Feeding of the oribatid mite Scheloribates laevigatus (Acari: Oribatida) in laboratory experiments

Food selection of Scheloribates laevigatus was tested. Leaf litter (Holcus lanatus), filter paper, green algae (Protococcus spp.) and fungal spores (Penicillium griseofulvum) were offered for consumption. Starved individuals and individuals extracted directly from soil were observed. Food preference tests, microanatomy, enzyme tests and faecal pellet counting were used for studying the palatability of food. All types of food were consumed. Cellulase and trehalase activity was not detected. Amylase activity was detected in all animals tested. The amylase activity was lower in reared individuals than in ones extracted directly from the soil. Laminarinase activity was detected in all animals tested. Xylanase activity was absent in some individuals extracted directly from soil, feeding on spores and in some starved ones. No significant difference among experimental groups was found in laminarinase and xylanase activity. No significant differences were observed in fresh body weight. The algae Protococcus seem to be the most suitable food for Scheloribates laevigatus. Most individuals preferred this food. The algae were observed in all parts of the alimentary tract. Great numbers of glycogen particles were found in the mesenchymal tissue of mites reared on algae. Spores of Penicillium griseofulvum were not favoured. Spores appear undamaged after passage through the digestive tract and large numbers of faecal pellets were produced on this food. Extraintestinal bacteria were observed in the mesenchymal tissue of the mites reared in chambers on Penicillium spores using soil as a substrate. Filter paper and litter (Holcus lanatus) were less preferred: however particles of these foods were observed along the whole alimentary tract. No increase of mortality was observed after one week of starvation. The caecal wall was thinner with a small number of granules and proliferation of its cells was lower in starved animals.