Marine FishesClass 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 theirposition within the water column.

Most bony fishes use a swim bladder for lift, whereas most sharks rely on theswimming 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 basicundulating motions of the body.

There are many exceptions though…

Marine Fishes

There is however great variationto the basic themes of movement,as well as the body shapes thatare best adapted to differentenvironments and differentswimming 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 dictatethe 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 pumpblood to the gills, from where the oxygenated blood is carried to the bodythrough arteries and capillaries, before returning to the heart through theveins.

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 theblood…

Marine Fishes – Reproductive System

A few species of fishes are hermaphroditic, but most have separate sexes… Sexesare 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 externalfertilization; and, oviparity, viviparity, and ovoviviparity strategies areall 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

CycloidRainbow 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 ScalesSole & 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 ofvertebrates and fishes:

By the way: Fish – single individual or more than one individual of the same species. Fishes – more than one kind of fish.