Mollusk / Annelids Mollusk

History of Worms

Section Objectives: Identify the characteristics of mollusks. Compare the adaptations of gastropod, bivalve, and cephalopod mollusks in their biomes.

Phylum Mollusca Snails, clams, squids, slugs and oyster are examples. Found freshwater, ocean or moist terrain.

Bilateral symmetry - Distinct regions mirrored on a left and right axis.

9 Structures

1. Radula Tongue like organ that protrudes from the mouth used for eating algae. Contains rows of tiny teeth that are used for scraping algae from surfaces. A radula may have as many as 250,000 teeth.

Radula Radula

2. Mantle soft, moist layer inside the shell of mollusks. Mantle

3. Shell outer layer. Most made of calcium carbonate. CaCO3 Shell

4. Gills gas exchange occurs through the mantle and the gills. Gills also filter food particles from the water.

5. Foot extends out and helps with movement. Foot

6. Heart Has a 3 chambered heart. a. Open circulatory system - blood moves through vessels and into spaces around the body organs. Ex: Snails, squid, and clam

6. Heart b. Closed circulatory system - blood moves through the body enclosed entirely in a series of blood vessels. Some mollusks, such as octopuses, move nutrients and oxygen through a closed circulatory system.

Mollusks have a well-developed circulatory system that includes a three-chambered heart.

7. Siphons act as devices to let water in and out of mollusks.

8. Nephridia tube like structure that form the excretory system.

9. Visceral mass area located between the muscular foot and mantle contains most of the internal organs.

Mollusk Diversity Form the second largest phylum. Contains 7 different types of mollusks. First animals to have evolved respiratory organs.

Classified according to shell type, muscular foot structure, and arrangement of internal body organs.

Chitons live on rocky surfaces in shallow water. Ex: Chitons ( KY - tunz) Most primitive mollusks, do not have a ganglia and have simple sense organs.

Chitons Have 8 overlapping plates.

Snails and Slugs largest class of mollusks. Have a radula that scrapes up algae or tears apart plants or one piece shells. Have sense organs concentrated in the head region. Open circulatory system. Aquatic gastropods use gills as respiratory organs.

Snails and slugs Sea slug Ex: snails or slugs snails

Bivalves Do not have a head, have two shells attached by a hinge, have sense receptors, ganglia, most are marine, and do not have a radula. Filter feeders.

Bivalves Ex: clams, mussels, scallops and oysters mussel scallop clam

Cephalopods Tentacled mollusk modified head and foot regions. Have a highly developed nervous system, sense organs, usually no external shell, closed circulatory system and can usually swim fast.

Octopus

Cephalopods Ex: squids, nautiluses, octopuses, Cuttlefishes. Most recently evolved mollusks. squids Cuttlefishes octopuses nautiluses

Cuttlefish

Nudibranch

Mollusks Octopus oysters

Mollusks

Trivia: The largest-known squid was 57 feet (17.5 m) long.

1. In shelled mollusks, the ___________ secretes the shell. 2. Bivalves obtain food by ______________. 3. ______________ have two shells. 4. The excretory structures that remove metabolic wastes from the bodies of animals such as mollusks and annelids are called ________________. Mantle Filter Feeding Bivalve Nephridia

5. An animal whose blood moves throughout its body within blood vessels has a(n) ___________________. 6. The ____________ is a tongue like organ with rows of teeth that is used by gastropods to scrape, grate, or cut food. 7. The most complex and most recently evolved mollusks are _______________. Closed Circulatory system Radula Cephalopods

8. What compound are most shells composed of? 9. ____________ are involved in removing wastes from a mollusk’s body. 10. Which animal is believed to be smarter a snail or a squid? CaCO3 and SiO2 Siphons or Nephridia Squid

Annelids

Annelids earthworms, leeches and many segmented marine worms. Classified by the presence or absence of setae or parapodia. brown Brown sea worm leech

Ex: earthworms

Earthworm movement

11 Structures or Systems of earthworm

1. Setae Bristles that help classify annelids depends on the number and presence of the bristles. Help to anchor each segment in the soil and help with movement.

2. Parapodia leglike structure

3. Nephridia excretes the wastes.

4. Crop temporary storage organ. 4

5. Gizzard Grinds up soil , freeing the organic matter and breaking it down. 5

6. Intestine long , straight tube where organic matter digested. Eat their way through the soil. (Casting - earthworm’s waste) 6.

7. Circulatory system closed system. (Aortic arches - muscular structures that functions as simple hearts by contracting and forcing blood into the ventral blood vessels. 7

8. Respiratory system Gas exchange takes place across the skin. Skin must be moist for diffusion of oxygen to take place. Produce a mucous secretion and have an outer cuticle that helps keep skin moist.

9. Nervous System has a small brain made up of fused ganglia At the anterior end of the digestive tract.

10. Reproductive system Reproduce sexually, are hermaphrodites, but cannot fertilize their own eggs. When mate join head to tail and secrete a mucus covering around the joined areas and each worm then releases sperm into a special sac in the other worm.

11. Skeletal system hydrostatic (fluid filled to hold shape).

Earthworm Anatomy

TRIVIA: Earthworm eggs hatch in 2-3 weeks.

Bristleworms Fan Worms bristleworm

Bristleworms largest and oldest class of phylum Annelids. Gas exchange takes place across the surfaces of the parapodia. Are typically free swimming or tube dwelling marine annelids.

leeches usually freshwater parasitic annelids. Attach to host with a pair of suckers or hooks.

Uses of Mollusks and Annelids Mollusks (clams, oysters , etc are important food sources.) Annelids - by burrowing through the soil, help to loosen , allowing water and air to pass easier.

Doctoring with Leeches

The medicinal leech is best known as the organism used for blood letting (people used to believe many health problems caused by getting rid of "bad" blood). Surprisingly, they are being used once again to remove blood from hematomas (areas of blood leakage) resulting from surgery (like re-attaching severed limbs, etc.). The ability of the leeches to parasitize humans and other mammals depends on a variety of adaptations that allow them to pierce or cut into skin without notice.  Hirudo uses three sharp cutting plates (teeth) like circular-saw blades to make a Y-shaped incision in the skin.  While cutting the skin, it secretes an anesthetic as well as a histamine-like substance that keeps the blood vessels open. The blood is then sucked into the pharynx. While it is being swallowed, an anticoagulant protein called hirudin produced by the salivary glands is added to the blood to prevent it from clotting. After the salt-water from this blood is eliminated by the nephridia, the concentrated blood is stored in within numerous diverticula (outpocketings) of the crop called gastric caeca (ceca). The proteins of hemoglobin and other components of the blood are then digested extremely slowly (as long as 200 days), which provides enough energy to live another 100 days without feeding!  Surprisingly, the gut does not secrete digestive enzymes.  Instead, the leeches rely on bacteria in the gut for enzymatic digestion.  In the medicinal leech, a single species of bacterium digests the blood and also produces an antibiotic that eliminates any other bacteria from the digestive tract, allowing the red blood cells to remain unspoiled within the leech for up to a year! This also means that you don't have to worry about getting a bacterial infection from the leech! Medical Leech

Leeches therapy

Trochophore ciliated, pear shaped larval form of mollusks and annelids.