The World of Worms

By: Brianna Collins

Platyhelminthes (Flatworms)


  • Free-living and parasitic unsegmented worms that are flattened
  • Acoelomoate, bilaterally symmetrical Spiral cleavage
  • Cephalization
  • Organ/organ system level of organization
  • Hermaphroditic; complex reproductive system
  • Body having 3 layers of tissues with organs and organelles.

Free-living Platyhelminthes


  • Planarians- Live fresh water and are sometimes seen in large masses, mostly a scavenger, also feeds on protists, hermaphrodites, has a simple brain and nervous system, plus 2 eyespots, acoelomoate, digestive system, and they can regenerate.
  • Turbellaria- Live in fresh water, flattened dorsoventrally, bilaterally symmetrical, unsegmented, digestive system, diffusion, and are acoelomates.

Parasitic Platyhelminthes

  • Trematoda (Flukes) - Symmetrical body of a fluke is covered with a noncellular cuticle, flattened, some are stout and circular in cross section, muscular suckers on the ventral surface, hooks, and spines are used for attachment, no circulartory system, hermaphroditic, incomplete digestive system, acoelomoate, and they live in more then one host during their life cycle
  • Cestoda (Tapeworm) - Endoparasitic, body is covered by tegument, anterior end is a scolex, no true body segments, reproductive structures called proglottids hermaphroditic, acoelomoate, lives in the intestine of their host, and each proglottid produces hundreds of eggs

Nematoda (Roundworms)

  • Bilaterally symmetrical bodies containing fluid
  • Internal organs and serves as a sponge area for eggs and sperm
  • It supports the body and provides a structure against, muscles contract
  • Pseudocoelomate
  • Digestive tract
  • Have a cuticle
  • Live on land, salt water, and fresh water

Free- living Nemotodes

  • Vinegar eels- feed on the microscopic culture within the vinegar, moves with a whip-like motion, male vinegar eels produce sperm, female vinegar eels produce eggs, live in oceans and lakes that are acidic, live an average of 10 month, pseudocoelomate
  • like a wide range of temperature from 60 to 90 degrees, eat rotten apples, and live in vinegar that is not pasteurized

Parasitic Nemtodes

  • Ascaris - Bilaterally symmetrical, pseudocoelomate, has a cuticle, obtains oxygen and food from host, has male and female digestive properties, affects humans and causes disease, lives in the intestines of pigs, horses, and humans, the eggs escape the hosts body in feces, they can remain in soil for years, when some one eats contaminated food it enters another host, larvae in intestines, the roundworm floats to the blood stream and ends up in the throat and lungs
  • Trichinella- Bilateral symmetry, pseudocoelomate, has a cuticle, gets food and oxygen from their host, infects humans and mammals, live in the wall of their hosts intestine, produces larvae that travels through the bloodstream to the muscles, they form cysts, people become infected from undercooked food
  • Hookworm- Some species exhibit free-living life styles, but most are endoparasites, these worms are characterized by their bent mouths, the anterior ends being bent dorsally, a well-developed buccal capsule, unsegmented, complex cuticle without cilia, intermal fertilization, 1cm to 8m in length, no circulatory system, pseudocoelomate

Phylum Annelida (Earthworm)

  • Bilaterally Symmetrical
  • Coelomate body plan
  • 3 tissue layers
  • Protostomes
  • Body divided into segments
  • Phylum name from "annulus" (Latin) for ring, "eidos" (Greek) for like

Free-living Annelida

  • Oligochaeta- Terrestrial and freshwater, live below soil surface to about 6ft, noturnal, digest organic material in soil, eaten by birds, coelomate, closed circulartory system, eat their weight in soil everyday, true coelom, moves w/ muscles and setae, hermaphroditic, segmented body, specialization in structure of reproductive system
  • Polychaeta- Metamerically segmented, bilateral symmetry, coelomate, chitinous setae called parapodia, closed circulatory system, complete digestive system, respiration through skin, gills or parapodia, hermaphroditic, asexual reproduction in some by budding, marine; some in fresh or brackish water, circular and longitudinal muscle layers enclosing a body coelom

Parasitic Annelida


  • Hirudinea (Leeches)- flattened bodies with suckers, ectoparasites, coelomate, freshwater annelids, some live in the ocean and some in moist soil or vegetation, predators on small invertebrates; most swallow their prey whole, but some suck the soft parts from their victims,suck the body fluids of their victims without killing them, hermaphrodites, and have a citeullm