Effects of High Salinity Stress on the Survival, Gill Tissue, Enzyme Activity and Free Amino Acid Content in Razor Clam Sinonovacula constricta

Abstract

Salinity can affect the physiological and productive characteristics of bivalves. The razor clam Sinonovacula constricta naturally distributing in intertidal zones and estuarine waters is extensively cultured in China. High-salinity is a serious threat to its culture, especially in pond culture model. Here, we investigated the effects of high-salinity on the survival, gill tissue, enzyme activity and free amino acid content of S. constricta. Individuals were randomly divided into six groups treated with different salinities of 20, 25, 30, 35, 40, and 45 ppt. The median lethal salinity calculated by linear regression and probit analysis methods were similar, with 46.61, 43.17, 36.99, 35.99, and 34.99 ppt by linear regression, while 44.63, 42.87, 38.45, 37.32, and 36.17 ppt by probit analysis at 72, 96, 120, 144, and 168 h, respectively. Furthermore, paraffin section revealed that the gill of razor clam shrunk quickly under high-salinity and dissolved at 48 h under salinity of 40 ppt, but not under 30 ppt. In addition, the activities of three enzymes including Na+-K+-ATPase, acid phosphatase and alkaline phosphatase changed significantly under high-salinity. Besides, the contents of total free amino acids (TFAAs) in the gill tissues were 61.25 ± 1.58, 89.36 ± 4.18, and 111.98 ± 1.46 mg⋅g–1 at salinity of 20, 30, and 40 ppt, respectively, indicating increasing TFAA contents with salinity. Notably, several amino acid species including taurine, alanine, proline, glycine and glutamic showed significantly changed contents in response to salinity variation, suggesting these amino acids might play an important role in razor clam’s adaptation to salinity stress. Combining all these results, it was referred that razor clams may adapt to moderately high-salinity of 30 ppt in a short time through osmotic adjustment. Although a small proportion of individuals could survive under the salinity of 35 ppt, the death of most individuals still suggested it can hardly be accepted in aquacultural production. Notably, living under a salinity of 40 ppt for more than 48 h could cause great damage to razor clams. Therefore, the seawater salinity is recommended to be lower than 30 ppt for S. constricta aquaculture. Overall, this study provides guidance for the culture and breeding of high-salinity tolerant razor clams.

Effects of Short-Term Salinity Stress on Ions, Free Amino Acids, Na+/K+-ATPase Activity, and Gill Histology in the Threatened Freshwater Shellfish Solenaia oleivora

“…The regulation of organic osmolyte content is an important strategy for the adaptation of organisms to hypotonic and hypertonic conditions because of the low effect on cell physiology [37]. As important organic osmolytes, FAAs have been proven to participate in osmoregulation in many marine mollusks under salinity stress, such as Crassostrea gigas [38], M. lusoria [16], and S. constricta [12]. Likewise, a previous study reported that a freshwater mollusk C. sandai uses FAAs as osmolytes under hyperosmotic conditions [38].…”

“…The gill is an important organ responsible for osmoregulation, and its histopathological changes can be used as markers of salinity adaptation [42]. In S. constricta, the salinity (30‰ and 40‰) stress induced the shrinkage of the gill filaments and decreased gill thickness [12]. In S. purpurata, salinity (35‰) stress resulted in shrunken gill filaments and increased filament spacing [13].…”

“…As an important organ responsible for osmoregulation, the gill directly contacts ambient water and is thus the main site of osmotic water loss and salt diffusion gain [10,11]. The histological structures of gills are altered under low or high salinity stress in mollusks, such as Sinonovacula constricta [12] and Saxidomus purpurata [13]. Additionally, inorganic ions are the main osmotic effectors in the hemolymph of mollusks.…”

Comparative Study on Morphological, Biochemical and Distribution Pattern of Villorita Cyprinoides and Meretrix Casta Bivalve Shells in Vembanad Estuary, Kerala, India.

“…The distribution of bivalves is determined by hydrodynamic variables, sediment types, and depth of substrates (Whetstone 2005). Sediment features in uence the number and form of clams, whereas salinity in uences the physiological and productive properties of clams (Cao 2022). A total of 306 nos of Villorita cyprinoides shells and 169 nos of Meretrix casta shells were obtained from the ten sample locations of Vembanad estuary.…”

Benefits of Alginate and Spirulina Supplementation to the Growth and Resistance Against Salinity Exposure in Litopenaues vannamei Post-Larvae

“…Low salinity disrupts the PL osmoregulation, necessitating an increased supply of oxygen. Therefore the high compound which is rich in antioxidant activity is urgently needed (Cao et al, 2022). This increased osmotic pressure disrupts shrimp immune system, rendering them more vulnerable to disease infections (Pang et al, 2019).…”