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Subphylum Vertebrata
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3 types of fishes (jawless (agnathan), cartilaginous
(gnathostome), and bony (gnathostome)
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Jawless fishes (Agnatha) - A” = without, “gnath” = jaw;
jawless fishes, i.e. hagfish (Class Myxini) and lamprey
(Class Petromyzontida)
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Class Chondrichthyes – cartilaginous fishes - sharks,
skates, and rays (Subclass Elasmobranchii); chimaeras
(Subclass Holocephali)
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Bony fishes (formerly Class Osteichthyes) - Class
Actinopterygii, ray finned fishes and Class Sarcopterygii,
lobe-finned fishes
Class Myxini – hagfishes (aka slime eels)
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primarily bottom dwellers
within mud in deeper water
scavenge on decaying fish
carcasses
produce large amounts of
mucus
can tie themselves in knots
while feeding
Class Petromyzontida - lampreys
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mainly live in freshwater, but
some migrate to ocean
Some parasitize fish by
attaching to side and sucking
blood
Class Chondrichtyes – sharks, skates, rays
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Sharks
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well adapted for fast swimming and predation
skin is sand paper like; placoid scales
rows of teeth are actually modified scales
Have specialized electrical sensory cells called
ampullae of Lorenzini
The largest shark (also largest fish) is the whale
shark
Check out
www.flmnh.ufl.edu/fish/sharks/ISAF/ISAF.htm
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Figure 8.08a
Figure 8.12a
Male claspers
Shark Reproduction
- all elasmobranchs reproduce via internal fertilization
- fetal development occurs in one of 3 ways; oviparous,
ovoviviparous, or viviparous development
Oviparity
- embryos are contained within an egg case and development
occurs outside the female often for several months
- embryo nourished by yolk within egg
- developed young “hatch” externally fully formed
- all skates and some sharks are oviparous
Ovoviviparity
- eggs are retained within uterus, young are nourished by
yolk within egg
- young hatch within uterus and are “born” live
- most sharks and rays are ovoviviparous
- many species exhibit intrauterine cannibalism; sand tiger
shark embryos eat smaller siblings, others eat
undeveloped eggs
- common ovoviviparous species include nurse, mako,
great white, thresher, whale, and dogfish sharks
Viviparity
- young are retained within uterus and nourished in some way
by a uterine attachment (approaches placental mammals)
- familiar species are hammerhead and bull sharks
Figure 8.04
Class Chondrichthyes – skates and rays
dorsoventrally flattened; most live on bottom
 sting rays have a poison tipped spine at base of tail
 skates do not have a poisonous spine
 electric rays have electric producing organs
 most have molar like teeth for crushing shell fish
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Manta rays and eagle rays “fly” through water using
pectoral fins
Figure 8.06b
Subclass Holocephali – chimaera/ratfish
Bony fish – The Osteichthyes
approx 23,000 species; about 96% of all fish species and half
of all vertebrates
 have rounded and flattened scales; cycloid, ctenoid, ganoid
 an operculum covers gills
 caudal fin usually homocercal
 fins consist of thin, flexible membrane covering bony spines or
fin rays
 have gas filled swim bladder to adjust buoyancy
 myriad shapes and forms adapted to almost every type of
marine habitat
 2 groups; lobe-finned (Class Sarcopterygii) and ray-finned
fishes (Class Actinopterygii)
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Lobe-finned fishes (Sarcopterygii)
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Extant species include lung fishes and coelacanths
Tetrapods evolved from ancestral lineage within this
group
Paired fins are stout and fleshy allowing for weight
bearing movement
Pg. 164
Figure 8.08b
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Swim bladder either
fills through direct link
to esophogus and
“breathes” or bladder is
filled by gas exchange
from blood vessels
4 gill arches contain anterior facing gill rakers and
posterior facing gill filaments with lamellae for gas
exchange for respiration.
Figure 8.16a
Figure 8.16b
Figure 8.19
Lateral line picks up vibration; allows fish to sense
proximity of other fish, structures
Fish Migration
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Some migrations involve daily feeding migrations to and
from feeding areas
The most spectacular ones involve breeding migrations
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Anadromous fishes – live in ocean and migrate to
freshwater rivers to spawn (salmon)
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Catadromous fishes – live in freshwater and migrate to
ocean to spawn (freshwater eels)
Bony Fish Reproduction
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The vast majority reproduce by external
fertilization, and external development
(oviparity)
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A few species fertilize internally with
internal development (ovoviviparity);
guppies, surfperch (book example)