Respiration
Jawless Fishes
 Gills - pore-like openings
 7 pairs of gill pouches in lamprey
 5-15 pairs of gill pouches in hagfish, but varying
numbers of openings (as few as one/side)
Hagfish gills
 Gill pouches connect directly to pharynx
 Two gills in each pouch
 May or may not open directly to outside (depending
on species)
 May play role in digestion/nutrient absorption
Lampreys
 Problems with respiration during feeding - no
water via pharynx
 Developed separate canal to carry respiratory
water - from pore on head to gill pouches
Lamprey gills
 Two gills per pouch
 Each pouch has separate exit pore to outside
Gills in Chondricthyes and
Osteichthyes
 Gill filaments attached to posterior sides of
bony or cartilaginous gill arches
 Gill rakers located on anterior sides of arches
Class Chondrichthyes
 Gills (pairs of them) located in separate chambers
leading from pharynx
 Chambers separated by septa (tissues) gills are
septate
 Each has separate gill slit to outside
Skates and rays
 Skates and rays have ventral gill slits
Skates and rays
 Spiracle behind each eye - better developed in skates
and rays than in sharks
 Likely a modified gill slit
 Used to take in respiratory water in benthic skates
and rays
Osteichthyes gills
 Respiration via 4
pairs of gills
 No individual
openings to outside
 Gills on each side
covered by single,
flap-like operculum
Branchiostegal rays
 Associated with
operculum
 Allow for expanding
volume of mouth,
pharynx chambers
while keeping
opercula closed
 Accordian-like action
Osteichthyes gills
 Each gill is actually a
pair of rows of
filaments each
attached to the
same gill arch
 Gills not separated
by septa - aseptate
Aseptate gills
Gill Structure
Gill fine structure
 Filaments are not simple finger-like tissues
 Each filament comprised of stacked plates or lamellae
 Greatly increases surface area for interaction with
water flowing across gills (water flows between
lamellae)
Dual Respiratory Systems
 Some fish have dual
respiratory systems
 Gills and lungs
Gills and lungs
 Gills are main respiratory organs
 Lungs serve as back-up system when gills no
longer capable of providing gas exchange
Lungs
Lungs
 Pouches branch off esophagus
 Breathe air at surface or when they remain
out of water
Paired lungs in lungfish
Lungfish lung - left
Lungfish lung
 Lungs are mostly
simple sacs with
network of arteries,
veins
 Only the most intricate
have beginnings of
internal
compartmentalization
Lungs
 Paired lungs
necessary because
of alternating wet
and dry periods
 Become main
respiratory organ
when gills become
useless
Lungs in many fish
 Lungs are present in
many of the more
primitive fishes
 Lungfish, bichir,
gars, bowfin
relatives, sturgeons
 All have varying
connections with
esophagus
Swim Bladder
 Swim bladder probably arose from paired
lungs of primitive fish
 Lungs were present before swim bladder
Other respiratory organs
 Mudskippers and European eels can derive
significant amounts (10-90%) of oxygen via
cutaneous respiration
Other respiratory organs
 Walking catfishes (Clariidae) use
suprabranchial arborescent organs to respire
during their “walks”
 Bush-like extensions from gills that do not
collapse when out of water
Other respiratory organs
 Mudskippers have folded and highly
vascularized interior walls of opercula/gill
chambers, diverticula in mouth and
pharyngeal cavities (snakeheads also have
the latter)
Other respiratory organs
 Armored catfishes
(Loricariidae) use
thin-walled stomach
for respiration
 Loaches (Cobitidae)
use middle/posterior
portions of digestive
tract