FLATWORMS Belong to the KINDGOM ANIMALIA PHYLUM PLATYHELMINTHES

Characteristics 1. Unsegmented 2. Bilateral symmetry 3. Cephalization (has a head) 4. Acoelomates = without coelom 5. Thin and flat body

FORM AND FUNCTION FEEDING: Free-living - carnivores or scavengers OR Parasites – feed on blood, tissues or pieces of cells from within a HOST Most do not have a complete digestive system because they absorb material directly from host

Respiration, Circulation, and Excretion 1. Thin bodies allow for materials to diffuse (respiration, excretion, etc) 2. Flame Cell – specialized cells that remove excess water

Ganglia – group of nerve cells that control the body (like a brain) Response Eyespot – group of cells that can detect light (like an eye)

Movement Flatworms move in 2 ways 1.Cilia helps them glide through the water 2.Muscle cells help them twist and turn

Reproduction Sexual Reproduction – most flatworms are hermaphrodites (have both male and female sex organs) Asexual Reproduction by fission – flatworms can split in two and regenerate

Groups of Flatworms CLASS TURBELLARIA - free living flatworms - live in fresh or marine water - ex. Planarian

Dugesia lives in freshwater, mostly a scavenger but can also feed on protists

Planarians are hermaphrodites They can also regenerate body parts and will sometimes split in half to reproduce (FISSION)

ANATOMY OF A PLANARIAN

Brain (ganglia) - planarian can process information about their environment Pharynx - used for suckling food in (the mouth is at the end of the pharynx) Eyespot - simple eye, can detect light Flame cells - located along the lateral edges, used for excretion Intestine - digestion (does not have an anus)

● Class Trematoda = parasitic flatworms ● a.k.a “flukes” live in mouth, skin, or gills of host Primary host = the host in which a parasite reproduces sexually Intermediate host = the host in which asexual reproduction occurs

Schistosoma mansoni - multiple host: Primary host = human Intermediate host = snail Causes Schistosomiasis -in humans; decays lungs liver, spleen, or intestines, occurs in tropical areas with poor sanitation/sewage.

Class Cestoda =tapeworms Long, flat, parasitic Live in intestines

Scolex = a structure that contains suckers and/or hooks Proglottids = body segments of the tapeworm

Each mature proglottid is a hermaphrodite Testes produce sperm, fertilize the eggs to produce a zygote Zygotes are passed out through the feces.

Sometimes, a dormant, protective cyst is formed in the intermediate host muscles ****This is why you should never eat incompletely cooked meat.

Tapeworm Symptoms: Weight loss Abdominal pain Nausea/Diarrhea Weakness Hunger OR Loss of appetite Fatigue Vitamin and mineral deficiencies In extreme cases, tapeworms can block intestines or travel to heart, eyes, liver, or brain. Rarely, no symptoms will be obvious but parts of the worm (or eggs) may be detected in feces.