ИСТИНА

I studied the development of skeleton in larvae of large piscivorous Drjagin charr endemic to the Taimyr Peninsula. Eggs were collected in late October from spawners at the spawning grounds in the Bunisyak River (a tributary of Lake Lama) and artificially fertilized. Eggs were incubated in 1,10С and larvae were reared in 3 temperature regimes. Even at the lowest temperature (1,10С) the first bones and fin rays, most important for early life, appear very early, during first 5 days after hatching. For a long time these elements retain simple juvenile shape, and do not undergo energy-consuming differentiation. The second stage of osteogenesis begins late, at the length of 25 mm. Transition to external feeding takes place at larger length than in many other charrs (26 mm), but at an earlier stage of morphological differentiation. Centra do not ossify for a long time, which presumably facilitates attaining large size with low investment of energy resources. Thus dissociation between somatic growth and osteogenesis is observed. It is supposed that such retardation of skeletal development is a genetically based adaptation promoting high growth rate at extremely low temperatures (0.2-2.70С) at the cost of differentiation. Due to profound heterochronic changes in early ontogeny accompanied with rapid growth, charrs start feeding early on large riverine benthic invertebrates and transit to piscivorous feeding at the age of 4-5 years. Comparative study of morphogenesis indicates that larval period is a determining stage in morphological specialization of Drjagin charr.