Ch. 8 Acoelommorpha, Platyzoa, and Mesozoa Flatworms Gastrotrichs Gnathiferans Mesozoa

Phylum Acoelomorpha (“without hollow form”) Clade Platyzoa (lophotrochozoans) Phylum Platyhelminthes (“flat worm”) Phylum Gastrotricha (“hairy belly”) Clade Gnathifera (“jaw bearing”) Phylum Gnathostomulida (“jaw mouth”) Phylum Micrognathozoa(“small jawed animal”) Phylum Rotifera (“wheel bearing”) Phylum Acanthocephala (“spine head”) Phylum Mesozoa (“middle animal”)

(“without hollow form”) Ph. Acoelomorpha (“without hollow form”) most are free living incomplete gut no ganglia hermaphroditic no circulatory, respiratory, excretory system

 organ-system level of organization Acoelomate Phyla  organ-system level of organization Triploblastic endoderm parenchyma Mesoderm (muscle layer) ectoderm bilateral cephalized

Ph. Platyhelminthes (“flat worm”) Class Turbellaria (planarians) Class Trematoda (digenetic flukes) Class Monogenea (monogenetic flukes) Class Cestoda (tapeworms) parasitic or free living incomplete gut flame cells hermaphroditic no circulatory system

Digestive, Nervous, Reproductive, and Excretory Systems protonephridia

Ladder-like Nerve Cord Nervous System Ladder-like Nerve Cord

Class Turbellaria ocelli auricles

pharynx Branched gut

Free Swimming Marine Turbellarians

Class Trematoda Parasitic flukes Structurally similar to the more complex turbularians Adapations for parasitic lifestyle glands attachment structures high reproductive rate

Subclass Digenea complex (indirect) life cycle: first host (intermediate host) = mollusc final host (definitive host) = vertebrate Great diversity in host location digestive tract circulatory system urinary tract reproductive tract

Clonorchis Life Cycle

Schistosoma Life Cycle

Class Cestoda scolex strobila (chain of proglottids) mouth & gut absent reproductive system repeated in each proglottid parasitic complex (indirect) life cycle with 1 or more intermediate hosts

Cestode Life Cycle evaginated cysticercus invaginated cysts in gravid proglottid evaginated cysticercus invaginated cysts in meat shelled larvae (in feces) Cestode Life Cycle small intestine

developing cysticercus

scolex

Phylum Gastrotricha “belly hairs” gastric gland pharynx male gonads ovary intestine pedal gland

Phylum Gnathostomulida “jaw mouth”

Phylum Micrognathozoa “tiny jawed animals”

Phylum Rotifera (“wheel bearers”)

Typical Rotifer Life Cycle environmental stimulus meiosis 2N female 1N egg 1N male 1N egg 2N egg (amictic) 2N egg 1N sperm fertilization environmental stimulus 2N female (amictic) 2N resting egg parthenogenesis sexual reproduction

Phylum Acanthocephala “spine head” proboscis with hooks & spines intestinal parasites

Acanth Reproduction

Phylum Mesozoa “middle animals”