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The assembly and succession of the gut microbiota are important events in animal growth and have a significant impact on the productivity of aquaculture organisms, which can be influenced by the environment, growth stages, and dietary changes. However, little is known about how the growth of aquaculture organisms and dietary differences during growth affect the assembly of the gut microbiota. In this study, we fed golden pompano (Trachinotus ovatus) a regular diet and a high-fat, high-protein diet, respectively. We then used bacterial 16 S rRNA gene sequencing to study the gut microbiota at different growth stages and under different dietary conditions. We found that the gut microbiota of T. ovatus changes in response to different dietary conditions. Moreover, this divergence does not change with the growth of the host. This suggests that dietary differences largely explained the gut microbiota succession, while growth stage had no significant influence on gut microbiota succession in T. ovatus from 30 to 120 dph. This study, which includes the effects of growth stage and diet, increases our understanding of how the gut microbiota of the T. ovatus assembles and colonizes and also provides new insights into the study of the gut microbiota of other aquaculture fish.

Fish venom has several biological activities, including enzyme activity, cytotoxicity, neurotoxicity, muscular toxicity, haemolytic, and cardiotoxicity, when they enter other species or a human being, they disrupt the physiological systems. Transcriptomic analysis of the fish venom glands revealed a large number of proteins relevant to the pharmacological activity even though they are not well-studied. The limitations in studying fish venoms also have an impact on their molecular characterization. This is partly because of the nature of fish venoms, as they are extremely unstable at normal ambient temperatures making them difficult to study. Venomous fish inhabit both marine and freshwater environments, they have specialized venom-delivery apparatuses. Venom delivery systems have evolved in a various animal species, originally for different purposes including defense, competition, as well as predation. In coastal areas, fish stings are a major problem because they have a serious toxic effect on fishermen, local communities, and visitors. In this study, we have discussed the general perspective of fish venom from marine and freshwater species in different aspects basically in their molecular evolution, physiology, diversity, transcriptome, and proteomic studies. We expect that this paper will provide readers with a unique perspective on understanding the current status of fish venom research as well as working for future studies. Therefore, the gap of knowledge acquired from this study will play as a baseline for researchers discovering new studies and using fish venom in a broader range of biomedical applications, and their biological information that can be used to develop drugs for pharmaceutical uses.

The peptide YY (Pyy) is a member of the Neuropeptide Y family of peptides known to play anorexigenic roles in the regulation of feed intake in several fishes. In this study, to examine the role of Pyy in the spotted scat (Scatophagus argus), the peptide was cloned from this fish for the first time. The peptide is made from a 294-bp open reading frame with a 97-amino-acid sequence that is highly conserved when compared to other organisms. The pyy gene is expressed widely throughout the spotted scat, with the highest levels in the intestine and muscle tissue. According to our pre-and post-prandial experiments, feeding has a minimal short-term effect on pyy mRNA levels. In comparison to fish that were refed on the 8th day after 7 days of starvation, pyy mRNA levels in the hypothalamus were considerably higher after 7 days of feeding. Results from this study also identified a local interaction between Pyy and some appetite-regulating peptides in spotted scat. We aimed to build a solid foundation for future research into feed intake regulation of the spotted scat, as this is one of the most cultured species.

Insulin-like growth factor 3 (IGF3) induces ovarian maturation in teleosts; however, research on its molecular regulatory mechanism remains deficient. Circular RNAs (circRNAs) and microRNAs (miRNAs) are involved in various biological processes, including reproduction. In this study, circRNAs and miRNAs involved in IGF3-induced ovarian maturation were evaluated in spotted scat (Scatophagus argus). In ovarian tissues, we identified 176 differentially expressed (DE) circRNAs and 52 DE miRNAs between IGF3 treatment and control groups. Gene Ontology (GO) enrichment analyses showed that host genes of DE circRNAs and target genes of DE miRNAs were enriched for various processes with a high degree of overlap, including cellular process, reproduction, reproductive process, biological adhesion, growth, extracellular region, cell junction, catalytic activity, and transcription factor activity. Enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways included cell adhesion molecules, ECM–receptor interaction, regulation of actin cytoskeleton, focal adhesion, cell cycle, Hedgehog signaling pathway, phosphatidylinositol signaling system, PI3K-Akt signaling pathway, Apelin signaling pathway, Notch signaling pathway, insulin signaling pathway, and Rap1 signaling pathway. A circRNA–miRNA–mRNA regulatory network was constructed, including DE genes involved in reproduction (e.g., oocyte maturation, oocyte meiosis, and ECM remodeling), such as ccnd2, hecw2, dnm2, irs1, adam12, and cdh13. According to the regulatory network and tissue distribution, we identified one circRNA (Lachesis_group5:6245955|6270787) and three miRNAs (novel_miR_622, novel_miR_980, and novel_miR_64) that may exert regulatory effects in IGF3-induced ovarian maturation in S. argus. Taken together, this study provides a novel insight into the molecular mechanisms by which IGF3 functions in ovaries and highlights the effects of circRNAs and miRNAs in reproduction in S. argus.