Freshwater ponds provide a home for a wide variety of aquatic and semi-aquatic plants, insects, and animals. The vast majority of pond inhabitants, however, are invisible until viewed under the microscope. Beneath the placid surface of any pond is a microscopic metropolis bustling with activity as tiny bizarre organisms pursue their lives; locomoting, eating, trying not to be eaten, excreting, and reproducing. In this collection of digital movies, observe the activities of microscopic organisms taken from a typical North Florida pond.

Annelids - Annelids are the phylum of segmented worms that includes earthworms, aquatic worms, leeches, and a large number of marine worms. There are over 9,000 species of annelids in the world.

• Aquatic Earthworm -As aquatic members of the class Oligochaeta in the phylum Annelida, aquatic earthworms are not an oxymoron, but rather relatively pollution-tolerant worms. They are typically found in and near the soft sediments of ponds, ditches, and wetlands. In common with other members of the microannelids, aquatic earthworm species feature tufts or bristles known as setae on their body segments, which facilitate tunneling through decomposing organic matter and bottom soils.

• Tubifex -Commonly known as sewage worms, Tubifex tubifex is a true earthworm (class Oligochaeta), easily recognized by its red color and mud tubes. As freshwater annelids in the family Tubificidae, bloodworms are among the few invertebrates that can thrive in sewage settling ponds, armed with an efficient manner of assimilating dissolved oxygen. They are available commercially, alive, frozen, or freeze-dried as a high protein aquarium food.

Arachnids - The phylum Arachnida is a widespread and diverse group of arthropods, including forms such as scorpions, spiders, ticks, and mites. They are primarily terrestrial and have a segmented body and tough exoskeleton, four pairs of legs, no antennae, and two specialized pairs of appendages used for feeding.

• Oribatida - The water mites, a grouping of nine superfamilies and more than 40 families of Hydracarina worldwide, comprise more than 5,000 named species in the suborder Oribatida that are truly aquatic. Occupying all types of freshwater habitat from tree hollows to hot springs, deep lakes, and torrential waterfalls, a few species have also invaded marine ecosystems.

Cnidaria (Coelenterata) - In the phylum Cnidaria, the name is derived from the threads (or cnidae) contained in the stinging cells that are common to all members of the phylum. Colenterata is another name for the same phylum, but is used as a description for the internal gut (coelenteron) that is also featured on members of the phylum. The most prominent members of Cnidaria are the sea anemones, corals, jellyfish, sea pens, and hydra.

• Hydra -In a phylum dominated by marine species as diverse as the jellyfishes and corals, the hydra (class Hydrazoa) are among the few commonly observed coelenterates in freshwater ecosystems. Skipping the medusa stage typical of the jellyfish, the stalked and tentacled invertebrate polyps can reproduce sexually or asexually. They follow the basic coelenterate radially symmetric body plan of two cell layers without a true body gut, having instead a gastrovascular cavity, with the mouth as a single opening.

Crustaceans - These primarily aquatic arthropods occur in a wide variety of habitats, but most species live in the ocean. Crustaceans are one of the most successful groups of animals, as abundant in the oceans as insects are on land.

• Cyclops - Recalling the mythological one-eyed giants of Homer's Odyssey, Cyclops are predominantly free-living crustaceans in the subclass Copepoda and the suborder Cyclopoida, and feature a central, anterior eyespot. Although largely marine, the specimen illustrated here is one of the 44 species of freshwater cyclopoids known from this genus worldwide.

Gastropoda - Included in the broad class Gastropoda are snails and slugs, which are usually endowed with a spirally coiled shell to protect the soft body. Gastropods have a broad muscular foot that is used for locomotion in most species, but it modified for swimming or burrowing in others. In addition, these creatures are equipped with a well-developed head that includes eyes, tentacles, and a concentration of nervous tissue, usually termed a ganglion.

• Aquatic Snail -Carrying their homes on their backs, snails are important in aquatic ecosystems, in which their grazing and scavenging of diatoms, algae and bacteria enhance nutrient recycling. The class Gastropoda in the phylum Mollusca includes the snails and slugs, encompassing many freshwater and marine species.

Insects - The widespread insect world is home to somewhere between one and ten million species, divided into 32 orders with the largest being the Beetles (Coleoptera). Insects are capable of inhabiting both wet and dry environments and are found in just about every part of the world. The average soil density of land-based insects is about 9 million per acre with about ten thousand "in flight" above it. Other insects live in or near ponds, streams, rivers, and lakes, where they feed and also breed.

• Chironomid - In addition to supporting the biomass of the freshwater fishes community, non-biting midges or chironomids are essential in the diets of many migratory shorebirds and waterfowl. Water pollution and aquatic habitat destruction, as well as land use practices and indiscriminant pesticide use, threaten these very diverse and widespread dipterans worldwide.

Nematodes - The roundworms, or nematodes, are among the most abundant multicellular animals on Earth, many of which are parasitic to plants or animals. These transparent, microscopic worms in the phylum Nematoda include free-living forms found in aquatic and terrestrial ecosystems. There are 10,000 described species, but perhaps another 100,000 that deserve taxonomic status.

Protozoans - Protozoans are one-celled organisms belonging to the Kingdom Protista, which includes algae and lower fungi. Although they are invisible to the naked eye, they dominate the Earth's environment, occurring everywhere and in an amazing diversity of forms and functions.

• Amoeba - Amoebas are primitive, unicellular animals known by their flowing, free-form movements and their prey capture techniques. Most members of the order Amoebida in the phylum Sarcodina are free-living, but some are endoparasites of plants and animals, and are well known disease vectors of ailments such as amoebic dysentery in humans.

• Spirostomum - Known for displaying the fastest contraction of any living cell, the relatively giant ciliates in the genus Spirostomum are the true speed demons of the microscopic world. With some species large enough to be observed without the aid of a microscope, these protozoans can reduce their body sizes to 25 percent of their normal lengths in less than 8 milliseconds, using very strong myonemes.

• Volvox - Straddling the plant and animal kingdoms, the protist Volvox forms stunning bright green colonial balls in water bodies that are enriched in nitrates. Found in puddles, ditches, shallow ponds and bogs, Volvox colonies reach up to 50,000 cells and may include daughter and grand-daughter colonies.

• Vorticella - As a member of the phylum Cilophora (ciliates), Vorticella grow in macroscopic clusters of stalked individual animals that may be mistaken for a colony of filamentous algae. Vorticella are transparent, range from 50 to 150 micrometers in length, and are easily cultured as the unicellular protist component of infusoria commonly utilized as food for fish fry.

Rotifers - First discovered in the 1600s by Antoni van Leeuwenhoek, they were originally called "wheel animalcules" or wheel animals because their coronas look like turning wheels. This appearance is caused by rippling (metachronal) waves of tiny beating cilia that draw food into their mouths and provide a means of locomotion. Rotifers are the smallest multicellular animals and occur worldwide in primarily freshwater habitats. 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).

• Collotheca - Rotifers in the genus Collotheca are sessile and may form spherical colonies or attach singly to the substrate or to submerged aquatic plants, using a stout foot terminated by a short peduncle. Each rotifer secretes a gelatinous tube up to 650 micrometers in length that is used as a safe haven into which to retreat when disturbed.

• Philodina - Placed in the class Bdelloidea, which is Greek for leech, species in the genus Philodina possess two ovaries and are solely parthenogenetic. Male rotifers in this class have not been observed, and members of Philodina, referred to as the world's most common metazoans, are unique to the animal kingdom.

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