This document contains information about different types of mollusks - bivalves, gastropods, and cephalopods. It includes details about their anatomical features such as whether they have a coelom or circulatory system. For each group, an interesting species is chosen - the northern quahog bivalve, green sea slug gastropod, and giant squid cephalopod. Fact sheets are provided for each organism detailing their characteristics, habitat, lifecycle, relationships and more. References are cited at the end.

1. Sandra Cash<br />March 16, 2011<br />Marine Science<br />Assignment 4.4.2- Mollusks Comparison and Fact Sheet<br />Part 1: <br />Group and common nameIs there a cephalization?Is there a coelom?Is there an excretory system with kidney/nephridium?Is there a muscular foot used for locomotion?Is there a protective shell that encloses a soft body?Are there gills for breathing?Is there a circulatory system is open with a well-defined heart?HabitatFeeding strategiesBivalves:oystersBivalves do not have the cephalization characteristic like other mollusks, but some have eyes.Yes, they have and a complete digestive tract, although they do not have a radula because they are filter feeders.Yes, they have a nephridia. Yes, bivalves use their muscular foot, which looks like a hatchet, to move from place to place.Yes, they have two shells hinged together.Yes, they have gills for breathing.Yes, they have a heart with open circulatory system. They can live deep in the sediment. Some of these bivalves can actually dig into wood.They are filter feeders. They have two siphons, one that pulls water into their bodies and over their gills, and another that sends the water out of their bodies.Gastropods: SnailsYes they have a cephalization, which possess a distinct head with tentacles, eyes, and mouth with a radula and varied feeding styles.Yes, there is a coelom in gastropods. Yes, they have an excretory system with a kidney.Yes, they have a muscular food used for locomotion.Yes, they have only one shell that protects the soft body. Though there is one group called the nudibranchs who do not have a shell.Kind of, gastropods have reduced gills and a trend towards lung development.Yes, they have an open circulatory system with a ventricle in the heart.They live in a watery environment.Herbivores, carnivores, scavengers, and filter feeders are found among the gastropods.Cephalopods: octopusYes, they have a cephalopod that is the most complex of the mollusks both behaviorally and anatomically.Yes, there is a coelom in cephalopods.Yes, they have a complete digestive tractKind of, they have a foot that is modified into a head-like structure surrounded by many tentacles.No, they do not all have do not all have external shells. The nautilus has an external shell, but the squid and octopus do not.Yes, they have highly vascular gills.Yes, they have a circulatory system is similar to other mollusks, but is slightly more complex.<br />Part 2: Choose one organism from each group of mollusk that you find interesting. Prepare a fact sheet for each organism. The fact sheet should include as much detail as possible related to the critter. Graphics (i.e., pictures of critter and habitat, relationships with other critters, drawings of lifecycle and/or anatomy, etc. ) will enhance your fact sheet.<br />GroupBivalvesGastropodsCephalopodsPicture of the organismNortherQuahogGreen Sea SlugGiant SquidCharacteristicsNorthern Quahogs they have shells consisting of two halves. The halves are joined at the top, and the adductor muscles on each side hold the shell closed. The clam's foot is used to dig down into the sand, and a pair of long siphons that extrude from the clams’ mantle out the side of the shell reach up to the water above. Northern quahog, are filter feeders. They are also known as hard shell, steamer, or cherrystone clams. Quahog comes from the Algonquin Indian language, and besides eating the clams, the Indians used the shells for ornaments and money.As a juvenile, it is reddish-brown in color. After feeding on the algae, the sea slug turns a brilliant shade of green. As the sea slug digests the algae, it is able to retain the algae's chloroplasts, or photosynthetic structures. These chloroplasts are sent to the surface of the sea slug's body—where, curiously, they continue to photosynthesize.The giant squid remains largely a mystery to scientists despite being the biggest invertebrate on Earth. The largest of these elusive giants ever found measured 59 feet in length and weighed nearly a ton. Giant squid have the largest eyes in the animal kingdom, measuring some 10 inches in diameter. These massive organs allow them to detect objects in the lightless depths where most other animals would see nothing. Like most squids, they have eight arms and two longer feeding tentacles that help them bring food to their beak-like mouths. Their diet likely consists of fish, shrimp, and other squid, and some suggest they might even attack and eat small whales. They maneuver their massive bodies with fins that seem diminutive for their size. They use their funnel as a propulsion system, drawing water into the mantle, or main part of the body, and forcing it out the back.HabitatNorthern quahogs are found along most of the East Coasts. The green sea slug is found along the eastern coast of North America, from Nova Scotia to Florida. The sea slugs live in coastal salt marshes, tidal marshes, tidal pools, and shallow creeks. They live in the inhospitable deep-sea habitat, which has made them uniquely difficult to study.Lifecycle and/or anatomyRelationship with other critters and it’s habitatCommon predators are blue crabs, mud crabs, conch, sting rays, horseshoe crabs, and snails. They mostly feed on juvenile or small clams. Wading birds may cause intensive destruction insome areas.It has been known for years to have a symbiotic relationship with its food, the algae. It was known that when the slug eats algae it integrates parts of the algae cells into itself, chloroplasts that are necessary for photosynthesis. This then allows the slug to gain energy from sunlight, like the algae does. Not only that, but the stolen chloroplasts are so efficient that it could live up to nine months without eating anything while still maintaining its normal nutritional rates, making it the longest-lived symbiotic relationship of its kind.We don’t know much about the relationships the giant squid has with other critters, other than their diet likely consists of fish, shrimp, and other squid, and some suggest they might even attack and eat small whales. We do not know much about them due to the fact that they live in the inhospitable deep-sea.<br />Works Cited BIBLIOGRAPHY BioZine. 14 June 2010. 17 March 2011 <http://biologybiozine.com/articles/strange-biology/a_sea_slug_powered_by_the_sun_1.php>.cephalopods. 26 January 2010. 17 March 2011 <http://ocean.si.edu/taxonomy/term/591/all/feed>.GeoChemBio . 2011. 17 March 2011 <http://www.geochembio.com/biology/organisms/aplysia/>.Milius, Susan. Wired.com. 11 January 2010. 17 March 2011 <http://www.wired.com/wiredscience/2010/01/green-sea-slug/>.Santa Berara Independent. 30 January 2010. 17 March 2011 <http://www.independent.com/news/2010/jan/30/first-known-photosynthetic-animal/?print>.Tebyan.net. 17 March 2011 <http://www.tebyan.net/index.aspx?pid=31159&BookID=23465&PageIndex=0&Language=3>.The Assateague Naturalist. 2001. 17 March 2011 <http://www.assateague.com/nt-bival.html>.<br />