What is "sea slug"

Trepang \Tre*pang"\, n. [Malay tr[=i]pang.] (Zo["o]l.) Any one of several species of large holothurians, some of which are dried and extensively used as food in China; -- called also b[^e]che de mer, sea cucumber, and sea slug. [Written also tripang.]

Note: The edible trepangs are mostly large species of Holothuria, especially Holothuria edulis. They are taken in vast quantities in the East Indies, where they are dried and smoked, and then shipped to China. They are used as an ingredient in certain kinds of soup.

n. Any of several marine opisthobranch gastropod mollusks of the (taxlink Nudibranchia clade noshow=1)

n. any of various marine gastropods of the suborder Nudibranchia having a shell-less and often beautifully colored body [syn: nudibranch]

Sea slug is a common name for some marine invertebrates that more or less resemble terrestrial slugs. Most creatures known as sea slugs are actually snails, i.e. they are sea snails (marine gastropod mollusks) that over evolutionary time have lost their shells, or have a greatly reduced shell or an internal shell. The name "sea slug" is most often applied to nudibranchs, as well as to a paraphyletic set of other marine gastropods without obvious shells.

The phrase "sea slug" is, however, also sometimes applied to taxa in other phyla, such as the sea cucumbers, which are not mollusks but echinoderms. Although the other animals sometimes called "sea slugs" are not gastropods, they are nonetheless soft-bodied, and their overall shape is slug-like.

Sea slugs come in an outstanding variety of shapes, colors, and sizes, with gills and pointed tentacles on their backs. Sea slugs have translucent bodies that have just about every color on the rainbow. Due to the bright, outgoing colors found on the reef, there is a constant threat of predators. This is the cause for a warning of color to show the sea slugs’ predators that they are poisonous with stinging cells, but their colors are mainly for disguise. Like all gastropods, they have razor-sharp teeth, called radulas. Most sea slugs have two pairs of tentacles on their head used primarily for sense of smell, with a small eye at the base of each tentacle. Many have feathery structures (ceratia) on the back, often in a contrasting color. These act as gills. All species of sea slugs have a selected prey, that is specifically fitted for them to hunt. This can be among other sea slugs, jellyfish, bryozoans, sea anemones, plankton, and other various organisms.

Seaslug was a first generation surface-to-air missile designed by Armstrong Whitworth (later part of the Hawker Siddeley group) for use by the Royal Navy. It came into operational service in the 1960s and was still in use at the time of the Falklands War.

Seaslug was intended to engage high-flying targets such as reconnaissance aircraft or bombers before they could launch stand-off weapons. Later improvements meant that it could also be used against ships.