Unveiling the molecular mechanisms of pigmentation control in Queen Loach, Botia dario (Hamilton, 1822): Insights from sesame seed and marigold-induced antityrosinase effects.

Fish pigmentation study can reveal understandings in dermatological research based on functional genomics. Cultured ornamental fish becomes dull coloured and antityrosinase activity through sesame seed may enhance skin colour, which has not been studied. Botia dario is an indigenous fish, having ornamental and aesthetic value and can be studied as a model for fish pigmentation genetics. In this study, fish specimens were fed with 15% marigold petal meal along with 5, 10 and 15% w/w sesame seed in diet. Pigmentation genes, that is, tyr, tyrp1a, asip1, gnaq, kitlga, mc1r, mitf, pax7a, rab38, slc7a11, sox9a, sox10, csf1r, bcdo2 and gsta2 in skin and immunogens, that is, il20, nramp, tlr9 and trail in kidney were studied. Gene expression in tissues revealed enhanced pigmentation and immunity as well as the role of tyr, tyrp1a and asip1 in pigmentation. Immunogenes and blood parameters confirmed the best pigmentation diet. Colorimetric analysis also showed the enhancement of pigmentation. Insights from sesame seed and marigold-induced antityrosinase effects will be applied in aquaculture to develop natural, dietary formulations that will enhance pigmentation in ornamental fish, leading to improved skin colour and market value.

Stocking density affects immune and stress-related gene expression of Butter catfish (Ompok bimaculatus) fry in biofloc landscapes.

Scientific research into fish wellness is critical, and the concerns about crowding-related stress due to increased stocking density are inevitable. Taking this into consideration, the study defines the physiological signature of Ompok bimaculatus (Butter catfish) in a biofloc system when subjected to varying levels of stocking density. Fish (mean weight = 1.21 g ± 0.08, n = 600) were randomly stocked in 40-L glass aquaria at stocking densities of 0.5 g/L (T1), 1 g/L (T2), 1.5 g/L (T3), and 2 g/L (T4) and fed a 35% protein diet. After the 90-day trial, the physio-biochemical, molecular, and tissue-level changes were assessed. An integrated biomarker response (IBR) analysis for the key stress indicators aided us in better understanding them. There was a significant difference in blood count between T1 and T4 (total erythrocyte count, hemoglobin, and packed cell volume). T1 had higher levels of globulin and total plasma protein, but T2 had higher levels of albumin. Only in T1 did the respiratory burst and lysozyme activity appear to be higher (p < 0.05). Increased stocking densities had a significant impact on the liver function enzymes, GOT and GPT (p < 0.05). In comparison to lower densities (T1 & T2), higher stocking density (T3 & T4) was found to raise glucose and cortisol levels (p < 0.05). Antioxidant enzymes such as catalase, glutathione-S-transferase, and malondialdehyde were found to be more pronounced in lower density tissues (T1). Furthermore, the IBR plots show that lower densities have better health than higher densities. At higher stocking densities, mRNA expression of HSP70, IL-1, and IL-20 increased (p < 0.05) in kidney and liver tissues. The Nrf-2 and Tlr-9 genes were also upregulated. Also, when stocking density was increased, tissue-level histo-architectural changes were more pronounced than when stocking density was kept low. The findings of this study show that the welfare of Butter catfish cultured at high density in biofloc systems suffers from severe stress, and therefore draw more attention to the development of a species-specific standard rearing methodology in the pursuit of a profitable aqua-farming enterprise.

Molecular characterization and structural dynamics of Aquaporin1 from walking catfish in lipid bilayers.

Aquaporin's (AQPs) are the major superfamily of small integral membrane proteins that facilitates transportation of water, urea, ammonia, glycerol and ions across biological cell membranes. Despite of recent advancements made in understanding the biology of Aquaporin's, only few isoforms of aquaporin 1 (AQP1) some of the teleost fish species have been characterized at molecular scale. In this study, we made an attempt to elucidate the molecular mechanism of water transportation in AQP1 from walking catfish (Clarias batrachus), a model species capable of breathing in air and inhabits in challenging environments. Using state-of-the-art computational modelling and all-atoms molecular dynamics simulation, we explored the structural dynamics of full-length aquaporin 1 from walking catfish (CbAQP1) in lipid mimetic bilayers. Unlike AQP1 of human and bovine, structural ensembles of CbAQP1 from MD revealed discrete positioning of pore lining residues at the intracellular end. Snapshots from MD simulation displayed differential dynamics of aromatic/arginine (ar/R) filter and extracellular loop C bridging transmembrane (TM) helix H3 and H4. Distinct conformation of large extracellular loops, loop bridging TM2 domain and HB helix along with positioning of selectivity filter lining residues controls the permeability of water across the bilayer. Moreover, the identified unique and conserved lipid binding sites with 100% lipid occupancy signifies lipid mediated structural dynamics of CbAQP1. All-together, this is the first ever report on structural-dynamics of aquaporin 1 in walking catfish which will be useful to understand the molecular basis of transportation of water and other small molecules under varying degree of hyperosmotic environment.

Genetics of colour variation in wild versus cultured queen loach, Botia dario (Hamilton, 1822).

The Queen loach (Botia dario), an ornamental fish species having export potential, belongs to family Cobitidae of order Cypriniformes. The dull colouration in captive condition as compared to nature is a drawback in ornamental fisheries. We report the first comparative transcriptomic analysis of Cultured (CBD) and Natural (NBD) B. dario using bioinformatics tools. Total 26 and 7 key genes for melanin and carotenoid colouration were found, respectively. KEGG pathway annotations of the genes were carried out, to annotate and describe their relevance for pigmentation. The qPCR validation of genes confirmed their expression pattern in the skin and muscle. Differential expression of, slc7a11, asip1, mc1r, dct, tyrp1a, tyr, bcdo2, csf1r, plin2, gsta2, star3 and stard5 in the skin and muscle tissues revealed the reasons for wild versus cultured colour variation. The molecular data was further supported by low yellowness and redness values of CBD skin and muscle in a colorimeter.

Immunity augmentation in Botia dario (Hamilton, 1822) through carotenoid: a dietary approach.

The immunity and health status of ornamental fish is an important aspect, as they are kept in a confined environment and various stressful conditions which lead to depletion of overall colourful appearance and mortality. The carotenoids can act as immunity boosters in captive aquarium system and may be supplemented in the feed as aquarium fish have no access to natural carotenoids. The study aimed to assess the role of carotenoid on the immunity of B. dario. Marigold petal meal is an important source of carotenoids and used in experimental diets. Four immunogenes namely IL20, TLR9, TRAIL, and Nramp in B. dario were characterized and also studied for their relative expression in the kidney after feeding the fish with marigold petal meal supplemented diet. The expression pattern of the genes was compared with the fish of nature. The IL20 and Nramp gene were upregulated significantly (p < 0.05) in the fish of nature as compared to the experimental fish at the 60th day of feeding carotenoid-rich diet. But the TLR9 and TRAIL gene was upregulated significantly (p < 0.05) in experimental fish as compared to nature. The haematological parameters of fish after feeding with the experimental enriched diet for 60 days also confirmed the role of carotenoids in immunity.