Marine WormsChapter 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 Contracts body

muscles Cilia move

backward—planarian moves forward along surface of substrate.

Reproduction Asexual—

regeneration Sexual—

hermaphrodites

Planarian Reproduction

Asexual Attaches to a

substrate—stretches its body—breaks in half.

Sexual 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 Break into pieces Each piece

regenerates

Sexual 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

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 Closed circulatory

system 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 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

Locomotion

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.