Download Coral Reef Organisms and Adaptations

Coral Reefs and Seagrass Beds Organisms and Adaptations
I. Sponges (Phylum Porifera)
Sponges are very simple animals that are sessile, or live permanently
attached to a location in the water. They were once believed to be plants,
but they are now known to be very simple animals with no close
relatives. There are 5-10 thousand known species of sponges, most living
in salt water. They evolved over 500 million years ago.
The sponge’s phylum name, Porifera, describes its body, in that it has
thousands of tiny pores, which let water flow through it continually. The
flowing water brings in nutrients and carries away wastes.
Habitats
Most sponges need a hard surface for attachment, but some can live in
soft sediment. A few species are able to bore into rocks and shells. Sponges are common on rocky reefs, shipwrecks, and coral reefs in
a wide range of temperatures and depths. The largest populations occur where there are strong tidal currents, which bring extra food.
Animals such as crabs and worms sometimes live inside sponges, but little manages to settle and grow on their surface. This is
because sponges produce chemicals to discourage predators and parasites.
Anatomy and Diet
Many sponges grow different shapes in different habitats. Some grow in tubes, spheres, or threadlike shapes. The body
plan of all sponges, however, is based on a system of water canals lined with special cells known as collar cells. Collar
cells are unique to sponges. They draw water into the sponge through pores, by each beating a long, whip-like flagellum.
A ring of tiny tentacles around the base of the flagellum traps food particles, and the water and waste material then flows
out of the sponge through larger openings, called osculum. Rigidity is provided by a skeleton made up of tiny splinters of
silicon dioxide or calcium carbonate. These are called spicules, and are scattered throughout the body.
Sponges are filter feeders. They eat tiny, floating organic particles and plankton that they filter from the water as it flows
through their body. Most sponges are hermaphrodites (each adult can act as either the female or the male in
reproduction). Sperm and egg are fertilized inside the sponge. Some sponges also reproduce asexually by a process called
budding. Fragments of their body are broken off by water currents and carried to another location, where the bud will
grow into a clone of the parent sponge.
II. Cnidarians
This phylum contains over 9000 species worldwide. They are more advanced than a sponge, but are the simplest of the “higher”
organisms in the invertebrate world. This ancient group of aquatic animals emerged about 600 million years ago. It includes reefbuilding corals, sea anemones, jellyfish, and hydroids. Cnidarians have a body shaped like a simple sac with radial symmetry.
Cnidarians are grouped together because they all have tentacles with stinging cells used to capture and subdue prey. The name,
Cnidarian, literally means “stinging creature”.
A. Anatomy
Cnidarians can have one of two basic body types, polyp or medusa. The polyp body type is exhibited by corals and sea anemones.
They are attached to a structure at one end, and their tentacles and mouth face upwards. Polyps are basically a tube closed at one end
that attaches to a hard surface by a basal disk. They live singly or in colonies.
Other cnidarians can be either polyps or medusae at different stages of their life cycle. Those
that exhibit the medusa body form in their adult stages are the jellyfish…they are free
swimming with their mouth and tentacles facing downward. Medusae are bell-shaped and
usually have a thicker mesoglea. Some also have a shelf of muscle for movement.The body wall
of both polyps and medusae consists of two types of tissue. On the outside is the epidermis,
which acts like a skin to protect the animal. The inner tissue layer lining the body cavity is the
gastrodermis, which carries out digestion and produces reproductive cells. In between these
two layers is a jelly-like substance called the mesoglea.
The tentacles have stinging cells called cnidocytes which are unique to this phylum. Inside each cnidocyte is a coiled, thread-like
stinger, called a nematocyst. When the nematocyst is called upon to fire, the thread is uncoiled and springs straight. The harpoon-like
thread punctures through the cnidocyte wall and into the prey. Most Cnidarians also have a toxin in their stinger which helps to disable
the prey. When triggered by touch or chemicals, the thread explodes outward and pierces the prey’s skin. The animal’s tentacles are
then used to haul the victim into its mouth. Cnidarians have a simple nervous system that responds to touch, chemicals, and
temperature. Not all cnidarians are harmful to humans because not all stingers can penetrate human skin to cause any harm. Some
jellyfish, however, can emit painful, or even fatal, stings to humans.
B. Cnidarian Groups
1. Corals
Coral polyps are small, invertebrate, bottom dwelling animals, mostly living in large
colonies. Colonies of coral polyps are connected together with living tissue and share
food resources.There are two types of corals, hard and soft. Hard corals have an
internal, rock-like, chalky skeleton that remains when they die. Huge colonies of hard
corals form coral reefs. Soft corals grow in colonies as well, but without the hard reef to
retract into.
Corals are found in seas around the world. Large colonies are found in some warm,
shallow waters, where colonies of millions of coral polyps form vast coral reefs. Reefs
are slow-growing; they only grow about an inch each year.
A coral polyp begins its life as a tiny, free-swimming larva. It settles on a hard support
and will never move again. Corals reproduce by budding (in which an identical polyp
sprouts out of the polyp's side) and by sexual reproduction (in which polyps release eggs
and sperm, which mix in the water).
The soft body of a coral polyp is about the size of a pencil eraser. The polyp of hard
corals makes a hard, protective shell out of calcium carbonate. When the polyp dies, the chalky skeleton remains, and another polyp
will grow on top of the old one. Many corals have symbiotic algae that live inside them. These algae (called Zooxanthellae) help form
the coral's stony exoskeleton, and give the coral its color. Corals are carnivores that eat zooplankton (like copepods and tiny marine
larvae). They catch food using tentacles that surround the mouth; the tentacles have stinging nematocysts, just like other cnidarians.
2. Jellyfish
The most mobile cnidarians are free-living jellyfish, which mainly drift
in water currents but also swim actively using a form of jet propulsion.
They have soft bodies and long, stinging, poisonous tentacles that they
use to catch fish. Venom is sent out through stinging cells called
nematocysts. A jellyfish is 98% water.
There are many types of jellyfish. The smallest jellyfish are just a few
inches across. The largest jellyfish is the lion's mane (Cyanea
capillata), whose body can be over 3 feet (1 m) across, with much
longer tentacles. Some jellyfish glow in the dark (this is called
phosphorescence). Some of the deadliest jellies include the box jelly
(Genus Carybdea) and the tiny, two-cm-across Irukandji jelly (Carukia
barnesi); the venomous sting of these jellyfish can kill a person.
Many animals eat jellyfish, including sea turtles and some fish
(including the sun fish).
3. Sea Anemones
There are over 1000 species of anemones found in coastal waters worldwide, in shallow
waters (including coral reefs), and in deep oceans. Although Sea Anemones look like
flowers, they are actually predatory animals. They live attached to firm objects in the seas,
usually the sea floor, rock, or coral, but they can slide around very slowly. Sea anemones are
very long lived.
Sea Anemones come in many shapes, sizes, and colors. Radially symmetric, they have a
columnar body with a single body opening, the mouth, which is surrounded by tentacles. The
stinging tentacles protect the anemone and catch its food. Sea Anemones are usually about 1
to 4 inches (2.5-10 cm) across, but a few grow to be 6 feet (1.8 m) across.
Sea Anemones are carnivores that eat fish, mussels, zooplankton (like copepods, other small
crustaceans, and tiny marine larvae), and worms. Sea Anemones reproduce by lateral fission
(in which an identical animal sprouts out of the anemone's side) and by sexual reproduction
(in which anemones release eggs and sperm, producing free-swimming larvae).
Hermit crabs sometimes attach sea anemones to their shells for camouflage.
Clown fish always live near anemones; they are immune from (and protected by) the stinging
tentacles. The clown fish help the anemone by cleaning the tentacles (as the fish eat detritus)
and perhaps by scaring away predators.
4. Sea Pens
Sea pens and sea whips are sessile (non-moving) cnidarian polyps that anchor themselves in mud, sand, or
sediments. The colony of polyps raise their tentacles and feed on plankton drifting by in the water around them.
They can also trap and eat fish or crustaceans passing by.
5. Sea Fans
Sea fans grow attached to the seabed and look like exotic plants. They have a supporting skeleton that
provides a framework and allows them to grow quite large. It is made mainly of a flexible, horny material
called gorgonin and consists of a rod that extends down the inside of all except the smallest branches. The
branches are mostly in one plane and form a mesh that is aligned at right angles to the main current flowing
throw the area where they live. This increases the amount of food brought within reach of the polyps,
which are arranged all around the branches. Sea fans grow very slowly and take a long time to re-colonize
if damaged. They are commonly collected, dried, and sold as souvenirs, also decreasing their populations.
6. Sea Whips
Sea whips have a very similar structure to sea fans but grow up as a single tall stem. They have a very strong central supporting rod
containing a lot of calcareous material as well as a gorgonin. Some sea whips reproduce asexually and grow in groups. Their fragile
tips fall off into the surrounding sediment where it attaches and grows.
III. Echinoderms – Phylum Echinodermata
This phylum contains over 6000 species and the name “echinoderm” literally means “spiny skin”. Many echinoderms do have spiny
skin, but a few do not. All members of this group live in the sea, and cannot be found on land or in freshwater. Members have radial
symmetry, with appendages usually in multiples of 5 (not all). This group of invertebrates includes starfish, sea urchins, brittlestars,
feather stars, sea cucumbers, and sand dollars. Echinoderms have radiating body parts, so most appear star-shaped, disk-shaped, or
spherical, and all have a skeleton of calcium-carbonate plates under the skin. Inside is a unique system of water-filled canals, called
the water-vascular system, which enables them to move as well as to feed and breathe. The water-vascular system consists of a
network of canals and reservoirs, as well as tentacles that extend through pores in the skin to form hundreds of tiny tube feet, used for
movement. Tube feet act like hydraulic suckers. They are operated by water squeezed in and out from a small reservoir similar to the
bulb on the end of an eye dropper. They are typically bottom-dwellers, living on reefs, shores, and the seabed.
A. Anatomy and Feeding
The echinoderm body is based on a five-rayed symmetry similar to the petals of a flower. This is apparent in starfish, brittlestars, and
urchin shells. The echinoderm skeleton is made of hard calcium-carbonate plates, which are fused to form a rigid shell (sea urchin) or
remain separate (starfish). Usually, it also features spiny or knoblike extensions that project from the body. Sea cucumbers have
minimal skeletons reduced to a series of small, isolated knobs.
Echinoderms range from peaceful grazers and filter feeders to voracious predators. Carnivorous species of starfish extend their
stomach over their prey and digest it externally. In contrast, most sea urchins are grazers, scraping rock surfaces using teeth that
resemble the end of an electric drill. Sea cucumbers have an important role as sea-bed cleaners, vacuuming up organic debris and mud.
Feather stars raise their arms to trap plankton using fingerlike tube feet. The food is coated in mucus and passed down the arms into
the mouth.
B. Echinoderm Groups
1. Brittle Stars
There are over 2,000 species of brittle stars. Most have five long,
thin, spiny arms that radiate from a flat, central disk. The arms do not
touch each other at their bases. Many of the arms are forked. If a
brittle star’s arm is cut off, it will regenerate. Most brittle stars are
under 1 inch in diameter. They have a hard exoskeleton and vary in
color. They have a simple ring of nerve cells that moves information
around the body. Tube feet located along the arms sense light and
smells.
Brittle stars are mainly detrivores, eating decaying matter and
plankton. So me brittle stars can kill small animals as well. They
push their stomach out through their mouth (which is on the
underside of the disk) and digest the prey. The mouth has 5 teeth.
2. Sand Dollars
The Sand Dollar is a spiny, hard-skinned animal that is shaped like a coin
(a flattened disk). There are many different species of sand dollars. They
live on the sandy sea floor, from the intertidal zone (the area between
high tide and low tide) down to the subtidal zone (the area below low
tide). Most sand dollars are found at depths of 30 to 40 feet (9-12 m).
Sand dollars partly bury themselves under the sand, with an edge poking
up out of the sand. You can often find the dead "shell" of a sand dollar
(called a "test") washed up on sandy beaches. If you break open a test,
there are many hard, loose, white pieces; these were the teeth of the Sand
Dollar.
Sand Dollars have 5-part radial symmetry. They have a hard exoskeleton
made of calcium carbonate plates, covered by a layer of rough skin. The
bottom surface contains the mouth, many tiny black spines (which trap food), and the cilia (small hairs) that help direct food into the
mouth. They eat tiny particles of food that float in the water. Sand Dollars have tiny tube feet that are used as gills. The holes on the
top surface are where the eggs and sperm are re leased.
3. Starfish (AKA Sea Stars)
Sea stars (also known as starfish) are spiny, hard-skinned
animals that live on the rocky sea floor. Most sea stars have five
arms (or a multiple of five) that radiate from a central disk. Sea
stars do not have a brain; they have a simple ring of nerve cells
that moves information around the body. Eyespots (primitive
light sensors) are at the tip of each arm. If a sea star's arm is cut
off, it will regenerate (regrow).
Sea stars move very slowly along the sea bed, using hundreds of
tiny tube feet. There are over 2,000 different species of sea stars
worldwide. Most species of starfish expel enormous numbers of
eggs and sperm into the ocean; fertilization is external. After
fertilization, the tiny, transparent, bilaterally-symmetrical larvae
(baby sea stars) travel many miles as they are swept along by
ocean currents for about two months. As they develop, the tiny
larvae swim in the sea, eat phytoplankton, and are a component
of zooplankton.
Sea stars are carnivores (meat-eaters). They eat clams, oysters,
coral, fish, and other animals. They use their tube feet to pry open bivalves, and push their stomach out through their mouth (located
on the underside of the sea star), digesting the prey in it’s own shell.
4. Sea Cucumber
Sea cucumbers are cylinder-shaped animals that live in seas
worldwide. They are found in a variety of sea floor habitats, from
warm tropical waters to cold deep sea trenches. They are nocturnal
(come out at night) animals and have a life span of about 5 to 10
years.
The body of the sea cucumber is elongated, leathery and muscular;
spines are contained with the skin. These echinoderms have no arms,
but do have five-part symmetry. Surrounding the mouth are 8 to 30
tentacles (modified tube feet). Five double rows of tube feet (with
tiny suction cups) run along the body; they are used for crawling
along the sea bed or anchoring to a rock. A sea cucumber breathes by pumping sea water in and out of an internal organ called a
respiratory tree. Some sea cucumbers burrow into the sea floor. Sea cucumbers have no brain. The biggest sea cucumber, the tiger's
tail sea cucumber (Holothuria thomasi), is about 2 m long - most sea cucumbers are much smaller than this.
Sea cucumbers eat decaying matter that floats in the water or is in the sand. For protection, they can expel most of their internal organs
to confuse predators - they later regrow the organs. Some sea cucumbers' bodies contain toxins that can deter attackers as well.
5. Sea Urchin
The sea urchin is a spiny, hard-shelled animal that lives on the rocky
seafloor, from shallow waters to great depths. There are about 700
different species of sea urchins worldwide. Many sea urchins have
venomous spines. The biggest sea urchin is the red sea urchin
(Strongylocentratus franciscanus); it has a test about 7 inches (18 cm) in
diameter.
Adult sea urchins have five-sided radial symmetry. Their skin has hard,
chalky plates, and is called the test. Sea urchins have a globular body and
long spines that radiate from the body. The spines are used for protection,
for moving, and for trapping drifting algae to eat. Among the spines are five paired rows of tiny tube feet with suckers that help with
locomotion, capturing food, and holding onto the seafloor. They move very slowly along the seabed. Tiny pedicellarines are small
stinging structures that are used for defense and for obtaining food. Like all echinoderms, sea urchins do not have a brain. The mouth
is claw-like and is located on the underside; it has 5 tooth-like plates that point inwards and are called Aristotle's lantern. The anus and
the genital pores are on the top of the sea urchin. Sea urchins eat plant and animal matter, including kelp, decaying matter, algae, dead
fish, sponges, mussels, and barnacles.
IV. Mollusks: Cephalopods
Cephalopods are a class of fast-swimming mollusk. Some have a hard external shell, such as the nautalus, but most do not.
Cephalopods are marine predators; these carnivores eat fish, worms, crustaceans, and other mollusks. Some cephalopods include the
octopus, squid, cuttlefish, nautilus, and ammonite (and other extinct animals). There are about 650 living cephalopods and over 7,500
known extinct cephalopods.
A. Anatomy and Feeding
Cephalopod means "head-foot." The foot of the cephalopod is a cluster of tentacles that connects directly to the head. The brain, the
eyes, and the other sensory organs are well-developed. Cephalopods breathe using gills. They swim by jet-propulsion; they rapidly
expel water from the mantle cavity through a specialized, tube-like organ called the hyponome. Many can also eject a cloud of ink to
confuse enemies.
B. Cephalopod Groups
1. Octopus
The word octopus means "eight feet." Octopuses are solitary, eight-armed
animals that live on the ocean floor. There are over 100 different species of
octopuses. The Giant Octopus is the biggest octopus. This huge mollusk is
up to 23 ft (7 m) from arm tip to arm tip, weighing up to 400 pounds (182
kg). The smallest is the Californian octopus, which is only 3/8 inch (1 cm)
long.
Anatomy and Feeding:
An octopus has a soft body and eight arms. Each arm has two rows of
suction cups. If it loses an arm, it will eventually regrow another arm. It has
blue blood. An octopus has an eye on each side of its head and has very
good eyesight, but an octopus cannot hear.
They live in dens, spaces under rocks, crevices on the sea floor, or holes it digs under large rocks or coral. Octopuses eat small crabs
and scallops, plus some snails, fish, turtles, crustaceans (like shrimp), and other octopuses. They catch prey with their arms, then kill it
by biting it with their tough beak, paralyzing the prey with a nerve poison, and softening the flesh. They then suck out the flesh.
Octopuses hunt mostly at night. Only the Australian Blue-ringed octopus has a poison strong enough to kill a person. Octopus often
secrete a black ink when they feel threatened. They use this as a diversion before swimming away.
2. Cuttlefish
The cuttlefish is a marine animal that has eight arms, two tentacles, and
a soft body. It is a cephalopod, a fast-swimming, intelligent mollusk
that can change its skin color and spew ink in the water to confuse
predators. The cuttlefish swims by using its fins and by spewing water
from its body (a type of jet propulsion). The cuttlefish is nocturnal; it
hunts during the night, and it hides and rests during the day. It has a life
span of about 18 months.
Cuttlefish average about 1 ft (30 cm) long. Cuttlefish have eight arms and two tentacles that surround the mouth and beak; the
tentacles are often kept in a pouch under the eyes. The body of the cuttlefish (the cuttle) is flattened and has fins that extend along the
entire length of the mantle. The skin changes both color and pattern to mimic the environment. Chromatophores in the skin change the
skin's color. The cuttlebone is a gas-filled shell inside the mantle that lets the cuttlefish regulate its buoyancy (the ability to float or
sink). Cuttlebones are used as calcium supplements for pet birds and for polishing silver (when powdered).
Cuttlefish eat fish, small mollusks (snails, clams, other cuttlefish, etc.), worms, crabs, and shrimp. Prey are killed with a venomous
bite fom the beak. The cuttlefish is eaten by sharks, fish and other cuttlefish. In order to escape predators, a cuttlefish can squirt black
ink into the water, allowing it to escape. Another defense that cuttlefish have is changing their skin color to blend into the background,
camouflaging themselves.
Squid
The Squid is an invertebrate (animal without a backbone) that swims in the oceans. This mollusk is closely related to the octopus.
Squid can change the color of their skin to mimic their
environment and hide from predators.
Squid are soft-bodied cephalopods. They move by
squirting water from the mantle through the siphon, using
a type of jet propulsion. When in danger, squid squirt a
cloud of dark ink in order to confuse their attacker and
allow the squid to escape. Squid reproduce by releasing
eggs into the water. Some squid eggs are free-floating,
others are attached to seaweed or to the ocean floor.
Anatomy: Squid range from 1 to 60 ft (0.3 to 18 m) long.
The biggest squid is the Giant Squid. Squid have a large
mantle/head (with a large brain), eight arms with suckers, two longer feeding tentacles, a beak, a large head, two large eyes, and two
hearts. Their large eyes are very similar in structure to people's eyes. They breathe using gills.
Diet: Squid eat fish, crustaceans (like shrimp), and other squid. These fast-moving carnivores (meat-eaters) catch prey with their two
feeding tentacles, then hold the prey with the eight arms and bite it into small pieces using a parrot-like beak. The esophagus runs
through the brain, so the food must be in small pieces before swallowing.