Pacific Sea Nettle
Jellyfish or jellies are the major non-polyp form of individuals of the phylum Cnidaria. They are typified as
free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing
tentacles. The bell can pulsate for locomotion,
while stinging tentacles can be used to capture prey.
Jellyfish are found in every ocean,
from the surface to the deep sea. A few jellyfish inhabit freshwater. Large, often colorful,
jellyfish are common in coastal zones worldwide. Jellyfish have roamed the seas
for at least 500 million years, and
possibly 700 million years or more, making them the oldest multi-organ animal.
·
The English popular name jellyfish has
been in use since 1796
· As jellyfish are not vertebrates,
let alone true fish, the word jellyfish is considered by some to
be a misnomer. Public aquariums may use the terms jellies or sea
jellies instead
·
A group of jellyfish is sometimes
called a bloom or a swarm
·
Another collective name for a group of
jellyfish is a smack
·
Medusa jellyfish may be classified as
scyphomedusae ("true" jellyfish), stauromedusae (stalked
jellyfish), cubomedusae (box jellyfish), or hydromedusae, according
to which clade their species belongs
·
Jellyfish employ a loose network of
nerves, located in the epidermis, which is called a "nerve net"
· Some jellyfish have ocelli:
light-sensitive organs that do not form images but which can detect
light and are used to determine up from down, responding to sunlight shining on
the water's surface. These are generally pigment spot ocelli, which have some
cells (not all) pigmented
·
Certain species of jellyfish, such as
the box jellyfish, have been revealed to have more advanced vision than
their counterparts .The box jellyfish has 24 eyes, two of which are capable of
seeing color, and four parallel information processing areas or rhopalia that
act in competition, supposedly making it one of the few creatures to have a
360-degree view of its environment.
|
No comments:
Post a Comment