Chordates

chapter 23

chordata characteristics

dorsal tubular cord, notochord, pharyngeal pouches/slits, endostyle, postanal tail

Notochord

Always found at some embryonic stage. replaced by vertibrate in most jawed vertibrates

Dorsal tubular nerve chord

Pharyngeal Pouches/ Slits

lead from pharyngeal cavity to outside

pharangeal cavity

tetrapods

pharyngeal pouches form tonsils, middle ear cavity

protochordate

marine-dwelling group of invertebrate chordates that act as a bridge between invertebrates and vertebrates

perforated pharynx filters food. led to evolution of internal gills in fish.

chordata subphylums

Vertebrata (vertebrates),

Tunicata or Urochordata (tunicates), and

Cephalochordata (lancelets).

endostyle

secretes mucus around pharynx, trapping food. a ventral, glandular, and ciliated groove in the pharynx of non-vertebrate chordates (like amphioxus and tunicates) and larval lampreys.

thyroid glad

a butterfly-shaped endocrine organ located in the lower front neck, just below the Adam's apple. It produces hormones (T3 and T4) that control metabolism, heart rate, temperature, and energy levels.

postanal tail

provides swimming ability for larval tunicates and lanceletes

coccyx

tail bone

subphylum tunicata

occur throughout oceans, most sessile as adults, have a tunic- outer covering/ test that contains cellulose. usually only larvae have all chordate hallmarks

tunicata class ascidiacea

sea squirts. most sessile as adult. colonial, solitary, or compound

sea squit structure

mantle/membrane that lines tunic. incurrent siphon leads to pharynx(with cilia and perforations) mucous net from endostyle spreads over pharnyx to trap food particles.

tunicata class thaliacea

salps. pelagic. solitary or colonial chains. many have bioluminescent.

tunicata class appendicularia

pelagic, resemble larval stages of other tunicates. to feed, they use a “house” of mucous with filters and water channels. new house every 4 hours when filters get clogged.

subphylum cephalochordata

lancelets. slender flattened body laterally. live in coastal sandy waters.

atriopore

an external, ventral opening in cephalochordates (such as lancelets/amphioxus) that serves as an exit for water used in feeding and respiration, as well as for the discharge of metabolic and reproductive products.

hepatic cecum

subphylum vertebrata

larger, more active than protochordates. modified skeletal structures and muscles.

vertebrata exoskeleton changes

endoskeleton

vertebrata muscle changes

myomeres / muscle segments have a folded shape. more control. fin rays.

lateral line receptor

557 × 372

detect water vibrations

electroreceptors.

detect electrical currents

ammocoete larvae

lamprey larvae, blind, worm-like, filter-feeding larval stage of lampreys that live burrowed in freshwater stream sediments for 3 to 7 years

Ammocoete features.