>Zooplankton

Zooplankton are the heterotrophic (sometimes detritivorous) component of
the plankton that drift in the water column of oceans, seas, and bodies of
fresh water. The name is derived from the Greek terms,  ("zoon") meaning
"animal", and  ("planktos") meaning "wanderer" or "drifter"[1]. Many
zooplankton are too small to be individually seen with the unaided eye.

Zooplankton is a broad categorisation spanning a range of organism sizes
that includes both small protozoans and large metazoans. It includes
holoplanktonic organisms whose complete life cycle lies within the
plankton, and meroplanktonic organisms that spend part of their life
cycle in the plankton before graduating to either the nekton or a sessile,
benthic existence.

>Sea Urchin

Sea urchins are small, spiny sea creatures of the class Echinoidea found
in oceans all over the world. (The name urchin is an old name for the
round spiny hedgehogs sea urchins resemble.) Their shell, which is also
called the "test", is globular in shape and covered with spines. The
size of an adult test is typically from 3 to 10 cm.

Typical sea urchins have spines that are 1 to 3 cm in length, 1 to 2
mm thick, and not terribly sharp. Diadema antillarum, familiar in the
Caribbean, has thin, potentially dangerous spines that can be 10 to 20
cm long. Common colors include black and dull shades of green, olive,
brown, purple, and red.

>Seahorse

These fish form territories, with males staying in about one square
meter of their habitat while females range about one hundred times that
area. They bob around in sea grass meadows, mangrove stands, and coral
reefs where they are camouflaged by murky brown and grey patterns that
blend into the sea grass backgrounds. During social moments or in unusual
surroundings, seahorses turn bright colors.

>Stingray

Dasyatids are propelled by motion of their large pectoral fins (commonly
mistaken as "wings"). Their stinger is a razor-sharp, barbed, or serrated
cartilaginous spine which grows from the ray's whip-like tail (like
a fingernail), and can grow as long as 37 cm (about 14.6 inches). On
the underside of the spine are two grooves containing venom-secreting
glandular tissue. The entire spine is covered with a thin layer of skin
called the integumentary sheath, in which venom is concentrated.[1]
The venom contains the enzymes 5-nucleotidase and phosphodiesterase
which breakdown and kill cells; and the neurotransmitter serotonin which
provokes smooth-muscle contractions.[2] This gives them their common
name of stingrays (a compound of "sting" and "ray")

>Thresher Shark

Named for and easily recognised by their exceptionally long, thresher-like
tail or caudal fins (which account for 1/3 (33%) of their total body
length), thresher sharks are active predators; the tail is actually used
as a weapon to stun prey. By far the largest of the three species is the
Common thresher, Alopias vulpinus, which may reach a length of 20 ft and
a weight of over 500 kg. The Bigeye thresher, Alopias superciliosus, is
next in size, reaching a length of 4.9 m (16 ft); at just 3 m (10 ft),
the Pelagic thresher, Alopias pelagicus, is the smallest.

Thresher sharks are fairly slender, with small dorsal fins and large,
recurved pectoral fins. With the exception of the Bigeye thresher, these
sharks have relatively small eyes. Coloration ranges from brownish, bluish
or purplish gray dorsally with lighter shades ventrally. The three species
can be roughly distinguished by the main color of the dorsal surface of
the body. Common threshers are dark green, Bigeye threshers are brown
and Pelagic threshers are generally blue. Lighting conditions and water
clarity can affect how any one shark appears to an observer, but the
color test is generally supported when other features are examined.


