Vol 50, No 4 (2024)

Hematological parameters of the peripheral blood of the walleye pollock Gadus chalcogrammus Pallas, 1814, saffron cod Eleginus gracilis Tilesius, 1810, and Pacific cod Gadus macrocephalus Tilesius, 1810 from the Sea of Okhotsk were studied. An analysis of the leukogram of the studied species revealed a large portion of segmented neutrophils and myelocytes in walleye pollock, which indicates a significant potential of the cellular factor of its innate immunity and a greater activity of corticosteroid hormones. The most active erythropoiesis observed in G. chalcogrammus is probably related to substantial vertical migrations, specific for the species, associated with sharp pressure variations and the necessity to provide the body with oxygen. The high level of leukopoiesis revealed in saffron cod is assumed to be caused by ecological adaptations of the species to inhabit both fresh and sea water.

Nutritious diet is one of the most important factors in the successful management of captive animals. Basic methods for selecting diets for marine mammals have been described in the literature, yet methods developed for certain marine mammal species kept under specific conditions are quite rare. The diets of three male and two female spotted seals, Phoca largha Pallas, 1811, kept in sea pens at the Primorsky Aquarium, Branch of the NSCMB FEB RAS (Vladivostok, Russia), are discussed in the article. The diets have been formulated based on the natural biological processes of this species in the wild. Information on them has been obtained from our own observations and from literature sources. Based on individual needs, adjustments have been made to the diets of the spotted seals, including pregnant and lactating females. The main food items of the spotted seal were Pacific herring, Clupea pallasii, Atka mackerel, Pleurogrammus monopterygius, commander squid, Berryteuthis magister, pink salmon, Oncorhynchus gorbuscha, chum salmon, Oncorhynchus keta, char, Salvelinus sp., capelin, Mallotus villosus, and shrimp, Pandalus sp. It has been found that the physiological condition of the animals (molting, reproductive status, sex, and age) directly influences the qualitative and quantitative parameters of food intake. The diet and body weight of the spotted seals were significantly influenced by seasonal changes (water and air temperature and natural biological rhythms). The obtained data can be used for selection of optimal feeding of P. largha.

Studies of the energy metabolism in a bivalve mollusk, the ark clam Anadara kagoshimensis (Tokunaga, 1906), were carried out for the first time under experimental conditions simulating dynamic variations in the seawater characteristics at the stages of development and end of upwelling event in the Black Sea. It was shown that the level of energy metabolism of A. kagoshimensis, while being in the zone of upwelling formation, reduced, on average, by 5% per degree of temperature decrease. During the upwelling relaxation phase (14→26°C), the restoration of the respiration intensity parameters of the clam was slower than expected, with a temperature coefficient Q₁₀ = 1.31. The acidification of the seawater by 1.0 (up to рН 7.2), combined with a temperature decrease (26→20°C), aggravated the negative effect by 25–45%. It has been found that the clam A. kagoshimensis reduces energy expenditure by approximately 60% under upwelling conditions (cold stress and acidification). Consequences of the negative effect of a sharp temperature variation lead to a delay in the metabolism recovery to normal values.

The effect of copper at concentrations of 10, 20, and 50 µg/L on population growth, chlorophyll a fluorescence, and content of photosynthetic pigments (chlorophyll a and carotenoids) of the diatom Thalassiosira nordenskioeldii was studied. It was shown that at metal concentrations of 10 and 20 µg/L, the cell number started to increase from the first days of the experiment and, by the end of the experiment, exceeded that in the control group 5.8- and 5.6-fold, respectively. The intensity of chlorophyll a fluorescence and the content of photosynthetic pigments under these conditions were higher than in control throughout the experiment. At a metal concentration of 50 µg/L, the growth of the cell population was inhibited at the beginning of the experiment; by the end of the experiment, the cell number exceeded that in control. The same pattern was recorded for the other parameter, too. Based on the obtained data, it is hypothesized that copper at the studied concentrations may contribute to the proliferation of T. nordenskioeldii in the natural environment.3

-