Cadmium effect on the structure of supra- and subpharyngeal ganglia and the neurosecretory processes in earthworm Dendrobaena veneta (Rosa).

Cadmium effects on the supra- and subpharyngeal ganglia, neurosecretion and RNA content in the neurosecretory cells were tested in earthworms Dendrobaena veneta exposed to 10 and 50 mg Cd kg(-1) in soil after 20 days of the experiment. Accumulation of cadmium in the ganglia of nervous system was also measured using AAS method. Cadmium was accumulated in the nervous system. The accumulated amount was proportional to Cd soil concentration and the exposure time. A considerable fall in neurosecretion and RNA content in the neurosecretory cells and neurosecretion in the neuropile (the axons) of both tested ganglia was induced by 50 mg Cd kg(-1). It seemed that neurosecretion synthesis and its axonal transport could be suppressed. Cadmium caused degenerative changes as vacuolization of the neurosecretory cells and neuropile in both tested ganglia.

Cadmium effect on the ovarian structure in earthworm Dendrobaena veneta (Rosa).

Cadmium effects on the ovary structure and oocytes were tested in earthworms Dendrobaena veneta exposed to 10 and 50 mg Cd kg(-1) in soil after 10 and 20 days of the experiment. In both experimental doses cadmium caused damage to the structure of the ovary but the effects were different in each group. At 10 mg Cd kg(-1) concentration in soil, young stages of oocytes and trophocytes were most sensitive to cadmium deleterious effects whereas somatic cells in the ovarian stroma were only slightly affected. Cadmium. at a concentration of 50 mg Cd kg(-1) in soil caused most damage in the somatic cells leading to the occurrence of unnaturally swollen elements and desmosomes destruction. At both experimental concentrations cadmium induced degenerative changes in cell nuclei and an increase in number of cell organelles (RER and Golgi complex elements) in the cytoplasm of oocytes and trophocytes. These also proved to be more active. No ultrastructural changes were manifested in oogonia. In both experimental groups degenerative changes occurred as early as after 10 days of Cd exposure.