Characterized by their ciliated head structure, bdelloid rotifers have ganglia, muscles, photosensitive and tactile sensory organs; structures for crawling, feeding, and swimming; digestive and secretory organs; and bilateral ovaries. Pictured here are bdelloids from three of the four families of the class.  Clockwise from upper left: Philodina roseola (with a digestive tract colored green from eating algae), Macrotrachela quadricornifera (note the large egg), Habrotrocha constricta, and Adineta vaga (Adinetidae).
Scale bar = 100 microns