Glutathione S-Transferases in Marine Copepods

The glutathione S-transferase (GST) is a complex family of phase II detoxification enzymes, known for their ability to catalyze the conjugation of the reduced form of glutathione (GSH) to a wide variety of endogenous and exogenous electrophilic compounds for detoxification purposes. In marine environments, copepods are constantly exposed to multiple exogenous stressors, thus their capability of detoxification is key for survival. Full identification of the GST family in copepods has been limited only to few species. As for insects, the GST family includes a wide range of genes that, based on their cellular localization, can be divided in three classes: cytosolic, microsomal, and mitochondrial. The role of GSTs might have class-specific features, thus understanding the nature of the GST family has become crucial. This paper covers information of the GST activity in marine copepods based on studies investigating gene expression, protein content, and enzymatic activity. Using published literature and mining new publicly available transcriptomes, we characterized the multiplicity of the GST family in copepods from different orders and families, highlighting the possible role of these genes as biomarker for ocean health status monitoring.

Non-lethal effects of the predator Meganyctiphanes norvegica and influence of seasonal photoperiod and food availability on the diel feeding behaviour of the copepod Centropages typicus

Predators can induce changes in the diel activity patterns of marine copepods. Besides vertical migration, diel feeding rhythms have been suggested as an antipredator phenotypic response. We conducted experiments to assess the non-lethal direct effects of the predator Meganyctiphanes norvegica (northern krill) on the diel feeding patterns of the calanoid copepod Centropages typicus. We also analysed the influence of seasonal photoperiod and prey availability on the intensity of copepod feeding rhythms. We did not detect any large effect of krill presence on the diel feeding behaviour of copepods, either in day-night differences or total daily ingestions. Seasonal photoperiod and prey availability, however, significantly affected the magnitude of copepod feeding cycles, with larger diel differences in shorter days and at lower prey concentrations. Therefore, the role of non-lethal direct effects of predators on the diel feeding activity of marine copepods remain debatable and might not be as relevant as in freshwater zooplankton.