Marine Worms Chapter 8

Platyhelminthes Flatworm Bodies are flat Fresh and salt water species Microscopic  20 meters long More than 10,000 species

Planarian Fresh water and marine habitats Microscopic Bilateral symmetry 3 cell layers Two way digestive tract Feed on small organisms and organic debris

Planarian, cont… Eyespots on head region Surrounded by ganglia Nerve cell dusters Act like a simple brain—send nerve impulses along 2 ventral nerve cords.

Planarian, cont… Locomotion Reproduction Contracts body muscles Cilia move backward—planarian moves forward along surface of substrate. Asexual—regeneration Sexual—hermaphrodites

Planarian Reproduction Asexual Sexual Attaches to a substrate—stretches its body—breaks in half. Two flatworms exchange sperm The sperm fertilizes the eggs of the opposite flatworm internally External development in tiny capsules/cocoons Hatch in 2-3 weeks

Ribbon Worm Largest free-living worm in the sea Phylum Nemertea Approximately 1000 species Average 1 meter long but can grow up to 10-12 meters Milky color Thin and flat

Ribbon Worm, cont… Probiscis Simple closed circulatory system for distribution of nutrients and oxygen Live in intertidal zone/inside clam and oyster shells Burrow in sand Swim among animals that live encrusted on rocks.

Ribbon Worm Reproduction Asexual Sexual Break into pieces Each piece regenerates External fertilization External development

Tapeworm Parasite Intestines of fish and other animals Attaches itself to the intestinal lining of its host and absorbs nutrients through its thin body wall. No need for a digestive system

Trematode Fluke Lives in the bodies of mollusks, fish, birds, and other animals Liver fluke-parasite in mammals Blood fluke-skin of a fish—forms a cyst and lives in tissues

Trematode Accidentally eaten in raw fish—reproduce in the digestive tracts of people Swimmers itch—caused by Trematode attaching to human skin.

Phylum Nematoda Cylindrical body shape Tapered at both ends. Range in size up to 1 meter Example: Roundworms The most numerous of all worms in the sea. More than 10,000 species Live in sand and mud at bottom of water column Intertidal zone Gravel of aquarium tanks.

Roundworms Male and female Some are hermaphrodites Internal fertilization External development of eggs Males and females differ in size and shape

Roundworms cont… One way digestive tract Feed on organic debris No circulatory or digestive system Nutrients diffuse into cells—gases and wastes pass through skin Some are parasitic Trichina Hookworm Ascaris All of the above cause diseases in humans

Annelida Segmented worms Body is divided into compartments Typically found in soil and other moist sediments “little rings” Three classes of annelids

Oligochaeta “few bristles Earthworms

Polychaeta “many bristles Sandworm Crawl around on the bottom and prey on tiny invertebrates Burrow in the sand and scavenge on organic debris (low tide)

Sandworm cont… Probiscis Two sharp hooks located in its mouth One way digestive tract Coelem Fluid filled space that separates the digestive tract

Sandworms cont… Locomotion: Parapodia Setae Paddle like appendages located on each segment Helps them wriggle through wet sand Setae Hair like bristles on each parapodium Nervous system Eyelike receptors Touch receptors Impulses to ventral nerve cord Ganglia Breathe through their skin Oxygen diffuses in CO2 diffuses out Nephridia-excretory system (like kidneys)

Sandworm Reproduction Closed circulatory system Sexual Dorsal blood vessel contracts and pumps blood Arteries and veins carry the blood back and forth Capillaries connect arteries with veins Reproduction Sexual Not hermaphrodites like earthworms

The Bloodworm Polychaete Open circulatory system Blood circulates through the tissue spaces rather than through blood vessels. Can see blood through its skin

Bloodworm, cont… Usually burrow in sand and hide in seaweed to avoid predators Some live inside a tube which they make themselves to avoid being eaten

Class Hirudinea Leech Some are free living Some are parasites Two suckers at the anterior and posterior ends Sharp teeth at anterior end pierce host’s skin Hirudin-chemical anticoagulant secreted into host’s wound Prevents clotting

Parchment worm Secretes a tube formed from a tough fibrous material Lies buried in sediments below low tide

Trumpet worm Tube looks like an ice-cream cone Made of sand grain and bits of shell cemented together

Atlantic tubeworm Secretes a hard tube composed of calcium carbonate Cemented to surfaces of mollusks, rocks, and corals.

Phylum Pogonophora Giant Tube Worms New species discovered in 1977 near hot water vents on ocean floor First photographed by submersible Alvin Measure up to 1 meter

Giant Tube Worms Water is rich in hydrogen sulfide Live in tubes made of proteins and minerals (up to 2m long) Symbiotic relationship with bacteria

Chemosynthesis The process by which the bacteria produce energy rich compounds from inorganic chemicals Bacteria us hydrogen from H2S and combine with CO2 from sea water to produce sugars Worms survive by using the carbs

Phylum Chaetognatha Arrow worm Live near the surface Tiny and transparent A few cm long

Arrow Worm: nervous system Simple Respond to stimuli 2 eyes in head region respond to light Papillae Sensory projections located on the surface of worms body Ganglia in head and trunk region

Arrow worms cont… Digestion Locomotion Mostly drift with plankton 1-way digestive tract Food is digested in narrow intestine Waste eliminated through anus Nutrients diffuse into cells Mouth bristles modified as hooks Eat copepods, fish eggs, and fish larvae Mostly drift with plankton Tiny fins that enable swimming

Arrow worms: reproduction Hermaphrodites Sexual reproduction Not self-fertilization Sperm and egg are shed into water Sperm from one arrow worm fertilizes the eggs of another.