Philodina (Rotifera) Videos
Philodina belongs to the class Bdelloidea (from the Greek for leech), rotifers that have two ovaries. This type of rotifer moves in two modes. Fully extended it moves like a leech or inchworm along aquatics and detritus. Contracted, with corona extended, it swims freely. To feed, they "cement" themselves to a surface and sway through the water, sifting for smaller organisms or particles of debris. Males have never been observed. Reproduction is solely by parthenogenesis (females producing only females), making rotifers of this class unique in the animal kingdom.
Rotifers are extremely common and can be found in many freshwater environments and in moist soil, where they inhabit the thin films of water surrounding soil particles. Their habitats may include still water environments, such as lake bottoms, as well as rivers or streams. They are also commonly found on mosses and lichens, in rain gutters and puddles, in soil or leaf litter, on mushrooms growing near dead trees, in tanks of sewage treatment plants, and even on freshwater crustaceans and aquatic insect larvae.
Nearly all rotifers have chitinous jaws called trophi that grind and shred food. The trophi are the only part of a rotifer that can be fossilized and have been found in amber dating back to the Eocene epoch (38-55 million years ago).
Many rotifer species have no males, females producing only females (parthenogenesis). In some rotifer species, stress can cause females to produce eggs that hatch as males. They have no mouth or digestive tract and die within hours or days. The appearance of males is followed by sexual reproduction. The females then produce resting eggs, which settle to the bottom to hatch when conditions permit. The tiny eggs can withstand desiccation for considerable periods of time and can be carried by wind or birds to any place that holds water (even bird baths and gutters) where they will hatch.