The Other Bacteria...
The entire animal is transparent, so you can see its food inside. To eat, Collotheca extends its body fully from its
tube and waits for small swimming organisms to get close. Once an organism touches the rotifer's cilia, it gets sucked
into its mouth. Common foods of rotifers include : algae, protozoa (such as amoeba and paramecium), small crustaceans
(such as water fleas and copepods), and small bits of plant or animal matter floating in the current. They'll pretty
much eat anything that fits into their mouths. Collotheca reproduce by parthenogenesis. This means they don't have to
mate, each rotifer can just make eggs by itself. When a Collotheca releases its eggs, they usually drift to the bottom.
Eggs are very tough ; they can last through the winter, and if the water level drops, they won't dry out. When Collotheca
hatch from their eggs, they are active swimmers, using their cilia to swim around in search of food and , eventually, a
resting place. Most rotifers live about a week. They are most plentiful in late Spring.
Populations of rotifers can vary ; one year a pond may have a great many, the next year almost none. Predators of rotifers
include aquatic insects, crustaceans (crayfish, water fleas, copepods), small fish, and amphibians. The phylum Rotifera
consists of 3 classes, 120 genera and approximately 2,000 described species. Rotifers are found in aquatic and semi-aquatic
habitats, but are predominantly freshwater inhabitants. Rotifers are very important in these systems because of their
incredible reproductive rates. Population densities often reach greater than 1,000 individuals per liter. Because of
their high feeding and assimilation efficiencies, they play important roles in energy flow and nutrient cycling,
accounting for more than 50 % of the zooplankton production in some freshwater systems. Rotifers contribute to both
the microbial loop and to higher trophic levels. In addition, species assemblages of rotifers are useful in characterizing
lakes in relation to their trophic status.
Rotifers may also be very abundant in the interstitial water of soils reaching densities up to 2 million per square meter.
Diagnostic features of rotifers include the ciliated corona ("wheel organ") and the mastax. The corona is located
anteriorly and functions in locomotion and food gathering. The corona is modified extensively in some species. The mastax
is a muscular pharynx containing a complex set of hard jaws or trophi and is found in all rotifers. These characteristics
of these structures have been used extensively in classifying rotifers. Rotifers are small animals, ranging in size from
100 to 2,500 microns. Most species are free-living herbivores, bacteriovores or predators. Rotifers move by swimming or
crawling. Some sessile species are permanently attached to freshwater plants. Rotifers display a variety of reproductive
modes. Individuals in the class Monogononta generally reproduce by cyclical parthenogenesis.
Females reproduce asexually for the most part, then in response to environmental cues they produce daughters that are
capable of producing eggs by meiosis. These haploid eggs develop into males if they are not fertilized. The males produce
haploid sperm that can fertilize other haploid eggs. These fertilized diploid embryos are enclosed in several protective
layers and are referred to as resting eggs. Resting eggs can be dormant for many years before hatching and developing into
parthenogenetic females. Males are degenerate, lacking functional organs other than the testis. In class Bdelloidea,
females are thought to have reproduced solely by asexual means for thousands years. Males have never been identified
from this class. The seisonids reproduce sexually and the males are fully developed.
Rotifers are a group of microscopic animals that live just about anywhere there is fresh water, including lakes, ponds,
streams, puddles, ditches, wet shorelines (especially sand), and even on wet mosses. On this page, we will focus on the
Collotheca genus of rotifers. Rotifers have a cylinder-shaped body made of three sections : head, trunk, and foot. The
"foot" usually has two "toes" at the bottom. The head of a rotifer has a large, cup-shaped mouth, surrounded by cilia.
Cilia are tiny hair-like things which wave back and forth. The rotifer's cilia are used to trap food and to move around
through the water. Some rotifer species spend most of their lives swimming around, but most Collotheca rotifers are
"Sessile" means it attaches to one place and stays there for the rest of its life. The one time Collotheca swims is when
it is young and hasn't found its place to attach yet. When the young rotifer is ready, it uses a sticky substance from
its foot to attach itself to an aquatic plant. Greater Bladderwort is a favorite plant for Collotheca to attach to.
Collotheca are large compared to most rotifers.
Pics of Rotifers...