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Last Updated: 8/9/07
Spiders and Mites
Worms - earthworms, flatworms including planaria, horsehair worms,
leeches, nematodes, proboscis worms, and blackworms
Microorganisms - cyclops, daphnia, euglena, gastrotrichs, infusuria,
paramecium, rotifers, and water bears
Miscellaneous - hydra, jellyfish, moss animals, and sponges
Books and Links
There are a number of aquatic mites that live in the water and spiders that live near ponds. Spiders and mites are arachnids, which means they have 8 legs. Insects have 6 legs.
The fisher spider (Dolomedes triton (the Roman god of the sea)) dives into ponds.
It catches insects and even small fish and tadpoles. The fisher spider grows 0.4 to 0.7 inches
long.
The stilt spider (Tetragnatha elongata) grows 0.3 to 0.4 inches long. It creates a
snare to catch flying insects.
Here is a photo of a spider living among the marginals of my pond on 9/29/01.
Candy sent this photo of a water snake in her pond on 5/30/07. There is also a neat spider in the
photo. I was told that it is a fishing spider, the six spotted Dolomedes triton. Here
is a web site
on them. The ones on that page seem a lot darker than this one below.
Water snake and fishing spider
Water mites range from 0.1 to 0.2 inches long. They eat small worms, insects, and crustaceans. Some mites are parasites. Some swim and some crawl but all must come up to breathe.
There are a number of species of earthworms or Oligochaeta. Tubifex are an inch long, are red, and live in tubes in bottom mud. Chaetogasters eat small animals with their large mouths and grow to half an inch. Deros build tubes in debris, grow to about half an inch, and have bristles. Aeolosomas grow to half an inch, live in debris or on plants, and can have colorful spots. All species tend to stay on the bottom or in debris, dirt, etc.
Flatworms or Platyhelminthes include flukes, tapeworms, and turbellarians. The first two are familiar parasites. The latter move around on surfaces using cilia and eat small living or dead animals. Planaria, a common turbellarian, often over-reproduce in aquaria but I do not think they are a problem in ponds. Other turbellarians are also rather harmless. Dugesias tigrina is the largest free-living flatworm, growing to an inch long.
Planaria:
If small white creatures are seen crawling all over the glass and ornaments, especially at night, they may be planaria. Planaria commonly show up in tanks with an excess of food. Most are introduced to an aquarium from other aquaria with live foods like black worms, live plants, or anything else moved from an active aquarium that has them. There is some belief that they can survive in freeze-dried or frozen foods. If a lot of food is left in a tank; including dead and dying fish, snails, other animals, and plants; then a few planaria may divide into hundreds very quickly. They usually reproduce by asexual fission. Their heads are shaped like arrow heads. If a tank is found to be infested, planaria can be controlled by a good vacuuming of the gravel and better tank maintenance. To remove more planaria, see the next section on controlling planaria. Planaria will eat dead fish, fish eggs, and immobile fish larvae (fry newly hatched). They do not pose any risk to mobile fry or adult fish.
Controlling planaria in aquaria:
1. Set out bait like meat in a mesh bag. Remove the bait a few hours after the lights go out on
the tank. It should be covered with planaria. Throw away and repeat until the population goes
down.
2. Add planaria eating fish to the tank. One species is the paradise
fish.
3. Vacuum the gravel very well and do a 50% water change. Often, planaria proliferate when
the tank is too dirty. This will remove not only some planaria but their food source as well.
4. Reduce the foods added to the tank. Planaria often proliferate if too much excess food is
provided.
5. As a last resource, tear down the tank. See here for
information on tearing down tanks.
Horsehair worms (Gordius), or Gordian worms, grow to a whopping 40 inches long. They look like horsehair. Even more remarkable, females can lay egg strands 8 feet long. The larvae are parasites on crustaceans, worms, and mollusks. The adults are parasites of crickets and grasshoppers. Their life cycle is amazing. The adults lay eggs in ponds which must be eaten by aquatic insects that then metamorphasize and must be eaten by a cricket where the worm feeds. Then, the cricket must die and fall into a pond for the long adults to being their short life as a free-living mouth-less adult worm.
Here are some links:
Gordian worms
Gordian (horsehair)
worms
Parasites of the extinct Rocky
Mountain grasshopper
Leeches prefer shallow, slow moving, warm water with lots of detritus. Some are scavengers, some hunt small animals, and others suck blood. Sizes range from a few inches to almost two feet! Some species of leeches, or Hirudinea, include helobdellas, erpobdellas, macrobdellas, and haemopsis. Colors and sizes range but all are flat and segmented. If your pond develops an overabundance of fish or people-sucking leeches, you can place a piece of raw beef or other bloody meat in the pond on a string. Remove later, and it should now be covered in leeches.
My ponds are absolutely FULL of leeches now. I believe they got in with some blackworms that I added to the pond. I have never seen the leeches attach to the fish or me so they most likely are just scavengers. Whenever I pull out something from inside the pond, there are leeches on it about 1/4 inches long. They stick to whatever I am working on. Even the hose at full blast cannot remove them sometimes (yes, I have to touch them!).
Leeches may also show up in aquariums (most often included with blackworms) but are most often harmless scavengers. There is no need to eradicate them if they are not harming the fish. If they are to be removed, it is better to do it with bait than chemicals which can harm other animals and plants in the tank.
For some interesting information on the biology of some leeches, visit the site on Australian parasitic leeches.
Nematodes, or Nemas, are roundworms. They live in the bottom of ponds and are common. Nematodes constantly thrash in an S shape. Some are parasites of crustaceans or larger worms; others eat animals and some eat plants. They only grow to 0.1 inches. One of the 1000 species in freshwater is Chronogaster gracilis.
Proboscis worms, or Nemerteans, are also called ribbon worms. They have a skinny, flat body less than an inch long. Their proboscis is an extension two to three times the length of their body which they can retract into their body. They move around eating small creatures. The only North American species is Prostoma rubrum.
Blackworms are sold to feed small animals. They work great to feed hatchling turtles, fish, newly morphed amphibians, and other small animals. I mean to create a page on my site one day on how to take care of the blackworms. I add water to mine and put them in the refrigerator. Each day after I remove some to feed my African dwarf frogs, I pour off a little water and add new water. Blackworms will survive/live in aquariums and ponds indefinitely. I have added them to my ponds in the past as well where they continued to live.
Cyclops are copepods often sold as fish food. These small crustaceans (0.1 inch) eat algae, bacteria, debris and a few species are harmless parasites of fish. Females carry egg sacks which make them easy to identify. They look somewhat like terrestrial sowbugs (isopods, a few species live in water eating rotting plants). The three groups of free-living copepods are calanoid, cyclopoid (the only real cyclops), and harpacticoid.
Daphnia (also called water fleas and cladocera) are often sold as fish food (Daphnia magna and Daphnia pulex specifically). These crustaceans eat algae and microorganisms. They wave their legs around while swimming with jerking motions to bring food to their mouths. They tend to hang out with the plankton and many animals eat them. They are one of the essential species for a healthy pond in many areas since they eat algae and in turn feed the fish. In captivity, they can be raised on yeast, bran flour, or dried blood but algae is best. Looking somewhat like terrestrial fleas, they grow up to 0.1 inch with females giving live birth to tiny babies fit for fish fry to eat. Typical lengths are 0.25 to 3 mm for small species. There are many species, and they vary in size. Daphnia breed both asexually (during good conditions) and sexually (during bad conditions). Females lay up to 100 eggs every three days in good conditions. Females can lay just four days after being born. Her young were developing while she was still inside her mother! If there is a lack of food, oxygen, or space or a drop in temperature, females will lay males. They will breed and produce resting eggs that can dry out just like brine shrimp.
For information on rearing daphnia to feed fish, go to the Daphnia FAQ. A visitor pointed out to me that this site no longer works. If anyone knows where it has gone, please e-mail me!
A drawing of a daphnia can be seen at this water bug site.
I guess no one likes to keep a site with daphnia!
Ok, here is one that someone sent! Thank you!
Daphnia - a site on
daphnia as raised as live food for other animals.
And here is a really great site sent to me by its webmaster on 3/4/05:
Daphnia: An Aquarist's Guide
Chuck sent this site on 1/6/06 that he runs on pond life that has a
daphnia section:
Pond Info
Euglena are green animals that many larger microorganisms, like daphnia, consume. They are a blob with a tail. Euglena make the water appear green.
Gastrotrichs are microscopic animals that live in bottom debris attached by tail secretions. There are 60 species that live in freshwater where they eat algae. One species is Chaetonotus anomalus.
I have read that infusuria is simply a mix of microorganisms, mostly paramecium. As I get more time, I will look further into this.
Paramecium are animals that look like a blob with many vibrating cilia around it. They are a major food for small fry. They eat smaller microorganisms by engulfing them.
There are nearly 2,000 species of rotifers which differ in their appearance and lifestyles. Some swim, some crawl, some stick onto surfaces using a sort of glue but they all are multi-celled tiny animals with cilia which they use for locomotion and food retrieval. Some eat plants, some algae, some other small animals but all are important foods for larger animals. A few species can survive their water being completely dried out.
Water bears look like bears, except they are only less than 0.05 inches long! Water bears have a
head and four pairs of legs with claws. They are also called Tardigrades or moss piglets and their
scientific name is Hysibius. They live among plants which they eat. A total of 40
some species live in North America. When the water they are in dries up, so do they. When wet
again, they come back to life.
While in the "tun" state, they produce protective chemicals, dehydrate, and roll up. They can
exist like this for 1000 years. In this state, they can withstand temperatures from -456 to 304
degrees F, 1,000 times the radiation a human can survive, and 6,000 atmospheres of pressure.
Sounds like they may outlive us. (The information in this paragraph was provided by the
June/July 1999 issue of National Wildlife.)
Hydra, or Coelenterata, look like small bags with tentacles. Growing to about an inch long, they eat whatever they can catch, mostly microorganisms. Their tentacles either stick to or sting their prey. In aquaria, they are the scourge of fry tanks; fry being a favorite food. While they tend to stay attached to some surface, they can move around to find better spots. The brown, green (contains algae), and American hydra are species common to North America.
Here are some photos sent to me by Mike of hydra in his aquarium that hitched a ride on some
plants. They are about 9 mm long from the anchor to the tip of their tentacles:
Hydra close up
Hydra group
Hydra with a victim - the hydra has caught a baby rosy red minnow; note that the fry is already growing fungus on it.
There is only one species of freshwater jellyfish in North America, Craspedacusta sowerbyi. It goes through life stages including one similar to the hydra and grows to only about a half inch to look like the more common marine species.
Similar to sponges, but with tentacles, moss animals or bryozoans are strange creatures. About 15 species occur in North American fresh waters. They grow in still, clean water. Many thousands of individuals may encrust onto rocks, pipes, etc.
Some bryozoans may form huge masses that may appear to be some sort of egg mass. Here are
some sites with photos and information:
Bryozoans
What's that stuff
in the water? - includes a bryozoan colony photo.
Blog - about two-thirds of
the way down this page is a photo of a large, ball-like, free freshwater bryozoan.
Joy sent me this photo of an "egg mass" to be identified on 5/31/07. I think it is a bryozoan colony. It is a rather large one that was at the water's surface, attached to a branch. They took it out of the water for the photo. I thought I had seen photos of similar colonies on the internet but now cannot find them. If you have further information about bryozoans or these photos, let me know.
Bryozoan - close-up of the individual animals in the colony from the above photo
There is only one family of fresh water sponges or Porifera. About 150 species live in ponds and lakes throughout the world. Larvae are free swimming but adults are brown or greenish globs from an inch to a dozen square feet in size. Green sponges have symbiotic algae. They eat microorganisms that get sucked in through their pores. A single sponge is actually a colony of animals like coral. In cold areas, sponges may drop gemmules which survive the winter on the bottom of the pond with the "parent" dying.
These are the books that I own and that I used as references for this web page.
Pond Life: A Guide to Common Plants and Animals of North American Ponds and Lakes by Dr. George K. Reid, Golden Press, 1967. A book chock full of information.
+ Knowledge I have gained and stored in my brain.
Web Sites:
Microcosmos - a new Dutch site (in English or Dutch via here) on all sorts of small fresh water animals.
Biomedia Associates - includes photos of some aquatic micro-critters.
Pond Life Identification Kit - A "simple guide to small and microscopic pond life." This UK-based site has information and microscopic photos of lots of micro-critters!
Aquatic Life - a page on freshwater worms.
Photos of the smallest pond life
Microorganisms - includes some real photos of daphnia, brine shrimp, water mites, hydra, cyclops, etc.
Pond Life - includes sections on some aquatic microorganisms
Bugs and Worms Part I and Bugs and Worms Part II - Some information and photos on daphnia, copepods, rotifers, hydra, planaria, leeches, and removing them.
What's that stuff in the water?
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