Abstract
It is well known that some tardigrades are found in the aeration tanks of sewage disposal plants. These tardigrades are generally called 'Macrobiotus' and coexist with the various types of bacteria, fungi, protozoans, rotifers, and other organisms that are presumably beneficial to wastewater treatment.
Activated sludge samples were obtained from several sewage disposal plants in Tokyo and other areas and examined for the occurence of tardigrades. The same species was observed from all samples, although the frequency of tardigrade varied depending on the region and the condition of activated sludge. Many exuviae with eggs and embryos were concurrently found in the activated sludge. Morphological observations of their mouth apparatus, eyespot, and double-claws showed the present species was not as 'Macrobiotus', but one of the aquatic tardigrades, Isohypsibius myrops (Du Bois-Reymond Marcus, 1944).
This species seems to live and reproduce in sewage aeration tanks as a scavenger.
