arthropoda
CLASS ASTEROIDEA(sea star)
Anatomy:
- Sea stars are radially symmetrical, and their arms are arranged around a central disk.
- Most species have five arms.
- The mouth of a sea star is found in the centre of the underside of the sea star (called the oral surface).
- Several rows of tube feet run from the mouth down each arm of the sea star.
- These rows of tube feet are guarded by movable spines that line the edges of the arms for protection.
- The back side of sea stars can be smooth, spiny, or slimy.
- Their tube feet have suckers on the ends, which they use to attach themselves to rocks and to trap prey items.
- This sea star uses their longer tube feet instead, to penetrate into the sand and other soft surfaces.
- Sea stars walk using their tube feet to move themselves along a surface. Sea stars that live on soft surfaces (such as sand) do not have suckers.
- Reproduction
- Sea stars reproduce by free spawning which means the eggs and sperm are released into the water from the male and female at the same time. The eggs and sperm then drift off until they meet up with each other and fertilization occurs.
Regeneration:
Sea stars have the remarkable ability to regrow their arms if they are damaged or eaten by predators.
Equal-arm stars are found along the west coast of North America from
Description:
Cushion stars are usually 6 inches across. They are yellow to tan to gray in colour and can even be checkered sometimes.
Habitat and distribution:
These sea stars are found from the
Other interesting facts:
To help protect itself from fish and other predators, the cushion star releases huge amounts of mucus.
CLASS ECHINOIDEA (SEA URCHIN)
Anatomy
Sea urchins are solitary animals that may live in loose groups.
They are generally spherical or globose (“regular urchins”) but may be flattened into a biscuit-like shape (“irregular urchins”).
The general body surface of sea urchins is dominated spiny protuberances of their internal skeleton.
The tube feet are also located on this surface among the spines of sea urchins.
Echinoids walk using their tube feet and their spines in order to gain leverage off the substrate.
Movement
Sea urchin tube feet have suckers at the tips and are used for locomotion and feeding.
In some species, like the pencil sea urchin (Phyllocanthus sp.), spines are the principal means of movement.
Irregular echinoids like sand dollars (e.g. Dendraster excentricus) have a limited degree of movement and spend most of their time half-buried within the sediments.
Habitat
sea urchins are found in all oceans from the equator to the poles.
They are also regularly collected from deep in the oceanic trenches.
Most urchins hide in crevasses by day and come out at night to feed.
Feeding
Echinoids feed in two main ways.
Regular echinoids graze on macroalgae like kelp (as above).
Irregular echinoids deposit feed, either by waiting for particles to settle on their body surfaces or by directly ingesting sediment as in the heart urchins.
Sand dollars feed by collecting particles on their body surface and by transferring these to the ventral mouth using their tube feet.
CLASS HOLOTHUROIDEA (SEA CUCUMBER)
Common name : Sea Cucumber
Scientific Name : Parastichopus californicus
Most species feed on the rich organic film coating sandy surfaces. The crawl over the bottom ingesting sand. The edible particles (organic matter such as plankton, foraminifera and bacteria) are extracted when passing through their digestive tract and the processed sand is expelled from the anus (as worm-like excrements).
Movement
Sea cucumbers move by means of tube feet which extend in rows from the underside of the body.
The tentacles surrounding the mouth are actually tube feet that have been modified for feeding.
Other holothurians feed on current-borne zooplankton.
Reproduction
Some species of holothurians have separate sexes others are hermaphrodites.
The sea cucumbers hold on to exposed rocks or corals, raise their body to a upright position, rock back and forth and release the sperm and eggs into the sea.
Sea cucumbers have a remarkable capacity for regenerating their body parts. When attacked they shed a sticky thread like structure which is actually parts of their guts. The so called Cuverian threads are toxic (the poison is called holothurin) and can dissuade many potential predators. These structures quickly regenerate.
CLASS PYCNOPODIA HELIANTHOIDES
(SUNFLOWER STAR)
Common name : Sunflower Star
Scientific Name : Pycnapodia helianthoides
Anatomy
The sunflower sea star (Pycnopodia helianthoides) is a large predatory sea starusuallywith 16–24 limbs called rays.
It is the largest sea star in the world.
Most sea star species have a mesh-like skeleton that protects their internal organs. Easily stressed by predators such as large fish and other sea stars, they can shed arms to escape, which will grow back within a few weeks.
Habitat
They generally inhabit low subtidal and intertidal areas rich in seaweed or kelp.
They do not venture into high- and mid-tide areas because the body structure is fleshy and requires water to support it.
Reproduction
Sunflower sea stars reproduce sexually and asexually. They also have separate sexes.
Sunflower stars breed from May through June.
In preparing to spawn, they arch up using a dozen or so arms to hoist its fleshy central mass free of the seafloor and release gametes into the water for external fertilization.
Feeding
Sunflower sea stars are quick, efficient hunters, moving at a speed of one meter per minute, using 15,000 tube feet which lie on the undersides of the body.
They commonly hang around urchinbarrens, as the sea urchin is a favorite food.
They also eat clams, snails, abalone, sea cucumbers and other sea stars.
Although the sunflower sea star can greatly extend its mouth, for larger prey, the stomach can extend outside the mouth to digest prey, such as gastropods like abalone.
CLASS STRONGYLOCENTROTUS PURPURATUS
(PURPLE SEA URCHIN)
Characteristics
The
This sea urchin species is deep purple in color and lives in lower intertidal and nearshore subtidal communities.
It normally grows to a diameter of about 4 inches and it may live as long as 70 years.
The purple sea urchin (Strongylocentrotus purpuratus) is a small sea urchin.
It is a spiny, hard-shelled animal that lives on the rocky seafloor, from shallow waters to great depths. The spines are used for protection, for moving,and for trapping drifting algae to eat.
It lives from the intertidal zone down to depths of about 33 feet (10 m). These globular marine invertebrates move very slowly along the seabed.
Adult sea urchins have five-sided radial symmetry.
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.
Moving
Among the spines are five paired rows of tiny tube feet with suckers that help with locomotion, capturing food, and holding onto the seafloor.
Tiny pedicellarines are small stinging structures that are used for defense and for obtaining food.
Feeding
It eat Sea urchins eat plant and animal matter, including kelp, decaying matter, algae, dead fish, sponges, mussels, and barnacles.
Sea urchins are eaten by crabs, sunflower stars, snails, sea otters, some birds, fish, and people.
Reproduction:
Fertilization is external.
Eggs or sperm are released through five gonopores.
As they develop, the tiny larvae (called the pluteus, which have bi-lateral symmetry) swim in the sea and are a component of zooplankton. It takes several months for juvenile sea urchins to form. The time from fertilization to a reproductive adult is from 2 to 5 years.
CLASS BOHADCHIA ARGUS (LEOPARD SEA CUKE )
Habitat
They are commonly spotted in the vicinity of coral reefs, usually on the shallow sandy bottom.
Feeding
The mouth of Sea Cucumbers is surrounded by ten to thirty mucusy tentacles.
These are retractile and are used to wipe, swipe, sieve and glom onto food "stuff" pretty non-selectively, and periodically wiped across and into the oral cavity.
It slowly plows along the ocean bottom, with padded, sticky tentacles (black with white fringes) picking up organic nutrient-coated sand particles and passing them to the mouth.
It eat nutrients extracted from sand
Reproduction
Most sea cucumbers are separate sexes (dioecious= "two houses") and contain a singlegonad, unlike all other classes of echinoderms which have pairs.
Regeneration:
Sea cucumbers are noted for being capable of varying degrees of regeneration. If cut into numerous sections at least the terminal piece containing the cloaca grows back.
Locomotion:
Podia, "feet", as in podiatrist, are generally to entirely absent, occasionally scattered randomly over the body and or arranged in rows.
The ten to thirty modified podia making up the feeding tentacles surround the mouth.
Sea Cucumbers live in or on the substrate, burrow into sand & mud, "swim" or float above the bottom, or hang out in the local flora; they're everywhere in marine environments.
Brittle stars, or ophiuroids, are echinoderms, closely related to sea stars.
The ophiuroids generally have five long slender, whip-like arms which may reach up to 60 centimetres (24 in) in length on the largest specimens.
They are also known as serpent stars.
They usually cling to coral with their arms which have little hook like spines.
In all brittle stars there is a central disk that can grow up to 20 mm in diameter.
They have a hard exoskeleton which means that they don't have a skeleton on the inside but a hard shell on the outside.
They do not have a brain; instead they have a simple ring of nerve cells that transfers information around the body.
Their arms are made of little rings held together with muscle-like tissue, all attached to the center disk.
Their five long legs (or arms)are also good for helping them move and capture food. Unlike star fish though, the Brittle star’s legs don’t touch at the center.
On each segment of the legs are seven glassy spines that collect plankton.
All of them can be different colors, the most common of the Brittle stars are: red, yellow, orange, violate, gray, and brown.
Movement
They crawl across the seafloor using their flexible arms for locomotion.
Unlike star fish the Brittle star rows their arms though the water, kind of like a snake, to get from place to place.
Star fish have to use their tubed feet to get around.
Instead of having eyes they use the hairs on their arms to feel along, and smell.
Most Brittle stars are separate sexes.
They discharge their eggs into the water though their “Bursal slits”.
The diameter of the eggs are around 1-0.18 mm. Like many other animals, Brittle Stars go though metamorphosis.
That means that they go through stages before they reach maturity.
These eggs start out as a sort of plankton only having legs.
They then go into a larva stage.
The body of the young eggs starts to flatten and close up, and then slowly forms into a Brittle star.
Common name: Bat Star
Bat stars come in a wide variety of solid and mottled colors, including red, orange, yellow, brown, green and purple.
They have webbing between their short, triangular arms, which gives them a batlike look.
Normally, bat stars have five arms, but they occasionally have as many as nine arms.
Gill-like structures on a sea star’s back, which aid with breathing, give its skin a fuzzy appearance.
Most sea stars have pincers (pedicellariae) that remove debris from the skin gills, but bat stars have no pincers and are free of debris.
As scavengers, bat stars play an important role in the ecosystem, helping clean dead animals and algae from the seafloor. Fortunately, more and more people know that we all depend on healthy oceans, and that the survival of ocean animals, including bat stars, is up to us.
The bat star’s ossicles are so large and defined that they look like rough shingles.
These shingles act like armor and protect the bat star’s vital organs.
Sea stars have external hard parts (exoskeletons) made up of little plates (calcified ossicles) joined by connective tissue.
They seem to be “arm wrestling” in a slow motion skirmish.
Bat stars reproduce by spawning.
The male broadcasts sperm and the female broadcasts eggs from pores near the bases of their arms.
Fertilization takes place in the sea, and currents carry the young to new homes.
CLASS PISASTER GIGANTEUS (PISASTER)
Tube feet enable pisasters to pull apart the valves of mussels.
They are then able to extend deep into the soft substrata, hauling out the prey from within
Sea stars have the ability to regenerate lost arms and can regrow an entire new arm in time.
Most species must have the central part of the body intact to be able to regenerate, but a few can grow an entire sea star from a single ray.
Habitat
The Giant sea star, Pisaster giganteus is a species of sea star that lives along the western coast of North America from Southern Californiato British Columbia. It makes its home on rocky shores near the low tide mark. It preys on mollusks. It can grow as large as 24 inches in diameter. Its color varies from brown to red or purple.
Very abundant. On rocks, occasionally sand. Most common predatory sea star in
Movement
Sea stars move using a water vascular system.
Feeding
Generalist diet includes barnacles, vermetids, turban snails, & many other sessile species.
Reproduction
Sea Stars are capable of both sexual and asexual reproduction.
Individual sea stars are male or female.
Fertilization takes place externally, both male and female releasing their gametes into the environment
Feather stars are curious looking organisms.
They consist of a mass of feather like arms radiating from a tiny body.
Feather stars have tube feet on their arms but these have no suckers at the end, unlike starfish and sea urchins.
Feather stars come in a great range of colours including some bright yellows and reds that appear to advertise the presence of the feather star to all around them.
As in other brightly coloured marine animals, the crinoid's bright colours may serve to remind fish and other predators of their poisonous nature.
Feather stars are found in oceans in the tropics, temperate and polar zones. They generally shelter by day under ledges and in caves and come out at night to feed.
They are often found hanging under caves and overhangs by day.
When nights falls, Feather stars migrate to the top of the reef or push their arms out into the currents usually present near dropoffs or at the entrance of caves.
Here, they trap fine particles using their tube feet.
Feather stars are usually solitary but may occur in small groups around their favourite haunts.
Feather stars are almost exclusively suspension feeders.
They are referred to as passive suspension feeders because they do not generate feeding currents but rather rely on the external movement of water by their feeding arms.
Reproduction
Feather stars have separate sexes which are impossible to distinguish.
In most species, larvae develop indirectly, meaning that they pass through one or more stages that look very little like the adult.
In species with indirect development, the larvae are called vitellaria larva.
These swim in the water column for 10-40 days (depending on the species and the temperature of the water) and eventually settle as baby feather stars.
Thereafter, the feather star grows gradually to become an adult feather star, usually 8 –12 months later.
Some species develop directly (have no different-looking larval stage) and are nourished during development by food in the egg supplied by the mother
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