1. Academic Validation
  2. Spawning acts as a metabolic stressor enhanced by hypoxia and independent of sex in a broadcast marine spawner

Spawning acts as a metabolic stressor enhanced by hypoxia and independent of sex in a broadcast marine spawner

  • Sci Total Environ. 2023 Nov 17:909:168419. doi: 10.1016/j.scitotenv.2023.168419.
Md Mahamudul Hasan Mredul 1 Eugene P Sokolov 2 Hui Kong 1 Inna M Sokolova 3
Affiliations

Affiliations

  • 1 Department of Marine Biology, Institute of Biological Sciences, University of Rostock, Rostock, Germany.
  • 2 Leibniz Institute for Baltic Sea Research, Leibniz Science Campus Phosphorus Research Rostock, Warnemünde, Germany.
  • 3 Department of Marine Biology, Institute of Biological Sciences, University of Rostock, Rostock, Germany; Department of Maritime Systems, Interdisciplinary Faculty, University of Rostock, Rostock, Germany. Electronic address: inna.sokolova@uni-rostock.de.
Abstract

Broadcast spawners, like the blue mussel Mytilus edulis, experience substantial energy expenditure during spawning due to extensive gamete release that can divert energy from other functions. This energetic cost might be intensified by environmental stressors, including hypoxia that suppress aerobic metabolism. However, the energy implications of spawning in marine broadcast spawners have not been well studied. We examined the effects of short-term hypoxia (7 days) and spawning on mitochondrial activity, Reactive Oxygen Species (ROS) production, and cellular energy allocation (ratio of tissue energy reserves to energy demand) in somatic tissues of M. edulis. Under normoxic conditions, post-spawning (72 h) recovery correlated with increased phosphorylation (OXPHOS) rate in mitochondria from the digestive gland, while hypoxia inhibited this response. Regardless of oxygen levels, mitochondrial ROS production decreased after spawning, indicating M. edulis' ability to prevent oxidative stress. Spawning led to reduced energy reserves in somatic tissues (the gills and the digestive gland), highlighting significant energy cost of spawning primarily fueled by lipid and protein breakdown. Additionally, cellular energy allocation dropped 3 h post-spawning, indicating a shift in energy demand and supply. Normoxic conditions allowed recovery in 72 h, but hypoxia hindered recuperation. These findings underscore spawning's bioenergetic challenge for broadcast spawners like M. edulis, potentially elevating post-spawning mortality risk, especially in hypoxic coastal habitats.

Keywords

Bioenergetics; Bivalve; Hypoxic stress; Mitochondria; Spawning activity.

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