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Aquaculture of red swamp crayfish, Procambarus clarkii (Girard, 1852), has developed rapidly worldwide in recent years with promising prospects. However, limited knowledge about temperature effects on reproductive performance and embryonic development has hindered the development of crayfish aquaculture. The two present studies were conducted to identify optimal water temperatures (17 °C, 21 °C, 25 °C, 29 °C and 33 °C) for reproductive performance (experiment 1) and embryonic development (experiment 2) of P. clarkii. Totally, there were 12 replicates, with 480 adults and embryos from 60 ovigerous crayfish selected for experiment 1 and 2, respectively. In the first experiment, the survival of adult crayfish was not significantly affected by the temperatures tested. However, significantly higher feeding rates, spawning rates, and fecundity were obtained at 21 °C and 25 °C when compared to those at 29 °C and 33 °C. Polynomial models and loess regression fitted to the experimental data showed that highest spawning rates and fecundity occurred at 21 °C while shortest duration from mating to spawning was found at 33 °C. In the second experiment, we found that optimal embryonic development was at 25 °C with shorter hatching time and no abnormalities observed. However, while embryos showed abnormalities and subsequently died at 29 °C and 33 °C. We further built a temperature-dependent developmental model for P. clarkii embryos: D (developmental time, days) = 3,140,837(T-2.03)−3.76. Based on these results, the temperature range 21 °C – 25 °C was recommended for adult crayfish reproduction and 25 °C was recommended for embryonic development. This study indicates that manipulating water temperature is an effective alternative to current artificial reproduction techniques (e.g. eyestalk ablation and injection hormones) to induce spawning and embryonic development and thus provides mass production of juvenile P. clarkii for aquaculture.

Overfeeding in aquaculture can lead to suboptimal growth and increased production costs. Red swamp crayfish, Procambarus clarkii, is one of the most noteworthy species cultured in China, but little information is available on the optimal feeding levels of this species, especially in ponds cultured with macrophytes. In this study, we tested the effects of five different feeding levels (20%, 40%, 60%, 80% and 100% satiation) of an artificial diet on growth performance and muscle composition of juvenile P. clarkii in 15 concrete ponds cultured with the macrophyte Hydrilla verticillata (three replicates for each treatment). The results showed that growth performance decreased only when feeding levels were below 60% satiation. Muscle composition analysis revealed that the moisture and ash contents of muscle did not vary significantly with feeding levels but that the lipid and protein contents of muscle significantly decreased when P. clarkii was fed to 40% satiation. Stable isotope analysis suggested a shift in crayfish diets to easily available H. verticillata when feeding levels decreased. With this study, we hope to encourage crayfish farmers to reduce feeding levels and increase natural food items such as macrophytes in cultured ponds to maximize crayfish yields and reduce production costs.

A 75-day experiment was conducted with 6 different feeding regimes to evaluate compensatory responses in growth, physiological state, and muscle biochemical composition of juvenile Procambarus clarkii (1.37 ± 0.03 g). P. clarkii were deprived of feed for 0 day (control group), 2 (treatment 2), 4 (treatment 3), 8 (treatment 4), 16 (treatment 5), and 24 days (treatment 6) before being fed daily until day 75. Each feeding regime was tested in 10 replicate tanks with four crayfish in each tank. The growth (survival, SGRw, FCR, feeding rate, moulting frequency, HSI, PI, growth trajectory analysed using schnute model), digestive enzymes (trypsin and lipase), energy reserves and metabolites (alkaline phosphatase, total protein, total cholesterol, triglyceride, aspartate transaminase, and pyruvate kinase), antioxidant enzymes (superoxide dismutase, catalase, and malondialdehyde), and muscle biochemical composition (crude protein, crude lipid, ash, and moisture) were evaluated every 25 days. Results showed that P. clarkii in treatments 3 and 4 had similar growth as those in the control group but higher feeding rates at the end of the experiment, indicating that full compensatory growth occurred, while crayfish in treatments 5 and 6 only showed partial compensation. No compensation was observed in treatment 2. Furthermore, P. clarkii in treatment 4 had better feed utilisation efficiency, with a significantly lower FCR than those in other groups. The feed-deprivation period significantly influenced the physiological state of P. clarkii, with significantly lower values of variables of energy reserves and metabolites observed in treatments 5 and 6, except for alkaline phosphatase. Furthermore, P. clarkii in treatment 6 had significantly lower catalase activity but higher trypsin activity and malondialdehyde content than those in other groups. Muscle biochemical composition analysis revealed that P. clarkii in treatments 5 and 6 had significantly lower crude protein and lipid contents than other groups. The physiological state and muscle biochemical composition of crayfish varied over time (days 25, 50, and 75), with markedly increased activities or contents of total cholesterol, triglycerides, aspartate transaminase, catalase, crude protein and crude lipid observed in all treatments except the control group at the end of the experiment. Collectively, these results demonstrate that long-term feed deprivation (16 and 24 days) could only elicit partial compensation in growth, physiological state, and muscle biochemical composition of P. clarkii, while feed deprivation for 4 and 8 days followed by refeeding until day 75 could effectively trigger full compensation, particularly with respect to improve feed utilisation efficiency.

The accumulation of amyloid-β (Aβ) peptides in the brain is considered to be the initial event in the Alzheimer's disease (AD). Neurotoxicity mediated by Aβ has been demonstrated to damage the cognitive function. In the present study, we sought to determine the effects of O-1602, a specific G-protein coupled receptor 55 (GPR55) agonist, on the impairment of learning and memory induced by intracerebroventricular (i.c.v.) of Aβ1–42 (400 pmol/mouse) in mice. Our results showed that i.c.v. injection of aggregated Aβ1–42 into the brain of mice resulted in cognitive impairment and neurotoxicity. In contrast, O-1602 (2.0 or 4.0 μg/mouse, i.c.v.) can improve memory impairment induced by Aβ1–42 in the Morris water maze (MWM), and novel object recognition (NOR) tests. Besides, we found that O-1602 reduced the activity of β-secretase 1 (BACE1) and the level of soluble Aβ1–42 in the hippocampus and frontal cortex. Importantly, O-1602 treatment reversed Aβ1–42-induced GPR55 down-regulation, decreased pro-inflammatory cytokines, and the level of malondialdehyde (MDA), increased the levels of glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT), as well as suppressed apoptosis as indicated by decreased TUNEL-positive cells, and increased the ratio of Bcl-2/Bax. O-1602 treatment also pronouncedly ameliorated synaptic dysfunction by promoting the upregulation of PSD-95 and synaptophysin (SYN) proteins. Moreover, O-1602 concurrently down regulated the protein levels of RhoA, and ROCK2, the critical proteins in the RhoA/ROCK2 pathway. This study indicates that O-1602 may reverse Aβ1–42-induced cognitive impairment and neurotoxicity in mice by inhibiting RhoA/ROCK2 pathway. Taken together, these findings suggest that GPR55 could be a novel and promising target for the treatment of AD.

The accumulation of amyloid beta (Aβ) in the brain is thought to be associated with cognitive deficits in Alzheimer's disease (AD). However, current methods to combat Aβ neurotoxicity are still lacking. G protein-coupled receptor 17 (GPR17) has become a target for treating inflammation in brain diseases, but it is unclear whether it has a role in AD. Here, we investigated the effects of cangrelor, a GPR17 antagonist, on neurotoxicity and memory impairment induced by intracerebroventricular (i.c.v.) injection of Aβ1–42 in mice. The behavior results showed that cangrelor (2.0 or 4.0 μg/mouse, i.c.v.) treatment reversed the deficits in memory and learning ability induced by Aβ1–42 in mice. Importantly, we demonstrated for the first time that GPR17 expression in the hippocampus and frontal cortex is increased in response to Aβ1–42 exposures. We also found that cangrelor treatment reduced the activity of β-secretase 1 (BACE1) and the levels of soluble Aβ1–42 in the hippocampus and frontal cortex. Meanwhile, cangrelor treatment suppressed oxidative stress induced by Aβ1–42, as proved by reduced production of malondialdehyde (MDA), and increased glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT), and promoted the expression of nuclear factor E2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1). Furthermore, cangrelor also suppressed Aβ1–42-induced neuroinflammation, characterized by suppressed activation of microglia, decreased the levels of pro-inflammatory cytokines, and nuclear translocation of NF-κB p65, as well as ameliorated synaptic deficits by promoting the upregulation of synaptic proteins, and increasing the number of Golgi-Cox stained dendritic spines. These results suggest that cangrelor may reverse Aβ1–42-induced cognition deficits via inhibiting oxidative stress, neuroinflammation, and synaptic dysfunction mediated by Nrf2/HO-1 and NF-κB signaling.

Water temperature plays a significant role in the reproductive processes of temperate fishes. In the present study, the effects of water temperature on the reproductive performance and offspring quality of rare minnow (Gobiocypris rarus) were evaluated by cultured parent fish at different temperature (18～30℃) in a 2-month trial. The results revealed that rare minnows could spawn continuously within the range from 18℃ to 30℃, and these at 24℃ and 27℃ spawned every 3-4 days. Batch size of rare minnow increased with increasing water temperature, while egg production increased with increasing water temperature and then decreased at 30℃. High water temperature (30℃) had significantly adverse effects on fertilization rate and hatching rate (P

Pseudocrossocheilus tridentris is an endemic fish species in the upper Pearl River with limited published genetic information. In the current study, the complete mitochondrial genome of P. tridentr...

Red swamp crayfish, Procambarus clarkii (Girard, 1852), aquaculture has developed rapidly in recent years. However, limited knowledge about the response of physiological processes to different feeding levels has hindered the expansion of scientific feeding strategies. The present study was conducted to evaluate the growth performance (specific growth rate: SGRw, survival, and moulting frequency), feed utilisation (feeding rates, feed conversion ratio: FCR, waste production ratio: WPR), and physiological response variables to different feeding levels (1%, 2%, 3%, 4%, 5%, and 6% body weight per day, BW day−1) of juvenile P. clarkii for 60 days. Each treatment was replicated ten times, with 40 juveniles per treatment. No significant differences were observed in the growth performance of P. clarkii fed at 3%, 4%, 5%, and 6% BW day−1. However, they exhibited a significantly higher feeding rate, and FCR and WPR values when fed at 6% BW day−1. Among the physiological variables, activities of digestive enzymes (trypsin, lipase, and AKP) and antioxidant enzymes (SOD, CAT, and MDA) were significantly correlated with feeding levels; the Pearson correlation coefficients of these enzymes were 0.82, 0.57, 0.39, 0.66, 0.70, and −0.38, respectively. The biochemical indicators of nutrient status (total protein, total cholesterol, triglyceride, and GOT and PK activities) increased with increasing feeding levels, as revealed by the Self-Organizing Map. The two-way ANOVA revealed that P. clarkii fed at 5% and 6% BW day−1 had significantly higher trypsin and PK activities, and total protein and total cholesterol contents, whereas when fed at 6% BW day−1, it was exposed to oxidative stress. When the physiological variables were grouped by principal component analysis (PCA), they varied over experimental dates. P. clarkii exhibited higher trypsin, lipase, and MDA activities on the 20th day, but lower triglyceride content and GOT activity than on the 40th day. This study indicated that P. clarkii did not benefit from high feeding level (6% BW day−1), providing an incentive for farmers to reduce dietary input and production costs, thus promoting the sustainability of P. clarkii aquaculture.

Background The red swamp crayfish, Procambarus clarkii (Girard, 1852), is one of the most promising freshwater species for aquaculture in China. Understanding its reproductive pattern and population dynamics is crucial for sustainable management, but there is currently a lack of fundamental knowledge of commercial P. clarkii populations. Therefore, the purpose of this study was to investigate the reproductive pattern and population dynamics of commercial P. clarkii throughout the yearly cycle. Methods A total of 2,051 crayfish (1,012 females and 1,039 males) were collected from March 2016 to February 2017 in the area of Selection and Reproduction Center of Crayfish. The reproductive pattern was evaluated by the gonadosomatic index (GSI), hepatosomatic index (HSI), ovarian development and fecundity. Growth, mortality rates and exploitation rate were estimated by electronic length frequency analysis by R package “TropFishR” based on data of cephalothorax length (CTL). Results Our results demonstrated that spawning activities of P. clarkii took place from September to November, with a mean fecundity of 429 ± 9 eggs per female. There were two recruitments yearly, a major one from October to November and a minor one from March to May. With respect to population growth, five growth cohorts were identified for both females and males. Crayfish grew faster but attained smaller asymptotic maximum CTL as indicated by higher growth coefficient (K), growth parameter index (Ø′) and lower asymptotic CTL (Linf). The estimates of total mortality rate (Z), natural mortality rate (M) and fishing mortality rate (F) were 1.93, 1.02, 0.91 year−1 for females and 2.32, 0.93, 1.39 year−1 for males, which showed that the mortality of male crayfish was mainly caused by fishing. The estimates of exploitation rate (E) indicated that male crayfish were overexploited, with the values of 0.47 and 0.60 year−1 for females and males, respectively. Discussion P. clarkii spawned from September to November while two recruitments were observed yearly. We inferred that some eggs, prevented from hatching by low water temperature in winter, were more likely to hatch in the next spring. Moreover, the fishing mortality rate was relatively high for males, which might be related to the males-directed selection during the reproductive period. The higher values of exploitation rate in our study confirmed that males P. clarkii were overexploited and were under high fishing pressure. We thus suggest reducing fishing intensity on immature crayfish and avoid sex selection during the reproductive period to improve the overall sustainability of commercial P. clarkii populations.

This study aims to evaluate the acute toxicity of pymetrozine to juvenile Procambarus clarkii. Two 96-h toxicity tests were conducted to assess the lethal concentration 50 (LC50) values, behaviors, and histopathology (at 50% of the 96 h LC50) after pymetrozine exposure. The results showed high toxicity of pymetrozine to juvenile P. clarkii in a dose and time dependent manner, with a decreasing LC50 from 1.034 mg/L at 24 h to 0.479 mg/L at 96 h. The maximum allowable concentration (MAC) of pymetrozine for P. clarkii was 0.106 mg/L. Behavioral abnormalities were observed in pymetrozine-treated crayfish, such as incunabular hyperexcitability, subsequent disequilibrium, lethargy, and increased defecation. Significant lesions were observed in all pymetrozine-treated tissues, including: (1) in gill, hemocytic infiltration and 33.27% of epithelial cells lesions; (2) in perigastric organs, 64.37%, 29.06%, and 13.99% of tubules with lumen atrophy, vacuolation, and cell lysis, respectively; (3) in heart, 2.5%, 8.55% and 7.74% of hemocytic infiltration, vacuolization, and hyperplasia, respectively; (4) in stomach, 80.82%, 17.77%, 6.98%, 5.24% of cuticula swelling, vacuolization, muscle fragmentation, hemocytic infiltration, respectively; (5) in midgut, 7.45%, 10.98%, 6.74%, and 13.6% of hyperplasia, tissue lysis and vacuolation, hemocytic infiltration, muscle fracture; and (6) in abdominal muscle, 14.09% of myofiber fracture and lysis. This research demonstrates that pymetrozine is highly toxic to juvenile P. clarkii, with significant effects on mortality, behavior and histopathology at concentrations of ≤1.1 mg/L, while the estimated practical concentration of pymetrozine in rice-crayfish culture water was around 20 times lower than the calculated MAC.

The transcription factor, signal transducer and activator of transcription-3 (STAT-3) contributes to various physiological processes. Here we show that mice with liver-specific deficiency in STAT-3, achieved using the Cre-loxP system, show insulin resistance associated with increased hepatic expression of gluconeogenic genes. Restoration of hepatic STAT-3 expression in these mice, using adenovirus-mediated gene transfer, corrected the metabolic abnormalities and the alterations in hepatic expression of gluconeogenic genes. Overexpression of STAT-3 in cultured hepatocytes inhibited gluconeogenic gene expression independently of peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1 alpha), an upstream regulator of gluconeogenic genes. Liver-specific expression of a constitutively active form of STAT-3, achieved by infection with an adenovirus vector, markedly reduced blood glucose, plasma insulin concentrations and hepatic gluconeogenic gene expression in diabetic mice. Hepatic STAT-3 signaling is thus essential for normal glucose homeostasis and may provide new therapeutic targets for diabetes mellitus.

The mixture of bensulfuron-methyl and acetochlor (MBA) has been widely applied as a rice herbicide in China, but the mixture toxicity of MBA to aquatic organisms is largely unknown. The current study aims to investigate the acute effects of MBA to juvenile red swamp crayfish, Procambarus clarkii. Firstly, a 96 h semi-static exposure was conducted to determine the Lethal Concentration 50 (LC50) values at 24, 48, 72 and 96 h, as well as to assess the behavioral and morphological effects. A second 96 h exposure was conducted at an MBA concentration of 50% of the 96 h LC50 (72.62 mg/L) to assess the histological changes in the gill, perigastric organ, muscle, heart, stomach, and midgut. The results showed that MBA exhibited low acute toxicity with the 24, 48, 72 and 96 h LC50 values of 191.25 (179.37–215.75), 166.81 (159.49–176.55), 154.30 (148.36–160.59) and 145.24 (138.94–151.27) mg/L, respectively. MBA-exposed crayfish showed body jerk, belly arch, equilibrium loss, body and appendage sway, and lethargy; and the dead crayfish showed dark gray or grayish-white body color and separated cephalothorax and abdomen. At 72.62 mg/L, MBA exposure caused significant histopathological alterations, mainly including the cuticular and epithelial degeneration of all the gills; atrophy of tubule lumina and cellular vacuolation of the perigastric organs (61.15 ± 9.90% of the tubules showed lesions); epithelial hyperplasia (48.40 ± 9.00%), myocardial fibers and epithelial cell lysis (17.30 ± 2.01%), and hemocytic infiltration of the hearts; cuticular swelling (15.82 ± 2.98%) and vacuolate connective tissue (11.30 ± 2.47%) of the stomachs; atrophied bladder cell and fragmented longitudinal muscles (95.23 ± 4.77%) of the midguts; and slight myofibers fragmentation and lysis (7.37 ± 0.53%) of the abdominal muscles. Our results indicate that MBA can cause behavioral, morphological and histopathological effects on juvenile P. clarkii at relatively high concentrations, but its acute toxicity is low compared with many other common herbicides.