Dried or defatted black soldier fly (Hermetia illucens) larvae meal has been shown an important ingredient in aquafeed, but little information is available about the effects of black soldier fly pulp (BSFP) on growth and health of fish. A 62-day feeding trial was conducted to assess the effects of dietary BSFP on growth performance, whole body composition, serum metabolites, antioxidant and immune response of Micropterus salmoides. Four isoproteic and isolipidic diets were formulated by adding BSFP (original substance) to the basal diet at the rate of 0% (BSFP0), 1% (BSFP1), 2% (BSFP2) and 4% (BSFP4), corresponding to inclusion of 0, 4.5, 9.0 and 18.0 g/kg DM in diets. Each diet was randomly assigned to triplicate groups of 35 fish per tank. Fish were fed twice daily to apparent satiation. Blood samples were collected at the terminal trial to analyse serum metabolites, antioxidant and immune enzyme activities. Results indicated that fish fed BSFP2 had higher (P<0.05) weight gain rate, specific growth rate and intraperitoneal fat ratio than those of fish fed other diets. Crude lipid, ash and calcium contents were higher (P<0.05) in BSFP2 than those in BSFP0. Fish fed BSFP2 and BSFP4 had lower (P<0.05) serum malonaldehyde but higher (P<0.05) acid phosphatase than other diets. It was concluded that dietary inclusion of BSFP improved growth performance of M. salmoides might be attributed to increased lipid and ash deposition. BSFP improved antioxidant and immune capacity but also increased intraperitoneal fat deposition of fish, suggesting BSFP should be careful to be used in M. salmoides diets.

In China, the Cranoglanis bouderius is classified as a national class II-protected animal. The development of C. bouderius populations has been affected by a variety of factors over the past few decades, with severe declines occurring. Considering the likelihood of continued population declines of the C. bouderius in the future, it is critical to investigate the currently unknown characteristics of gonadal differentiation and sex-related genes for C. bouderius conservation. In this study, the Illumina sequencing platform was used to sequence the gonadal transcriptome of the C. bouderius to identify the pathways and genes related to gonadal development and analyze the expression differences in the gonads. A total of 12,002 DEGs were identified, with 7220 being significantly expressed in the ovary and 4782 being significantly expressed in the testis. According to the functional enrichment results, the cell cycle, RNA transport, apoptosis, Wnt signaling pathway, p53 signaling pathway, and prolactin signaling pathway play important roles in sex development in the C. bouderius. Furthermore, the sequence characterization and evolutionary analysis revealed that AMH, DAX1, NANOS1, and AR of the C. bouderius are highly conserved. Specifically, the qRT-PCR results from various tissues showed significant differences in AMH, DAX1, NANOS1, and AR expression levels in the gonads of both sexes of C. bouderius. These analyses indicated that AMH, DAX1, NANOS1, and AR may play important roles in the differentiation and development of C. bouderius gonads. To our best knowledge, this study is the first to analyze the C. bouderius gonadal transcriptome and identify the structures of sex-related genes, laying the foundation for future research.

This study examined the diversity and responses of intestinal microbiota in hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) fed diets with varying levels of fishmeal replaced by black soldier fly larvae (BSFL). The 10% BSFL substitution (BSFL10) group showed the highest levels of trypsin and amylase. Substituting fishmeal with 30% and 50% BSFL weakened the intestinal wall, resulting in vacuoles, sparse striatal boundaries, and fewer villi. Microbiota diversity, measured through Shannon’s index, was higher in the BSFL10 and BSFL50 groups than in the control. 16S rRNA amplicon data revealed the dominance of Firmicutes, Proteobacteria, Bacteroidetes, Spirochaetota, and Verrucomicrobia phyla. The BSFL-replacement groups showed an increase in Proteobacteria, Bacteroidetes, and Spirochaetota compared to the control, but fewer Firmicutes. PICRUSt analysis indicated significant alterations in microbial function, particularly enhanced protein, carbohydrate, lipid, and energy metabolisms in the BSFL-fed group. Substituting 10% fishmeal with BSFL enhanced nutrient metabolism and gut microbiota in juvenile hybrid grouper. Further research is needed to explore factors affecting the efficacy of insect feed as a sustainable aquaculture diet.

The effects of selenium supplementation in Tachysurus fulvidraco (T. fulvidraco) on low-temperature stress are not known. In this study, 280 healthy T. fulvidraco were divided into two groups, the G0 group (a control group) and the T0 group (a selenium treatment group on a 0.22 mg/kg diet), for a 6-week feeding time. Then, low-temperature stress (water temperature dropped from 26 to 13 °C, with a rate of 1 °C/h) was administered after that. The feeding results showed that selenium increased the percent weight gain (PWG), specific growth rate (SGR), and survival rate (SR) of T. fulvidraco and decreased the feed conversion rate (FCR), but these differences were not significant (p > 0.05). Under low temperatures, selenium still has no significant effects on antioxidant indexes such as glutathione peroxidase (GSH-Px) activity, superoxide dismutase (SOD) activity, and malondialdehyde (MDA) content in serum (p > 0.05). However, metabolomic analysis revealed that selenium caused changes in lipids and lipid-like molles, organic acids and their derivatives, and fatty acyls. Choline, linoleic acid, and glycerophospholipid metabolism pathways; d-arginine and d-ornithine metabolism; valine, leucine, and isoleucine degradation; and biosynthesis pathways, as well as pyrimidine metabolism pathways, were activated to produce these metabolites to combat against this stress. In addition, selenium increased the diversity of intestinal microbes in T. fulvidraco and decreased the relative abundance of Plesiomonas. However, the combined analysis showed the intestinal microbe changes did not affect metabolite production. In summary, selenium activated lipid, carbohydrate, and amino acid metabolism for energy substance provision, reduced the oxidation and production of other harmful substances, and increased the intestinal microbe diversity of T. fulvidraco to improve resistance to low-temperature stress.

Microplastics (MPs) are plastics with diameters less than 5 mm, which are carriers that can enrich harmful substances.[1] However, MPs are difficult to detect due to their tiny size and indetermina...

This experiment was conducted to investigate the optimum lipid requirement for largemouth bass larvae. A total of 2,000 larval largemouth bass (0.06 ± 0.01 g) were randomly divided into five groups with four replicates per group. The fish were fed lipid contents of 11.22%, 13.22%, 16.25%, 19.28%, and 22.45%, denoted as L11, L13, L16, L19, and L22, respectively. The rearing trial lasted for 4 weeks. The results showed that with the dietary lipid levels increased, the weight gain rate (WGR) and specific growth rate (SGR) of largemouth bass first increased and then decreased, and the L19 group was the largest. The feed conversion ratio (FCR) decreased. The condition factor (CF) of the L11 group was significantly higher than that of other groups (p < 0.05). According to the line model calculation, when the lipid content was 20.22%, the WGR reached its maximum value. Increasing dietary lipid levels elevated crude lipid content, while moisture content significantly decreased (p < 0.05). The protein retention (PR) and lipid retention (LR) showed an upward trend (p < 0.05). The lipase content in the L22 group were significantly higher than that in the L11 group (p < 0.05). The aspartate transaminase (AST) and alanine transaminase (ALT) content in the L22 group was significantly lower than those in other groups as dietary lipid increased (p < 0.05). With increasing lipid levels, the activities of triglyceride (TG) and glucose (GLU) first increased and then decreased (p < 0.05). Furthermore, the L22 group had a higher malondialdehyde (MDA) than the other groups (p < 0.05). The alkaline phosphatase (AKP) of the L19 group was significantly lower than that of the L11 group (p < 0.05). ALT was correlated with the dietary lipid level, and the regression equation was y₃ = −2.6651x₃² + 85.629x₃ − 566.91. The width of intestinal villi in the L16 group was significantly higher than that in the other groups (p < 0.05). In summary, on the basis of the growth performance of largemouth bass larvae, the suitable dietary lipid level was 20.16%. According to liver biochemical indicators, the appropriate dietary lipid level was 16.06%.