OPISTHOBRANCHS
"Opisthobranchs have been described as the most beautiful animals inhabiting the oceans. They are both dramatically colorful or remarkably invisible due to camouflage."
"When observing or studying any group of living organisms, the first step to knowledge is identification. By knowing the animal's name one can communicate his findings to others as well as investigate pertinent references to increase one's knowledge on this fascinating group of molluscs. Although considerable research has been done on this group of marine animals, much remains to be understood. Each observation can bring forward new information to help increase the understanding of Opisthobranch biology."
"Presently totaling more than 3000 described species worldwide, this group of molluscs is extremely diverse. Its members, while mostly shell-less, include a few with reduced or internal shells. All but a small group occur in saltwater and range in length from 1/8 inch to more than 12 inches."
"The subclass Opisthobranchia belongs to the class Gastropoda in the Phylum Mollusca. Unlike the more typical marine snails, (prosobranchs), which are popular among shell collectors, opisthobranchs exhibit an evolutionary trend toward the reduction, internalization, and complete loss of the shell. Referred to by numerous names - sea slugs, "branchs" (pronounced branks), naked snails, etc.., these animals commanded the attention of only a handful of divers and tidepoolers. Fascination in color and form, they receive much attention from their human admirers."
-David W. Behrens (Pacific Coast Nudibranchs 2nd Edition,1991)
The American Heritage ® Dictionary of the English Language: Fourth Edition. 2000
NUDIBRANCH:
SYLLABICATION: nu·di·branch
PRONUNCIATION: nudibranch.wav
NOUN: See sea slug .
ETYMOLOGY: From New Latin N
dibranchia , order name : nudi– + branchia .
OTHER FORMS: nu
di·bran
chi·ate (-br
ng
k
-
t) , nu
di·bran
chi·an (-k
-
n) — ADJECTIVE & NOUN
nu·di·branch [nd brŕngk ] noun
ZOOLOGY "sea slug"
[Mid-19th century. From modern Latin Nudibranchia , order name.]
nu·di·bran·chi·ate [nd brángkee t ] adjective
nu·di·bran·chi·an [nd brángkee n ] adjective
Sea Slug (plural sea slugs) noun
Creature resembling sea snail without shell: a marine mollusc without gills that resembles a sea snail with no shell and is often brightly colored. Order Nudibranchia Also called nudibranch.
The American Heritage ® Dictionary of the English Language: Fourth Edition. 2000
Opisthobranchia:
SYLLABICATION: o·pis·tho·branch
PRONUNCIATION: opisthobranch.wav
NOUN: Inflected forms: pl. o·pis·tho·branchs
Any of various marine gastropod mollusks of the subclass Opisthobranchia, characterized by gills, a shell that is reduced or absent, and two pairs of tentacles.
ETYMOLOGY: From New Latin Opisthobranchia , order name : Greek opistho- , behind; see opisthognathous + Greek brankhia , gills.
Invertebrate Zoology: A subclass of mostly marine gastropod mollusks having two pairs of tentacles and a reduced or absent shell and mantle cavity; includes the sea slugs, sea butterflies, sea hares, and bubble shells.
The members of this order have no shell or mantle cavity and their body shape is elongated and symmetrical. The gills are exposed, thus the name "nudi" (naked), "branchia" (gills). Usually encircle the anus on the upper side. Individuals of this group are among the most brightly colored and attractive animals on the reef. Nudibranchs usually remain under coral heads where waves or currents will not disturb them. Most nudibranchs are carnivores, feeding on coral polyps and other shell animals. some coral polyp eating nudibranchs are able to incorporate live, stinging nematocyst cells (derived from the cnidarians) into their own skins, using these for their own protection.
The Columbia Encyclopedia, Sixth Edition. 2001
SEA SLUG:
Sea Slug (plural sea slugs) noun
Creature resembling sea snail without shell: a marine mollusc without gills that resembles a sea snail with no shell and is often brightly colored. Order Nudibranchia Also called nudibranch.
name for a marine gastropod mollusk that lacks a shell as an adult and is usually brightly colored. Sea slugs, or nudibranchs, are distributed throughout the world, with the greatest numbers and the largest kinds found in tropical waters. They creep along the bottom or cling to submerged vegetation, usually in water just below the low tide line. Members of a few species swim on the surface in open ocean. Most sea slugs are under 1 in. (2.5 cm) long, although the largest, found in the Great Barrier Reef of Australia, reaches 12 in. (30 cm). Regarded by many people as the most beautiful of marine animals, sea slugs display a great array of solid colors and patterns. Many have feathery structures (ceratia) on the back, often in a contrasting color. Most sea slugs have two pairs of tentacles on the head, used for tactile and chemosensory reception, with a small eye at the base of each tentacle. Sea slugs graze on small sessile animals such as coelenterates, sponges, and bryozoans. Certain sea slugs that feed on corals and sea anemones ingest the stinging cells of their prey without discharging them; these then pass from the slug’s digestive tract to the ceratia, where they are used by the slug for its own defense. Sea slugs are classified in the phylum Mollusca , class Gastropoda, subclass Opisthobranchia, order Nudibranchiata.
