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Effects of Stocking Density on the Growth Performance, Physiological Parameters, Redox Status and Lipid Metabolism of Micropterus salmoides in Integrated Rice-Fish Farming Systems.

ABSTRACT: Stocking density has been identified as one of the main factors affecting fish growth, welfare and behavior. However, few studies have focused on the effects of stocking density on fish health in integrated rice-fish farming systems. Thus, the aim of this study was to evaluate the effects of different stocking densities on the growth performance, physiological parameters, redox status and lipid metabolism of Micropterus salmoides in an integrated rice-fish farming system. The fish were reared at three densities: low density (LD, 40 g/m³), medium density (MD, 80 g/m³) and high density (HD, 120 g/m³) for 90 days. At the end of the experiment, fish reared in the MD and HD groups showed lower growth performance than those from the LD group. The HD treatment significantly altered the physiological parameters, including glucose and lactate. Meanwhile, the HD treatment induced oxidative stress and lipid peroxidation after 90 days of farming. Furthermore, transcriptomic analysis revealed that HD treatment led to abnormal lipid metabolism. Interestingly, we found the suppression of three key pathways related to lipid metabolism, including the PPAR, insulin and adipocytokine signaling pathways, in the HD group. Overall, our data indicated that the HD treatment inhibited growth and caused physiological responses, oxidative stress and abnormal hepatic lipid metabolism in M. salmoides in an integrated rice-fish farming system.

SUBMITTER: Jia R

PROVIDER: S-EPMC9312047 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundLargemouth bass (Micropterus salmoides) are an economically important freshwater fish species that have been investigated for both the short and long-term effects of stress, secondary to angling. Limited data has been published on the hematological parameters of this species and blood sample stability is a notable limitation of hematologic field studies. A relatively novel technique using 10% neutral buffered formalin preserves heparinized whole blood and maintains blood cell stability beyond one month in striped bass. The objective of this study was to evaluate the differences in hematological parameters between tournament-caught and captive-raised largemouth bass using whole blood preservation with neutral buffered formalin.MethodsTwo populations of largemouth bass (n = 26 wild; n = 29 captive) underwent coccygeal venipuncture to collect heparinized whole blood for packed cell volume, total solids, and manual differential. Formalin preservation of heparinized whole blood facilitated manual hemocytometer analysis. Results were compared between the populations (tournament-caught, and captive-raised) with Wilcoxon rank sum test, a Hotelling's T 2 test, and Bonferroni simultaneous 95% confidence intervals to determine significance.ResultsThe mean packed cell volume (44.9 ± 5.4%) and total solids (7.2 ± 1.1 g/dL) were significantly higher, while the total leukocyte count (7.08 ± 1.86 × 103/µL) was significantly lower in the wild tournament-caught population of largemouth bass, as compared to the captive-raised counterparts (PCV 34.4 ± 7.2%; TS 5.2 ± 1.0 g/dL; WBC 16.43 ± 8.37 × 103/µL). The wild population demonstrated a significantly distinct leukogram characterized by a neutropenia (24.1 ± 12.7%), lymphocytosis (67.7 ± 13.0%), and monocytopenia (8.3 ± 2.9%), while the erythrocyte and thrombocyte counts were not significantly different between populations.DiscussionNumerous factors have been demonstrated to influence hematologic parameters in fish including age, size, sex, temperature, environmental oxygen level, population density, and infection. The wild population endured stress during angling capture, live-well hypoxia, transport, and extended air exposures at weigh in, which may have caused a stress leukopenia as well as osmoregulatory dysfunction and subsequent hemoconcentration. Further evaluation of seasonal impact as well as increased sample size is warranted to enhance our understanding of largemouth bass hematology.ConclusionThis study concluded that wild largemouth bass captured via tournament angling have higher packed cell volume and total solids, and lower total leukocyte counts, compared to captive-reared individuals. Through the completion of this study, we demonstrated the successful use of 10% neutral buffered formalin to preserve heparinized whole blood for precise hemocytometer cell counts in a new teleost species, the largemouth bass.

Project description:The largemouth bass is an important species, and its culture has risen sharply with the surge in fish aquaculture in China. Due to the lack of selective breeding technology for the largemouth bass, the growth rate and disease resistance are low, its sexual maturation is slow, and other serious problems are contributing to a sharp decline in the safety and quality of largemouth bass products in recent decades. Therefore, comprehensive breeding programs to improve the economic performance and promote the modern industrial development of largemouth bass must be considered a priority. Here, a total of 152 adult largemouth bass, including two parents and 150 progenies, were selected to produce the genetic mapping family. Then, a high-density linkage map was constructed based on restriction site-associated DNA sequencing using 6,917 single-nucleotide polymorphisms (SNPs) located in 24 linkage groups (LGs). The total genetic length of the linkage map was 1,261.96 cM, and the length of each LG varied from 24.72 cM for LG02 to 117.53 cM for LG16, with an average length of 52.58 cM and an average SNP number of 286. Thirteen significant quantitative trait loci (QTLs) for sex determination were located on LG04, LG05, LG08, LG12, LG15, LG21, and LG23. An informative QTL cluster that included six QTLs was detected on LG12. However, one notable QTL, which accounted for 71.48% of the total phenotypic variation, was located in the region of 1.85 cM on LG05. In addition, 32 identified QTLs were related to growth, including body weight, body length, body height, and head length. The QTLs for these growth-related traits are located in 13 LG regions and have little effect on phenotypic variation. This high-density genetic linkage map will enable the fine-mapping of economic traits and support the future genome assembly of the largemouth bass. Additionally, our study will be useful for future selective culture of largemouth bass and could potentially be used in molecular-assisted breeding of largemouth bass for aquaculture.

Project description:Toxaphene is an organochlorine pesticide and environmental contaminant that is concerning due to its atmospheric transport and persistence in soil. In Florida, toxaphene and other organochlorine pesticides were used heavily in agriculture on the north shore of Lake Apopka and they are still detectable in soil. Wild largemouth bass that inhabit the lake and the marshes along the north shore have been exposed to a variety of organochlorine pesticides including dieldrin, methoxychlor, and p,p'-DDE, among others. While these other organochlorine pesticides have been studied for their endocrine disrupting effects in largemouth bass, there is little information for toxaphene. In this study, male and female largemouth bass were given food containing 50 mg/kg toxaphene for almost 3 months, to achieve tissue levels similar to those found in fish at Lake Apopka. Sex-specific toxicity was then evaluated by measuring various reproductive endpoints and transcriptomic changes. In females, gonadosomatic index showed a trend towards reduction (p = 0.051) and plasma vitellogenin was reduced by ~40% relative to controls. However plasma levels of 17β-estradiol and testosterone were not perturbed by toxaphene exposure. These data suggest that toxaphene does not act as a weak estrogen as many other organochlorine pesticides do, but rather appears to be acting as an antiestrogen in female fish. There were no obvious changes in the gonadosomatic index and plasma hormones in male bass. However, ex vivo explant experiments revealed that toxaphene prevented human chorionic gonadotropin-stimulated testosterone production in the testis. This suggested that toxaphene had anti-androgenic effects in males. Subsequent transcriptomic analyses of the testis revealed that androgen receptor/beta-2-microglobulin signaling was up-regulated while insulin-related pathways were suppressed with toxaphene, which could be interpreted as a compensatory response to androgen suppression. In the male liver, the transcriptome analysis revealed an overwhelming suppression in immune-related signaling cascades (e.g. lectin-like receptor and ITSM-Containing Receptor signaling, CD16/CD14 Proinflammatory Monocyte Activation, and CD38/CD3-JUN/FOS/NF-kB Signaling in T-cell Proliferation). Overall, this study showed that toxaphene induced sex-specific effects. The transcriptomic and physiological responses observed can contribute to the development of adverse outcome pathways for toxaphene exposure in fish.

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Effects of Stocking Density on the Growth Performance, Physiological Parameters, Redox Status and Lipid Metabolism of Micropterus salmoides in Integrated Rice-Fish Farming Systems.

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