sp. 1 and S. ferax) and other more distantly related oomycetes. Next, the limit of detection (LOD) of the assay was established by using serial dilutions of the S. parasitica genomic DNA. The determined sensitivity of the assay was high: LOD was 15 fg of pathogen’s genomic DNA per µL of the reaction mixture. Assay performance was further assessed with environmental DNA samples isolated from water from the trout farms and natural environments, as well as (ii) biofilm from the host surface (swab samples). Water samples were collected from 21 different locations in Croatia, while swab samples were collected from S. parasitica host/carrier species: (i) skin and eggs of the rainbow trout (Oncorhynchus mykiss Walbaum, 1792) and brown trout (Salmo trutta Linnaeus, 1758), and (ii) cuticle of signal crayfish (Pacifastacus leniusculus Dana, 1852) and narrow clawed crayfish (Pontastacus leptodactylus Eschscholtz, 1823). Samples were classified into agent levels A0 to A6, depending of the number of S. parasitica ITS copies per ng of total DNA. Saprolegnia parasitica was detected in 76 % of water samples (16/21) and the range of pathogen’s ITS copies in positive samples was between 0.02 and 14 copies/ng of total DNA (agent levels A1 to A3). Regarding the swab samples, S. parasitica load was significantly higher in diseased trout than in those with healthy appearance: 9375 vs 3.28 S. parasitica copies/ng of total swab DNA (average agent level A6 vs. A2, respectively). Despite the fact that none of the sampled crayfish had signs of infection, the pathogen was detected in all tested cuticle swabs. Swabs of P. leniusculus, a known S. parasitica host, had significantly higher S. parasitica load than swabs of P. leptodactylus, S. parasitica carrier: 390 vs 83 S. parasitica copies/ng (agent level A5 vs. A4, respectively). In conclusion, our results demonstrate the applicability of the newly developed ddPCR assay in monitoring and early detection of S. parasitica in aquaculture facilities and natural freshwater environments. This would help in a better understanding of S. parasitica ecology and its effects on the host populations.

Force and Boldness: Cumulative Assets of a Successful Crayfish Invader

Multiple causes can determine the disturbance of natural equilibrium in a population of a species, with a common one being the presence of invasive competitors. Invasives can drive native species to the resettlement of the trophic position, changing reproduction strategies or even daily normal behaviours. Here, we investigated the hypothesis that more effective anatomical features of an intruder (Faxonius limosus) come with increased boldness behaviour, contributing to their invasion success in competition against the native species (Pontastacus leptodactylus). We tested the boldness of specimens representing the two species by video-based assessment of crayfish individuals’ attempts to leave their settlement microenvironment. The experiment was followed by a series of measurements concerning chelae biometry, force and muscle energetics. The native species was less expressive in terms of boldness even if it had larger chelae and better muscular tissue performance. In contrast, because of better biomechanical construction of the chelae, the invasive species was capable of twice superior force achievements, which expectedly explained its bolder behaviour. These findings suggest that, in interspecific agonistic interactions, the behaviour strategy of the invasive crayfish species is based on sheer physical superiority, whereas the native crayfish relies on intimidation display.

Blue Color Anomaly in Turkish Crayfish Pontastacus leptodactylus (Eschscholtz, 1823) (Crustacea, Decapoda, Astacidae) From Atikhisar Reservoir in Çanakkale, Turkey

Two individuals of Pontastacus leptodactylus (Eschscholtz, 1823) were collected from Atikhisar Reservoir in Çanakkale, Turkey. The individuals were caught by using a fyke-net. The fyke-nets were collected after 3-days soaking time from the reservoir on 18 July 2020. The sampling was carried out during the daytime. The sediment of the sampling location had a muddy substrate. Both blue colored individuals of crayfish (Pontastacus leptodactylus) were female. Blue color anomaly was observed in all parts of the bodies of both individuals. Morphometric characteristics were measured and the total lengths were 104.83 mm and 76.92 mm, and weights were 36.09 g and 11.76 g, respectively. The genetics of the mutant species should be examined in future studies to better understanding of the main factors causing color anomalies.

The Pontastacus leptodactylus (Astacidae) Repeatome Provides Insight Into Genome Evolution and Reveals Remarkable Diversity of Satellite DNA.

Pontastacus leptodactylus is a native European crayfish species found in both freshwater and brackish environments. It has commercial importance for fisheries and aquaculture industries. Up till now, most studies concerning P. leptodactylus have focused onto gaining knowledge about its phylogeny and population genetics. However, little is known about the chromosomal evolution and genome organization of this species. Therefore, we performed clustering analysis of a low coverage genomic dataset to identify and characterize repetitive DNA in the P. leptodactylus genome. In addition, the karyogram of P. leptodactylus (2n = 180) is presented here for the first time consisting of 75 metacentric, 14 submetacentric, and a submetacentric/metacentric heteromorphic chromosome pair. We determined the genome size to be at ~18.7 gigabase pairs. Repetitive DNA represents about 54.85% of the genome. Satellite DNA repeats are the most abundant type of repetitive DNA, making up to ~28% of the total amount of repetitive elements, followed by the Ty3/Gypsy retroelements (~15%). Our study established a surprisingly high diversity of satellite repeats in P. leptodactylus. The genome of P. leptodactylus is by far the most satellite-rich genome discovered to date with 258 satellite families described. Of the five mapped satellite DNA families on chromosomes, PlSAT3-411 co-localizes with the AT-rich DAPI positive probable (peri)centromeric heterochromatin on all chromosomes, while PlSAT14-79 co-localizes with the AT-rich DAPI positive (peri)centromeric heterochromatin on one chromosome and is also located subterminally and intercalary on some chromosomes. PlSAT1-21 is located intercalary in the vicinity of the (peri)centromeric heterochromatin on some chromosomes, while PlSAT6-70 and PlSAT7-134 are located intercalary on some P. leptodactylus chromosomes. The FISH results reveal amplification of interstitial telomeric repeats (ITRs) in P. leptodactylus. The prevalence of repetitive elements, especially the satellite DNA repeats, may have provided a driving force for the evolution of the P. leptodactylus genome.

Only one can remain? Environmental and spatial factors influencing habitat partitioning among invasive and native crayfishes in the Pannonian Ecoregion (Hungary)

Biological invasions have increasingly threatened indigenous species, influence metacommunity organisation and consequently, global biodiversity. World-wide expansion of non-indigenous crayfish (NICS) is associated with dramatic changes in species poor indigenous crayfish (ICS) assemblages challenging conservation planning. We analysed long-term changes of crayfish occurrences from the pre-invasion state, through the first appearance of NICS, to their intensive spread in Hungarian waters. Further, we analysed present-day crayfish metacommunity patterns for co-occurrences and influence of spatial and environmental factors. Historic data revealed a marked pre-invasion decline in indigenous noble crayfish Astacus astacus and stone crayfish Austropotamobius torrentium populations, but not in the narrow-clawed crayfish Pontastacus leptodactylus. Historic data provided no direct evidence for the impact of NICS on ICS, rather it supported that NICS often entered areas where ICS had been extinct or were not present at all. Crayfish species extremely rarely co-occurred which could indicate their strong competition and be related to utilization of empty sites by NICS. Crayfish metacommunities were predominantly spatially structured indicating the primary influence of ongoing invasion. Crayfish species also exhibited different environmental preferences mainly along the altitude and temperature gradients. We conclude that the invasion is still in the expanding phase and without an effective conservational program the future of ICS is doubtful in Hungary. Conservation policy should focus on the preservation and reintroduction of the stone and noble crayfishes in highland refugees. Expansion of NICS should be prevented in refugee areas by utilizing possibilities provided by natural and artificial barriers, and education and strict ban should be simultaneously applied to prevent further illegal releases by aquarists.