Ishfaq Nazir Mir

In recent years, the production of economically important crustaceans, and decapods in inland saline areas has increased considerably. The osmoregulatory capacity of these decapods renders them culturable in wide salinity ranges, contributing to a global industry valued at billions of dollars. Therefore, gaining insights into the fundamental mechanisms that drive the adaptive capacity of crustaceans to thrive in diverse salinity ranges is essential. This comprehensive review paper unveils the pivotal adaptations of decapods that allow them to flourish in diverse salinities, ranging from freshwater to saline waters. This article discusses the molecular mechanisms of osmoregulation in decapod crustaceans with more emphasis on Litopenaeus vannammei. Moreover, the importance of maintaining an ideal osmotic balance for efficient digestion and nutrient absorption in L. vannamei is discussed. Furthermore, the effect of salinity on disease resistance in these species is explored, highlighting the need for effective disease management in aquaculture. Overall, this review explores the multifaceted factors influencing decapod crustaceans' adaptation to shifting salinities and also emphasizes the ongoing need for continued research in this domain.

The present study evaluated the dietary substitution effect of silkworm pupae meal (SWP) for fish meal (FM) on growth performance, feed utilisation, whole-body proximate composition, amino acid profile and digestive enzyme activities of Pacific white shrimp (Penaeus vannamei). The shrimp were fed with six isonitrogenous (36% crude protein), isolipidic (8% crude lipid) and isocaloric (16 MJ kg-1) experimental diets, containing 0, 20, 40, 60, 80 and 100% SWP, respectively, to replace dietary FM. A total of 360 shrimps (average initial weight of 3.86±0.20 g) were distributed into 18 tanks (20 shrimp per tank). The experimental diets were fed to triplicate groups of P. vannamei three times a day until satiation for 45 days. Significantly (p0.05) were observed in the survival rate, whole-body proximate composition and amino acid profile of shrimp fed SWP meal-incorporated diets. Additionally, higher specific activities of digestive enzymes such as amylase, trypsin and lipase were observed in shrimps fed diet with 60% incorporation level of SWP meal. The present study revealed that dietary fish meal protein up to 60% can be substituted with SWP without compromising growth performance, feed utilisation, whole-body proximate composition, amino acid profile and digestive enzyme activities of Pacific white shrimp fed on SWP meal based diets. Keywords: Amylase, Feed ingredient, Waste utilisation, Weight gain

This study was designed to evaluate the effect of dietary lipid levels on the mRNA transcripts of lipid metabolic regulatory genes. Nine combinations of experimental diets containing graded lipid (80, 100, and 120 g/kg) and protein (450, 500, and 550 g/kg) levels were fed to the Clarias magur (Indian walking catfish) larvae from 14 to 35 dph (day post hatching). All the lipolytic genes, such as pancreatic triacylglycerol lipase (PL), lipoprotein lipase (LPL), and bile salt-activated lipase (BAL), and genes for long-chain polyunsaturated fatty acid (LC-PUFA) biosynthetic enzymes like fatty acyl desaturase-2 (FADS2), fatty acyl desaturase-5 (FADS5), and elongase (ELOV) were expressed in a wide range of tissues. A high abundance of mRNA transcript levels of lipolytic genes was detected in the intestine and liver, and similarly, desaturases and elongase were predominantly found to be expressed in the liver, brain, and intestine. Among the diets, a significantly high expression of both lipolytic and LC-PUFA biosynthetic genes were observed at 8% dietary lipid level. The mRNA expression of all the studied genes was down-regulated at 12% dietary lipid contents. Hence, the present study concludes that the efficient nutrient utilization and the lipid metabolic pathway occur at the optimum dietary lipid level of 8% in C. magur larvae.

The study was conducted to investigate the expression and activity of key lipolytic enzymes during the ontogenetic development of Clarias magur. After partial characterization, the messenger RNA (mRNA) expression analysis of lipoprotein lipase (LPL), pancreatic triacylglycerol lipase (PL), and bile salt‐activated lipase (BAL) genes along with the specific lipase activity were performed in larvae from Day 1 after hatching till 34‐day posthatch (dph). Heterogeneous patterns of mRNA expression were shown by the important lipolytic enzymes and were detected before first exogenous feeding during the yolk‐sac stage. LPL started increasing from 13 dph and peaked at 16 dph followed by a declining trend till 34 dph. However, the PL observed to be peaking at 9, 22, and 30 dph. Similarly, BAL showed an increasing trend from 11 to 22 dph with a significantly high level of mRNA expression at 16 dph. Later, the specific lipase activity was evaluated which appears at Day 1 after hatching with a progressive increase from 7 to 16 dph and a further declining trend afterwards with a peak at 22 dph. The results indicated the development of exocrine pancreas at 16 dph. Furthermore, the transcript levels and the activity of lipases were regulated with the age. Hence, the present study can be helpful in devising different strategies containing optimum lipid levels at a suitable stage of development for improving the survival during larval rearing. Furthermore, the study could be a baseline for elucidating the optimized dietary lipid levels of this catfish during its larval rearing.