Abstract
The nutritional biology of the oribatid mite Archeqozetes longisetosus Aoki was examined using a control (starvation) and four types of food: Protococcus sp. algae from tree bark, two fungi- Stachybothrys sp. and Alternaria sp. and filter paper. Direct observations, histology, enzymology and plating techniques were employed to record contact with food, contents and structure of the alimentary tract, presence and viability of bacterial microorganisms inside the mite body, and chitinase and cellulase activity of mite homogenates.
Algae were highly palatable, resulting in high apocrine secretion and guts that were continuously full. Initially there was no evidence of chitinase or cellulase production.
Chitinase activity started after 10 days, probably due to consumption of fungi that invaded the algal cover, and correlated with the presence of chitinolytic bacteria (Serratia rubidea) in the mite homogenate. Alternaria was grazed intensively, but cell walls of spores and hyphae remained intact and no chitinase was detected suggesting that only cell contents were enzymatically digested.
Stachybothrys sp. was rejected as food. The bacterium Alcaligenes faecalis was dominant in homogenates in each of the treatments, but under starvation Achromobacter xylosoxidans became co-dominant.
Cellulase activity was not detected in any treatment, but strong chitinase activity was induced with a filter paper (colonized by invasive fungi) diet. Furthermore, bacteria were common in mesenchyme between the internal organs in the filter paper and starvation treatments.