Impact of salinity changes on growth, oxygen consumption and expression pattern of selected candidate genes in the orange mud crab ( Scylla olivacea )

Abstract

Change in environmental salinity level is a major limiting factor for the aquaculture productivity because it imposes severe stress on organisms that in turn retards growth. The orange mud crab (Scylla olivacea) is an important coastal aquaculture species (farming is practised in 10‰–20‰ salinity levels) in Bangladesh. The present study was conducted to investigate the changes in growth, O2 consumption and mRNA expression levels of five selected genes in the orange mud crab (S. olivacea) exposed to three different experimental salinity levels (0‰, 10‰ and 20‰) for three months. Crabs reared at 10‰ and 20‰, showed significantly higher (p < .05) growth performance and expression of growth regulatory genes (Actin and α‐amylase). The highest levels (p < .05) of O2 consumption and expression of ion regulatory genes (Na+‐K+‐ATPase, V‐type H+‐ATPase and Diuretic Hormone) were obtained at 0‰. Moderate levels of growth and expression of selected candidate genes were observed at 10‰ treatment while the highest levels of growth and gene expression were obtained at 20‰ (control salinity). Strong interactions were observed between growth performance and expression of growth genes (R2 = 0.81–0.91), and rate of O2 consumption and expression of ion regulatory genes (R2 = 0.83–0.93), implying that the selected genes are important candidates for growth and ionic balance in S. olivacea. Growth performance was found to be very low at 0‰ initially, after 30 days crabs showed better growth performance at this salinity level. It is thus inferred that orange mud crab individuals might require 3–5 days for acclimation to salinity stress but it can take at least 30 days for acclimation to regular growth. Results indicate that with proper acclimation, the orange mud crab (Scylla olivacea) can be farmed at low salinity conditions and possibly in freshwater condition.

Effects of Salinity on Physiological, Biochemical and Gene Expression Parameters of Black Tiger Shrimp (Penaeus monodon): Potential for Farming in Low-Salinity Environments

“…Significantly negative correlations (Figure 15) between growth and serotonin (R 2 = −0.51, p < 0.05) as well as growth and glucose (R 2 = −0.50, p < 0.05) levels further support the interpretation that glucose and serotonin levels indicate the magnitude of stress on experimental shrimp, and that imposed stress impedes growth. NKA is well known for its important functional role in ionic balance under a wide range of salinities by establishing strong electrochemical gradients [10][11][12][68][69][70]. Very high expression levels (1.5-3 fold higher than the control) of NKA at low salinities (0-5‰), 30‰ and moderate expression levels (1.2-1.5 fold higher) at 10‰ (Figure 7) suggest its important role in ionic regulation under a wide range of salinity levels for black tiger shrimp.…”

“…Biochemical aspects involve changes in: (i) the amount of free fatty acids (FFA) and free amino acids (FAA) in the hemolymph and in the gill (that create an impermeable membrane to restrict diffusive ion loss or gain) to establish a condition of osmotic equilibrium [19,20]; (ii) the number of hemocyte cells in the hemolymph that indicate immunity status (hemocyte cells break down under stressful conditions and the amount of hemocyte cell lysis depends on the intensity of stress) [20]; and (iii) increased serotonin (crustacean stress hormone) and glucose levels in the hemolymph [3]. Genetic or genomic responses may include changes in expression patterns of certain genes, modifying mRNA production for subsequent protein synthesis [10,[21][22][23].…”

“…The main challenge for acclimation and survival in low-salinity environments is to maintain ionic regulation (osmoregulation) between body fluid (hemolymph in crustaceans) and the surrounding medium [ 8 , 9 , 10 ]. Organisms must regulate internal physiological, biochemical and genetic mechanisms rapidly to deal with salinity changes [ 2 , 11 , 12 , 13 ].…”

Growth and survival of diploid and triploid bata, Labeo bata (Hamilton, 1822)

“…The survival rate of triploids was superior over the diploids due to the heat shock treatment that probably made the triploids to acclimate well (due to their ability to tolerate thermal stress at early stage of life) with culture conditions and minimise stress. It is also thought that the presence of extra genetic materials may also be a potential reason for higher survivability in triploids, which increase their immune functions and hormonal secretion for adaptability (Li et al, 2009;Rahi et al, 2020).…”

Characterization of p53 From the Marine Crab Portunus trituberculatus and Its Functions Under Low Salinity Conditions

“…Organisms often experience stress resulting from changes in environmental salinity, although there are differences among species. The ion regulation mechanisms of freshwater and marine species have been studied extensively, for example, low salinity induced mRNA expression levels of Na + -K + -ATPase , V-type H + -ATPase , and Diuretic Hormone in the orange mud crab Scylla olivacea ( Rahi et al, 2020 ); the ion transport-related genes chloride channel protein 2 and ABC were significantly downregulated in mud crab Scylla paramamosain under high salinity ( Zhang et al, 2020 ); and however, only a few studies have focused on the role of apoptosis. Changes in cell contact with the outside environment and ion transport depend on the external osmotic pressure, which is affected to the greatest extent by changes in salinity.…”