Female Crayfish Research Articles

Modeling and predicting meat yield and growth performance using morphological features of narrow-clawed crayfish with machine learning techniques

In recent studies, artificial intelligence and machine learning methods give higher accuracy than other prediction methods in large data sets with complex structures. Instead of statistical methods, artificial intelligence, and machine learning are used due to the difficulty of constructing mathematical models in multi-parameter and multivariate problems. In this study, predictions of length–weight relationships and meat productivity were generated by machine learning models using measurement data of male and female crayfish in the narrow-clawed crayfish population living in Apolyont Lake. The data set was created using the growth performance and morphometric characters from 1416 crayfish in different years to determine the length–weight relationship and length-meat yield. Statistical methods, artificial intelligence, and machine learning are used due to the difficulty of constructing mathematical models in multi-parameter and multivariate problems. The analysis results show that most models designed as an alternative to traditional estimation methods in future planning studies in sustainable fisheries, aquaculture, and natural sources management are valid for machine learning and artificial intelligence. Seven different machine learning algorithms were applied to the data set and the length–weight relationships and length-meat yields were evaluated for both male and female individuals. Support vector regression (SVR) has achieved the best prediction performance accuracy with 0.996 and 0.992 values for the length–weight of males and females, with 0.996 and 0.995 values for the length-meat yield of males and females. The results showed that the SVR outperforms the others for all scenarios regarding the accuracy, sensitivity, and specificity metrics.

Dietary Threonine Promoted the Growth and Ovarian Development of the Red Swamp Crayfish (Procambarus clarkii).

To explore the effects of dietary threonine on growth and ovarian development of red swamp crayfish (Procambarus clarkii), crayfish (5.48 ± 0.19 g) were fed six isoproteic and isoenergetic diets with varying levels of threonine (7.16 g/kg (control), 9.19, 12.74, 16.44, 20.83, and 23.78 g/kg) for 8 weeks. The results showed that weight gain rate, feed conversion ratio, protein efficiency rate, protein deposition rate, and essential amino acid deposition rates obtained the optimal values when the dietary threonine level was 12.74 or 16.44 g/kg. Compared to the control group, the 12.74 g/kg group exhibited enhanced nonspecific immunity and antioxidant properties. The 16.44 g/kg group demonstrated a significant increase in the frequency of B cells and R cells in the hepatopancreas, the length and width of intestinal villi, and the activities of protease and lipase. It also showed elevated ecdysterone hormone, gonadal index (GI), cAMP content, and the relative abundance of beneficial intestinal microflora. Compared to the control group, the mRNA expression of mTOR, S6K1, 4EBP1, EcR, RXR, chitinase, PKA, Vg, cdc2, and cyclin B was significantly upregulated, and the mRNA expression of MIH was significantly downregulated in the 16.44 g/kg group. Overall, optimal dietary threonine could improve intestinal health, regulate immune function, and enhance protein utilization, molting, and growth performance of red swamp crayfish. Additionally, it improved the synthesis of yolk substance and facilitated the development of ovarian cells of female crayfish. The optimal threonine level was 14.87-16.94 g/kg (dry matter), corresponding to 42.51-48.42 g/kg of dietary protein in red swamp crayfish.

Understanding the effects of egg loss from fisher handling to improve conservation of a threatened freshwater crayfish (Euastacus armatus)

Context Handling of wild animals can have adverse effects on individuals that scale up to affect populations and ultimately species. Limited mobility and high harvest pressure expose the threatened Australian freshwater crayfish (Euastacus armatus) to multiple handling events by fishers that cause egg loss. Aim Our aim was to assess the effects from harvest pressure on the reproductive output of an E. armatus population. Methods A stochastic model based on empirical data and estimated harvest pressures was used to predict the effect of repetitive handling of individuals on a population of E. armatus subject to harvest and consequent egg loss. Key results Egg loss resulted in substantial predicted population-level declines, most pronounced in populations subject to high and extreme harvest pressures. Conclusions We advocate educating fishers to visually determine the reproductive condition of female crayfish by inspecting gonopore setation, eliminating the need for unfurling the tail. Implications Maximising species reproductive output through limiting handling loss supports the management and conservation of E. armatus populations.

Surveillance for rhabdomyolysis after the consumption of crayfish in Wuhan, China, 2016-2022.

To analyze the epidemiological characteristics and etiology of crayfish-related rhabdomyolysis. Cases of crayfish-related rhabdomyolysis in Wuhan were monitored, and professional training of city's surveillance personnel was conducted. Unified questionnaires were used to collect data. The first case of crayfish-related rhabdomyolysis occurred on July 12, 2016. Subsequently, 423 patients were reported over the next 7 years, with muscle pain, weakness, and chest distress as main symptoms. In total, 64.54% (273/423) of patients were females, and young adults (aged 20-49 years) account for 86.22% (363/423) of patients. The primary clinical presentations were muscle pain, muscle weakness, and chest discomfort. The median incubation time was 6 h. And the number of cases may be related to water levels in Yangzi river. Laboratory tests revealed elevated creatine kinase and myoglobin levels. In total, 95.16% (236/248) of patients had consumed crayfish tail shrimp and 91.53% (227/248) had consumed crayfish liver and pancreas (Female crayfish also contain ovaries). Only 25.00% (62/248) of patients had a history of alcohol consumption. On average, 227 patients consumed 15 (3-50) crayfish, of whom 84.14% (191/227) consumed more than 10 crayfish. All patients had a favorable prognosis. Crayfish-related rhabdomyolysis is a kind of a case or cluster of patients present with severe myalgia or weakness of unknown etiology and mechanism disease in Wuhan, China, 2016-2022. Excessive consumption of crayfish may be a risk factor for the disease. The relationship between the specific parts of crayfish consumed and the onset of the disease is unclear, suggesting further research is needed to identify the relevant risk factors for the disease.

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.

Monthly variation of fatty acids, lipid quality index and metal content of Pontastacus leptodactylus (Eschscholtz, 1823) in Atikhisar Dam Lake (Çanakkale, Türkiye)

This study aims to investigate the metal content, fatty acid composition, lipid quality, and potential health risks of Pontastacus leptodactylus crayfish inhabiting Atikhisar Dam Lake. The research covers a 12-month period and includes both male and female individuals. The study investigated the metal content of crayfish specimens. In female individuals, the metal concentrations were ranked as Fe > Zn > Al > Cu > Mn > Se > As > Hg > Cd > Pb, while in male individuals, the ranking was Fe > Al > Zn > Cu > Mn > Se > As > Hg > Pb > Cd. The results demonstrate that Atherogenicity Index (AI) values for both genders range between 0.21 and 0.31, and Thrombogenicity Index (TI) values fall within 0.14 and 0.20. This indicates that crayfish meat is composed of healthy and high-quality fatty acids. In male individuals, omega-3 values range from 25.28 ± 0.380% to 28.34 ± 0.430%, and in female individuals, they vary from 22.98 ± 0.195% to 28.73 ± 0.871%. These findings underscore the absence of significant health risks associated with mercury levels in crayfish meat. Monthly meal calculations reveal that consuming female crayfish at an average of 4.35 servings per month for adults and 2.24 servings per month for children presents no health hazards. Similarly, the consumption of crayfish meat at an average of 5.29 servings per month for adult males and 2.72 servings per month for male children is deemed safe for health. Based on these results, the lipid quality of both male and female individuals from this species is found to be beneficial, as confirmed by risk–benefit assessments.

Study of the embryonic period of female crayfish egg development in different species

Freshwater crayfish farming is a promising area of production in the food market. This aquaculture industry is currently gaining popularity around the world, but given the high consumer demand, it requires modernisation. The efficiency of aquaculture production is based on the introduction of innovative methods into production processes, which are based on knowledge of biological characteristics, including reproductive capacity and the embryonic period of caviar development. The study aims to assess the reproductive quality of females and determine the incubation period of caviar, its quantity, weight, and survival rate. The study presents the results of research on the reproductive qualities and embryonic period of crayfish eggs of four species (Cherax quadricarinatus, Procambarus clarkii, Procambarus fallax forma virginalis, Cherax destructor) kept in separate closed water supply tanks at an optimal planting density of 4 individuals per 0.45 m2 . Studies have shown that the colour range of caviar and the duration of the incubation period for its maturation varies among different crayfish species. Thus, the first stage of incubation was the shortest and ranged from 2.80 (Florida crayfish) to 3.55 (destructor crayfish) days, while the second stage lasted the longest – from 13.17 to 15.80 days for Australian and broad-toed crayfish, respectively. Based on the analysis of the physiological characteristics of the female crayfish micropopulation, they were divided into quality categories, considering the following indicators: female weight, egg weight, total number of eggs, and number of eggs per 1 g of female. Females of the Australian red snapper of the excellent category was the best among all species in terms of live weight (63.0±0.67 g), egg weight (5.0±0.05 g) and total number of eggs (376.8±16.34 pcs.), the lowest similar indicators were in the marble species (16.8±0.15 g, 1.6±0.03 g, 124.5±2.66 pcs.), respectively. In terms of the number of eggs per 1 g of female weight, Florida crayfish prevailed (7.8±0.19). Instead, the destructor crayfish had intermediate results in these characteristics. The study results can be used in the economic activities of enterprises producing aquatic organisms

Sex differences in antioxidant ability and energy metabolism level resulting in the difference of hypoxia tolerance in red swamp crayfish (Procambarus clarkii)

Sexual dimorphism widely exists in crustaceans. However, sex differences in the hypoxia tolerance of crayfish have rarely been reported. In this study, the differences in hypoxia tolerance between the two sexes of crayfish were assessed according to mortality, pathological features of hepatopancreas, antioxidant enzyme activity and differentially expressed genes (DEGs) analysis using transcriptome. The results showed that male crayfish displayed significantly higher mortality than the female under hypoxia stress (p < 0.05). Furthermore, female crayfish demonstrated higher levels of antioxidant enzyme activity. Hematoxylin-eosin staining analysis revealed that the damage of hepatopancreas was more severe in the male crayfish compared to the female crayfish. Additionally, there was higher expression level of the DEGs in hypoxia-inducible factor (HIF) pathway and higher energy metabolism level in the female compared to the male. Together, these findings suggest that the female crayfish with higher antioxidant ability and energy metabolism level exhibits stronger hypoxia tolerance than the male crayfish, providing the theoretical support for investigating sex differences in hypoxia tolerance among crustaceans.

Investigating the Allometric Relationship for Total Mercury in Male and Female Signal Crayfish (Pacifastacus leniusculus) from Three Regions in the Columbia River Basin, USA.

The objective of this study was to evaluate the relationship between clawless body mass (CBM) and total mercury concentration (THg) in male and female crayfish captured from three different sites in the Columbia River Basin: the Spokane River, Boise River and Hangman Creek. It was found that the allometric relationships for THg in male and female crayfish did not differ from one another at any of the three locations (Spokane River: ANCOVA, F1,49 = 0.001, p = 0.63; Hangman Creek: ANCOVA, F1,73 = 0.007, p = 0.93; Boise River: ANCOVA, F1,38 = 0.02, p = 0.88. Furthermore, the slopes of the CBM and THg regression lines were not significantly different from one site to the next (ANCOVA, F2,166 = 1.5 p = 0.24), despite considerable differences in mean mass-adjusted THg across locations (Spokane River: 26.8 ± 2.6; Hangman Creek: 75.2 ± 2.1; Boise River: 99.0 ± 2.9). For signal crayfish (Pacifastacus leniusculus) from the Columbia River Basin, size and sex standardization can be accomplished with a single linear relationship.

Reproductive season-based plasticity in the size and strength of female crayfish (Faxonius obscurus) claws.

Animal weapons are morphological traits that improve the fighting ability of the wielder and are associated with competition. These traits are typically sexually dimorphic, with males possessing weaponry and females lacking weaponry. However, in some cases, like in many crustaceans, both males and females wield enlarged claws, which may function as weapons. Further, animal weapons may vary in their size, shape, and performance, with theory predicting that selection pressure for weaponry should be the highest when the importance of fights is the greatest, such as during a reproductive season. However, the degree and direction of selection may vary based on sex and season, with females potentially benefiting from wielding larger weapons during nonreproductive seasons. Crayfishes offer an ideal system to investigate how weapon phenotypes change across reproductive seasons since both males and females undergo a form alteration associated with reproduction. Thus, we investigated whether female Allegheny crayfish, Faxonius obscurus, claws change in size, shape, or pinching strength based on whether a female is in a reproductive or nonreproductive form. We found that female F. obscurus claws are larger and stronger during the reproductive season. These findings align with previous research on males of the same species. We discuss how predictions about the relationship between seasonality and weapon investment may differ based on sex.

Effect of dietary Ginkgo biloba leaf on the growth performance and nonspecific immunity of red swamp crayfish Procambarus clarkii

This trial investigated the effect of dietary Ginkgo biloba leaf (GBL) on the growth performance and nonspecific immunity of red swamp crayfish Procambarus clarkii. 180 Crayfishes were randomly divided into three groups. One group was fed with basic diet, whereas the other two groups were fed with diets containing 1% and 3% GBL. After 32 days of feeding, GBL addition tended to increase the body weight gain rate compared with control. In 3% GBL group, the bodyweight gain rate of male crayfish was higher than that of female crayfish. While female crayfish were advantageous in terms of meat yield. Liver-related indexes were influenced by GBL addition and 3% GBL could reduce glutamic pyruvic transaminase and glutamic oxaloacetic transaminase as well as total cholesterol in male crayfish, showing its function in liver protection. Moreover, GBL addition effects on liver protection was better in male crayfish than female crayfish.

Description of the mantle lure and novel mimicry of the endangered Cumberlandian Combshell (Epioblasma brevidens) in the Clinch River, eastern United States.

The Cumberlandian Combshell (Epioblasma brevidens) is an endangered freshwater mussel endemic to the Tennessee and Cumberland River drainages, major tributaries of the Ohio River of the eastern United States. We conducted mask and snorkel surveys in May and June of 2021 and 2022 to locate, observe, photograph, and video female E.brevidens to document their unique mantle lures at sites in the Clinch River in Tennessee and Virginia. The mantle lure is morphologically specialized mantle tissue that mimics prey items of the host fish. The mantle lure of E.brevidens appears to mimic four distinct characteristics of the reproductive anatomy of the underside (ventral) of a gravid female crayfish, to include: (1) the external apertures of the oviducts located on the base of the third pair of walking legs, (2) crayfish larvae still encased in the egg membrane, (3) pleopods or claws, and (4) postembryonic eggs. Surprisingly, we observed males of E.brevidens displaying mantle lures that were anatomically complex and closely resembled the female mantle lure. The male lure similarly mimics oviducts, eggs, and pleopods but is diminutive (2-3 mm smaller in length or diameter) to those same structures in females. We describe for the first time the mantle lure morphology and mimicry of E.brevidens, showing its close resemblance to the reproductive anatomy of a gravid female crayfish, and a novel form of mimicry in males. To our knowledge, mantle lure displays in males have not been previously documented in freshwater mussels.

Short-term artificial incubation before hatching limits vertical transmission of Aphanomyces astaci from chronically infected females of a host species susceptible to crayfish plague

Crayfish plague, caused by the oomycete Aphanomyces astaci and spread primarily by its original crayfish hosts from North America, not only threatens populations of endangered crayfish but also impacts their fisheries and aquaculture. This includes the narrow-clawed crayfish (Pontastacus leptodactylus) in Turkey, where its fishery and export used to grow until the mid-1980s when the accidental introduction of crayfish plague caused stock collapses. Although crayfish densities in some Turkish lakes returned to levels where fishery is feasible, persistent chronic infections by A. astaci prevent full crayfish population recovery and stock exploitation. The establishment of closed culturing systems faces the problem of substantial mortality of both broodstock and juveniles originating from the wild, apparently associated with the stress-induced development of crayfish plague symptoms. In our experiment, we evaluated whether A. astaci is vertically transmitted to juveniles during maternal incubation, and to what extent hatching of crayfish eggs in artificial conditions, coupled with antifungal baths, limits the infection by this pathogen. Egg-carrying (berried) crayfish females were caught from the Lake Eğirdir, Turkey, shortly before juvenile hatching. Eggs stripped from females were assigned into four experimental groups: two groups were treated with antifungal baths (formaldehyde or peracetic acid), the other two groups were controls kept without antifungal treatment but set up in conditions differing in the likelihood of accidental A. astaci transmission. Eggs on five berried females were kept for maternal incubation. The results confirmed that nearly all wild-caught females tested for the presence of A. astaci DNA by quantitative PCR were infected, and A. astaci infections were frequently confirmed in the maternally incubated juveniles. In contrast, we did not confirm unambiguous A. astaci infection in any juvenile from eggs treated by antifungal baths and from one of the control groups, which were all kept on a strictly separated flow-through system. However, juveniles from the control group on a recirculating system, in which also infected crayfish (e.g., maternal incubation group) were present, suffered elevated mortality, likely related to the accidental introduction of the pathogen that was confirmed in this treatment. The separation of the eggs from infected mothers before hatching apparently substantially reduces pathogen vertical transmission, and combination with an antifungal treatment further increases juvenile survival. Although it cannot be guaranteed that the juveniles that hatched and developed in artificial conditions are entirely A. astaci-free, the approach seems suitable for routine aquaculture applications in regions where chronic infections by this pathogen are widespread.

Ecological conditions and phenotypic characteristics of Austropotamobius torrentium (Schrank, 1803) in the Subotica and Toplik Rivers

Austropotamobius torrentium (Schrank, 1803) lives in two watercourses, namely Subotica (Sana) and Toplik (Tilava). The influence of the ecological conditions of these rivers on individuals of this species is analyzed based on 22 morphometric parameters. The assessment of abiotic conditions was done through the measurement of physical and chemical water parameters and the analysis of the composition of phytobenthos and macrozoobenthos. Sampling was carried out in June, September, and October 2021. Water quality at the investigated localities (on the basis of abiotic and biotic parameters) is oligo to betamesosaprobic. A total of 37 crayfish were analyzed (20 from Subotica and 17 from Toplik). Female crayfish have shown significant differences in the head width (HEW) and abdominal thickness (ABH). Males differed significantly in a number of parameters, including the weight (W), head shape (HEL and HEW), rostrum length (ROL), carapace width (CPW), and abdominal shape (ABH and ABL). Higher values of the indicated parameters have been found in the males from the Subotica River. The obtained results are influenced by different ecological conditions of their habitats. The Subotica River is a larger watercourse in the lowland belt with a large number of microhabitats, and the Toplik is a small river in the mountain belt, with uniform sediment and a small number of ecological niches of the analyzed species. The general ecological conditions in the water of both watercourses are also affected by aquaculture facilities, where wastewater has a direct influence on the distribution of Austropotamobius torrentium individuals in the watercourses of the Subotica and Toplik Rivers. For more detailed and complete data, it is necessary to analyze a larger number of individuals in both populations, and to include additional morphometric-meristic parameters and molecular-genetic analyses.

Effects of herbicide atrazine on reproductive hormonal levels, Cytochrome P450, and gonadal structure of adult male and female crayfish, Procambarus clarkii

Effects of herbicide atrazine on reproductive hormonal levels, Cytochrome P450, and gonadal structure of adult male and female crayfish, Procambarus clarkii

Seasonal context of Bristly Cave Crayfish Cambarus setosus habitat use and life history

Cave crayfishes are important members of groundwater communities, but many cave crayfishes are threatened or endangered. Unfortunately, we lack basic life history and ecological data that are needed for developing conservation plans for most cave crayfishes, especially the role of seasonal and annual fluctuations in structuring populations. Therefore, we determined the seasonal life history and habitat use of Cambarus setosus in Smallin Civil War Cave, Christian County, Missouri, United States. We conducted visual crayfish surveys over a 400 m section of the cave from 2006 to 2019. We used multinomial logit, multiple linear regression, and logistic regression models to estimate crayfish substrate, water depth, and water velocity use, respectively. All models included sex, carapace length, season, distance into the cave, and interactions between all variables and sex as predictor terms. We also used t-tests to assess morphometric differences between male and female crayfish. Six mark-recapture events (2010 to 2019) were used to estimate population sizes using a nil-recapture model. We attempted to age eight individuals using gastric mill bands, but annual bands were not discernable. We found reproductively active males during all seasons. We captured one ovigerous female during the spring, though ovigerous females were observed during show cave tours during spring, summer, and autumn. Male C. setosus were more likely to use homogenous and heterogeneous rock substrates and shallower and calmer water when compared to females; however, these relationships varied based on distance into the cave and season. Females sampled were significantly larger than males, and males regenerated chelae more often. Minimum population size estimates ranged from 9 to 159 individuals and indicated the population was relatively stable. Our data provide both a baseline population estimate for comparison with future studies and valuable trait information that is often lacking but useful for developing conservation efforts.

Effects of dietary phospholipid and cholesterol levels on antioxidant capacity, nonspecial immune response and intestinal microflora of juvenile female crayfish, Procambarus clarkii

The current study is conducted to evaluate the interactive effects of different phospholipids (PL) and cholesterol (CH) levels on the immune response and intestinal microbiota of juvenile female red swamp crayfish, Procambarus clarkii. A total of 270 healthy crayfish with an average initial weight of 5.92 ± 0.03 g were fed nine semi-purified diets containing three different levels of PL (0, 20 and 60 g/kg of diet) and CH (0, 5 and 10 g/kg of diet, as a 3 × 3 experiment design) for 60 days. The superoxide dismutase (SOD) activity in serum was enhanced by dietary supplementation of PL and CH (P < 0.05), and the activity of alkaline phosphatase (AKP) and phosphatase (ACP) decreased significantly with increasing dietary PL levels (P < 0.05). There was a significant interaction between PL and CH on malondialdehyde (MDA) content, catallase (CAT), total antioxidant capacity (T-AOC) and glutathione peroxidase (GPx) activities (P < 0.05). Optimal dietary PL and CH levels could significantly improve the abundance of intestinal microflora, change and optimize the intestinal flora composition and decrease pathogenic bacteria relative abundance. When CH addition level at 5 g/kg, the Bacteroidetes abundance was the highest and the relative abundance of Candidatus Bacilloplasma was the lowest compared with the other groups (P < 0.05). Considering antioxidant capacity, nonspecial immune response and microbial community structure, the optimal PL and CH requirements were estimated to be 60 g/kg and 5 g/kg for juvenile female P. clarkii, respectively.

HUBUNGAN PANJANG BERAT DAN NISBAH KELAMIN UDANG KARANG MUTIARA (Panulirus ornatus) DI SEKITAR PULAU SALEMO KABUPATEN PANGKEP

The purpose of this study is 1) The composition of the type of catch of crayfish caught in the water around the island of Salemo. 2) Long-weight crayfish pearl (P. ornatus) and Sex ratio. This research will be conducted on October 1, 2021 to February 28, 2022 in the Salemo Island Waters in the Kabupatan Pangkep area. The research method used to identify the type of crayfish was carried out visually by looking at the color patterns found in the body segments based on the book Moosa and Aswandy (1984), identification of crayfish types was carried out using the identification key from William. The results of this study showed that there were 3 types of crayfish or lobsters, namely pearl crayfish (P. ornatus) as many as 38.23 heads or 38.23%, pearl crayfish (P. versicolor) as many as 218 heads or 41.05%, and batik crayfish (P. longipes) as many as 110 heads or 20.72%. With the largest size is pearl crayfish (P. ornatus). The sex ratio of male and female crayfish pearl crayfish (P. ornatus) is 0.45 : 0.55 or a ratio of 1 : 1. The relationship between the length and weight of pearl crayfish is classified as a minor allometric growth pattern.

Morphometric characteristics and condition indices of stone crayfish Austropotamobius torrentium (Shrank, 1803) from the Mlinska River

Regarded as a protected species on the IUCN list of endangered species, and classified as data deficient species, the stone crayfish (Austropotamobius torrentium) is one of the five European species from the Astacidae family that lives in freshwater ecosystems across Bosnia and Herzegovina. The aim of this study was to investigate the variability of selected morphometric characteristics of male and female crayfish of the A. torrentium species from the upper reaches of the Mlinska River. The crayfish were sampled in June 2021 when 62 individuals (22 males and 40 females) were caught. They were analyzed fresh in the field and in the laboratory. The treatment included the measurement of 12 morphometric features: total body length (TBL), weight (W), claw length (CLL), claw width (CLW), carapace length (CPL), carapace width (CPW), rostrum length (ROL), rostrum width (ROW), abdominal length and width (ABL, ABW) and telson length and width (TEL, TEW). The mean body length ± SD was 79.05 ± 7.35 in males and 60.54 ± 10.03 mm in females. The mean recorded body weight ± SD was 17.51 ± 8.3 g in males and 7.02 ± 4.41 g in females. Using the linear regression method, a positive correlation was found between body length and weight (♂ R2=0.7644; ♀ R2=0.8222), body weight and claws length (♂ R2=0.876; ♀ R2=0.9661), as well as carapace width and body length (♂ R2=0.7216; ♀ R2=0.8411). Using the T-test, a statistically significant difference of the analyzed morphometric parameters was found between the sexes, which is explained by the pronounced sexual dimorphism of stone crayfish. The calculated values for Condition factor and the Crayfish constant indicate that the males are of better fitness, which is in line with the results of previous research in Europe. Data presented in this paper can serve as a basis for further research of A. torrentium in this area.

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.