# Metabolic and Biochemical Responses of Juvenile Babylonia areolata to Hypoxia Stress

## TL;DR

This study explores how juvenile Babylonia areolata snails respond to low oxygen levels, finding that prolonged hypoxia increases mortality and disrupts their metabolism and biochemical functions.

## Contribution

The study reveals that B. areolata snails switch to anaerobic metabolism under hypoxia and highlights the importance of managing dissolved oxygen levels during farming and transport.

## Key findings

- Prolonged hypoxia increases mortality in B. areolata after 2–3 days of exposure to low oxygen levels.
- Hypoxia suppresses metabolic activity and biochemical functions in juvenile B. areolata.
- Transportation time should not exceed 48 hours to reduce mortality in B. areolata under hypoxic conditions.

## Abstract

The snail Babylonia areolata has important economic and ecological values, yet it frequently encounters varying degrees of hypoxic conditions during farming and transportation. These low-oxygen environments are influenced by factors such as high farming density, degradation of substrate quality, and transport without water. Currently, there is limited information regarding the metabolic and immune responses of B. areolata under hypoxic stress. Based on previous acute stress experiments, we investigated the effects of prolonged hypoxia on mortality, metabolic rates, enzyme activities related to metabolism and immunity, and gene expression in B. areolata. Our study demonstrated that B. areolata is sensitive to hypoxic stress, with mortality observed after 2–3 days of exposure to dissolved oxygen concentrations of 2 and 0.5 mg O2/L. Concurrently, both metabolic activity and biochemical functions were found to be suppressed. Furthermore, we discovered that B. areolata may respond to hypoxic stress through an anaerobic energy metabolic pathway. This study underscores the critical importance of maintaining appropriate levels of dissolved oxygen in aquatic environments and ensuring suitable transportation durations for this species.

As an important aquaculture species, the marine snail Babylonia areolata is frequently subjected to fluctuation in dissolved oxygen concentration during farming and transportation processes. In the present study, we investigated the metabolic rates, transcription, and enzyme level responses of juvenile B. areolata exposed to long-term stress (144 h). The results showed that the mortality rate of juvenile B. areolata was higher in the 0.5 mg O2/L group compared to the 2 mg O2/L group. During the hypoxic stress period, both oxygen consumption and ammonia excretion rates were observed to be lower in juvenile B. areolata than those in the control group. As hypoxic stress duration prolonged, juvenile B. areolata demonstrated significantly elevated activities of pyruvate kinase (PK) and alkaline phosphatase (AKP), alongside reduced activities of lactic dehydrogenase (LDH), acid phosphatase (ACP), and superoxide dismutase (SOD). Significant changes in the expression levels of PK and LDH genes were observed during the hypoxic stress. The expression levels of ACP and SOD genes were significantly downregulated, while juvenile B. areolata exhibited elevated AKP gene expression levels under 0.5 mg O2/L. Our findings suggest that under long-term exposure to hypoxia, B. areolata failed to maintain energy homeostasis and suffered biochemical disruptions, leading to a reduction in survival. The mortality rate of B. areolata can be substantially decreased by ensuring that transportation time does not exceed 48 h.