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 The large claw, the last part of the body to be withdrawn, often acts as a door, closing off the interior of the shell from predators.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 Invertebrates

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Purple and Yellow Tube Sponge
The purple and yellow tube sponge displays one of the many different body forms typical of sponges. Sponges, considered to be the most primitive of the multicellular animals, are represented in the fossil record back to the Cambrian Period, at least 600 million years ago. The interior body cavities of sponges provide shelter for a variety of small crabs, sea stars, and other marine invertebrates.




Scorpion
This species of scorpion is one of approximately 40 species of scorpion native to the southwestern United States. A jointed, external exoskeleton provides the scorpion with a protective outer shell. Defense and prey capture involves grasping of the prey or potential predator with the large powerful claws while the jointed tail delivers a disabling sting. Although the sting of most scorpions is not fatal to humans, the sting of this particular species has proven to be fatal to younger children.




Sheep Tick
Ticks are members of the class Arachnida, which includes spiders, scorpions, daddy longlegs, and mites. All ticks are carnivorous, feeding on the blood of various species of birds, reptiles, and mammals, including human beings. Ticks use their mouthparts to anchor themselves to the skin, where they cut a small hole and suck the blood. A number of tick species transmit diseases infecting livestock, pets, and humans.




Silverfish
The silverfish, like other insects of its order, displays vestigial legs in addition to the usual six. Among the most primitive of all animals, the silverfish belongs to the bristletails order of insects. A common household pest also known as “sugar mites,” silverfish feed on starchy materials such as foods in kitchen pantries and the glue in book bindings and wallpaper.




Snail
Some groups of snails have shells that coil to the left (left-handed), while others have shells coiling to the right (right-handed). In some groups both right- and left-handed members are present. The shell affords protection from predators and the rigors of the environment. When threatened, the snail pulls its entire body inside. A small, circular structure called the operculum closes securely behind the snail to form a tight seal that keeps out predators and keeps in moisture.




South African Tsetse Fly
The South African tsetse fly, common to central Africa, is responsible for transmitting the parasitic protozoan that causes sleeping sickness, a disease that can be fatal to humans and domestic cattle.







Sow Bug
The sow bug is actually a type of crustacean. Sow bugs are commonly found in rotting wood, wood piles, or under the loose bark of old stumps or fallen trees. When threatened by predators, the sow bug curls up into a tight, little ball, protected by its hard outer shell.






Starfish
Although many starfish have 5 arms, or rays, some species may have as many as 44 arms. All starfish can grow back arms lost through predation and physical injury. Starfish have a flattened body with the mouth located on the oral, or lower body surface. Many starfish can evert their stomach through their mouth to feed on food items too large to ingest.




Tapeworm
Tapeworms are parasitic worms that infest the intestinal lining and other organs of vertebrates. Tapeworms, having no mouth or digestive tract, are able to absorb partially digested material through their body surface.







Velvetworm
The velvetworm is an unusual animal because it shares some characteristics with arthropods but has other features that resemble segmented worms, or annelids.






Zebra Mussel
Accidentally introduced from Europe in the mid-1980s, zebra mussels have spread throughout many North American lakes and rivers. These hardy freshwater mussels grow and reproduce quickly. They attach to almost any submerged surface, frequently coating or clogging boat hulls, fishing equipment, and water intake pipes.