Nutritional biology: the basic step in the autecological studies (multi-methodical approach)

Studies of soil animal communities should be based on the autecology of at least dominant species. For these model studies, some species of Oribatida and Acaridida were tested by several methods. Their nutritional biology, indeed, consists of several phenomena of varying nature: searching for food, testing of it, consumption, digestion, transport of nutrients through body, content of faecal pellets, interaction with external or internal microorganisms. Moreover, each named phenomenon exhibits its own intrinsic variability in expression resulting in the mutual relations, influences and synergisms of such ‘subphenomena’ to each other. For example, i) Food can be consumed by various patterns according to its mechanical and chemical characteristics, although the food type appears to be uniform. ii) Some types of gulped food can be digested thoroughly, but others only partially, although animals graze intensively on them. iii) The term ‘palatability’ consists of several parameters and, in many cases, ‘palatable’ food is not synonymous with high nutritional content or optimum food as a whole. iv) Animals are able to survive on food of lower quality or lower nutrient content (in extreme cases, on their own excrements). v) Many bacteria can be very scarce in the soil, but they dominate within the animal body. vi) Type of cuticle and motility of species can be correlated with the food selection or, directly specialization. vii) Through consumption and digestion, some soil animals are able to affect some abiotic parameters in soil (e.g. pH) with consequences for nutritional biology.