Living fishes
 The
living fishes (not a monophyletic
group) include:




the jawless fishes (e.g. lampeys),
cartilaginous fishes (e.g. sharks and rays),
bony, ray-finned fishes (most of the bony
fishes such as trout, perch, pike, carp, etc)
and
the bony, lobe-finned fishes (e.g. lungfishes,
coelacanth).
Figure 24.01
16.1
Figure 24.02
16.2
Bony fishes: Osteichthyes
 The
term osteichthyes does not describe a
monophyletic group, but is a term of
convenience to describe the fishes whose
skeletons are made of bone that replaces
cartilage during embryonic development.
 There
are two classes the Actinopterygii
(the ray-finned fishes) and the
Sarcopterygii (the lobe-finned fishes)
General characteristics of bony fish
 Skeleton
made of bone of endochondral
origin (derived from cartilage).
 Paired and median fins supported by
dermal rays.
 Respiration mainly by gills. Gills covered
with operculum.
 Swim bladder often present.
 Complex nervous, circulatory and
excretory systems present
Class Actinopterygii (ray-finned
fishes)
 This
is by far the larger of the two living
classes of fishes with more than 27,000
species.
 Includes
probably every fish you can think
of. E.g. salmon, cod, herring, tuna, marlin,
pike, sardine, clownfish, goldfish.
Divisions of Actinopterygii
 The Actinopterygii
are divided into two
subclasses


Chondrostei, which includes several relic
species.
Neopterygii, which includes the most derived
and most recent group of ray-finned fishes the
infraclass Teleostei, which includes more
than 20,000 species and a small number of
primitive species including the gars and
bowfins in the infraclass Holostei.
Class
Actinopterygii
Subclass
Chondrostei
[37 species]
Subclass
Neopterygii
Order Acipenseriformes
(paddlefish and sturgeons)
Order Polypteriformes
(bichirs)
Infraclass
Holostei
[8 species]
Order
Lepisosteiformes
(gars)
Order
Amiiformes
(bowfin)
Infraclass
Teleostei
12 superorders
Ancestral ray-finned fishes
 Ancestral
ray finned fishes in the Devonian
were small and heavily armored with

ganoid scales
• Thick, bony, non-overlapping, relatively inflexible
scales.

and heterocercal tails (shaped like that of
modern sharks).
Figure 24.18
Subclass Chondrostei
 A few
relic species still possess such
characteristics. These are grouped in the
sublass Chondrostei.
 The
Chondrostei include sturgeon and
paddlefish which are included order
Acipenseriformes and the bichirs
(Polypteriformes).
Figure 24.19
Subclass Chondrostei
 The
relatively few surviving Chondrostei
are the remnant of what was once a much
more diverse group.
 The
chondrosteans were the first bony
fishes and were most diverse in the
Carboniferous and Permian.
Subclass Chondrostei
 Early
chondrosteans were mostly small <
0.5m with a fusiform shape which
suggests they were active foragers.
 They were covered with small diamondshaped scales.
 The base of each scale was made of
bone, the middle of dentin and the surface
with an enamel-like substance called
ganoine. Hence the name ganoid scales.
Order Acipenseriformes: Sturgeons
and Paddlefish

Modern Acipenseriform fish are almost scaleless except
for in sturgeons, which have a few isolated rows of large
plate-like, boney ganoid scales scales that run along the
sides of the body.

The skeleton is almost entirely cartilaginous, which has
resulted from the loss of mineralization.

Vertebrae are poorly developed and the notochord is
large.

Both groups have distinctive forked heterocercal tails
and both have enlarged rostrums.
Paddlefish

The two species of paddlefish are found in fresh water in
North America and China. The Chinese species known
only from the Yangtze may be extinct.

About 2m long, paddlefish possess a distinctive
elongated flattened rostrum, which is believed to be used
to detect tiny, electric fields.

The North American paddlefish occurs in the Mississippi
River watershed and is one of North America’s largest
freshwater fish (commonly 5 feet and 60lbs, record
official weight is 144lbs).
http://blocs.xtec.cat/englishcornersallaresipla/files/2008/01/paddlefish2.jpg
Paddlefish
 Paddlefish
are filter feeders that sieve
zooplankton from the water using
filaments on their gill rakers.
 The
rostrum’s ability to detect electric
fields is thought to help in finding prey, but
fish with damaged or missing rostrums do
not appear to be handicapped.
Paddlefish
 Previously
paddlefish were abundant in
most central U.S. river systems.
 However,
numbers have declined because
dams have prevented the fish from
reaching their spawning areas and as a
result of poaching for their eggs.
Missouri paddlefish clip
 http://www.youtube.com/watch?v=fysqA0tr
4qo
Sturgeons

Sturgeons have been around and little changed for about
200 million years and are some of the most ancient rayfinned fishes.

There are 24 species of sturgeons, which are native to
subtropical, temperate and sub-Arctic rivers, lakes and
coasts of Eurasia and North America

Sturgeons are very distinctive being very large (up to 6m
in length and 2000kg in weight) with heavy bony scutes
rather than scales and a distinctive flattened rostrum and
barbels.
http://www.fishingmagic.com/news/images/Canada_Record_Sturgeon_lg.jpg
http://fish.dnr.cornell.edu/nyfish/Acipenseridae/shortnose_sturgeon.jpg
Sturgeons

Sturgeons are anadromous, spawning upstream but
feeding in river deltas and estuaries.

Sturgeon are bottom feeders and have a protrusible jaw
(evolved independently of the teleosts) which they use
for suction feeding.

They use their snout to stir up sediment and use their
barbels to detect small invertebrates and fish. They
possess no teeth and so cannot seize prey, but can
swallow quite large fish whole.
Sturgeons
 They
are commercially important for their
meat, but especially their eggs (caviar).
http://cordonnoir.com/images/Caviar_fresh.jpg
Sturgeons
 Sturgeon
are long-lived (some living well
over 100 years) and slow reproducing
(they don’t become sexually mature until
20 or more years of age, which makes
them very vulnerable to fishing pressure.
 Most
species are considered to be at risk
of extinction.
Canadian Lake Sturgeon clip
 http://www.youtube.com/watch?v=aCMNB
qg6fH4
Class
Actinopterygii
Subclass
Chondrostei
[37 species]
Subclass
Neopterygii
Order Acipenseriformes
(paddlefish and sturgeons)
Order Polypteriformes
(bichirs)
Infraclass
Holostei
[8 species]
Order
Lepisosteiformes
(gars)
Order
Amiiformes
(bowfin)
Infraclass
Teleostei
12 superorders
Order Polypteriformes: Bichirs

There are 10-15 species [depends on the authority] of
bichir and they are considered the most primitive
surviving group of the ray-finned fishes.

They are heavily armored with dermal bone and a thick
layer of ganoid scales.

Dorsal fin is distinctive and has independent rays and is
segmented into small “flags” called pinnules.

Generally elongated, eel-like in shape up to 1.2m in
length.
Armored Bichir
http://www.aquarticles.com/images/Gallo/Armoured%20bichir%202.gif
http://www.fbas.co.uk/Bichir.jpg
Order Polypteriformes: Bichirs
 Bichirs
are warm water fish and are found
in swamps and streams in Africa.
 They
hunt at twilight and lie in wait on the
bottom for prey to pass by. They will take
any suitably sized aquatic animal.
Order Polypteriformes: Bichirs

Bichirs have a swim bladder that acts like a paired
ventral lung. They will drown if unable to gulp air at the
surface.

Larvae have external gills very similar to those of
amphibians.

The lungs allow bichirs to survive in low oxygen
environments.

They can also survive buried in silt or outside water
during the dry season.
Order Polypteriformes: Bichirs
 Because
bichirs have paired fleshy
pectoral fins and lungs they were formerly
classified with the lungfishes, but are now
considered to have evolved these traits
independently.
 Bichirs
are a popular aquarium fish
Bichir clip
 http://www.youtube.com/watch?v=SEpqY3
NJIIg
Class
Actinopterygii
Subclass
Chondrostei
[37 species]
Subclass
Neopterygii
Order Acipenseriformes
(paddlefish and sturgeons)
Order Polypteriformes
(bichirs)
Infraclass
Holostei
[8 species]
Order
Lepisosteiformes
(gars)
Order
Amiiformes
(bowfin)
Infraclass
Teleostei
12 superorders
Neopterygii: infraclass Holostei

There are two orders of primitive Neopterygians
grouped together in the infraclass Holostei

Both have more flexible jaws than
chondrosteans, but these are less flexible than
those of more advanced Neopterygians.

These are the seven species of gars
(Lepisosteiformes) and the single species of
bowfin (Amiiformes).
Order Lepisosteiformes: Gars

Gars are medium to large (1-3m) predatory fish with a
distinctive elongated body and long jaws filled with sharp
teeth.

Found now only Central and North America and the
Caribbean gars are last survivors of a once more widely
distributed group that was widespread in the Mesozoic.

They have hard, interlocking, multilayered ganoid scales
which provide excellent protection and are similar to the
scales of many extinct Paleozoic and Mesozic
actinopterygians.
Note heterocercal tail, and dorsal fins are
located close to the tail and long jaws.
http://animals.nationalgeographic.com/staticfiles/NGS/
Shared/StaticFiles/animals/images/primary/gar.jpg
Longnose gar
http://www.biokids.umich.edu/files/12296/gar_large.jpg
Order Lepisosteiformes: Gars

Occur in slow moving water bodies preferring
shallow and weedy areas. They are voracious
predators and feed on a wide range of
vertebrate and invertebrate prey.

Gar are tough hardy freshwater fish that can
survive in stagnant or warm water where oxygen
levels are low.

Vascularized swimbladder functions as lungs (as
in related bowfin).
Order Amiiformes: Bowfin

There is only one species of bowfin still extant,
the only survivor of a group that was previously
more diverse in the Jurassic and Cretaceous.

Bowfins occur throughout eastern North
America, typically in slow moving fresh water.
When oxygen levels are low bowfin will gulp air
from the surface into the heavily vascularized
swimbladder, which can serve as a lung.
Bowfin
http://pond.dnr.cornell.edu/nyfish/Amiidae/bowfin.jpg
Bowfin possess a distinctive long dorsal fin and a black “eyespot.”
Order Amiiformes: Bowfin

Scales are of a single layer of bone as in
teleosts, but the caudal fin is asymmetric and
similar to that of more primitive fishes.

The skull is much more solid and heavily built
than that of teleosts

Bowfin are aggressive predators that feed on a
wide variety of invertebrate and vertebrate prey.
Bowfin skull
http://bio.sunyorange.edu/updated2/THINKING_EVOLUTION/anatomy1a/s_face.htm
Bowfin
http://www.savalli.us/BIO370/Diversity/04.OsteichthyesImages/BowfinL.jpg