Echinodermata

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Echinoderm, common name for about 6000 living species constituting a phylum of marine animals, such as starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers. They usually show a superficial five-part radial symmetry, and generally are equipped with peculiar tube feet. The phylum name is derived from the spiny skin.

An echinoderm such as the starfish typically has a mouth surrounded by five arms that bear minute, fleshy tube feet with which the animal clings and crawls. The tube feet are supported by a complex internal hydraulic system that is inflated with seawater. Some echinoderms, especially brittle stars, crawl or swim by moving their arms. Often, as in sea urchins, rows of tube feet extend along the body surface, and arms are absent. The spines are particularly well developed in sea urchins. The skeleton, made up of calcium carbonate, may form a large proportion of the body, or, as in some sea cucumbers, it may be greatly reduced. The fossil record shows that the five-rayed pattern is a late evolutionary acquisition, and deviations from it are common. The animals have a well-developed gut, but the nervous and circulatory systems are simple. Echinoderms are slow-moving and without complex behavior patterns.

Echinoderms are common on the ocean bottom at all depths; in the deep sea they often make up the bulk of living material. They may be grazers (most sea urchins), feeders on small particles (many brittle stars), or predators (most starfish). Starfish and a few others are pests, as when found in oyster beds. Sea cucumbers and sea urchins are eaten by humans.

Scientific classification: Echinoderms make up the phylum Echinodermata. The living echinoderms are commonly divided into two subphyla. The stalked or attached Pelmatozoa consist of the single class Crinoidea, or sea lilies and feather stars, with 650 species. The free-living Eleutherozoa consist of the classes Holothuroidae, or sea cucumbers, with 900 species; Echinoidea, or sea urchins and sand dollars, with 850 species; Asteroidea, or starfish, with about 1500 species; and Ophiuroidea, or brittle stars, with about 2000 species. Many authorities, however, unite Asteroidea and Ophiuroidea into a single class, Asterozoa (or Stelleroidea). About 20 extinct classes are found in the fossil record.

Pictures of Invertebrates

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Gooseneck Barnacles
Gooseneck barnacles are crustaceans that live in the intertidal zones of temperate and cold water oceans, particularly in areas of heavy surf. The hard-shelled portion of the gooseneck barnacle’s body, which contains the internal organs, is supported on a long muscular stalk. Gooseneck barnacles use this stalk to latch onto floating objects or rocks, where they cluster in dense groups.





Gray Snakelocks Anemone
The gray snakelocks anemone, sometimes called the pink-tip, is related to the jellyfish, corals, and hydroids. Although sea anemones can move, they do not actively pursue prey but rather capture fish, shrimp, or other invertebrates that swim past or fall on them from above. The sea anemone’s color results from the presence of a symbiotic algae, called zooxanthellae, living in the anemone’s body tissues.





Great Gray Slug
All species of marine and terrestrial slugs are shelless mollusks. Terrestrial slugs, such as the great gray slug, generally feed on leaves and can cause considerable damage to trees and cultivated plants in gardens and greenhouses.







Green Hydra
The green hydra is the freshwater counterpart of the sea anemone, belonging to the same phylum as the sea anemone, coral, and jellyfish. Possessing six to ten tiny tentacles armed with potent stinging cells, the hydra captures small organisms from the surrounding water. It is often found in colonies of many individuals. The hydra is capable of regenerating lost body parts, even in cases where the injury has been extensive.




Hermit Crab
Hermit crabs are distinguished from other crabs by the lack of a shell on the abdomen. As a result, hermit crabs must find empty snail shells to temporarily inhabit. While walking or feeding, hermit crabs extend their antennae, claws, and two pairs of walking legs out of the shell opening. When threatened by predators, hermit crabs quickly withdraw their bodies back into the protection of the shell. The large claw, the last part of the body to be withdrawn, often acts as a door, closing off the interior of the shell from predators. As hermit crabs grow, they must continually find new, larger shells in which to live.


Human Head Louse
The human head louse, Pediculus humanus, is one of several kinds of lice with mouthparts specialized for sucking blood. The small, wingless insect has a flattened body about 3 mm long, with a claw on the end of each leg that helps it cling to the hair of its host. Females lay whitish eggs, called nits, once a day, attaching them to the hair with a sticky substance until they hatch in about a week. Head lice are unpleasant and undiscriminating guests. They infest people who bathe often as well as those who do not, leaving itchy red spots on their hosts’ scalps.


Millipede
The millipede is a segmented arthropod found in damp, moist habitats worldwide. The body of the millipede may have from 9 to over 100 individual segments, each of which bears a pair of legs. Millipedes feed on decaying vegetation and are generally harmless. When threatened or handled, they curl up in a tight ball. For defense against insect predators, millipedes rely on their stink glands, which secrete a noxious chemical substance that repels predators.



Murray River Crayfish
Although identical in shape to the marine lobster, the freshwater crayfish is more adaptable, being able to live in freshwater streams, ponds, and even terrestrial burrows. In some agricultural areas of Spain, crayfish are so abundant they are considered pests.






Portuguese Man-of-War
The Portuguese man-of-war is actually a colony of specialized polyps that all contribute to the well being of the colony by performing specific tasks, such as feeding or providing buoyancy control. The man-of-war has a relatively large, gas-filled bladder that provides flotation for the entire colony. A large collection of feeding polyps suspended from the underside of the float, each with a single, long tentacle, captures and digests food, which is then shared with the entire colony by means of interconnecting digestive cavities. Although the Portuguese man-of-war resembles a jellyfish, it belongs to Class Hydrozoa in the phylum Cnidaria, while true jellyfish belong to Class Scyphozoa in the same phylum.

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Pictures of Invertebrates

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Black Widow Spider
The female black widow spider, distinguished by the red hourglass marking on the underside of her abdomen, is probably the best known and most feared of all North American spiders. In spite of the female black widow’s small size of 1.2 cm (0.5 in.), its venom is quite toxic and may cause a wide range of symptoms in humans, including pain, swelling, nausea, and sometimes death. The male of this species is harmless to humans and lacks the hourglass marking on the abdomen.



Blue Spotted Sea Urchin
This underside view of the blue spotted sea urchin shows its mouth apparatus, commonly called Aristotle’s lantern. This structure is composed of five jaws arranged in a radial, or concentric, pattern. This arrangement allows the sea urchin to feed efficiently on a variety of marine algae and kelps.







Branching Coral Colonies
Branching coral is actually a colony of very small individual animals called coral polyps. Branching corals are considered hard corals, since they have a hard calcium carbonate skeleton. Their bright colors result from the presence of symbiotic algae that live in their body tissues and produce most of the food that the coral needs to survive.




Chambered Nautilus
A cutaway view of the shell of the chambered nautilus reveals the compartments that housed the nautilus when it was smaller. These smaller chambers, now connected together by a small calcified tube, regulate the buoyancy of the nautilus as it swims along. The compartments are filled with nitrogen gas, which is produced by the nautilus.






Clams
Clams have long been one of the most popular of the edible shellfish. Referred to as bivalve mollusks because of the two valves, or shells, that enclose the body, these small filter-feeding animals are commonly found in intertidal areas throughout the world. Strong internal muscles, a hinge ligament, and a calcified hinge at the apex of the shell allow the clam to protect itself against many types of predators by keeping the shell tightly closed. The prominent growth rings found on the outer surface of the clam shell are useful in determining the clam’s age.


Common Cuttlefish
Related to the octopus and squid, the common cuttlefish is an open water species of cephalopod mollusk that swims by undulating a continuous fin along the length of its short, fat body. The cuttlefish is commercially important throughout many parts of its range. A supporting rod of calcium carbonate present within the cuttlefish, called cuttlebone, is used commercially as a polishing agent and as a source of calcium and salts for captive birds and other animals.



Common Octopus
The common octopus has the typical octopus body form consisting of three main regions: the mantle, limbs, and head. The mantle, a large, muscular, bulbous sac, contains most of the internal organs, including the gills, digestive tract, ink sac, and reproductive organs. The limbs consist of eight arms. Along the length of each arm is a double row of suckers equipped with tactile and olfactory receptors.





Earthworm
Earthworms have a segmented, compartmentalized, cylindrical body and range in length from several centimeters (a few inches) to nearly 3.3 m (11 ft). They have no eyes, ears, or lungs. Earthworms breathe when air that is present between soil particles diffuses through their thin skins, and they are forced to the surface if these air pockets fill with rainwater. When a worm moves, it uses its longitudinal muscles to extend the front of its body into the soil ahead of it, pulling the back part up behind it. Setae, tiny projections from each segment of the worm, stick into the surrounding soil to keep the worm from slipping. The digging action of earthworms helps to aerate and mix the soil. Earthworms actually consume some of the soil as they dig, and their fecal deposits, called castings, also help enrich the soil.

Echinoderms
Members of the phylum Echinodermata, commonly called echinoderms, or spiny-skinned animals, are so named because of their spiny outer body coverings. Echinoderms differ from other animals in that they have a water vascular system that uses seawater to accomplish respiration, locomotion, and reproduction. The echinoderms include marine groups such as the sea stars (top, left), sea cucumbers (bottom, left), brittle or serpent stars (top, center), sand dollars (bottom, center), sea lilies (right), sea urchins, basket stars, heart urchins, and feather stars.

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Pictures of Insects

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Luna Moth
The full-grown luna moth has transparent circles bordered by light yellow and blue rings on its light green wings. Luna moths reproduce twice a year and eat the leaves of trees in the deciduous forests they inhabit. Now endangered because of contaminated food sources and pesticides, the luna moth is found only in North America.




Peacock Butterfly
The conspicuous eyespot markings of the peacock butterfly, Inachis io, make the insect unmistakable. The butterfly uses its patterning in self-defense, opening its wings if threatened by a bird and attempting to alarm the attacker by turning the pattern towards it. The butterfly also rubs its wings together to make a noise that helps scare off predators.





Praying Mantis
The praying mantis is so named for the prayerlike posture it assumes while waiting for its prey. Although the praying mantis generally eats insects and small tree frogs, the female will devour part of her own mate. Commonly found in tropical and warm temperate climates, the mantis was introduced into the United States to help control certain insect populations.







True Locust
The true locust is one of over 5000 species of grasshopper in the family Acrididae. Locusts travel in huge numbers capable of feeding on and destroying entire fields of cultivated plants and any nearby vegetation. Approaching swarms create an ominous hum and sometimes are large enough to block out sunlight.






Tumblebug
The tumblebug is one of 30,000 species of scarab beetles, which include dung beetles and chafer beetles. The tumblebug forages on decaying plant material and lays its eggs in small balls of dung, which then serve as a food source for the emerging larvae.



Walkingstick
Walkingsticks have the colors and shapes of the plants on which they live, resembling twigs, or dried leaves. The eggs of many species resemble seeds. Walkingsticks are vegetarians, feeding on leaves. Shown here is Extatosoma tiaratum, an Australian species resembling a spiny, leafy twig.





Worker Honey
As they fly from flower to flower, worker honey bees collect pollen grains and pack them onto their hind legs in special hair-fringed pockets known as pollen baskets (shown here holding a glob of yellow pollen on the hind leg). Nectar, the sweet liquid produced by flowers, is sucked into the honey stomach, an internal storage sac. In the hive, field bees deposit their pollen pellets into empty storage cells of the comb and regurgitate nectar to waiting hive bees. The hive bees mix some nectar with the pollen to make bee bread, a spoilage-proof larval food, and gradually concentrate the rest of the nectar into honey by dehydration.

Pictures of Insects

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American Cockroach
The American cockroach is one of the hardiest species of cockroaches. Unlike most other cockroach species, the American cockroach can fly and is also attracted to light.







Aphids
Aphids are small insects found throughout temperate regions of the world. They parasitize a variety of wild and commercially important plants by sucking out plant fluids. Because aphids exude a sweet, sticky fluid that can be used by certain species of ants, herds of aphids are often found guarded and tended by ants.





Blue Damselfly
After mating, blue damselflies deposit their eggs in water. The eggs hatch and develop into an aquatic larval form, which eventually leaves the water, undergoes metamorphosis, and changes into an adult.







Caterpillar
The larva of a butterfly or moth, known as a caterpillar, has a plump cylindrical body and chewing mouthparts. Most caterpillars eat leaves or other parts of plants and grow rapidly, shedding their skin several times as they grow. The caterpillar of a death’s head hawkmoth, Acherontia atropos, is pictured here.



Firefly
The firefly, belonging to the family Lampyridae, is one of a number of bioluminescent insects capable of producing a chemically created, cold light. Both males and females can generate the light, which is believed to attract them to each other. The light is produced when two chemical substances created by the firefly, luciferin and luciferase, come into contact with oxygen.





Forager Ant
A forager ant searches for food among blades of grass in South Africa’s Karoo National Park.






Fruit Fly Laying Egg
The small vinegar flies of the family Drosophilidae, commonly called fruit flies, have been exceptionally useful in scientific research. Their short reproductive cycle (a new generation of adults develops in only two weeks) and uncomplicated genetics make them ideal subjects for studies of heredity. This fly lays its eggs in rotting fruit and therefore does not need the stiff, sharp ovipositor that other fruit flies use to drill into fruits and stems.

Great Diving Beetle
The great diving beetle has adapted to an aquatic environment. A voracious predator, the diving beetle feeds on tadpoles, small fish, and other insects and their larvae. Not strictly limited to the aquatic environment, diving beetles are capable of flying from one pool to another.






Hornet
The European hornet is the wasp Vespa crabro, common on the east coast of the United States, where it is also called the giant hornet. This wasp, introduced from Europe in the mid-1800s, constructs its nest of hexagonal cells inside hollow trees. Wasp nests are paper, made of partially digested wood and plant fiber. Hornets may emerge from their nests at night and cluster around sources of light. Like other wasps, hornets have a painful sting.




Katydid
The katydid gets its name from the characteristic sound made by males as they rub their wings together to attract females. It is a tree-dwelling insect in the grasshopper family. The katydid resembles a folded green leaf in both color and appearance and uses this mimicry to escape detection from predators. Pictured here is an insect of the scudderia species.

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