Red Swamp Crayfish Procambarus Clarkii Research Articles

Effects of dietary replacement of fishmeal by cottonseed meal on the growth performance, immune and antioxidant responses, and muscle quality of juvenile crayfish Procambarus clarkii

The current research was aimed to determine the impacts of cottonseed meal substitution levels for fishmeal on the growth performance, immune indices, antioxidant ability, and muscle texture of red swamp crayfish (Procambarus clarkii). Five isonitrogenous and isolipidic diets were formulated to feed the crayfish for 8 weeks. The basal diet contained 20% fishmeal (FM), while the other four experimental diets substituted fishmeal in FM diet with cottonseed meal at levels of 25%, 50%, 75%, and 100%, referred to as CM25, CM50, CM75, and CM100 respectively. A total of 750 crayfish with an average initial weight of 4.00 g were selected and randomly allocated to fifteen cages. Each diet was randomly assigned to triplicate groups of crayfish. Weight gain and specific growth rate declined, and feed conversion rate, asparate aminotransferase and alanine transaminase activities appear to increase as cottonseed meal substitution levels increased. Serum total cholesterol levels declined in crayfish fed CM100 diet compared to crayfish fed the FM diet. Serum phenoloxidase and lysozyme activities, and muscle hardness and mef-2a mRNA expression were the highest for crayfish fed fishmeal-based diet and showed no significant difference among other four groups. Dietary cottonseed meal levels did not significantly influence hepatopancreas index, viscerosomatic index, condition factor, serum glucose, triglyceride, albumin, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol and creatinine contents, as well as the contents of acid phosphatase, and alkaline phosphatase, and muscle texture profile (cohesiveness, springiness, adhesiveness, and chewiness) and mef-2b and mstn mRNA expression. High dietary fish meal replacement by cottonseed meal tended to upregulate mRNA expression of nuclear factor erythroid 2-related factor 2, glutathione peroxidase, glutathione reductase, manganese superoxide dismutase, glutathione S-transferase, and catalase. Taken together, dietary cottonseed meal reduced growth performance and feed utilization, induced hepatopancreas oxidative stress, and influenced some serum and muscle parameters. The gossypol content and unbalanced amino acid profile are considered the limiting factor influencing the fish meal replacement by cottonseed meal.

Genomic adaptive potential to cold environments in the invasive red swamp crayfish

Biological invasion refers to the introduction, spread, and establishment of non-native species in a novel habitat. The ways in which invasive species successfully colonize new and different environments remain a fundamental topic of research in ecology and evolutionary biology. Here, we investigated the genomic and transcriptomic characteristics of the red swamp crayfish (Procambarus clarkii), a widespread invader in freshwater environments. Targeting a recently colonized population in Sapporo, Japan that appears to have acquired a high degree of cold tolerance, RNA-seq analysis revealed differentially expressed genes in response to cold exposure, and those involved in protease inhibitors and cuticle development were considered top candidates. We also found remarkable duplications for these gene families during evolution and their concerted expression patterns, suggesting functional amplification against low temperatures. Our study thus provides clues to the unique genetic characteristics of P.clarkii, possibly related to cold adaptation.

Aquatic macroinvertebrate abundance in French experimental polyculture fishponds

Abstract Ponds host a variety of invertebrate species and contribute greatly to global biodiversity. Aquaculture influences macroinvertebrate diversity and productivity in ponds through several practices, such as macrophyte and water management. Fish stocking is also considered controversial for preserving biodiversity through the direct predation upon natural species and changes induced on the biotope. An experiment examined whether compartmentalized ponds with temporarily fish‐free areas had higher fish productivity and macroinvertebrate abundance and diversity than open ponds. The experimental design consisted of two treatments—compartmentalized (C) or open (O)—each applied to three ponds. Roach (Rutilus rutilus), tench (Tinca tinca) and common carp (Cyprinus carpio) were stocked in the ponds in March 2021. Juvenile pikeperch (Sander lucioperca) were stocked in the ponds in June. In the C ponds, three areas were created and opened successively: (C1) corresponding to ¼ of the pond surface to host roach, tench and common carp from March to May; (C2) ¼ of the pond surface restricted to fish from March to May; and (C3) ½ of the surface restricted to fish from March to July, except for juveniles of pikeperch which were stocked in June. We investigated patterns in abundance, dry biomass and productivity of macroinvertebrates four times from March to October. This article presents observed macroinvertebrate abundances and weighted dry biomass, and productivity estimated from them. Overall, 77,749 individuals were identified, of which one‐third were Chironomini and another one‐third were Oligochaeta. The invasive red swamp crayfish (Procambarus clarkii) was found in one pond in October. The two highest taxonomic richness values were found in C ponds (71 and 69 taxa). The lowest taxonomic richness (61 taxa) was in an O pond. Although dry biomass was clearly higher in the C ponds in March, no tendency could be seen between C and O ponds throughout the experiment. No difference in productivity was found between the C and O ponds among the experiment. By reporting macroinvertebrate abundance, biomass, productivity, size classes, developmental stages and high‐resolution taxonomic identification in a freshwater polyculture system, this dataset is one of the first of its kind.

Seasonal Changes in the Diet of Urban Raccoon Dogs in Saitama, Eastern Japan

We examined the food habits of raccoon dogs (Nyctereutes procyonoides) at an urban high school in Saitama, Japan. The study place is surrounded by residential areas but is adjacent to a pond. Fecal samples (n = 126) were collected from January to December 2022 and analyzed using the point frame method. Fecal composition was diverse in winter, including leaves, fruits, seeds, and artificial materials. In spring, the proportion of Japanese toads (Bufo japonicus formosus) and insects increased, whereas in summer, proportion of hackberry (Celtis sinensis) fruits, insects, and red swamp crayfish (Procambarus clarkii) increased. In autumn, fruits of hackberry and muku tree (Aphananthe aspera) were predominant. Consumption of toads and swamp crayfish suggests that the raccoon dogs are opportunistic feeders. We recovered seeds from only ten species, including fruits from five wild plants; these numbers were lower than those reported previously in rural areas of the same district, where raspberries (Rubus spp.), mulberries (Morus spp.), and Eurya japonica have often been recovered at great proportions. A wide range of artificial materials were recovered but in low quantities. These results reflect the characteristics of the study area, which is an urbanized environment with limited trees and adjacent to a pond.

Genetic Diversity Analysis of the Red Swamp Crayfish Procambarus clarkii in Three Cultured Populations Based on Microsatellite Markers.

With the increasing scale of crayfish breeding, the self-propagation and "catch large and keep small" breeding patterns have led to serious degradation of the fry, so the selection and breeding of high-quality fry is very important. Selecting a population with a high genetic diversity as the base population for breeding can greatly improve the breeding efficiency. Fifteen microsatellite loci were used to understand the genetic structure and diversity of three Procambarus clarkii populations in Chongming, Shanghai; Gaoyou, Jiangsu; and Xuancheng, Anhui. The results indicated that the three populations were diverse and the number of alleles, observed heterozygosity, expected heterozygosity, Shannon information index, and polymorphic information content ranged from 4.8 to 6.2, 0.5567 to 0.6257, 0.6166 to 0.7086, 1.1292 to 1.3987, and 0.5446 to 0.6452, respectively. The Xuancheng population had the highest genetic diversity. The genetic differentiation coefficient and gene flow of the three populations were between 0.0553 and 0.1068 and 2.0908 and 4.2708, respectively, and there was extensive genetic exchange between the Chongming and Xuancheng populations. Analyses of molecular variance indicated that the genetic variation was mainly within the population (91.51%) and inter-population genetic variation accounted for 8.49%. The unweighted pair group method with an arithmetic mean clustering map was utilised based on the genetic distance between groups, and the results showed that the Gaoyou group was grouped alone, while the Chongming and Xuancheng groups were clustered together. The structural results indicated that the Chongming and Xuancheng groups had the same origin, although the Xuancheng group possessed a more complex genetic structure. This study indicated that all three populations had a high genetic diversity, with the Xuancheng population exhibiting the highest diversity. The results of the study provide a reference for the selection of base populations in breeding programs and confirm that the Xuancheng population in Anhui has a better genetic background. The selection of the Xuancheng population as one of the base populations for genetic breeding will be more efficient to accumulate superior traits.

Identification and function analysis of a scavenger receptor B gene in red swamp crayfish Procambarus clarkii.

Scavenger receptor (SRs) are pattern recognition receptors that play important roles in innate immunity. However, studies on SR in Procambarus clarkii are still lacking. In the present study, a novel scavenger receptor B on P. clarkii (PcSRB) was identified. The ORF of PcSRB was 548 bp and encoded 505 amino acid residues. It was a transmembrane protein with two transmembrane domains. The molecular weight was about 57.1kDa. The tissue analysis by real-time PCR showed that the highest expression level was found in hepatopancreas, while the lowest expression level was found in heart, muscle, nerve and gill. After P. clarkii were infected with Aeromonas hydrophila, the expression of SRB in hemocytes increased rapidly at 12h, and SRB in hepatopancreas and intestine also increased rapidly at 48h after infection. The recombinant protein was obtained by prokaryotic expression. The recombinant protein (rPcSRB) could bind to bacteria and different molecular pattern recognition substances. The present study confirmed that SRB may be involved in the immune regulation process and play a certain role in the immune defense of P. clarkii, especially in the recognition and binding of pathogens. Therefore, this study provides theoretical support for further improving and enriching the immune system of P. clarkii.

Antioxidation, immunity and hepatopancreatic histology of red swamp crayfish (Procambarus clarkii) subjected to low-temperature aerial exposure stress and re-immersion

Desiccation is a stressful situation that decapods often experience during live transportation. This study investigated the effects of low-temperature aerial exposures (LTAEs) (dry exposure (DL) and moist exposure (ML) at 6 °C) and re-immersion on the antioxidative and immune responses and hepatopancreatic histopathology in P. clarkii. Compared to the control group (normally feeding at 24.0 °C water temperature), the crayfish under LTAEs showed overall severe hepatopancreatic oxidative damage, with significantly increased malondialdehyde (MDA) contents and significantly reduced total antioxidant capacity (T-AOC), and oxidant damage was not fully recovered even after 12 h of re-immersion; the expression of hsp70 was significantly increased within 24–48 h of stress and re-immersion. The activity of hemolymphatic acid phosphatase (ACP) was significantly increased during 24–48 h of the stress and at 12 h of re-immersion; the activity of aspartic aminotransferase (AST) and alanine aminotransferase (ALT) was significantly increased throughout the experiment; and the gene expression of proPO or TLR was significantly increased during 12–48 h of the stress. Severe histopathological changes (lumen dilatation, vacuolation of epithelial cells and reduced cell numbers) were observed in hepatopancreas at 48 h of stress and 12 h of re-immersion. These results indicated that 48 h of low-temperature aerial exposure stress stimulated the non-specific immunity but adversely affected the antioxidation and hepatopancreatic histomorphology of P. clarkii, whereas 12 h of re-immersion was not sufficient to restore crayfish from stress to a normal state.

PcTrim prevents early infection with white spot syndrome virus by inhibiting AP1-induced endocytosis

Viruses have evolved various strategies to achieve early infection by initiating transcription of their own early genes via host transcription factors, such as NF-κb, STAT, and AP1. How the host copes with this immune escape has been a topic of interest. Tripartite motif (TRIM) family proteins with RING-type domains have E3 ubiquitin ligase activity and are known as host restriction factors. Trim has been reported to be associated with phagocytosis and is also believed to be involved in the activation of autophagy. Preventing the virus from entering the host cell may be the most economical way for the host to resist virus infection. The role of TRIM in the early stage of virus infection in host cells remains to be further interpreted. In the current study, a crayfish TRIM with a RING-type domain, designated as PcTrim, was significantly upregulated under white spot syndrome virus (WSSV) infection in the red swamp crayfish (Procambarus clarkii). Recombinant PcTrim significantly inhibited WSSV replication in crayfish. RNAi targeting PcTrim or blocking PcTrim with an antibody promoted WSSV replication in crayfish. Pulldown and co-IP assays showed that PcTrim can interact with the virus protein VP26. PcTrim restricts the expression level of dynamin, which is involved in the regulation of phagocytosis, by inhibiting AP1 entry into the nucleus. AP1-RNAi effectively reduced the expression levels of dynamin and inhibited host cell endocytosis of WSSV in vivo. Our study demonstrated that PcTrim might reduce early WSSV infection by binding to VP26 and then inhibiting AP1 activation, resulting in reduced endocytosis of WSSV in crayfish hemocytes.BjibKXcktbHxsdfgurhU3PVideo

Growth Performance, Molting Frequency and Carapace Coloration of Two Different Size Classes of Red Swamp Crayfish (Procambarus clarkii) Fed with Different Diets

In this study, the effects of three different commercial aquarium feeds were tested on the growth performance, molting frequency and carapace coloration of red swamp crayfish (Procambarus clarkii) in two different size classes (4 and 5 cm). For this purpose, six experimental groups were formed according to crayfish size (S1: Size 1 and S2: Size 2) and feed type (BF: bottom fish food, CF: cichlid food and CG: crustacean granules) as S1BF, S1CF, S1CG, S2BF, S2CF and S2CG, and the crayfish were fed with these diets for 12 weeks. The final mean weight (FMW) of the S1CG was higher than the S1BF (P<0.05). The final mean total length (FMTL) and final mean carapace length (FMCL) of S2BF were the lowest (P<0.05). No significant differences were recorded in the feed conversion ratios (FCR), specific growth rates (SGR) and survival rates (SR) of red swamp crayfish in two different size classes (P>0.05). The lowest cheliped injury and cannibalism rates were found in the crayfish fed with crustacean feed in both size classes. The mean molting frequencies (MMF) of the S1CG and S2CG were statistically higher than the S1CF and S2BF, respectively (P<0.05). S2CG has the highest final lightness (L*) value (P<0.05). The final redness (a*) and final yellowness (b*) values of the S1BF and S2BF groups were the lowest (P<0.05). The results showed the positive effects of crustacean feed on all the tested parameters in both size classes. Further studies are needed to investigate the efficient use of species-specific rations in the crayfish species.

Identification and characterization of a Reeler domain containing protein in Procambarus clarkii provides new insights into antibacterial immunity in crustacean

Crayfish, as an invertebrate, relies only on the innate immune system to resist external pathogens. In this study, a molecule containing a single Reeler domain was identified from red swamp crayfish Procambarus clarkii (named as PcReeler). Tissue distribution analysis showed that PcReeler was highly expressed in gills and its expression was induced by bacterial stimulation. Inhibiting the expression of PcReeler by RNA interference led to a significant increase in the bacterial abundance in the gills of crayfish, and a significant increase in the crayfish mortality. Silencing of PcReeler influenced the stability of the microbiota in the gills revealed by 16S rDNA high-throughput sequencing. Recombinant PcReeler showed the ability to bind microbial polysaccharide and bacteria and to inhibit the formation of bacterial biofilms. These results provided direct evidence for the involvement of PcReeler in the antibacterial immune mechanism of P. clarkii.

Suitable natural astaxanthin supplementation with Haematococcus pluvialis improves the physiological function and stress response to air exposure of juvenile red swamp crayfish (Procambarus clarkii)

High mortality during transportation has restricted industrial development of red swamp crayfish (Procambarus clarkii), especially juveniles, in China. Supplementation with Haematococcus pluvialis has been proved to promote crustacean survival and growth. Therefore, this study investigated the effects of dietary natural astaxanthin derived from H. pluvialis on the growth performance, pigmentation, digestion, antioxidant capacity, immunity, and response to air exposure stress of juvenile red swamp crayfish. Five isonitrogenous and isolipidic diets were formulated containing a graded H. pluvialis powder inclusion (0, 0.15, 0.30, 0.45 and 0.60%) level. The results indicated that dietary astaxanthin significantly improved the survival rate and weight gain rate of juvenile crayfish (P < 0.05). As dietary astaxanthin levels increased, a* values in the carapace, muscle, and ovaries improved and the carotenoid content significantly increased (P < 0.05). Lipase (LPS), and cellulase (CL) activities in the hepatopancreas and intestines, and α-amylase, and pepsin (PEP) activities in the hepatopancreas, significantly increased and then decreased with increasing dietary astaxanthin levels (P < 0.05). Dietary astaxanthin significantly decreased the malondialdehyde (MDA) content in the hemolymph (P < 0.05). Total superoxide dismutase (T-SOD), total antioxidant capacity and acid phosphatase (ACP) activities in the hepatopancreas and hemolymph, as well as alkaline phosphatase in the hepatopancreas, followed a similar pattern as the digestive enzymes (P < 0.05). Furthermore, dietary astaxanthin significantly improved succinate dehydrogenase (SDH) activity in the hepatopancreas and muscle after a 24-h air exposure stress test, while decreasing the MDA and lactic acid content (LD) in muscle (P < 0.05). Based on the quadratic regression analysis of LPS, PEP, CL, T-SOD, ACP and SDH in hepatopancreas, and MDA and LD in muscle, the optimal dietary natural astaxanthin content for juvenile red swamp crayfish ranges from 63.55 to 84.40 mg kg−1.

The invasive red swamp crayfish (Procambarus clarkii) as a bioindicator of microplastic pollution: Insights from Lake Candia (northwestern Italy)

Microplastic pollution has become pervasive. Identifying a bioindicator species to track the occurrence and effects of microplastics (MPs) on ecosystems is crucial for determining their impact on the environment. The digestive tract of Procambarus clarkii was thought to be of interest for investigating MPs accumulation in freshwater organisms. Our hypothesis was that the same type of MPs found in abiotic compartments (water and sediment) could be found in P. clarkii, which would make it an ideal candidate for use as a bioindicator of MP pollution in freshwater ecosystems. Water, sediment, and P. clarkii specimens were collected from four sites in a lentic ecosystem (Lake Candia; northwestern Italy) for two consecutive years (2021–2022). The mean MPs abundance was 1.75 ± 0.95 items/m3 in 2021 and 2 ± 0.81 items/m3 in 2022 in the water samples and 6.75 ± 1.5 items/kg and 8 ± 0.81 items/kg in the sediment samples in 2021 and 2022, respectively. In 2021, the average was 0.06 ± 0.07 items/g in the males and 0.05 ± 0.05 items/g in the females; in 2022, the average was 0.04 ± 0.05 items/g and 0.05 ± 0.06 items/g in the males and the females, respectively. MP fibers and fragments (black, white, blue, light blue) of polypropylene and polyethylene terephthalate were found in the biotic and the abiotic compartments. The generalized linear mixed model revealed that the number of items/g was predicted only by total weight: the lowest number of items/g was recorded for crayfish with the highest weight probably due to the feeding habits of P. clarkii. Our findings suggest that the invasive P. clarkii (smaller individuals, in particular) could be a good candidate bioindicator for MP pollution since the same type of MP items were recorded in the abiotic compartments. Further research is needed to better understand the feeding behavior of P. clarkii and the dynamics of MPs in aquatic ecosystems.

PcEiger links the Imd/Relish pathway to ROSproduction in the intestine of the red swampcrayfish.

In the arthropod gut, commensal microbiota maintain the immune deficiency (Imd)/Relish pathway for expression of antimicrobial peptides, whereas pathogenic bacteria induce dual oxidase 2 (Duox2) for production of extracellular microbicidal reactive oxygen species (ROS). The Imd/Relish pathway and the Duox2/ROS system are regarded as independent systems. Here, we report that these two systems are bridged by the tumor necrosis factor (TNF) ortholog PcEiger in the red swamp crayfish Procambarus clarkii. PcEiger expression is induced by commensal bacteria or the Imd/Relish pathway. PcEiger knockdown alters bacterial abundance and community composition due to variations in the oxidative status of the intestine. PcEiger induces Duox2 expression and ROS production by regulating the activity of the transcription factor Atf2. Moreover, PcEiger mediates regulation of the Duox2/ROS system by commensal bacteria and the Imd/Relish pathway. Our findings suggest that the Imd/Relish pathway regulates the Duox2/ROS system via PcEiger in P. clarkii, and they provide insights into the crosstalk between these two important mechanisms for arthropod intestinal immunity.

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.

Reduced protein intake in Procambarus clarkii fed diets containing graded levels of purslane: Effects on growth and quality

AbstractIn this study, 144 red swamp crayfish (Procambarus clarkii, initial mean weight 3.9 ± 0.3 g) juveniles were fed diets containing graded levels of purslane (Portulaca oleracea), with a decreasing percentage of proteins (from 17.3% to 1.0%) for 10 weeks. Six diets were administered: four fishmeal diets containing 5%, 15%, 25%, and 50% purslane, a diet with 100% purslane, and a commercial diet. Growth performance and the amounts of fatty acids and carotenoids were measured. Crayfish fed 25% and 50% purslane diets showed optimal contents in fatty acids (FAs) and astaxanthin, and their growth was comparable to that of the control group. Significant differences in FA content of the crayfish groups were observed for saturated FAs, monounsaturated FAs (MUFAs), and polyunsaturated FAs (PUFAs). The highest levels of n − 3 α‐linolenic acid (ALA) and n − 6 linoleic acid (LA) were found in the groups fed 25%, 50%, and 100% purslane diets. This study shows that the best purslane content to be included in the crayfish diet should range between 25% and 50%. Although the nutritional value of purslane is low, its inclusion at up to 50% in crayfish diets seems to improve the carotenoid content and FA quality, while reducing the daily intake of animal protein, without affecting growth performance, thus contributing to the goal of more sustainable crustacean aquaculture.

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.

Sub-chronic ammonia exposure induces hepatopancreatic damage, oxidative stress, and immune dysfunction in red swamp crayfish (Procambarus clarkii)

Ammonia, as one of the primary water pollutants in aquaculture, has been shown to induce a wide range of ecotoxicological effects on aquatic animals. In order to investigate the antioxidant and innate immune responses in crustaceans disrupted by ammonia, red swamp crayfish (Procambarus clarkii) were exposed to 0, 15, 30, and 50 mg/L total ammonia nitrogen for 30 d, the alterations of antioxidant responses as well as innate immunity were studied. The results showed that the severity of hepatopancreatic injury were aggravated by the increasing ammonia levels, which were mainly characterized by tubule lumen dilatation and vacuolization. The swollen mitochondria and disappeared mitochondria ridges suggested that oxidative stress induced by ammonia targets the mitochondria. Concurrently, enhanced MDA levels, and decreased GSH levels as well as the decreased transcription and activity of antioxidant enzymes, including SOD, CAT, and GPx were noticed, which suggested that high concentrations of ammonia exposure induce oxidative stress in P. clarkii. Furthermore, a significant decrease of the hemolymph ACP, AKP, and PO along with the significant downregulation of immune-related genes (ppo, hsp70, hsp90, alf1, ctl) jointly indicated that ammonia stress inhibited the innate immune function. Our findings demonstrated that sub-chronic ammonia stress induced hepatopancreatic injury and exert suppressive effects on the antioxidant capacity as well as innate immunity of P. clarkii. Our results provide a fundamental basis for the deleterious effects of ammonia stress on aquatic crustaceans.

Effects of Shelter on the Hatching, Immune Performance, and Profitability of the Ovigerous Red Swamp Crayfish Procambarus clarkii under High Stocking Density

To develop the intensive breeding technology of the seed of the red swamp crayfish Procambarus clarkii, the survival rates, hatching effects (hatching rate, incubation level, and number of juveniles), and immune performance of ovigerous P. clarkia as well as economic benefits are evaluated under different shelter conditions under a high stocking density in this study. The experimental design includes three different forms of shelter treatments (D1: experiment without any shelters; D2: experiment with closed shelters; D3: experiment with open shelters), each with three replicates. The results show that the concentration of the total antioxidant capacity (T-AOC) and activities of phenoloxidase (PO), catalase (CAT), and acid phosphatase (ACP) in the D3 treatment are higher than those in the D1 treatment (all p &lt; 0.05), with the highest concentrations of total antioxidant capacity (T-AOC) and malondialdehyde (MDA) and the highest activities of phenoloxidase (PO), superoxide dismutase (SOD), catalase (CAT), acid phosphatase (ACP), and alkaline phosphatase (AKP) among the treatments being present in the ovigerous P. clarkii in the D3 treatment. The hatching rates of the three treatments vary from 69.51% to 94.28%, with the highest rate found in the D3 treatment and the lowest in the D1 treatment, but there is no significant difference among them (p &gt; 0.05). The highest incubation level (ind.·m−2) and the highest number of juveniles (ind.·m−2) among treatments are found in the D3 treatment, with the incubation level (ind.·m−2) in the D3 treatment being significantly higher than that in the D1 treatment (p &lt; 0.05). The benefit–cost ratios (BCRs) of the D2 and D3 treatments remain significantly higher than that of the D1 treatment when P. clarkii prices change (all p &lt; 0.05). Our results indicate that a high stocking density habitat with open shelters could effectively improve the hatching and immune performance of ovigerous P. clarkii. Our findings are relevant for the indoor aquaculture management of ovigerous P. clarkii.

Phylogenetic Diversity of the Red Swamp Crayfish Procambarus clarkii and Its Dispersal Pattern in Northern and Central Italy

The red swamp crayfish Procambarus clarkii is one of the most threatening freshwater species in the world. The aim of this study is to provide a better understanding of the phylogeography and the invasion routes of P. clarkii populations in the Italian Peninsula through the analysis of mitochondrial phylogeny. Mitochondrial control region and cytochrome c oxidase subunit I (COI) sequences of 153 samples collected from six Italian basins were analyzed and compared to worldwide data. Except for the lakes Bolsena and Posta Fibreno, a high genetic variability was found in the other basins. The mitochondrial DNA pattern of P. clarkii from the lakes Candia and Massaciuccoli confirmed the hypothesis of double introduction events. Another entry point could be represented by Lake Trasimeno, which shows haplotypes originating from Louisiana and not shared with other Italian basins. Moreover, unique lineages were also found in the Stella River, thus enhancing the hypothesis that multiple introductions of P. clarkii occurred in northern and Central Italy and strengthening the idea that knowledge about the dispersion routes of this alien species can be useful to predict its invasiveness and elaborate control strategies to preserve biodiversity.

Exploration of the optimal stocking density of red swamp crayfish (Procambarus clarkii) larvae by using the biofloc technology

Exploration of the optimal stocking density of red swamp crayfish (Procambarus clarkii) larvae by using the biofloc technology