The Paramecium - The Most Studied Of All The Protozoa.
, an image of one of the more common Paramecium types and one of the smaller varieties, growing to about 125 microns in size.
Paramecia are found in ponds and other quiet waters among the muck and decaying vegetation. A large number of Paramecia in your backyard pond would indicate less than desirable water conditions.
Paramecia have a weapon defense system that they deploy against their enemies. When attacked, they release dart-like objects from capsules located on their undersides. It usually works, however, it is completely ineffective against the Paramecium's most deadly enemy - the Didinium. The Didinium simply forges ahead, undeterred, gulping down as many as two Paramecia a minute.
The second image shows a bit more clearly the water expelling vesicle of the Paramecium (sometimes called the
"). Through a complex metabolic process, excess water from the animal's cytoplasm is drawn into the vesicle and expelled as waste matter. A trapdoor at the opening of the vesicle opens and closes to contain the vesicle's contents until the pressure inside forces it open. Truly remarkable behavior - the breathing and excretory functions of a multi-celled animal with complex organ functions - but all occurring within just one "organless" cell. See the section on "Size" for an animation of the Paramecium's vesicle.
, a species of Paramecium that appears green because of the presence of symbiotic Zoochlorella
This image of two Paramecium bursaria displays the symbiotic relationship between the Paramecium and the single celled Zoochlorella algae. The algae gains protection, and possibly some essential nutrients from the general protoplasmic soup inside the Paramecium. The benefit to the Paramecium probably is that the algae sustains the animal during absences of sufficient food sources by providing vitamins and proteins. During severe food shortages, the Paramecium most likely would consume the entire algal mass.
This image shows in unusual color the intricate details of this amazing one celled animal - the Paramecium.
The Paramecium is the most studied of the one celled Protozoa because of its complex makeup. It's a ciliate, so you can see the cilia surrounding the body, although blurred. The cilia
propel it through the water and it moves quickly, rarely stopping for a breath.
The colored circular objects are the two water expelling vesicles, a food digesting vesicle, circulating food vesicle, gullet and nucleus. Amazing complexity for a one celled creature.
Paramecium increase their numbers by a process known as " binary fission
", the simplest of the reproductive processes of Protozoa. The Paramecium pictured here will split into two, and each one might again divide by the end of the day.
Paramecia have a defense system that they can deploy when attacked or when they feel threatened.
When the Paramecium is attacked or feels threatened, it unleashes its defense system
- a battery of harpoon-like spears called trichocysts. This defense system can be triggered by allowing a drop of vinegar to seep between the cover slip and the microscope slide. When the vinegar hits the Paramecium it immediately deploys its harpoons in the hope that the attacker will back away. Often, as in the cases displayed in these images, the Paramecium will release everything at its disposal, including undigested food, digested waste and waste water through its several water expelling vesicles and anal pore. This release is readily apparent in the image at the right. The long trichocysts too are plainly visible. Most remain attached to the Paramecium, but some are actually thrown off a short distance.
Under very high magnification these trichocysts appear as long spears, with sharp pointed ends, much like whalers' harpoons.
All ciliates also can multiply by a process known as conjugation
. Here is a rare image of two Paramecium engaged in true sexual reproduction.
The upper image shows two Paramecia reproducing by conjugation. The two are joined and a cytoplasmic bridge is formed between the two animals. The nuclei from both Paramecia divide several times. One of the divided nuclei from each Paramecium travels across the bridge and fuses with one of the nuclei from the other animal. The nuclei form another nucleus and cell, the others dissolve, and the new cell separates. This cell can divide several times, creating a wholly new Paramecium in each case.
The lower image shows a single Paramecium. Paramecia travel rather quickly, and they "corkscrew" as they move through the water. These creatures were slowed (but not stopped) by adding methyl cellulose to the water sample and it enabled the obtaining of reasonably clear images at 400x. The oral groove, which unmistakably identifies the Paramecium is not visible in either image.
Get a real sense of the size
of these critters. The following picture is of a swarm of Paramecium inside a speck of water that is smaller than the "period" on your keyboard's "period key".
Actinosphaerium (or an Actinophyrs)
. The spikes are used to spear other protozoa. The protoplasmic "soup" is then sucked out of the victim into a food vacuole where it is digested.
These are most likely Actinophrys. Their size is in the vicinity of 40 to 50 microns, whereas the Actinosphaerium is much larger at 200 to 1,000 microns.
An excellent image of an Actinophyrs digesting a meal.
This Actinophyrs is enjoying its recent lunch - the brown spot at the top of the animal. It appears it has no other meals "in storage" as the spikes (skewers) are clean. Not a problem, however - the Actinophyrs is an excellent hunter and food for the next meal will not be a problem. Although found in vegetation in well oxygenated waters, it is an omnivore.
An excellent image of an Actinosphaerium.
Actinosphaerium can grow up to 1,000 microns in size. This specimen certainly is close to that figure.
The white spot just to the right of the pointer tip is a food vacuole. The dark spot within it is the latest meal being digested. At about 9:00 or 10:00 is an out-of-focus yellow food morsel that has been impaled on one of the Actinosphaerium's spikes. That's the unfortunate next meal. At about 2:00 is an out-of-focus Vorticella that wandered by. The Actinosphaerium seemed unconcerned, and the Vorticella moved on.
An image of three different Protozoa
, all in a space not much bigger than a pin head.
A Stentor is seen in the upper portion. An Amoeba is in the lower left portion. The Actinosphaerium is sucking on the piece of protoplasm that it had skewered - the out-of-focus blob between the Amoeba and the pointer. Neither of these three Protozoa were a threat to one another. The Stentor feeds on bacteria and algae, and the Amoeba eats whatever it can engulf and digest. The Actinosphaerium couldn't handle the size of either one.
Images of the Vorticella
Cilia create currents in the water to draw food into the Vorticella's huge anterior opening. Bits of ingested food are clearly visible. Because the cilia are constantly moving, they are blurred in the photo but still visible.
There are in excess of 100 species of Vorticella.
The following is an image of a species that clearly shows all of the creature's internal parts and functions
In this unusually clear image, we can see (faintly) the three rows of beating cilia that surround the anterior opening, the contractile stalk, the mouth, the (waste) water expelling vesicle, several food vesicles, macronucleus and micronucleus. All the parts needed to function as we humans do, but in just one cell.
Another image of a Vorticella. The trailing stalk is faintly visible in this photo. See the picture along with a description of the Vorticella's unusual behavior.
The stalk of the Vorticella
extends back to about 15 times its body length. The sticky end allows the Vorticella to attach its stalk to suspended objects, or more likely, the pond bottom. The Vorticella then slowly patrols a circular area, sweeping food into its huge mouth. When startled, the creature instantly recoils to the point of its anchored stalk, then slowly extends itself once again.
Five Vorticella in one spot.
Vorticella are sensitive to the slightest vibrations and water movements. When startled, their stalks instantly recoil, backing them away from the apparent danger.
A bit of misfortune that befell an inattentive Vorticella is seen in the following picture.
The Vorticella's stalk is fully extended and anchored as the creature sways back and forth, swirling bits of food into its mouth. Slightly below the black pointer is a brown-colored worm, the larva of one of the many midge-type flies. Shortly after this photo was taken, the worm began wildly whipping its body (that's how they move) and it inadvertantly cut the Vorticella's stalk. The picture at the right shows the critter rolled into a ball and wandering aimlessly. The stub of the stalk can be seen at the edge of the body, at about 10 o'clock.
Here is an image of a Vorticella dividing
Ciliates multiply by fission in varying forms. The Vorticella divides by budding, a form of fission. On this animal a bud is clearly seen developing at the base of the body where it meets the stalk. The bud, with its own nucleus, will break away and form its own stalk. Because each Vorticella has its own stalk they cannot be considered communal animals, although they usually can be found grouped together. In this image the Vorticella is attached to a piece of decayed matter.
Some Common and Not So Common Stentor
Here's a protozoa that appears quite different from a Vorticella but has many of the same behavior and feeding patterns, the Stentor.
The Stentor is one of the largest single celled protozoa, growing as large as 2mm. The one pictured here, however, is nowhere near that size. Their behavior is similar to that of the Vorticella, in that they can be free swimming or they can attach themselves to other objects - usually the pond's bottom. When startled they quickly retract into a ball, then slowly emerge into their characteristic trumpet shape. They feed on the bacteria from decaying vegetable matter. They are most abundant and easily found in the fall when dead leaves and other vegetation falls into the pond and bacteria are plentiful. The red specimen here came from the bottom of a pond in the cold early spring among some decaying leaves.
This is an excellent image of two Stentor.
The Stentor is not a communal creature, but it is possible to encourage them to "huddle" together.
Here's a Stentor consuming a Closterium
The Stentor's diet is primarily bacteria and assorted algae. Here a Stentor has ingested a whole Closterium, a common single cell algae. The Closterium appears to be breaking down as it is slowly digested by the food vacuoles inside the Stentor's tubular body.
Here is an image of two Stentor.
It's a pair of aquamarine colored Stentor
, much like the common brown ones. The green color tone in this pair is probably due to the presence of symbiotic green algae. These two protozoa are really no different than any of the other Stentor species. The only difference is their vivid coloring. These two are not really a "pair". They multiply simply by sprouting a new "bud" from the side of the body.
Here is an image of a blue Stentor showing the large, fully extended mouth opening and the surrounding cilia.
The head and mouth are fully extended and open, showing the Stentor's unique horn shape. Because the head is facing slightly upward the mouth shape and size are clearly visible. Some of the beating cilia are visible also - the method by which they channel food into their mouths. Some of the Stentor's diet can be seen inside the body tube - assorted species of algae and bacteria. Food vacuoles along the inside length of the body gather the food and digest it.
Other interesting specimens of the Blue Stentor
When the Stentor is first dropped on the slide, it appears to have some trouble finding a good spot to settle down. This composite shows four images of the same Stentor as it wanders about the water drop. Some will wander around for several minutes before they find a suitable open area. In the final image it appears comfortable, and has settled into its spot - fully extended, mouth open, with the cilia swirling food into its mouth.
This one celled Protozoan continues to show its many fascinating faces.
This is an intriguing creature for a one celled animal. Besides being able to perform all the functions of eating, breathing, moving, reproducing and excreting waste, it presents fascinating, almost artistic, faces. The shape of the mouth opening is not circular or oval but contains indentations for reasons unknown, lined with constantly moving cilia for directing food into its mouth. This specimen appears to have just consumed and digested a nice sized meal. The circular marks along the Stentor's inside tube are food vacuoles, where the ingested meals are captured and digested. With several of these "stomachs", the Stentor can enjoy several meals at once - gluttony at a primitive level!.
Crustaceans (Free Living Copepods)
Crustaceans are abundant in ponds and are easily spotted once the water warms. The microscopic ones feed on algae, decaying matter, other protozoa and even bacteria.
All crustaceans have segmented limbs and a hardened external skeleton. This Macrothrix is similar in shape to the common Daphnia, but is slightly larger, has more limbs and larger antennae. The Macrothrix also has two separated and distinct compound eyes. The heart, which was visible along the upper back behind the head, could be seen beating in the microscope. This image is at 400x magnification showing that the Macrothrix is about twice the size of a Paramecium.
Here's another picture of a common crustacean - a Chydorus
, a relative of the Daphnia. A dead Chydorus, but one worth a look anyway.
This Chydorus has apparently been dead for a while, perhaps a day or so. Its eye is gone, probably consumed by an efficient scavenger. What's interesting, is the worm that's trapped inside the Chydorus's body cavity. These small worms are the larvae of flies - they can't see, and they move by wriggling their bodies, more or less aimlessly, until they bump into something worth exploring as a possible food source. Apparently the worm wriggled its way into the Chydorus through the mouth and was unable to find its way out. The worm eventually worked its way into the head cavity, and stuck its head out the Chydorus's mouth. A little more squirming and it was free - none the worse for the experience.
Here's an image of a copepod that doesn't look like a copepod, nor is it free living. It's a parasitic Anchor Worm
. Unfortunately, for the fish from which it was removed, its head remained in the fish.
The inset shows a complete Anchor Worm.
Anchor Worms should be dabbed with turpentine, which causes the worm to release its hold. Then it can be removed safely with tweezers.
When looking for protozoa one wouldn't expect to see anything colorful, since 99% of these microbes are transparent. The following is a picture of a red-colored, and not often seen Blepharisma
Blepharisma are ciliates, although the cilia are not apparent in this photo. They move quickly, much in the same way as a paramecium, and are about the same size. It normally takes an elongated shape. Note the paramecium above (it looks ready to attack - it won't), and some type of out-of-focus worm to the left extending under the black pointer.
This image shows the more normal, elongated body of the Blepharisma. Also visible is the dark undulatory membrane on the upper right - this is the feature that produces the waves that allow locomotion, much in the same manner as the Paramecium. In bright sunlight the pink color disappears. In fact, under intense bright artificial light, the pink pigment will emit a poisonous toxin that causes the Blepharisma to completely disintegrate.
The life of a microbe in a pond isn't all fun and games, or eat and sleep.
Starting out the day as breakfast for another critter is about as bad as it gets, I would think. But the blepharisma that you saw in the previous image is seen again here. Unfortunately, it's in the stomach of a hideous-looking, hairy glassworm or ghostworm
and a Colurella
are all the larvae of the many different kinds of black flies (midges) that we see around our ponds.
The first picture and inset are images of a Bloodworm, the larva of the midge. Bloodworms are easily spotted because of their bright red color. The second image shows the final stage of the pupa. When the metamorphosis reaches this stage the pupa must find dry land - the ground, a rock, a floating leaf - so the adult can crawl out of its protective shell. The third image shows the perfectly formed outer shell that's left behind after the adult breaks out. When the fly emerges, the dry wings unfold and the midge is ready to fly off, leaving behind a perfect mold of itself.
Amoebas are amorphous so they are seen in a variety of shapes and sizes. They also have developed a variety of ways to cope with the dangers of their environment. The following is an image of an Arcella, an Amoeba that has developed an unusual method of protection.
The Arcella, known as a domed Amoeba, builds a transparent dome from whatever building materials it can find in the pond, usually sand. It then encloses itself in the dome for protection. These four Arcella are munching on what appears to be an egg sac, but because most of what they have been eating is gone, it's difficult to identify.
Diatoms are unicellular algae in a siliceous box formed by two hulls or thecae, the upper of which is bigger and covers the lower one like the cover of a box. The cell lives inside the box. These cases are covered in minuscule holes, incisions and reliefs arranged in regular patterns to form attractive grids. The variety and the beauty of their forms is so great that there are enthusiasts exclusively devoted to the collection and the study of diatoms. The system of locomotion of these algae is special. The lower hull has some holes in it and a longitudinal fissure, named a raphe. Part of the cell's cytoplasm escapes from this crack and produces a sticky secretion which flows along the raphe, allowing the diatom to move as though it were on tracks. Diatoms appeared about 135 million years ago.
Blue-green algae are eubacteria that can perform photosynthesis. They are also called Cyanophyceae. They were probably the first organisms on Earth able to produce nutrients to feed themselves. They originated over 3.8 billion years ago. Often their colour is blue - green (cyan). Sometimes they are surrounded by a mucous envelope.