Short communication: The boring sponge (Pione vastifica, Hancock, 1849) induces oxidative stress in the Pacific oyster (Magallana gigas, Thunberg, 1793).

Boring sponge infection affects growth, development and reduces the soft tissue weight of oysters. In this study, we investigated the effects of boring sponge on the activity of three antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GP)) in the mantle, and the production of reactive oxygen species (ROS) and potential genotoxicity in hemocytes of the Pacific oyster Magallana gigas. Our results showed a significant increase in ROS production and DNA damage in hemocytes. Notably, the activity of SOD, CAT, and GP in the mantle was not significantly affected by boring sponge infection. Collectively, these results suggest that sponge invasion may cause oxidative stress in Pacific oyster hemocytes through ROS overproduction.

Newly Discovered AqE Gene is Highly Conserved in Non-tetrapod Vertebrates.

Studying the diversity of energy production pathways is important for understanding the evolutionary relationships between metabolic pathways and their biochemical precursors. The lactate/malate dehydrogenase (LDH/MDH) superfamily has been a model system for structural and functional evolution for a long time. Recently, the type-2 family of LDH/MDH (or LDH2/MDH2 oxidoreductase) has been identified. The LDH2/MDH2 oxidoreductase family is now known to have functionally more diverse enzymes than the LDH/MDH superfamily. In channel catfish, the gene encoding the LDH2/MDH2 oxidoreductase has been found (and was provisionally termed AqE). Homologs of this enzyme are predominantly present in organisms living in an aquatic environment. In this work, we studied the AqE gene distribution among non-tetrapod vertebrates. It was found that the AqE gene is present in the genomes of bony and cartilaginous fish and in the genomes of hagfishes and lampreys. In addition, it has been confirmed that in representatives of Cypriniformes, the AqE gene has been lost. AqE in representatives of Salmoniformes underwent significant deletions, which most likely led to its pseudogenization. In most orders of non-Tetrapoda vertebrates, the AqE gene remains highly conserved, suggesting that the AqE gene in aquatic vertebrates is an essential gene and undergoes rigorous selection. The AqE gene has the highest sequence similarity with the archaeal ComC gene that encodes sulfolactate dehydrogenase (SLDH). Based on the similarity of substrates, the enzyme encoded by the AqE gene is likely involved in the malate-aspartate shuttle mechanism or the biosynthesis of the energy coenzyme M equivalent.