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Touch Tank: Capitellid Thread Worms (Heteromastus filiformis and Mediomastus ambiseta)


Picture of Capitellid Thread Worms

A capitellid thread worm (Heteromastus filiformis) is exposed in a handful of sandy mud.
Courtesy: Nature Web site of the Netherlands

What type of habitat do capitellid thread worms prefer?
Capitellid thread worms most commonly occur in sandy mud habitats at various depths, ranging from a few meters to several hundred meters.

Where can they be found in the coastal U.S.?
Capitellid thread worms are found in most marine sediments on the Atlantic and Gulf coasts of the U.S., and they range into estuaries at shallow depths.

What do capitellid thread worms look like?
In general, they look like earthworms and grow to approximately 4 to 5 inches in length. They have tiny appendages (parapodia); slightly swollen, dark red head regions; and long, slender, paler abdomens.

Why are they important benthic species?
In addition to being critical links in the food web, capitellid thread worms eat through the substrate, consuming detritus and sediment grains, similar to earthworms. Both species are known as "head-down" deposit feeders, consuming subsurface sediment grains and excreting wastes at the sediment surface. This behavior is important for mixing sediments and bringing oxygen below the surface. By mixing and aerating the sediments, these species promote nutrient cycling and condition the sediments for colonization by other benthic animals.

Did you know…?
Capitellid thread worms are one of the first groups of animals to re-colonize an area impacted by dredge spoil dumping or by an oil spill. They are particularly known for their high tolerance for organic pollution.

References
Gosner, K.L. 1978. A Field Guide to the Atlantic Seashore. Peterson Field Guides. Houghton Mifflin Company. New York.

Weiss, H.M. 1995. Marine Animals of Southern New England and New York. State Geological and Natural History Survey of Connecticut. Department of Environmental Protection.

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