Vertebrate zoology (02 bony fishes, student version)

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Fishes

Vertebrate Zoology
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OSTEICHTHYES – BONY FISH

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OSTEICHTHYES – BONY FISH

Basic vertebrate (Kardong, 2009; p. 82, 300)

+ Bony vertebrae replace the notochord.
+ The notochord may become enclosed in the
centrum, or more usually is lost.
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OSTEICHTHYES – BONY FISH
about 97% of living fishes

- Class Actinopterygii: ray-finned fishes.

- Class Sarcopterygii: lobe-finned fishes.

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CLASS ACTINOPTERYGII
Class Actinopterygii (ak’ti-nop-te-rij’ee-i) (Gr. aktis, ray, pteryx, fin,
wing): ray-finned fishes.
+ Subclass Cladistia (clə-dis’tē-a) (Gr. cladi, branch): bichirs.
+ Subclass Chondrostei (kon-dros’tē-ī) (Gr. chondros, cartilage, osteon,
bone): paddlefishes, sturgeons.
+ Subclass Neopterygii (nee’op-te-rij’ee-i) (Gr. neo, new, pteryx, fin,
wing): gars, bowfi n, teleosts.

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Subclass Cladistia
Primitive ray-finned fishes
+ Have rhombic heavy ganoid scales;
lungs; spiracle present;
+ Dorsal fin consisting of 5 to 18 finlets.
+ About 16 species, freshwater.

Bichir, Polypterus bichir, of equatorial West Africa.
A nocturnal (night active) predator.

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Subclass Chondrostei
Primitive ray-finned fishes
+ Skeleton primarily cartilage; caudal fin
heterocercal; large scutes or tiny ganoid
scales present; spiracle usually present;
+ More fin rays that ray supports
+ 29 species, freshwater and anadromous
(Gr. anadromos, running upward).

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Subclass Neopterygii
+ Skeleton primarily bone; caudal fin usually homocercal; scales cycloid,
ctenoid, absent, or rarely, ganoid.
+ Fin ray number equal to their supports in dorsal and anal fins.
+ About 28,000 species

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Subclass Neopterygii
Early neopterygians (nonteleost neopterygians): Two living genera
+ The bowfin, Amia (Gr. tunalike fish).
Live in shallow, weedy waters of the Great Lakes and Mississippi River
basin.

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Subclass Neopterygii
Early neopterygians (nonteleost neopterygians): Two living genera
+ Gars, Lepisosteus (Gr. lepidos, scale, osteon, bone).
- Live in eastern and southern North America.
- 7 species are large, ambush predators with elongate bodies and
jaws filled with needlelike teeth.

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Subclass Neopterygii
The modern bony fishes: teleosts (Gr. teleos, perfect, osteon, bone)
+ Representing about 96% of all living fishes or about half of all vertebrates
+ Heavy dermal armor of primitive ray-finned fishes was replaced by light,
thin, flexible cycloid and ctenoid scales (some lack scales).
+ Homocercal caudal fin

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Subclass Neopterygii
The modern bony fishes: teleosts (Gr. teleos, perfect, osteon, bone)
+ Teleosts range in size from 7 mm adult minnows to 17 m oarfish and 900
kg, 4.5 m blue marlin.

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Subclass Neopterygii
The modern bony fishes: teleosts (Gr. teleos, perfect, osteon, bone)
+ Occur from elevations up to 5200 m in Tibet to 8000 m below the surface
of the ocean

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Subclass Neopterygii
The modern bony fishes: teleosts (Gr. teleos, perfect, osteon, bone)
+ Some species live in hot springs at 44 0C, while others live under the
Antarctic ice at - 2 0C

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Subclass Neopterygii
The modern bony fishes: teleosts (Gr. teleos, perfect, osteon, bone)
+ may live in lakes with salt concentrations three times that of seawater,
caves of total darkness, swamps devoid of oxygen, or even make extended
excursions onto land (mudskippers)

Almost every
conceivable habitat

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Characteristics of Class Actinopterygii
1. Skeleton with bone of endochondral origin; caudal fin heterocercal
in ancestral forms, usually homocercal in descendant forms; skin with
mucous glands and embedded dermal scales; scales ganoid in
ancestral forms, scales cycloid, ctenoid or absent in derived forms

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Characteristics of Class Actinopterygii
2. Paired and median fins present, supported by long dermal rays
(lepidotrichia); muscles controlling fin movement within body

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Characteristics of Class Actinopterygii
3. Jaws present; teeth usually present with enamaloid covering; olfactory
sacs do not open into mouth; spiral valve present in ancestral forms,
absent in derived forms

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Characteristics of Class Actinopterygii

4. Respiration primarily by gills supported by arches and covered with an
operculum

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Characteristics of Class Actinopterygii
5. Swim bladder often present with or without a duct connecting to
esophagus, usually functioning in buoyancy

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Characteristics of Class Actinopterygii
6. Circulation consisting of a heart with a sinus venosus, an undivided
atrium, and an undivided ventricle; single circulation; typically four
aortic arches; nucleated erythrocytes

Atrium

Ventricle
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Characteristics of Class Actinopterygii
7. Excretory system of paired opisthonephric kidneys; sexes usually
separate; fertilization usually external; larval forms may differ greatly
from adults

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Characteristics of Class Actinopterygii
7. Excretory system of paired opisthonephric kidneys; sexes usually
separate; fertilization usually external; larval forms may differ greatly
from adults
8. Nervous system of a brain with small cerebrum, optic lobes, and
cerebellum; 10 pairs of cranial nerves; three pairs of semicircular
canals

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CLASS SARCOPTERYGII
Class Sarcopterygii (sar-cop-te-rij’ee-i) (Gr. sarkos, flesh, pteryx, fin,
wing): lobe-finned fishes
+ Powerful jaws;
+ Heavy, enameled scales with a dentinelike material called cosmine;
+ Strong, fleshy, paired lobed fins - used to clamber over benthic
substrates filled with woody debris.

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CLASS SARCOPTERYGII
Class Sarcopterygii (sar-cop-te-rij’ee-i) (Gr. sarkos, flesh, pteryx, fin,

wing): lobe-finned fishes

+ Lungfishes: 6 species

+ Coelacanths: Latimeria. 2 species

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Lungfish
+ Neoceratodus (Gr. neos, new, keratos , horn, odes, form), the living
Australian lungfish, may attain a length of 1.5 m
+ Lepidosiren (L. lepidus, pretty, siren, mythical mermaid): South American
lungfish
+ Protopterus (Gr. prōtos, first, pteron, wing): African lungfish

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Coelacanths
The tail is diphycercal but possesses a small lobe between the upper
and lower caudal lobes, producing a three-pronged structure

The last coelacanths were believed to have become extinct 70 million
years ago
The remains of a coelacanth were found on a dredge off the coast of
South Africa in 1938
The new species of coelacanth was found in Sulawesi, Indonesia,
10,000 km from the Comoros in 1998

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Sarcopterygians:
(a) Dipterus, fossil lungfish of the
Devonian. Note the heterocercal tail.
(b) Osteolepis, a rhipidistian of the
Devonian that also had a
heterocercal tail.
(c) Latimeria is a living sarcopterygian
(coelacanthiformes) exhibiting a
diphycercal tail.

(Kardong, 2009; p.101)
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Characteristics of Class Sarcopterygii
1. Skeleton with bone of endochondral origin; caudal fin diphycercal
in living representatives, heterocercal in ancestral forms; skin with
embedded dermal scales with a layer of dentinelike material,
cosmine, in ancestral forms
2. Paired and median fins present; paired fins with a single basal
skeletal element and short dermal rays; muscles that move paired fins
located on appendage

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Characteristics of Class Sarcopterygii

3.

Jaws present; teeth are covered with true enamel and typically are
crushing plates restricted to palate; olfactory sacs paired, may or
may not open into mouth; intestine with spiral valve

4.

Gills supported by bony arches and covered with an operculum

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Characteristics of Class Sarcopterygii
5.

Swim bladder vascularized and used for respiration and buoyancy
(fat-filled in coelacanths)

6.

Circulation consisting of heart with a sinus venosus, two atria, a
partly divided ventricle, and a conus arteriosus; double circulation
with pulmonary and systemic circuits; characteristically five aortic
arches

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Characteristics of Class Sarcopterygii
7.

Nervous system with a cerebrum, a cerebellum, and optic lobes; 10
pairs of cranial nerves; three pairs of semicircular canals

8.

Sexes separate; fertilization external or internal

Kardong, 2009; p. 647
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