ИСТИНА

Embryos of Bufo bufo are extremely sensitive to all environmental factors at the so-called 'critical stages' of normal development. Under an influence of various critical environmental factors (high density, hypoxia and other) maximal levels of anomalies concurs with the critical stages. In the course of experiments I revealed the long-term developmental arrest. The embryonic development has been stopped at the mid-blastula or mid-gastrula stages (Dmitrieva, 2016). I can consider these anomalies as a non-specific adaptation to adverse environmental conditions. In addition, some typical anomalies of Bufo bufo development have been identified. One such anomaly is persistent yolk-plug at the gastrula stage. The number of anomalous embryos differed in different clutches. For example, under controlled condition (illumination, temperature and egg density) this anomaly was observed in about 10% of embryos in one of the clutches, while in other clutches it did not occur at all. This anomaly can lead to the failure of development or be completely regulated in the course of development by thehatching stage. In ecotoxicological experiments the following developmental anomalies were identified at low copper concentrations (0.1 and 1 mg/L). 1. Autolysis. The embryo reaches the hatching stage, and when the egg-shell is broken, it immediately collapses. 2. Heterochrony. Usually, these anomalies are observed at the neurulation stage and the tail bud stage. 3. Disturbance of embryo pigmentation. Also, when exposed of low copper concentrations, some nonspecific abnormalities, such as "turning out" the embryo resulting in cellular dissociation and yolk exudation to the perivitelline space, were observed.