Chapter 21: Chordata

chordate characteristics

notochord, dorsal hollow nerve cord, pharyngeal gill slits, post anal tail, endostyle

flexible rod for structural support

notochord

notochord becomes _____ in vertebrates

spinal column

enlarged to form a brain

dorsal hollow nerve cord

invertebrate nerve cord

ventral solid

dorsal hollow nerve cord origin

ectodermal ridge

pharyngeal slits evolve into

glands, jaws, ears

post anal tail added to body after

digestive tract

endostyle evolution

protein secreting for filter feeding → hormone secreting for thyroid

which characteristic do all chordates have at one point in their lifetime

endostyle

subphylum urochordata common name

tunicates/sea squirts

subphylum urochordata species count

1600

subphylum urochordata tough tunic made of

cellulose

larva possess all chordate characteristics

subphylum urochordata

subphylum urochordata adults lose ____ during metamorphosis

tail, notochord, nerve cord

classes of subphylum urochordata

ascidiacea, appendicularia, thaliacea

can be solitary, colonial, or compound

subphylum urochordata

subphylum urochordata mantle

inner membrane

subphylum urochordata two siphons

internal/oral and excurrent/atrial

subphylum urochordata water flow

oral siphon → ciliated pharynx → atrial cavity → atrial siphon

subphylum urochordata heart

ventral

subphylum urochordata blood flow

tidal (one way then reverse)

subphylum urochordata high proportion of

vanadium and niobium

subphylum cephalochordata common name

lancelets/amphioxus

subphylum cephalochordata roots

amphi (both ends) and oxys (sharp)

subphylum cephalochordata species count

30

retain chordate characteristics throughout life

subphylum cephalochordata

subphylum cephalochordata digestive system flow

endostyle → hepatic cecum → atriopore

subphylum cephalochordata circulatory system

closed; peristaltic pumping, no heart, no gills (gas exchange through body)

subphylum cephalochordata musculature

segmented trunk muscles like vertebrates

subphylum vertebrate/craniata key additions

brain in skull, vertebral column, ductless glands, tripartite brain

subphylum vertebrate/craniata interment

epidermis and dermis

subphylum vertebrate/craniata keratinized structures

hair, claws, feathers, horns

subphylum vertebrate/craniata endoskeleton allows for

unlimited body size

subphylum vertebrate/craniata muscles

w-shaped myomeres

subphylum vertebrate/craniata digestive tract

muscular to pump water

subphylum vertebrate/craniata circulatory/excretory system

closed and complex

subphylum vertebrate/craniata nervous system

enlarged brain (forebrain, midbrain, hindbrain), neural crest, ectodermal placodes

chordate evolution paths

sessile (urochorates) and free swimming (cephalochordates and vertebrates)

ancestral vertebrates

fish like with chordate characteristics

ancestral vertebrate example (not a true vertebrate)

haikouella

haikouella lack

skull, ear, anterior brain

ancestral chordates

free swimming and similar to amphioxus

urochordates or cephalochordates more closely related to vertebrates

urochordates

agnathan classification

paraphyletic

gnathostome classification

monophyletic

gnathostomes jaws are modifications of

first and second gill arches

gnathostomes evidence for modified jaws

arches are in similar positions; derived from neural crest cells

gnathostomes fins/appendages derived from

fins

class myxini common name

hagfish

class myxini species count

70

skull but no vertebrate, secretes slime, eel-like

class myxini

class myxini lifestyle

scavengers; eat carrion

tie in knots for leverage

class myxini

class petromyzontida common name

lampreys

class petromyzontida species count

40

no jaws; funnel shaped sucking mouth

class petromyzontida

class petromyzontida lifestyle

scavenger or parasitic

class petromyzontida habitat

temperate (larva cannot stand high temps)

anadromous species

class petromyzontida

invasive sea lamprey flow

north atlantic/lake ontario/new england → lake erie → great lakes

class chondrichthyes species count

1000

50 species, split off from sharks 400 mya, deep-sea, carnivorous

holocephali (ratfish)

550 species, wing-like pectorals fused to head, diverse reproduction, venomous barbed spines

batoidea (rays)

500 species, 5-7 gill slits, pectoral fins not fused to head, apex predators

selachii (sharks)

selachii earliest fossils

420 mya in ordovician

modern selachii

100 mya in cretaceous

devonian, 2 meters, predatory

cladoselache

2-28 mya, 14–18 meters (60 ft)

carcharodon megalodon

resemble rays (angel sharks, wobbegongs)

bottom dwellers

huge (basking sharks, whale sharks)

filter feeders

sleeper sharks, goblin sharks, cookiecutter sharks

odd predators/scavengers

requiem, mackerel, hammerhead sharks

apex predators

hammerhead cephalofoil

electroreception, lateral vision, eye protection

45 mph, second fastest fish

mako sharks

largest bulk-feeding predators; 20 feet

white and tiger sharks

largest rod and reel caught fish (3500 lbs)

white shark

actinopytergii classification

monophyletic

actinopytergii species count

30,000

actinopytergii lepidotrichia

fin rays

actinopytergii fossil record

silurian
420 mya

actinoptyergii groups

chondrostei (primitive/polyphyletic) and neopterygii (modern fish/monophyletic)

sturgeon, paddlefish, bichirs

chondrostei

chondrostei species count

50

chondrostei lack

scales

cartilaginous skeleton and shark-like jaw

chondrostei

african reedfish, 12 species, sister group to all other ray-finned fish

bichirs

texas native (protected), filter feeders, electroreceptive paddles

paddlefish

~25 species, holarctic distribution, up to 5m long, endangered

sturgeon

neopterygii groups

holostei, gar, teleosts

holostei include

gar and bowfin

mix of chondrichthyan, chondrostei, and teleost features

holostei

gar species count

7

ganoid scales that interlock, highly predatory

gar

sportfish

alligator gar

teleosts species count

26,000

teleosts fossil record

triassic

parental care, viviparity/one baby at a time

teleosts

sarcoptyergii species count

8

sarcoptyergii groups

actinistia and dipnoi