Nutritional biology of oribatid mites from different microhabitats in the forest

Abstract

Two or three microhabitats were defined within each of several habitats within a forest. For example, if `tree' is a habitat, its microhabitats are the moss cover on the tree, the moss at the foot of the tree in contact with the soil, and the soil around the tree. The microhabitat community structure of oribatid mites was recorded. The nutritional biology, especially the type of food and the digestion pattern, of the more dominant species was monitored. Mites were extracted in Berlese-Tullgren funnels, collected in modified Bouin-Dubosque-Brasil fixation fluid, sectioned in paraplast, and stained with Masson triple. Faecal pellets in the rectum were also stained with acridine orange and observed under fluorescent light. Mite microanatomy was evaluated based on nutritional parameters (food bolus, food type, activity of the walls of the intestine, faecal pellets, bacteria within the body, nutritive deposits, metabolites). Some species consume and digest a specific type of food in all microhabitats of one habitat. But others are able to shift diet according to current food supply in a particular microhabitat. A third type of species is ubiquitous and usually consumes a mixture of unspecified food types in every microhabitat studied. Obligate mycophagous oribatids (e.g., Damaeus, Belba or Metabelba) seem to be highly specialized. These genera inhabit mostly soil or microhabitats in contact with soil (e.g., mosses on soil), and are rarely found in moss cover on trees, away from the soil. Other species inhabiting soil microhabitats as well as moss covers on trees (Achipteria coleoptrata, Hermannia gibba) can adapt to the nearly pure fungal food in soil microhabitats, although they graze on a different type of food in a micro habitat consisting of moss covering a tree.