Collotheca (Rotifera)

Collotheca belongs to the rotifer class Monogononta, rotifers with only one ovary. These rotifers are sessile; they are either attached to each other forming a spherical colony, or attached individually to the substrate. Each rotifer secretes a gelatinous tube into which it withdraws when disturbed. After a period of time, it extends and the infundibulum opens like a blossom. Collotheca have extremely long tentacle-like cilia surrounding the corona. Although they are flexible enough to be folded up and pulled inside when the rotifer retreats into its tube, for feeding they are extended and appear to become rigid. Wavelike ripples along the cilia create currents that sweep smaller microorganisms into the mouth at the bottom of the infundibulum.

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.

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