ИСТИНА

In lake Sobach'e spawning of the «goggle-eye charr» typically takes place in the сoastal slope zone at the depth 1-10 m in August-September, one month earlier than that of sympatric large piscivorous Drjagin charr, which spawns at the depth of 30 m in homothermic zone (2 oC). However, in 1993 pucheglazka spawned during unusually warm (+2-+4oC) early October, the spawning periods of the two forms overlapped, and I had an opportunity to make a cross between a female of Drjagin charr and males of pucheglazka. Reciprocal hybrid eggs perished during transportation. Eggs were incubated at 3oC and developed normally till hatching. However after larvae attained 20 mm, their growth seized and undulating deformations of body took place leading to mass death due to the loss of swimming ability. The subsequent osteological analysis of these individuals showed that they had abnormal osteogenesis manifested in the development of globules of skeletogenic tissue stained with alizarin, ventrally to the chord, of thread-like curved bony structures within it and of deformed vertebrae centra. Several individuals with low number of skeletal anomalies transited to mixed feeding, and three larvae with abnormal caudal vertebrae lived till the end of the experiment (11 months) attaining FL 35-41 mm. The observed anomalies of skeletal development in hybrids may result from the conflict between genetically-based developmental programs of the two parental forms with highly specialized early ontogeny. Thus, reproductive isolation between sympatric forms is sustained by both prezygotic and postzygotic mechanisms.