ИСТИНА

In a series of experiments, eggs of the common toad (Bufo bufo) had been placed in different environments. Additionally, tadpoles that came from the eggs were split into groups varying in density of individuals per given volume of water and placed under observation. The resulting groups differed significantly in their ventral body length (nasal tip to anus), dorsal body length (nasal tip to the end of notochord) and full body length. A range of parameter to environment correlations had been observed. Ventral body length differed most in response to egg density: tadpoles in the group with 5 specimen per 0,3 liter were significantly larger than those in the 2 tadpoles per 0,3 liter group. Density-dependent effect on ventral body length was seen already at the egg stage: tadpoles that came from the eggs that developed in low density environment (30 eggs per 0,133 l) were significantly larger than those in the high density group (120 eggs per 0,133 l). The effect was manifested the most in individuals from the 5 specimen per 0,3 l group. Tadpoles hatched from the eggs that have been developing in a stretched egg cord had much greater dorsal body length than those hatched from the lose cord eggs. For tadpoles reared from individually isolated eggs, the parameter in which they differed most was their ventral body length. Additionally, for some of the individually reared eggs half of the water in which they were sitting had been repeatedly replaced with water from the high egg density tanks (once every 8 hours). The rest of those solitary confined ones were kept in standard conditions. These two groups differed significantly in ventral body length. This parameter was higher in the sample from experimental tanks. Thus, growth parameters of Bufo bufo tadpoles depend on the history development in the eggs.