Mollusks (“soft-bodied”)
Bivalves / Gastropods / Cephalopods“Two shells” / “Stomach foot” / “Head foot”
Clams, mussels, scallops, oysters / Snails, slugs / Squid, octopus, cuttlefish
Two shells / One shell or none / Internal “shell”
Simple brain / Brain and sense organs / Most advanced mollusk brain and sense organs
Gills / Gills or lungs / Gills
Ocean / Land, ocean, freshwater / Ocean
Sexual reprod. / Sexual reprod. / Sexual reprod.
Filter food from water / Use radula to scrape food / Beak-like radula tears prey apart
Anchored to sea floor OR open and close shells to propel themselves / Slide on slime / Jet propulsion
Ink as a defense
Banana Slugs
The Banana Slug (Ariolimax columbianus) is a gastropod found in the Northwest United States. It travels on a muscular foot leaving a trail of slime, which serves several purposes. They have a hump on their back, a radula with 27,000 teeth-like structures, and a mantle with a cavity.
The Banana Slug can grow up to 12 inches (26 centimeters) and is the world's second largest slug. The coloration of the Banana Slug may be a bright yellow, slate-green, or white with or without black spots.
Ariolimax columbianus
Banana Slug
One way that the slug can breathe is using a small lung. The slug can also breathe through its skin so long as the skin remains moist for gas exchange to take place.
Besides aiding in breathing, the slime has several other functions. One function is protection. Some predators do not care for the taste of the slug's slime. The slime makes it easier for the slug to crawl along the forest's floor. During mating season, the slime contains a chemical, which other slugs follow.
Slugs have both male and female reproductive organs. Normally, slugs trade sperm with other slugs, but they can fertilize their own eggs. They may lay 12 to 100 eggs at a time and up to 50 to 150 eggs each year. The eggs are pearl-like in color and about the size of a person's pinky fingernail. The eggs are laid in clusters under logs, rocks, and in the soil. Eggs are laid in the early spring, late summer and early fall. Most adults die after laying eggs. The eggs laid in the late summer or early fall may not hatch until spring. It takes three to four weeks for the eggs to hatch.
Slugs may feast upon a variety of plants as well as fungi and decomposing plants. The slugs use their radula to scrape food off the source. The slugs may be preyed upon by snakes, ducks, geese, shrews, moles, beetles, crows, and salamanders. Raccoons have a trick to deal with the slime;they will roll the slug in dirt to coat the slime!
Slugs have a pair of tentacles, which they use to gather information about their environment. The pair of tentacles located on the top of the head has a small black spot at each tip. These tentacles are used to detect lightness and darkness. Slugs prefer dark and moist areas. The second pair of tentacles functions as a nose. These tentacles pick up smells especially during mating season. Most of the food sources are located by using both pairs of tentacles.
Banana slug
Snails
The Snail is a gastropod, a soft-bodied type of mollusk that is basically a head with a flattened foot. The soft body is protected by a hard shell, which the snail retreats into when alarmed. These invertebrates are found worldwide in the seas, in fresh water, and in moist areas on land.
Locomotion: Snails move by crawling, swimming, or floating with currents. Land snails crawl on the ground, creeping along on their large, flat foot; a special gland in the foot secretes a slimy fluid that helps the snail move. The common garden snail is the slowest moving animal; it can travel about 0.03 mph.
Anatomy: Snails range in size from 0.02 inch (less than a millimeter) long to over 30 inches long! The largest land snail is the Giant African Snail; it is over 15.5 inches long and weighs about 2 pounds.
Snails have two pairs of tentacles on the head. Land snails have a light-sensitive eyespot located on each of the larger tentacles; water-dwelling snail eyespots are at the base of the tentacles. The smaller pair of tentacles is used for the sense of smell and the sense of touch.
Diet: Most snails eat living and decaying plants, but some are predators. They eat using a radula, a rough tongue-like organ that has thousands of tiny teeth.
Predators of the Snail: Many animals eat snails, including birds, fish, frogs, snakes, turtles, beetles (and other insects), and people.
Label the Land Snail: External Anatomy
Read the definitions; then label the land snail diagram below.
eyespots - located at the tips of the long tentacles on land snailsfoot - the soft, muscular part of the snail that allows the snail to move
shell - the hard, spiral, protective covering of the snail
head - the front part of the snail, containing the tentacles, eyes, and mouth / mouth - on the underside of the head - it contains the radula, a file-like tongue that breaks down the snail's food
respiratory pore - a small hole in the side of the body, used for breathing
tentacles - two long and two short sensory tentacles on the upper surface of the snail's head
Blue Ring Octopus
The Blue Ring Octopus is the most venomous octopus. This small mollusk lives in warm, shallow reefs off the coast of Australia, New Guinea, Indonesia, and the Philippines. It has a life span of about 1 1/2 years.
Anatomy: The Blue Ring Octopus has distinctive blue rings on its body and on its eight arms. It is only about 8 in. with the tentacles spread wide. Like all octopuses, if an arm is lost, it can be regenerated.
Diet: The Blue Ring Octopus hunts during the day. It eats invertebrates and wounded fish. It hides in the reef, then catches prey with its arms, bites it with its tough beak, and kills it by delivering a poison in its saliva. The poison is strong enough to kill a human being.
Protection: The Blue Ring Octopus also defends itself using its poisons. Like other octopuses, it lives in dens: spaces under rocks, cracks on the sea floor, or holes it digs under large rocks. It piles rocks to block the front of its den. The den protects the octopus from predators (like moray eels) and provides a place to lay eggs and care for them (a mother octopus doesn't eat during the entire 1 to 2 months she is caring for her eggs). In order to escape predators, an octopus can squirt black ink into the water, allowing the octopus to escape. The octopus swims by spewing water from its body, a type of jet propulsion.
Squid
The Squid is an invertebrate (animal without a backbone) that swims in the oceans. Squid are 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 and sperm into the water.
Anatomy: Squid range from 1 to 60 ft long. The biggest squid is the Giant Squid. Squid have a large mantle and a large head (with a large brain), eight arms with suckers, two longer feeding tentacles, a beak-like radula, 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, 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!
Predators: Many animals prey upon squid, including many sharks and other fish, some whales, squid, and people.
Label Squid External Anatomy DiagramUsing the definitions listed below, label the squid diagram.