Cadmium is a heavy metal that is treated as an environmental pollutant (air, water, soil). In order to understand the potential effects of cadmium in soil and soil invertebrates, it is important to describe all alterations which appear at different levels in organisms. The main aim of this study was to investigate, analyze and describe the alterations caused by cadmium short-and long-term intoxication at different levels in the organisms: from tissues to cells and organelles. In addition, the activation of cell death mechanisms that take part in homeostasis maintenance according to cadmium has been studied. Therefore, as the species for this project, a terrestrial and well-known widespread European speciesthe centipede Lithobius forficatus (Myriapoda, Chilopoda, Lithobiomorpha)was chosen. This omnivorous species lives under upper layers of soil, under stones, litter, rocks, and leaves, and it is also commonly found in human habitats. The animals were divided into three groups: Cthe control group, animals cultured in a horticultural soil; Cd1animals cultured in a horticultural soil supplemented with 80 mg/kg (dry weight) of CdCl 2 , 12 daysshort-term exposure; Cd2animals cultured in a horticultural soil supplemented with 80 mg/kg (dry weight) of CdCl 2 , 45 dayslong-term exposure. The midgut was isolated from each specimen and it was prepared for analysis using some histological, histochemical and immunohistochemical methods. Our studies showed that short-term intoxication causes intensification of autophagy and digestion of reserve material, while long-term exposure to this heavy metal causes activation of cell death processes together with inhibition of autophagy connected with the lack of reserve material. Additionally, we can infer that autophagy and cell death are nutrient deprivation-induced processes. Finally, we can conclude that short-and long-term exposure of soil centipede to cadmium affects different mechanisms and processes of cell death.

The process of autophagy has been detected in the midgut epithelium of four millipede species: Julus scandinavius, Polyxenus lagurus, Archispirostreptus gigas, and Telodeinopus aoutii. It has been examined using transmission electron microscopy (TEM), which enabled differentiation of cells in the midgut epithelium, and some histochemical methods (light microscope and fluorescence microscope). While autophagy appeared in the cytoplasm of digestive, secretory, and regenerative cells in J. scandinavius and A. gigas, in the two other species, T. aoutii and P. lagurus, it was only detected in the digestive cells. Both types of macroautophagy, the selective and nonselective processes, are described using TEM. Phagophore formation appeared as the first step of autophagy. After its blind ends fusion, the autophagosomes were formed. The autophagosomes fused with lysosomes and were transformed into autolysosomes. As the final step of autophagy, the residual bodies were detected. Autophagic structures can be removed from the midgut epithelium via, e.g., atypical exocytosis. Additionally, in P. lagurus and J. scandinavius, it was observed as the neutralization of pathogens such as Rickettsia-like microorganisms. Autophagy and apoptosis ca be analyzed using TEM, while specific histochemical methods may confirm it.

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The midgut epithelium of Acheta domesticus (Insecta, Orthoptera, Gryllidae), which is composed of columnar digestive cells and regenerative crypts, degenerates in two manners: necrotic and apoptotic. While necrosis was described in our previous paper, programmed cell death was the aim of the present studies. The first morphological signs of programmed cell death in midgut epithelium cells are alterations in the cytoplasm connected with shrinkage of the cells. Gradual modifications in a cell's structure cause it to be discharged into the midgut lumen, where it disintegrates. Autophagy is involved in the disintegration of organelles. The transitions of apoptotic cells are described at the ultrastructural level. Immunostaining methods were used in order to indicate the early stages of apoptosis when DNA fragmentation, which results from apoptotic signaling cascades, occurs.

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