Marine Fishes
Class Osteichthyes – Bony fishes; the most prominent group of vertebrates, they
include about 24,000 species.
In addition to having a
bony skeleton,
there are some other
major differences
between bony and
cartilaginous fishes.
Marine Fishes
Bony and cartilaginous fishes also have very different strategies for maintaining their
position within the water column.
Most bony fishes use a swim bladder for lift, whereas most sharks rely on the
swimming generated lift that is a function of the fluid dynamics of their fins and tail.
Both groups do however use bands of muscle called myomeres to generate the basic
undulating motions of the body.
There are many exceptions though…
Marine Fishes
There is however great variation
to the basic themes of movement,
as well as the body shapes that
are best adapted to different
environments and different
swimming habits…
Marine Fishes - Coloration
The color of bony fishes is typically found in special cells in the skin called
chromatophores.
Different chromatophores, each with varying amounts of pigments, can dictate
the basic color pattern of the different fishes.
Many fishes can even change their coloration based on their environmental
conditions (for predation, avoidance of predation, and communication with
others of the same species).
Examples of general fish coloration patterns:
Warning coloration
Cryptic coloration
Disruptive coloration
Countershading
Marine Fishes – Circulatory System
The circulatory system of all fishes are based on a two-chambered hearts that pump
blood to the gills, from where the oxygenated blood is carried to the body
through arteries and capillaries, before returning to the heart through the
veins.
Marine Fishes – Circulatory System
The mechanism for irrigating the gills is different for bony and cartilaginous fishes.
Cartilaginous fishes:
Bony fishes:
Spiracles
Marine Fishes – Circulatory System
Gas exchange occurs in the gills,
where a counter-current flowing
blood/water system allows for
very efficient oxygenation of the
blood…
Marine Fishes – Reproductive System
A few species of fishes are hermaphroditic, but most have separate sexes… Sexes
are not always definitive though, with many species exhibiting sex reversal.
What are the advantages of each of these strategies?
Depending on the species of the fishes, they all have a wide range of behaviors
associated with mating. Also, different species exhibit internal versus external
fertilization; and, oviparity, viviparity, and ovoviviparity strategies are
all utilized…
What may be the advantages and disadvantages of each?
Broadcast Spawning
Coelacanth Evolution
Scales: 4 types (fig. 8.8)
• 1. Ganoid: Bony scales found in oldest known
species including sturgeon.
• 2. Cycloid: Simple thin disc lik escales with smooth
surface which have circular rings to determine
growth.
• 3. Ctenoid: same as cycloid, but have been found in
most advanced teleosts which have posterior spikes
from scales. Perch
• 4. Cosmoid: Similar to placoid scales and probably
evolved from the fusion of placoid scales.
Ganoid
• Ganoid scales of the Florida Gar,
Lepisosteus platyrhincus. Photo:
C. Bento © Australian Museum
Ctenoid & Cycloid Scales
Sturgeon
Cycloid
• Cycloid scales of Jungle Perch, Kuhlia rupestris.
Photo: C. Bento © Australian Museum
Cycloid
Rainbow Trout on lower left
Ctenoid
• Dried scale of a Barramundi
showing the growth rings,
or annuli
• Ctenoid scales of the
Paradise Fish, Macropodus
opercularis. Photo: S.
Lindsay © Australian
Museum
Ctenoid Scales
Sole & Sea Perch
Cosmoid
• Cosmoid scales of the
Queensland Lungfish.
Photo: C. Bento ©
Australian Museum
Red muscles
• Game fish have large amounts of red muscles which
contain more blood vessels = more energy and O2.
• Red muscles produce greater heat energy b/c
separate smaller blood vessels carry oxygenated
blood to muscles and not dorsal aorta. The blood
vessels are close to the veins which are 10 degrees
warmer, thus heating the blood, producing more
power.
Red Muscle - Myomeres
Cryptic coloration (fig 8.10a)
• a pattern of
pigmentation that
allows an organism to
blend into the
background of its
preferred habitat.
Disruptive Coloration(fig.8.28, 14.30)
• Color stripes, bars, or
spots
Warning Coloration(fig.8.10c)
• Dangerous, poisonous,
or taste bad
Countershading
• Dark top, light bottom
Symbiotic Relationships
1.Several species of small
bony fishes, such as the
cleaner wrasse
(Labroides dimidiatus),
are "cleaners" that eat
debris and parasites
from the skin and scales
of larger fishes.
Symbiotic Relationships
2.Remoras (family Echeneidae)
commonly attach
themselves to sharks or
other large fishes, whales,
and sea turtles using a
modified dorsal fin. They
eat scraps left over from the
meals of their hosts. They
may eat parasites as well.
Symbiotic Relationships
3.Some bony fishes have
symbiotic relationships with
nonfish species.
Clownfishes (family
Pomacentridae) live
unharmed among the
venomous tentacles of sea
anemones, which protect
the clownfish from potential
predators
Commensalism
• a situation in which two
organisms are associated in
a relationship in which one
benefits from the
relationship and the other is
not affected much. The two
animals are called
commensals.
• The word derives from the
Latin com mensa, meaning
sharing a table.
• + and 0 = Commensalism.
Mutualism
• + and + = Mutualism. Both species benefit by
the interaction between the two species.
• Examples???
• Cleaner Shrimp Video
Parasitism
• When one organism, usually physically smaller
of the two (the parasite) benefits and the
other (the host) is harmed.
• + and - = One species benefits from the
interaction and the other is adversely
affected. Examples are predation, parasitism,
and disease.
• Examples???
Basic classification of
vertebrates and fishes:
By the way:
Fish – single individual or
more than one individual
of the same species.
Fishes – more than one kind
of fish.