A 15‐day trial was conducted to determine the effect of dietary potassium on the requirement of aqueous potassium in P. vannamei under inland saline water (ISW). Two experimental diets viz. control (C) and control with 1% KCl (K) were fed to P. vannamei as six treatments viz. FW (reared in freshwater and fed on C), ASW (reared in artificial seawater and fed on C), ISW (reared in inland saline water and fed on C), ISW+eK (reared in potassium fortified ISW and fed on C), ISW+fK (reared in ISW and fed on K) and ISW+½eK+fK (reared in 50% K fortified ISW and fed on K). The samples were collected on selected intervals (0^th day, 1^st day, 7^th day and 15^th day), and mortality was recorded continuously. Total mortality (100%) was observed in FW and ISW. 100% survival was recorded in ASW and ISW+½eK+fK, while a lower survival was observed in ISW+fk. The haemolymph osmotic and ionic concentrations were lowest in FW and ISW. The principal ions (Na⁺, K⁺ and Cl⁻) and osmolality of ISW+½ eK+fK were restored to the level of ASW within 15 days. Na⁺K⁺ATPase activity was increased in ISW while lowered by K supplementation. HSP70 expression was upregulated in ISW fortified with K partially or entirely. However, the groups reared in ISW and ISW supplemented with feed potassium alone could not enhance HSP protection up to the level of ISW+eK and ISW+½ eK+fK groups. Overall, 50% of aqueous potassium can be compensated with 1% dietary KCl, without affecting survival and ionic homeostasis.

In the present study, the DNA barcoding of the nematode parasite infecting Ompok bimaculatus and Nemacheilus anguilla fish species was carried out in Barvi Reservoir, Maharashtra. To ascertain the taxonomic status of these nematode parasites, an 18S gene marker was used. Accurate identification of fish parasites is essential to formulate preventive strategies and to study host–environment relations. The present study did barcoding of the nematode parasites of the fishes caught from the Barvi Reservoir using the nuclear 18S rDNA (SSU) sequence. The nuclear 18S rDNA (SSU) was amplified into two overlapping amplicons and sequenced to identify the species based on the sequence similarity with the NCBI GenBank database. The present study sequences (both fragments) showed 98% similarity with the species of Eustrongylides. The average genetic distance value between the present study sample and species of Eustrongylides was 0.003. In the phylogenetic tree also, the sequence was clustered with the species of Eustrongylides with significant bootstrap values. The present study identified the nematode parasite of the fish caught from the Barvi Reservoir, as species of Eustrongylides. The species‐level identification could not be possible due to the insufficient/lack of reference sequences in the database. It indicates the knowledge gap concerning the species‐specific molecular markers for nematode parasites of the fish.

The present study was conducted to determine the effect of curcumin supplement diet (CSD) on growth, non-specific immunity and pro-inflammatory cytokine gene expression in Labeo rohita fingerlings. 60-day (0-45 days pre-challenge and 15 days post challenge;Aeromonas hydrophila) experiment was conducted for with four treatment groups: T1 (0.5% curcumin level), T2 (1% curcumin level), T3 (1.5% curcumin level), T4 (2% curcumin level) and a control group (0% curcumin level). Kidney tissue samples were collected for RT-PCR from all the treatment groups at 15 days of interval. After 45 days of feeding, a sub-sample of fish (15 fish from each replicate) were challenged with a virulent strain ofA. hydrophila. The mRNA expression levels of immune-related genes, viz. tumour necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) and Toll-like receptor-22 (TLR-22), were evaluated along with nitro blue tetrazolium (NBT) assay and lysozyme activity. TNF-alpha mRNA expression levels were significantly lowered in CSD treatment with the lowest level observed in the T(2)treatment group, followed by T(1)during pre-challenging period respectively. The IL-1 beta and TLR-22 expression levels also followed the similar trend in different treatment groups. Similarly, NBT and serum lysozyme activities were significantly different among treatment groups. Fish fed with 1.5% level curcumin diet (T3) had significantly highest relative percentage survival (63.64%) compared to the rest of the treatment groups. The results suggested that the diet supplemented with 1.5% curcumin level provides protective effect againstA. hydrophilainL. rohita by increasing immunity and reducing the activity of pro-inflammatory genes.