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Sterility caused by triploidization holds promising commercial implications in aquaculture. In this study, we conducted a thorough investigation into the spermatogenesis of triploid male oysters (Crassostrea gigas) to evaluate their fertility. Histological analysis and immunostaining revealed the presence of numerous immature spermatocytes and a markedly low abundance of mature spermatozoa in triploid males, indicating a robust blockade in spermatogenesis. Ultrastructural analysis and apoptosis analysis demonstrated that triploid males underwent normal spermatogonial mitosis during early spermatogenesis, like diploids. Analysis of phosphorylated histone H2AX (γ-H2AX) displayed heightened γ-H2AX staining in developed triploid male gonads, with a significantly higher number of apoptotic cells confirmed by the TUNEL assay compared to diploid counterparts. These findings suggest a potential arrest at the zygotene stage, preventing the completion of the zygotene-pachytene transition and ultimately leading to cell apoptosis. Flow cytometry results confirmed aneuploidy in spermatozoa from triploid oysters, containing approximately 1.5 times the DNA content of spermatozoa from diploid oysters. Notably, the sperm head size and flagella length in triploid oysters surpassed those in their diploid counterparts. Occasional observations of two-tailed spermatozoa in triploid males were noted. This study provides novel insights into the blocked spermatogenesis in triploid oysters, emphasizing the sterility of triploid male oysters and its relevance in aquaculture practices. • Spermatogenesis in triploid oysters undergoes meiotic prophase I arrest, failing to progress beyond the zygotene stage. • The meiotic arrest induces cell apoptosis and restricts the growth of gonadal tubules. • Triploid males generate a small number of abnormal aneuploid spermatozoa, which may lead to failed fertilization outcomes. [ABSTRACT FROM AUTHOR]

Transportation stress is considered the major cause of production and economic losses in aquaculture. Here, we examined the effects of dried ginger extract (GE) and 1,8-cineole (CIN) on juvenile largemouth bass (Micropterus salmoides) subjected to simulated transport by quantifying serum metabolites, antioxidant enzyme activity, and haematological features in conjunction with whole transcriptome analysis. Under transportation stress, the addition of dried ginger extract (20 μg/L) or 1,8-cineole (30 μg/L) significantly reduced serum cortisol levels in juvenile largemouth bass. Additionally, CIN administration was associated with a significant increase in total protein and glucose levels in serum, and reduced alkaline phosphatase (AKP) and alanine aminotransferase (ALT) enzyme activity. GE and CIN significantly increased serum lysozyme activity, glutathione peroxidase (GSH-Px) activity and total antioxidant capacity (T-AOC), thereby counteracting lipid peroxidation. Transportation stress-induced malondialdehyde (MDA) production was reduced under exposure to GE and CIN, while white blood cell (WBC) counts were increased in the treatment group compared with controls. Whole transcriptome analysis of M. salmoides liver tissue identified 533 significantly differentially expressed genes (DEGs) between the CIN and transport-only control treatment groups. DEGs were mainly enriched in endocrine system, immune system and metabolic pathways. This study demonstrates that dried ginger extract or 1,8-cineole can potentially regulate M. salmoides response to transportation stress, thereby providing novel insights into the mechanisms underlying immune response and antioxidant pathways during sedation, supporting 1,8-cineole as an effective potential antioxidant agent in aquaculture. • Impact of dried ginger extract (GE) and 1,8-cineole (CIN) in largemouth bass was assessed. • GE (20 μg/L) and CIN (30 μg/L) reduced cortisol and increased glucose in serum of juvenile largemouth bass during transport. • CIN (30 μg/L) increased antioxidant activity and WBC counts in largemouth bass. • CIN alleviated stress responses via regulating endocrine, immune systems and carbohydrate metabolic pathway. [ABSTRACT FROM AUTHOR]

The enrichment of the fish feeds with the essential amino acids like methionine is a common strategy in Aquaculture. Leaching of the amino acids in the water environment and rapid absorption from the Gastro-Intestinal tract are some issues with the free amino acids supplementation strategy. The study aimed to investigate the use of Solid Lipid Microparticles as microencapsulation system for an essential amino acid, methionine. Solid Lipid Microparticles (SLMs) of two lipids, Trimyristin (TM) and Tristearin (TS) were fabricated using a melt emulsification method to encapsulate methionine and compared for their leaching protection and release characteristics in vitro and in vivo. Leaching study performed in the simulated water environment showed that the microparticles were leaching free. In simulated Gastro-Intestinal medias, release was minimal in the gastric media for both systems, while Trimyristin based microparticles showed better release in the simulated intestinal media than Tristearin based microparticles. Oral delivery study in Tilapia by mixing SLMs with the feed showed that the encapsulated methionine can provide slow release compared to the free methionine. Among the two lipids, Trimyristin based SLMs were found to be better digested by the fish. The encapsulation of methionine in lipids can be a suitable alternative for traditional free supplementation strategy for preventing leaching losses and better absorption characteristics for enhanced utilization by the fish. • Solid Lipid Microparticles (SLMs) are suitable for encapsulation of Methionine. • The microparticles prevented leaching of Methionine in water. • The SLMs showed slow release of Methionine. • Shorter carbon chain lipid, Trimyristin showed better release properties in gastrointestinal tract. • In vivo absorption study in Tilapia demonstrated the slow-release ability of the SLMs. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Rapid, sensitive, and specific detection of pathogens is important for effective disease control in aquaculture. However, the use of conventional microbiological methods for pathogen detection is often limited by the time required to complete the assays. The aim of this study was to develop a DNA microarray assay to detect 8 species of pathogenic bacteria, i.e., Vibrio harveyi, V. alginolyticus, V. parahaemolyticus, V. anguillarum, V. cholerae, Nocardia seriolae, Aeromonas hydrophila, and Streptococcus iniae, in cultured aquatic animals. Probes were designed according to a variable region of the bacterial 16S rRNA gene and gryB sequences, and 23 probes were finally selected by hybridization with 25 bacterial type cultures. The microarray sensitivity for V. anguillarum detection in healthy fish blood was ≥100CFU/mL. Pathogenic bacteria in blood samples from 21 diseased aquacultural samples were analyzed in a blinded fashion by using the microarray, conventional culture, and 16S rRNA gene sequencing methods; the results of the microarray assay agreed well with those of the conventional culture and 16S rRNA gene sequencing methods. The results of this study show that the microarray method described is suitable for preliminary diagnoses or for confirmation of the main potential pathogens in aquatic animals. [Copyright &y& Elsevier]

Abstract The Pacific oyster (Crassostrea gigas) is one of the highly fecund marine aquaculture species and has a large variance in reproductive success, these characteristics can result in loss of genetic diversity and inbreeding especially when conducting mass selection. In the current study, we investigated the level of genetic diversity and effective population size over three successive mass-selected generations in the black shell strain of C. gigas assessed by 11 microsatellites as well as mitochondrial COI region. The results showed that the genetic variation over three generations were maintained since no detectable depression of expected heterozygosity (H e = 0.647–0.681), number of alleles (N = 5.6–6.0) and haplotypes (N h = 2). The difference in alleles and haplotypes number between the base population (BP) and three mass selective generations (M5-M7) could be mainly due to the loss during preceding family selection process. Pair-wise F ST values along with AMOVA analysis from both markers indicated unremarkable differentiation within each generation including BP. There was no deleterious effect on genetic diversity and population structure for mass selected generations imposed by our artificial breeding practice. The N eb estimation for M5, M6 and M7 was 29.8, 40.7 and 52.7, respectively. The different number of broodstocks used for each generation implied that using a balanced sex ratio and large size of broodstock as well as low selection pressure would help to increase the effective population size and avoid high level of inbreeding. The estimated linkage disequilibrium-based effective breeders size (N eb) was significantly lower than sex-ratio correction effective population size (N e), which indicated high variance in family contribution. It is suggested during mass spawning to simply undertake several mini-spawn groups and then pool the embryos to produce next generation, which can be a hedge to the high variance in reproductive success, thus, the loss of effective populations size and diversity. Other practical strategies against the loss of genetic diversity were also discussed, however, it remains to be investigated how diverse selection and follow-up procedures will benefit retaining genetic variability. This study will provide an insight into the level of genetic diversity and effective population size within mass-selected black shell line and enable a better understanding of how efficient current breeding practices are at maintaining genetic variation. This information can be applied for future selective breeding program and in the design of suitable management guidelines for sustainable breeding of C. gigas. Highlights • Genetic diversity and effective population size over successive mass-selected generations in the black shell strain were assessed. • There was no detectable loss of genetic diversity revealed by 11 microsatellites and mtDNA COI region. • A large size and balanced sex-ration of broodstock and lower selection pressure would alleviate effective population size loss. • It is suggested to simply undertake mini-spawning during mass spawning to against high variance in reproductive success. [ABSTRACT FROM AUTHOR]

The Pacific oyster ( Crassostrea gigas ) is an important aquatic animal species with enormous production and economic benefits, but heritability estimation for shell color applying mixed-family approach and computer vision system has not been performed. In this study, heritability for shell color-related traits was estimated in the golden shell strain of Pacific oyster by fostering a single cohort of 30 families in a nested mating design consisting of 10 sires and 30 dams. After parentage assignment inference based on six microsatellite markers, 690 offspring were included in the subsequent analyses. Using an animal model, at 16 months of age, heritability estimates were 0.10 ± 0.12 for L ⁎ , 0.41 ± 0.16 for a ⁎ , 0.23 ± 0.15 for b ⁎ and 0.33 ± 0.19 for Δ E . Genetic correlation between shell color-related traits and growth-related traits were generally inconspicuous ranging from − 0.02 to 0.11. Conclusions can be obtained from our study that favourable improvement in aquatic selective breeding would be predictable for the genetic potential of the golden shell color in this strain of Pacific oyster, whereas independent selection conducted at the same time rather than correlative selection would be feasible in the improvement of both types of traits. [ABSTRACT FROM AUTHOR]