Aquatic mites
See how they move!
SCIENTIFIC NAME: Hydracarina
Number Of Species/Distribution
There are approximately 5,000 described species of water mites worldwide.
It is expected that this number is an underestimate however because Watermites have not been well-studied in Asia, Africa, and much of South America.
It is estimated that in North America, over 1,500 species of water mites exist.
Diet/Feeding
As adults, most aquatic mites are predatory, feeding on zooplankton and insect larvae.
When feeding, mites grasp their prey and use specialized piercing mouthparts to puncture their food and suck the juices out.
Some aquatic mites, however, feed on detritus and plants.
Young mites are parasitic; they do not usually cause the death of their host but they can damage its health if they are present in very high numbers.
Habitat
Both the adult and young stages of the aquatic mite live beneath the water's surface.
Water mites are present in a wide range of freshwater habitats, but prefer to live in still waters, such as ponds, slow-moving rivers and streams.
They are not as common in fast-moving waters.
They can be found among aquatic plants, and are sensitive to highly polluted or salty waters.
Diversity and abundance of water mites is greatest on vegetation in shallow regions of ponds and lakes.
AQUATIC MITES: INTERESTING FACTS
Aquatic mites are often brilliantly coloured, making them very visible amongst green and brown aquatic plants. Some common colours include red, yellow, scarlet, and orange colours. Brightly coloured mites usually don't taste very good to fish.
Many mites are able to colonise new bodies of water. They do this by becoming parasites on other aquatic insects that are in their larval or pupae stages, and waiting until they become terrestrial adults. They then travel around to new aquatic habitats with their unaware winged host.
Only about half of the species of mites in North America are known, while many of those that are known have only been seen in a few preserved samples.
Water mites can survive at very low oxygen concentrations. They don't need gills as they can absorb oxygen from the water through their body surface.
Life Cycle
Aquatic mites undergo incomplete metamorphosis as they do not have a pupal stage. This involves passing through 4 life stages which are egg, larvae, nymph and adult.
Egg
The female typically attaches the fertilized eggs to submerged water plants.
After hatching from their underwater eggs, aquatic mite larvae either swim to the surface or crawl along the water substrate to find a food source.
Larvae
For a period ranging anywhere from a few days to several months, the larvae parasitizes a host, and feeds on the host fluids until the larvae reaches maturity.
The mites parasitize hosts such as damselflies, dragonflies, and other types of flies.
Nymph
After the mite has completed its parasitic stage in which it was feeding off a host, it transforms from a larvae into a nymph called a deutonymph.
The deutonymph feeds on aquatic insects, crustaceans, and other mites, and grows in size as it feeds.
It is a stage that resembles the adult form, but is not reproductively mature.
When it is ready, the deutonymph becomes a tritonymph.
During this time, it transforms into the sexually mature adult form.
Adult
As an adult, the water mite feeds on similar prey as it did as a deutonymph, has a fully developed reproductive system, and is ready to mate.
When they mate, the male grasps the female and transfers a sperm packet to the female and fertilizes her eggs.
Role in Food Chain
Aquatic mites play an important role in regulating the populations of other invertebrates.
Since hosts that they may parasitize span a range of insect groups, including stoneflies, caddisflies, and beetles, the populations of these groups in an ecosystem are greatly impacted by water mites.
Sources
Bureau of Land and Water Quality (2005). Water Mites (Acariformes). Available here.
Discover Life in America (2010). Subcohort Hydrachnidiae (Aquatic Mites).
Environment Protection Authority (2010). Mites, Spiders, Crustacean and Insects.
Tree of Life Web Project (1998). Hydracarina. Water mites. Available here.