Origin of the type I antifreeze gene in flounders in response to Cenozoic climate change

Antifreeze proteins (AFPs) inhibit ice growth within fish and protect them from freezing in icy seawater. Alanine-rich, alpha-helical AFPs (type I) have independently (convergently) evolved in four branches of fishes, one of which is a subsection of the righteye flounders. The origin of this gene family has been elucidated by sequencing two loci from a starry flounder, Platichthys stellatus, collected off Vancouver Island, British Columbia. The first locus had two alleles that demonstrated the plasticity of the AFP gene family, one encoding 33 AFPs and the other allele only four. In the closely related Pacific halibut, this locus encodes multiple Gig2 (antiviral) proteins, but in the starry flounder, the Gig2 genes were found at a second locus due to a lineage-specific duplication event. An ancestral Gig2 gave rise to a 3-kDa "skin" AFP isoform, encoding three Ala-rich 11-a.a. repeats, that is expressed in skin and other peripheral tissues. Subsequent gene duplications, followed by internal duplications of the 11 a.a. repeat and the gain of a signal sequence, gave rise to circulating AFP isoforms. One of these, the "hyperactive" 32-kDa Maxi likely underwent a contraction to a shorter 3.3-kDa "liver" isoform. Present day starry flounders found in Pacific Rim coastal waters from California to Alaska show a positive correlation between latitude and AFP gene dosage, with the shorter allele being more prevalent at lower latitudes. This study conclusively demonstrates that the flounder AFP arose from the Gig2 gene, so it is evolutionarily unrelated to the three other classes of type I AFPs from non-flounders. Additionally, this gene arose and underwent amplification coincident with the onset of ocean cooling during the Cenozoic ice ages.

The influence of the climatic and oceanological conditions on the stock dynamics of some commercial species of pelagic and bottom fish communities of the eastern part of the Sea of Okhotsk

Stepwise multidimensional regressive analysis was carried out based on the long-term data (1971–2018), including biological statistics and series of observations on 10 climate indices, allowing to identify the most meaningful climatic factors affecting the numbers of some fish species at different stages of the ontogenesis in the Eastern part of the Sea of Okhotsk. All the results obtained indicate of existing true correlations with the number of the two-years-old individuals and the number of the fish reached the age of the mass (>50%) maturation. Threedimension regression models, describing the dynamics of the initial number of some fish satisfactorily. Were made, based on the obtained equations of multiple regression of the relationship between the number of the fish and the most effective climatic indices selected. The major indices affecting the abundance of different fish species are: SST, NPGO, SanSpot – Pacific herring; NPA – saffron cod; PDO – Pacific cod; NPA, SanSpot – great sculpin; SanSpot, PNA, AO – yellowfin sole; PDO, SSTa – Pacific halibut; Ice SanSpot, NPGO – Greenland turbot. Pelagic, demersal and bottom species are under the complex influence of the oceanographic, meteorological and planetary-space indices.