BIOL 422 — Lab (Section 2)

invert and vert chordates
subphyla
tunicate/sea squirt
insiphon, pharyngeal basket, filter feeding and excurrent siphon

subph cephalochordata
lancelet
vert subph
jawless fish
lamprey larva

5 sdc

• all present through development stages
• hollow (tubular) dorsal nerve chord; prominent, easy to spot; structurally complex in vertebrates and has more developed brain vs. anterior sectioning of inverts; brain and spinal chord on vertebrates, straight cord on invert
  • landmark
• notochord; directly underneath nerve chord; flexible rod-like structure direct ventral to nerve chord, likely touching it; used for motility/muscle attachment
  • vertebrate modification → vertebral column; not bones, but the intervertebral disks
• pharyngeal gill slits/clefts
  • pharyngeal basket: large pharyngeal region with openings; high surface area, gas exchange and filter feeding
  • gill bars where slits slot between
  • embryonic development in many vertebrates who do not have them now
  • region multidevelops: ears, jawbones, tonsils, thymus gland
• post-anal tail: extension beyond the anus
• endostyle *
  • ventralmost side of pharyngeal basket
  • gland that secretes mucus
  • mucus coats gill bars and gels, making food particles stick to gills during filter feeding
  • u-shaped gland, slightly larger than gill bars
  • vertebrate modification: thyroid gland in neck
    3 subphyla
• cephalochordata:
  • lancelets
  • notably different regions; comparable to planaria platyhelminth dissections
  • caecum modification: hepatic caecum: homologous to liver: runs across pharyngeal basket; darker region
    • atrium chamber, atriocore
• urochordata
  • tunicates
  • large middle focal pharyngeal basket; literal basket
  • excurrent incurrent siphons
  • sessile in adulthood, motile larvae
  • 5 minute metamorphosis, torsion, retraction
  • solitary or colonial
• vertebrata
  • ammocoetes (lamprey)
    • larva