Biological features and intraspecific variation of three spine stickleback Gasterosteus aculeatus (Linnaeus, 1758), the Kola peninsula

The biological characteristics and intraspecific variability of threespine stickleback, Gasterosteus аculeatus, from the estuary of the River Tuloma and lakes Venzin and Kulonga on the Kola Peninsula have been studied. Four morphotypes of threespine stickleback ( trachurus with a keel, semiarmatus with а keel, leiurus with а keel, leiurus without keel) have been discovered. There are differences in the number of plates on the body of the stickleback, of plastic traits in different habitats, namely length and body height, the length of the first dorsal, middle dorsal and ventral spines. In the lakes there are morphs with a small number of plates, namely leiurus (3-6), and semiarmatus (13-16). In the estuary of the River Tuloma, the morphotype of trachurus with keel (22-26) is mostly found. The size and weight parameters of stickleback are also different in the investigated water bodies. On average, the length of freshwater stickleback is 53 mm, and the weight is 1.3 g, seawater stickleback, respectively, 72 mm and 4.4 g. These differences point to the adaptation to living in different conditions. In fresh reservoirs, the bone carapace is relieved by reducing the number of plates, while in water with a lower salinity, it is more difficult to extract the calcium needed to build bone plates, than in water with increased salinity. In the estuary of the River Tuloma during the tides there is an increase in salinity from 1 to 22 ‰, therefore, to extract calcium for building these scutes is more easily. Also, many-plate individuals after grasping by predators experience less damage than low-plate, and consequently the chances of escaping from the teeth of a predator increase. The dependence of the size-weight characteristics approximated by the power function equation of the form W = aLb has been determined. The coefficient b > 3 indicates the preservation of the shape of the body as the stickleback grows, and suggests that the rate of increment of mass is similar in the studied reservoirs.