Siphons of Tresus capax (Gould, 1850)
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Veneroida
Family: Mactridae
Genus: Tresus
Gray, 1853

See text

Tresus is a genus of saltwater clams, marine bivalve mollusks in the family Mactridae.[1] Many of them are known under the common name the horse clam or as species of gaper clam. They are similar to geoducks.


Species within the genus Tresus include:


These species' habitat is the lower intertidal zones on out to waters as deep as 5060 feet (13–15 m). They prefer sand, mud, and gravel substrates, normally burying themselves 1216 inches (3041 cm), so they are much easier to dig than geoducks. Their preferred substrates are also preferred by butter and littleneck clams, so horse clams are often taken incidentally in commercial harvesting.

Tresus clams often have a relationship with small commensal pea crabs, often a mating pair, which enter through the large siphon and live within the mantle cavity of the horse clam.[2] The crabs are easily seen and in no way affect the clam as food. The meat is good and makes excellent chowder. They tend to be ignored by sport diggers in Washington but not in Oregon.

Notes and references

  1. Tresus Gray, 1853.  Retrieved through: World Register of Marine Species on 30 September 2008.
  2. Beach watchers
This article is issued from Wikipedia - version of the 6/24/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.