Volume 50, Nº 3 (2024)

Intensive population interactions between components of plankton and virioplankton of the World Ocean have formed ancient and, at the same time, versatile mechanisms for protecting marine bacteria and archaea from the effects of ocean viruses on them. One of such mechanisms is exopolysaccharides, which are secreted by marine prokaryotes to interact with surface proteins of viral particles and prevent the binding of viral peplomers to receptors of potential target cells. Therefore, antiviral drugs with a wide spectrum of actions, exhibiting also the ability to modulate intercellular interactions, are found in large numbers among exopolysaccharides of marine bacteria. The review analyzes the modern views on exopolysaccharides of marine bacteria, their antiviral potential, and antioxidant and immunomodulatory activity. A brief description of the structural, physical, and chemical properties of such compounds is given and the main mechanisms of antiviral activity of the best-known representatives of this class of organic polymers are disclosed. Exopolysaccharides of marine bacteria are shown to be a promising and extremely rich source of antiviral medicinal substances.

The antioxidant (AO) defense complex in tissues of the scallop Flexopecten glaber ponticus (Bucquoy, Dautzenberg et Dollfus, 1889) from a natural habitat in the Black Sea was studied for the first time. The results indicated a pronounced tissue specificity of the scallop AO complex along with close levels of TBA-reactive substances in all the studied organs. In the gills of the scallop, the activity of glutathione reductase (GR), superoxide dismutase (SOD), and catalase was higher compared to the hepatopancreas. The activity of glutathione peroxidase (GP), GR, and catalase in the gills was higher than in the muscle. The reduced glutathione (GSH) reserve in the gills was lower than in the hepatopancreas. This indicated that both the glutathione system and the key antioxidant enzymes, SOD and catalase, significantly contributed to the antioxidant defense of the scallop gills. In the hepatopancreas, the level of glutathione was the highest and the activity of GP was high and similar to that in the gills. This reflects their significant role in the AO defense of this organ. However, the activity of GR, SOD, and catalase in the hepatopancreas was significantly lower than in the gills. The scallop muscle was characterized by the lowest GP activity and a low GSH level, close to that in the gills. The SOD activity in the muscle was comparable to its value in the gills, and the activity of catalase and GR was comparable to the values in the scallop hepatopancreas.

The effect of concentration of the microalgae, haptophyte Isochrysis galbana and dinophyte Prorocentrum cordatum, on the daily grazing rate (G) and daily egg production rate (EPR) of the brackish-water copepods Arctodiaptomus salinus and Calanipeda aquaedulcis was studied under experimental conditions. Daily grazing rates of copepods increased logarithmically with increasing microalgae concentration. The maximum grazing rates in both species were observed when feeding on I. galbana at a concentration of 170–196 µg C/mL. The maximum daily EPR in females of C. aquaedulcis (129% of body weight in carbon equivalent) were obtained when they fed on I. galbana at a concentration of 15.4 µg C/mL, or on P. cordatum at 4 µg C/mL. The maximum EPR values in A. salinus females were 34% of their weight in carbon equivalent when feeding on P. cordatum at a concentration of 26 µg C/mL, and 45% in their carbon equivalent at 8.9 µg C/mL of I. galbana. The further increase in the microalgae concentration led to the decrease in EPR values. The efficiency of ingested food utilization for egg production in carbon equivalent (gross growth efficiency, GGE, %) of C. aquaedulcis was significantly higher than that of A. salinus, regardless of the species and concentration of microalgae.

A vessel-based survey of marine mammals was carried out at transects in the southern part of the Tatar Strait and during passages within the Sea of Japan and the La Perouse Strait in October 2018. Such surveys had not been previously conducted in these areas during the fall. A total of five species of cetaceans (including the Dall’s porpoise, harbour porpoise, common dolphin, killer whale, and minke whale) and two species of pinnipeds (the Steller sea lion and northern fur seal) were sighted. The study showed a low occurrence of marine mammals in the area during the fall season.