Dellebarre Compound Microscope (circa 1777)


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Pond Life

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.

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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.

  • Acanthocystis - Acanthocystis belongs to the class Heliozoa , or "sun animalcules." Some species in this genus are called "green sun animalcules" because their bodies are colored by harmless symbiotic green algae (zoochlorellae). Heliozoans feed in the same way as amoebas, by engulfing their prey.

  • Actinophrys - These heliozoans are found most often in freshwater, floating in the open water amongst reeds and filamentous algae. Heliozoans are spherical and are frequently enveloped by a shell made of silica or organic material. Actinophrys generally has more than one nucleus. Pseudopodia (axopodia) that extend outward in a rayed pattern are used for capturing food.

  • Amoeba - Amoebas are primitive organisms characterized by their flowing movements, considered to be the most primitive form of animal locomotion. Many species that belong to the order Amoebida are free living, but some are well-known parasites of plants, animals, and humans (e.g. amebic dysentery).

  • Bursaria - Bursaria is one of the ciliates, generally considered the most complex of the protozoans. These organisms are large enough to be barely visible, and are characterized by a large opening, a mouth of sorts, which they use to scoop up protozoan prey.

  • Coleps - This barrel-shaped ciliate is covered by a layer of protective, calcareous plates and is commonly found in freshwater. Coleps is a rapid swimmer, revolving as it travels and using this motion to bore out chunks of other protozoans it is feeding upon.

  • Didinium - Didinium is an oval-shaped ciliate that lives in freshwater habitats and is frequently seen in samples of pond water. It preys almost exclusively on Paramecium, injecting trichocysts into its prey when it bumps into it. These paralyze the much larger organism and making it possible for Didinium to engulf and ingest it. The trichocysts are only ejected when it bumps into something it's interested in eating.

  • Dileptus - Dileptus is a slender, elongated ciliate that can stretch several times its body length to reach for prey, subduing it with chemical weapons called extrusomes before apprehending it.

  • Epistylis - The genus Epistylis, also called Heteropolaria, belongs to the order Peritrichida, a group of ciliated vase-shaped protozoans. Many species in this genus are sessile and form branching colonies. Colonies of Epistylis can cause "red sore disease" in freshwater fish. The organisms secrete an enzyme that breaks down tissue at the attachment site and leaves a wound that is vulnerable to bacterial and fungal invasion.

  • Euglena rostrifera - This species is a member of the protozoan order Euglenida, a remarkable group of single-celled creatures, many of which exhibit characteristics of both plants and animals. Like many protozoans, they are free-living, using a whiplike flagella to move about. Euglena is one of the euglenoid genera that contain chlorophyll, allowing them to create their own food through photosynthesis. Euglenas live in a variety of aquatic habitats, both freshwater and marine.

  • Euglena rubra - Red pigment protects this species of Euglena from ultraviolet radiation, which can cause a red "bloom" in ponds or lakes when the population suddenly increases.

  • Euplotes - Euplotes belongs to the ciliate order Hypotrichida whose species are characterized by rows of fused cilia called cirri on the ventral surface. A freshwater inhabitant, Euplotes uses its cirri for swimming and also to "walk" along a substrate.

  • Frontonia - A common resident of freshwater ponds and lakes, this ciliate is related to Paramecium. Both genera belong to the order Peniculida and are sometimes called "slipper animalcules" because of their slipperlike shape.

  • Loxocephalus - This free-living ciliate thrives in fresh or brackish water where it is commonly found in decaying vegetation. It has a long taillike cilia and uses a collar of cilia to swirl particles of food into its mouth.

  • Loxophyllum - A relative of the ciliate Didinium, Loxophyllum lives in freshwater habitats where it preys upon rotifers and other ciliates.

  • Metopus - Unlike most other ciliates, which are aerobic, Metopus is anaerobic and lives in oxygen-depleted sediments. Some species have even been found living in sediments off the coast of Antarctica. In place of mitochondria, Metopus has respiratory organelles called hydrogenosomes.

  • Oikomonas - In this genus of colorless flagellates, the organisms carry symbiotic cyanobacteria (blue-green algae) on their surface membranes.

  • Paramecium - A well-known visitor to the classroom microscope, this slipper-shaped ciliate is commonly found in freshwater ponds. They feed on other microscopic organisms, sweeping them into a funnel-shaped gullet.

  • Peranema - Peranema is a colorless euglenoid with two flagella, although only one is usually visible through the microscope. These flagellates live in both freshwater and marine, environments as well as soil and as parasites.

  • Spirostomum - Some of the largest ciliates belong to the genus Spirostomum, some species large enough to see with the naked eye. These organisms hold the record for the fastest body contractions of any living cell, contracting it's length to 25% of its normal size in 6-8 milliseconds. Spirostomum feeds on bacteria and during cold weather forms large clusters of organisms that hibernate together.

  • Stentor - Also known as the "trumpet animalcule," Stentor is one of the largest cilated protozoans. The organisms generally spend their lives attached to a surface, but can use their cilia to move to other places when necessary. Cilia lining the "trumpet" beat rhythmically, drawing food into the mouth of the organism.

  • Stylonychia - This genus belongs to the ciliate order Hypotrichida whose species are characterized by rows of fused cilia called cirri on the ventral surface. Stylonychia uses its cirri to "walk" across a surface as well as for swimming. It is a common inhabitant of ponds, living in shoreline films where it preys on smaller organisms.

  • Urocentrum - A relative of the paramecium, Urocentrum is a rotund ciliate slightly bifurcated by a two distinct bands of cilia and sporting a tufted "tail" of fused cilia on its posterior. The organism spins on this tail, swimming rapidly in a slightly irregular spiral. It commonly occurs in decaying pond vegetation in which it feeds on bacteria and particles of organic matter.

  • Volvox - Volvox is a colonial organism made up of 500 to 60,000 bi-flagellated cells embedded in a gelatinous wall. It has something of a dual identity amongst biologists, placed by zoologists into the order Volvocida and classified by botanists as a green algae, Chlorophyta. Twenty species of Volvox occur worldwide.

  • Vorticella - These bell-shaped ciliates live in fresh or salt water attached by a slender stalk to aquatic plants, surface scum, submerged objects, or aquatic animals. The stalk contains a contractile fibril called a myoneme that causes it to coil like a spring when stimulated. Vorticella eat bacteria and small protozoans, using their cilia to sweep their prey into mouth-like openings.

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).

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.

  • Brachionus - These rotifers have a transparent turtle-like shell called a lorica and are found in a variety of habitats, freshwater and marine. Several species are cultured to provide food for fish larvae in aquaculture. Like most rotifers, Brachionus rotifers have pedal glands and extrude a small amount of sticky cement to anchor themselves temporarily on substrate. They also anchor, then spin out a length of filament at the end of which they stay with corona extended to feed.

  • Cephalodella - About 200 species belong to this genus. They are found in many habitats including soft sandy substrates called psammon. They are fast swimmers with a typical turning movement. Some are raptorial. The shape of the toes, their proportion to body length, and the type of trophi (chitinous jaws) are important characteristics for identifying individual species.

  • Collotheca - Collotheca rotifers are sessile; they are attached to each other forming a spherical colony, or attached singly to the substrate. Each rotifer secretes a gelatinous tube into which it withdraws when disturbed. When it feels safe, it extends and the infundibulum opens like a blossom. Ciliae at the rim's edge sweep food into the mouth at the bottom of the infundibulum.

  • Dicranophorus - Dicranophorus species are found in littoral and benthic habitats. Some are predatory; D. isothis has been observed attacking the cladoceran Chydorus. The trophi (chitinous jaws) can be thrust partly out of the mouth to capture prey. Dicranophorus belongs to the largest class of rotifers, the Monogononta , species that have only one ovary.

  • Euchlanis - Euchlanis rotifers have glasslike shells called loricas. When threatened, they withdraw like turtles into the lorica. While most are littoral, E. arenosa is psammophylic, living in soft sandy soils. It lacks an eyespot, which it does not need in that dark, sandy habitat.

  • Lecane - Rotifers of this genus are mostly loricate (having shells) and live in littoral areas of freshwater bodies. They are found in many habitats, grazing among aquatics and algae. The dorsal plates of some of these rotifers are ornamented with ridges and folds, important characteristics in identifying species.

  • Mytilina - Species belonging to this genus are loricate and are found mostly in littoral habitats. Since the lorica is glasslike, like Euchlanis, it is easy to view their internal organs.

  • Philodina - 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.

  • Squatinella - Rotifers belonging to this genus are commonly found in littoral (shoreline) habitats among aquatics. In most species, the corona is covered by a semicircular shield, which is used to scrape small organisms into the mouth while browsing over underwater plants. In the laboratory, it is nearly impossible to pick them up with a pipette as they glide swiftly along the surface of a dish or slide.

  • Trichocerca - These loricate rotifers are found in many habitats. Members of this genus are easily recognized for their twisted and arched shapes. They have one long left toe, one short right toe and substyles at their bases. Their trophi (chitinous jaws) are asymmetrical. They swim with a strong turning motion.

Algae - Members of the Kingdom Protista, algae are most common in aquatic habitats, but occur in nearly every environment. They range in size from microscopic to giant kelp that reach 200 feet (60 meters) in length. Algae produce a significant percentage of the Earth's oxygen, are the base of the food chain for nearly all aquatic life, and provide food and industrial products for humans.

  • Closterium - Closterium is a desmid, a microscopic green algae that occurs in all types of freshwater habitats. Desmids are typically one-celled, though sometimes filamentous or colonial, and are divided symmetrically into semicells connected at a central point. Closterium is characterized by a sickle shape and sometimes contains gypsum crystals.

  • Frustulia - Frustulia is one of 16,000 species of diatoms, one of the many groups of organisms that make up the algae. Diatoms are photosynthetic, but have rigid cell walls reinforced with silicon rather than cellulose. They can be found in all aquatic environments and, although they're unicellular, often live in large colonies.

  • Oscillatoria - A type of blue-green algae, this genus is characterized by the gliding movement that it exhibits as it makes its way across the substratum. Species belonging to this genus can be found in hot springs, freshwater, marine, estuarine, and sulfur environments. The Red Sea gets its name from occasional blooms of a reddish species of Oscillatoria.

  • Phormidium - Phormidium is a benthic blue-green algae made up of a filamentous chain of cells. Although normally non-toxic, in the spring of 2000 a toxic form was found living in a water tank in Australia.

  • Polycystis - This blue-green algae is commonly found in freshwater lakes.

  • Spirulina - Spirulina grows in pondwater and is utilized as a source of protein by people in many parts of the world. This blue-green algae is recognized as one of the best plant sources of protein. It is also a proven source of beta carotene, vitamin B12, and gamma linolenic acid.

Gastrotrichs - Gastrotrichs are a group of aquatic invertebrates that live in both seawater and freshwater, commonly inhabiting stagnant waters and bottom muds. These tiny wormlike creatures are related to nematodes (round worms) and rotifers and lack circulatory, respiratory, and skeletal organs.

  • Chaetonotus - Chaetonotus is the largest freshwater gastrotrich and can be found in plant-choked ditches and mossy ponds. Like many other gastrotrichs, it is parthenogenetic, giving birth only to females.

Nematodes - One of the most abundant animals on Earth, many species of these transparent, microscopic worms are parasites, causing important diseases of plants, animals, and humans. Other nematodes exist as free-living forms in soil and aquatic environments and some even live in food products such as beer and vinegar.

Platyhelminths - Also known as flatworms, members of this phylum are flattened, soft-bodied invertebrates ranging in size from microscopic to more than 50 feet (15 meters) in length. Most species that belong to this phylum are parasitic, some of which parasitize animals and humans. The class of flatworms featured here are turbellarians, which are primarily free-living.

  • Dalyellia - Dalyellia belongs to the order Rhabdocoela, a highly diverse group with many free living representatives and some species that live symbiotically within the bodies of larger organisms. Members of Rhabdocoela are simple organisms, having either a simple sac-like intestine or no intestine.

  • Microstomum - These are small, elongated turbellarians, with an anterior mouth, and simple gut. They can be found under rocks, submerged leaves, and other debris, where they feed on tiny crustaceans, microrganisms, and organic particles. Microstomum belongs to the order Rhabdocoela.

  • Stenostomum - This genus belongs to the order Catenulida, a mainly freshwater group, with some marine representatives. This group is different from other turbellarians, with a ciliated, sac-like intestine, simple pharynx, and unpaired gonads.

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.

  • Aeolosomas - These oligochaetes (aquatic worms) are transparent microannelids, similar to earthworms but much smaller, ranging from 1-180 millimeters. They inhabit soils and decaying material in stagnant water.

  • Naidadae - The Naididae family of aquatic worms is an ecologically diverse group, common in both running and standing waters. This is one of the largest families of freshwater worms, they are small rarely exceeding 1 inch (25mm) with some as little as 1/8th inch (3mm) long. Many naidids live in the sediment, but other species live among aquatic plants.

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.

  • Hydracarina - Water mites belong to the arachnid suborder Hydracarina and have a worldwide distribution. They live in all types of freshwater bodies, tree holes, hot springs, deep lakes, and torrential waterfalls. A few species even live in oceans. The water mite is very small and has leg hairs that help the mite propel itself through the water.

  • Oribatida - Mites belonging to the suborder Oribatida, also called "beetle" or "box" mites, are one of the world's most numerous arthropods found living in soil. Although most species live in soil or forest litter, and play an important role in decomposing organic matter, four families of oribatids contain species that live in or on the water.

Dipterans - The two-winged or true flies, such as house flies, midges, gnats, and mosquitoes, are one of the most common and important groups of insects in the world, both ecologically and economically.

  • Ceratopogonids - Biting midges, also called sand flies, no-see-ums, and punkies, are the smallest of the biting flies. They are well known for their painful bites to humans and animals, but some species bite only other insects. As adults, they can be found living in moist soil, rotting wood, cow dung, salt marshes, tree holes, and cacti. As larvae, they live in the water where they feed on detritus, yeast, or algae. One genus of ceratatoponigid, Forcipomyia, holds the world record for wing beat frequency in insects -- 1046 Hertz (cycles per second) or 62,760 wing beats per minute.

  • Chironomids - Non-biting midges are one of the most diverse and widespread dipteran groups known. They inhabit virtually the entire range of aquatic ecosystems, both fresh and marine, as well as semi-terrestrial and terrestrial habitats. Most species have aquatic wormlike larval stages that start as egg masses laid on the water surface. After going through a pupal stage, floating at the surface of the water, a full-grown midge emerges and flies away.

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.

  • Chydorus - Chydorus is a cladoceran, a group of tiny crustaceans, most of which live in fresh water. It is one of the many types of water fleas and is related to the well-known Daphnia. Like most water fleas, Chydorus is a filter feeder, consuming tiny pieces of organic material. It prefers quiet waters and can be found living among underwater weeds, although some species of this genus live in sediments.

  • Cyclops - Cyclops is a genus of copepods named for the animal's single eyespot, reminiscent of the one-eyed monster in Greek mythology. Although most species of Cyclops are marine, many are commonly found in quiet freshwater habitats.

  • Ostracod - Also known as seed shrimp, most ostracods live on the sea floor where they are important scavengers, cleaning up the remains of dead fish. Other species of ostracods live in the ocean waters or in freshwater lakes and streams. A few species are terrestrial, residing in damp areas of forests.

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