Crustacean bioenergetics: Mitochondrial adaptive molecular responses to face environmental challenges

Mitochondria are essential organelles that provide energy for most eukaryotes. Even though the basic functions performed by this organelle are widely recognized, considerable variations exist on mitochondria from different species because of specific energetic demands and environmental conditions. The respiratory functions of marine invertebrates are known to be highly specialized because these species face continuous environmental challenges affecting their biological fitness and energetic equilibrium. Among marine invertebrates, Crustacea is an ancient and highly diverse phylum that includes numerous biologically, ecologically, and economically valuable species; some of them evolved specific adaptations in response to habitat preferences, such as energy-regulatory mechanisms or alternative adenosine triphosphate (ATP)-producing pathways, which allow them to survive in low-oxygen environments. This review highlights some relevant characteristics of mitochondria from crustaceans, and describes the current state of knowledge about mitochondrial genes, proteins, and their expression. In addition, this paper discusses the ability of crustacean species to synthesize ATP and to elicit a complex response to the oxidative stress induced by the frequent occurrence of hypoxic and re-oxygenation events. The reported inability of crustacean mitochondria to undergo a permeability transition, as a strategy to avoid cell apoptosis, is also discussed. Finally, the strategies adopted by shrimp to face oxidative stress, and the mitochondrial adaptations that allow hypoxia-tolerant shrimp species to survive in low-oxygen environments are examined.