Another stage of research on the Baikal seal has been finished, being part of a long-term endemic research program under the leadership of Lake Baikal Foundation. Scientists have completed a pilot comprehensive study to assess the physiological state of the Baikal seals, including hormonal and serological analysis.
Through the laboratory work, the analysis of seropositivity, hormonal and immunological status of animals was carried out on the biomaterial samples of the Baikal seals collected during the expedition in 2019. Concentrations of sex hormones (testosterone, progesterone), stress hormone (cortisol) were measured in 12 blood samples and 21 animal hair samples, and the level of free triiodothyronine (a hormone that reflects a metabolic rate) was measured in the blood. Seropositivity was assessed on 12 blood serum samples for the following pathogens: Trichinella, canine plague virus, mycoplasma, chlamydia, Toxoplasma, herpes simplex virus, Candida sp., Brucella sp. Assessment of an innate immunity was conducted by three methods: hemagglutination reactions to assess the concentration of available nonspecific antibodies (natural antibodies), assessment of the concentration of lysozyme, and the ability of sera to kill bacteria (bacteria-killing assay).
Conclusions. The average level of sex hormones (testosterone and progesterone) does not differ in immature Baikal seals of different sexes, which corresponds to the data obtained on other species. Apart from one animal, the level of free triiodothyronine indicates a good food supply. Determination of the level of the stress hormone, cortisol, in the blood allows obtaining information about the stress reactivity of the animal, i.e., how strongly it reacts to stress stimuli, and, accordingly, about its resistance to external impacts. Whilst the determination of the content of this hormone in the hair and vibrissae of the animal gives information about the level of stress/well-being over a long period.
Serological studies have shown that most often the Baikal seals face bacterial (chlamydia, mycoplasma) and fungal (candida) infections. Perhaps this is related to the fact that the seals have a high level of innate immunity, firstly, by its antibacterial components. Of the eight tested pathogens, the seals had antibodies to seven. Surprisingly, seropositive animals have not been identified only to Toxoplasma which is one of the most common pathogens.
Complex physiological studies of the biomaterial of the Baikal seals are carried out within the framework of the Baikal Seal project. The results of such studies were obtained for wild Baikal seals for the first time. Therefore, they will be considered as reference values for further research and can form the basis for the long-term environmental monitoring of the Baikal seal population.