ROUNDWORMS WHAT IS A ROUNDWORM MEMBERS OF PHYLUM

ROUNDWORMS

WHAT IS A ROUNDWORM? • MEMBERS OF PHYLUM NEMATODA • SLENDER, UNSEGMENTED WORMS WITH TAPERED ENDS. • MOST ARE FREE-LIVING – FOUND IN SOIL, SALT FLATS, AQUATIC SEDIMENTS, AND WATER. OTHERS ARE PARASITIC. • HAVE A BODY CAVITY PARTIALLY LINED WITH MESODERM – CALLED A PSEUDOCOELOM (PSEUDO MEANS FAKE). • HAS A COMPLETE DIGESTIVE TRACT (2 OPENINGS) – A MOUTH AND ANUS

FEEDING • FREE-LIVING ROUNDWORMS ARE PREDATORS THAT EAT OTHER SMALL ANIMALS. THERE A FEW THAT EAT ALGAE, FUNGI, OR DECAYING ORGANIC MATTER.

RESPIRATION, CIRCULATION, EXCRETION, RESPONSE, MOVEMENT, AND REPRODUCTION • IN MOST OF THESE ROUNDWORMS ARE SIMILAR TO FLATWORMS. • MOVEMENT IS A LITTLE DIFFERENCE BECAUSE THEY HAVE A HYDROSTATIC SKELETON THEY THRASH AROUND.

ROUNDWORM AND HUMAN DISEASE • TRICHINOSIS-CAUSING WORMS – THIS IS CAUSED BY THE ROUNDWORM TRICHINELLA. LIVE IN THE INTESTINES OF THE HOST. THE LARVAE WILL BURROW INTO ORGANS AND TISSUES AND THAT CAN BE VERY PAINFUL. • TWO COMMON HOSTS ARE RATS AND PIGS. HUMANS CAN GET TRICHINOSIS BY EATING RAW OR INCOMPLETELY COOKED PORK.

• FILARIAL WORMS – FOUND MOSTLY IN THE TROPICAL REGIONS OF ASIA. THESE WORMS LIVE IN THE BLOOD AND LYMPH VESSELS OF BIRDS AND MAMMALS. THEY ARE TRANSMITTED THROUGH INSECT BITES. • THE MAIN THING THEY CAUSE IS ELEPHANTIASIS WHERE PART OF THE BODY SWELLS ENORMOUSLY.

• ASCARID WORMS - CAUSES MALNUTRITION IN MORE THAN 1 BILLION PEOPLE. IT ABSORBS FOOD FROM THE HOST’S SMALL INTESTINE. SPREAD BY EATING VEGGIES THAT ARE NOT PROPERLY WASHED. • THEY LIVE IN THE INTESTINES BUT GET CARRIED TO THE LUNGS.

• HOOKWORMS – ARE FOUND IN THE SOIL. THEY CAN BURROW INTO FEET AND ENTER THE BLOODSTREAM. THEY TRAVEL THROUGH THE BLOOD INTO THE LUNGS AND INTESTINES. THEY SUCK THE HOST’S BLOOD AND CAUSE WEAKNESS AND POOR GROWTH.

C. ELEGANS • C. ELEGANS IS A FREE-LIVING ROUNDWORM. IT IS USEFUL IN SCIENCE BECAUSE OF IT’S DNA. IT HAD DNA THAT WAS THE FIRST TO BE COMPLETELY SEQUENCED. • SCIENTISTS HAVE LEARNED A LOT ABOUT HOW GENES WORK AND CELL DIFFERENTIATION FROM STUDYING C. ELEGANS.