Gen. Zoology unit 2

worms and mollusks

acoelomate

not true gut cavity

general Platyhelminthes features

flatworms, bilateral symmetry, sense organs, nerve control centers, dorso-ventrally flattened, triplopblastic

Dugesia- planarian

mucous sheath, muscle fibers, carnivorous (crustations, insects, rotifers, nematodes), can entangle prey in mucous, osmoregulatory system, ventral pair of nerve chords,

pharynx

flatworm mouth

ganglion cell mass

planarian brain

ocelli

light sensitive eyespots

chemoreceptors

tactile cells all over body that can sense chemicals

auricles

found on side of planarian head, detect water current and equilibrium

planarian reproduction

Asexual Repro.- fission and regenerating

Sex. Repro.- develop female and male parts, cross fertilize, cocoon zygote, emerge as tiny adults

Liver Fluke

leaf-like, adults are parasitic of vertebrates, eastern Asia, have oral and ventral sucker, monoecious, cross fertilization common, heavy infestation can cause liver cirrosis and death

planarian (Dugesia) life cycle

eggs are shed in water, live in snails, bore into fish and encyst, mammals ingest raw fish and cyst dissolves to infect

blood fluke (schistosoma)

Africa, Middle and Far East, West Indies. males are broader and heavier, infect small or large intestine along with bladder, females live inside groove in male. dioecious

Blood fluke life cycle

eggs discharged in feces/urine, hatch in water, burrow into snail, leave snail, burrow into human skin and travel to intestine/bladder through circulatory system