Phylum Hemichordata - Dr. Moran PDF

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Dr. Moran...

Description

Class Enteropneusta: ● “Acorn worm” ● Large, solitary, mobile Class Pterobranchia: ● Pterobranchs - “sea angels” ● Small ● Colonial ● Sessile Phylum Hemichordata: ● 90 species ● All marine ● Suspension and deposit feeders ● Hydrostatic skeleton ● Open circulation with a heart-kidney ● Stomochord (diverticulum of the foregut) ● Dorsal and ventral nerve cords ● Perforated pharynx (gills) ● Separate sexes - indirect development ● Dipleurula larva called a tornaria Phylum Hemichordata: ● Cleavage pattern - radial ● Body cavity - coelom (mouth second) ● Coelom formation - enterocoely (or other) ● Skeleton - hydrostatic ● Circulation - open ● Respiratory - pharyngeal gills ● Excretory - heart kidney ● Asexual reproduction - budding ● Sexual reproduction - separate sexes ● Development - indirect ● Lifestyle - solitary or colonial Class Enteropneusta (acorn worms): ● 70 species ● Solitary ● Live in U-shaped burrows ● Deposit feeders - secret mucus to feed with proboscis to capture particles ● Mucus moved to mouth by cilia on proboscis ● Proboscis also used for burrowing

Class Enteropneusta: ● Trimeric body ● Protostome - anterior pre-oral region; protocoel ● Mesosome - mouth-bearing region with mesocoel ● Metasome - gut and gonad region with metacoel

Cross - section

Excretion (heart-kidney): ● Metanephridial excretory system ● Located in protocoel ● Folded heart wall - glomerulus ● Glomerulus contains podocytes ● Ultrafiltration at podocytes ● Large cells retained - hemocytes ● Waste molecules passed into coelom ● Coelomic waste removed by a pair of ducts Respiration (pharyngeal gills): ● Water enters mouth and exits by gill slits ● As water exits gills, it exchanges gases with the adjacent blood vessels

Feeding: ● Water and food passes through proboscis ● Food sticks to mucus net ● Mucus is moved to mouth by cilia ● Mucus goes down intestine ● Water exits by gill slits Enteropneusta: ● Tornaria larva ● Specialized dipleurula larva ● Ciliary bands for feeding on plankton (planktotrophic)

Class Pterobranchia (pterobranchs): ● 10 species ● Colonial ● Tubes connected by stolons ● Proboscis modified into two or more arms covered in tentacles ● Secretes mucus to capture food ● Mucus pulled into pharynx by water ● Water exits through gill slits ● U-shaped gut with mouth and anus outside of tentacles

Hemichordata Phylogenetic Tree...