Experimental teratogeny in the tick Hyalomma marginatum marginatum (Acari : ixodida : ixodidae): Effect of high humidity on embryonic development

The effect of 90% RE on the embryonic development of Hyalomma marginatum ma rginatum Koch was investigated at 25 degreesC. Under the influence of this factor, 2.1% dead eggs, 13.0% dead embryos, 6.9% abnormally hatched larvae, 0.2% larvae with malformations, and 77.8% normal larvae appeared. The embr yos died during the cleavage of nuclei, the formation of the blastoderm, th e formation of the germ band and its metamerization, and the differentiatio n of the leg anlagen. Egg hatch was also inhibited in various phases. Vario us kinds of anomalies were observed in larvae of Hyalomma m. marginatum. Mo st teratological changes (70.8%) occurred within the idiosoma. They were he tromorphose (32.6%), oligomely (15.4%), heterosymely (12.3%), symely (1.5%) , atrophy (6.1%), and ectomely (3.1%). Anomalies within the gnathosoma occu rred rarely (3.1%). As many as 26.2% larvae had composite anomalies (oligom ely, heterosymely, atrophy) together. They contained various structures of the gnathosoma or idiosoma. These anomalies decreased the survival rate of the larvae. The investigations showed that during the formation of the blas toderm, the formation of the germ hand and its metamerization the embryos h ave the largest susceptibility of being affected by high humidity. Some ano malies in specimens collected from nature may develop under influence of un favorable humidity levels.