Effects of hypoxia on survival, behavior, metabolism and cellular damage of Manila clam (Ruditapes philippinarum)

Abstract

The Manila clam Ruditapes philippinarum has become a common and dominant macrobenthic species in coastal areas of the northwestern Pacific and temperate waters of Europe; it is also a major cultured shellfish, with annual worldwide production exceeding 3.3 million tonnes. This species faces greater risk of exposure to hypoxia as eutrophication worsens throughout its coastal habitats; however, its tolerance to hypoxia remains unclear, and the toxicological indicators including LC 50 and LT 50 have not yet been assessed. Previous studies on the effects of hypoxia on marine benthos have focused largely on functional responses, such as metabolism and gene expression, leaving potential structural damage to the mitochondria or the cells unknown. In this study we assessed the effects of hypoxia on Manila clam in terms of survival, behavior, metabolism and cellular damage, using a newly designed automated hypoxia simulation device that features exceptional accuracy and good stability. The clams exhibited strong tolerance to hypoxia as the 20-day LC 50 for dissolved oxygen (DO) was estimated to be 0.57 mg L -1 , and the LT 50 at 0.5 mg L -1 DO was 422 hours. Adaptations included fewer buried clams and a depressed metabolism, while the unexpected rise in the activities of key enzymes involved in glycolysis may indicate a diverse strategy of shellfish under hypoxia. Cellular damage was observed as collapse of the mitochondrial cristae and both cellular and mitochondrial vacuolization. This multi-level study complements and updates our knowledge of the effects of hypoxia on marine benthos, by improving our understanding of the potential for marine ecological transformation under hypoxic conditions and providing useful information for Manila clam farming.

Temperature adaptations of the thermophilic snail Echinolittorina malaccana: insights from metabolomic analysis

“…taurine) and methylammonium compounds [e.g. trimethylamine-N-oxide (TMAO) and glycine betaine] (Gleason et al, 2017;Li et al, 2019;Sokolov and Sokolova, 2019;Zhang et al, 2017). Amino acids play multiple roles as building blocks of proteins and substrates for ATP generation, as well as osmolytes (Somero and Bowlus, 1983;Venter et al, 2018;Yancey, 2005).…”

Transcriptome analysis reveals differential immune related genes expression in Ruditapes philippinarum under hypoxia stress: potential HIF and NF-κB crosstalk in immune responses in clam

“…Hypoxia activates a variety of complex pathways at both the cellular and organism level, with the ultimate aim of reinstating oxygen homoeostasis. In the past decades, physiological and biochemical responses to hypoxia have been studied in several marine bivalve species [26,28,31,32]. Adenosine-5′-triphosphate (ATP), the major energy source for cells in the body, is predominantly supplied by a series of metabolic pathways including glycolysis, the citric acid cycle, and the electron transport chain [33].…”

“…Hence, the tolerance of the bivalves for hypoxia and/or anoxic conditions has been investigated by a number of researchers [1,26,27]. More recently, the effects of hypoxia on survival, behavior, metabolism and cellular and tissue damage of R. philippinarum were conducted, suggesting that severe hypoxia significantly affects the physiology of R. philippinarum [28,29]. Until now, however, little effort has been put towards elucidating the molecular mechanisms combined with physiological and biochemical response of clams to the hypoxia resistance and acclimations.…”

Transcriptome analysis reveals differential immune related genes expression in Ruditapes philippinarum under hypoxia stress: Potential HIF and NF-κB crosstalk in immune responses in clam

“…Hypoxia activates a variety of complex pathways at both the cellular and organism level, with the ultimate aim of reinstating oxygen homoeostasis. In the past decades, physiological and biochemical responses to hypoxia have been studied in several marine bivalve species [26,28,39,40]. Adenosine-5-triphosphate (ATP), the major energy source for cells in the body, is predominantly supplied by a series of metabolic pathways including glycolysis, the citric acid cycle, and the electron transport chain [41].…”

“…Hence, the tolerance of the bivalves for hypoxia and/or anoxic conditions has been investigated by a number of researchers [1,25,27]. More recently, the effects of hypoxia on survival, behavior, metabolism and cellular and tissue damage of R. philippinarum were conducted, suggesting that severe hypoxia significantly affects the physiology of R. philippinarum [28,29]. Until now, however, little effort has been put towards elucidating the molecular mechanisms combined with physiological and biochemical response of clams to the hypoxia resistance and acclimations.…”