Rotifers

Identification

• Have vase-shaped bodies
• Range from 40-2,000 µm in length
• Have a jaw, or mastax, in their gut
• Forked foot on their posterior end with two protrusions called toes

Why Do I Have It?

• Moderately old sludge age

Treatment

If dead rotifers are observed, it can be an indication of toxicity. If you are concerned about your plant conditions contact a technical rep for information and recommendations.

Under the Microscope an in Your Plant

Rotifera, or Rotifers, are a diverse type of metazoan that feed on dead and decomposing matter as well as bacteria, algae, and smaller protozoa. This helps produce a clear effluent. The name “Rotifera” is derived from the Latin word meaning “wheel bearer.” This name was chosen as some rotifers have a funnel like structure with circles of cilia at the front of their bodies which resembles rapidly revolving wheels (seen in the second video above). If live rotifers are observed in a wastewater plant, it is usually indicative of a slightly old sludge age. This is because it takes up to three days for their eggs to hatch, with an average of a 6 to 45 day lifespan.

The size of rotifers ranges from 40-2,000 µm. Rotifers have a forked foot on their posterior end with two protrusions, which are called toes, and can easily be identified under 100x magnification. Under 100x magnification their mastax, or jaw, in their gut that aids in eating and digestion can also be viewed.

Rotifers are commonly found in healthy wastewater plants; however, they should never be dominant. One of the roles of rotifers is to aid in developing floc by secreting mucus from their mouth or foot. If visibly damaged rotifers are observed, it is a strong indication of toxicity within a system as they are usually the first to be affected.

Rotifers are classified into one of three classes: sesionidea, bdelloid, and monogononta. The majority of rotifers in a wastewater system are female as the only purpose for the male’s existence is to fertilize the female and die. However, most female bdelloids reproduce asexually. Almost all rotifers lay unsegmented eggs, which are commonly kept near the mother’s foot. Only a small amount of rotifers keep the developing eggs inside until birth.

Interesting Facts

• There have been approximately 1,500 species of rotifers identified
• They have been suggested for studies of developmental biology in space because they are not affected by low gravity
• Can survive radiation blasts