What is the taxonomy of fish?

Kingdom: Animalia

Phylum: Chordata

Subphylum: Vertebrata

Classes:

 Class Myxini - Hagfishes (jawless)

Class Cephalaspidomorphi- Lampreys (jawless)

Class Chondrichthyes- Sharks, skates, rays, ratfish

Bony Fishes

Class Actinopterygii- Ray-finned fishes

Class Sarcopterygii- Lobe-finned fishes 

What are the characteristics of fish?

What are the challenges of aquatic habitats? How do fish respond to these challenges?

Challenges of living in the water

1. Temperature control: most fish have the same body temperature as the water they live in.

2. Exchange of ions with environment

   1. In air, not too much loss. When water contacts the gills, the water has a higher concentration of water than the blood. Freshwater fish are constantly peeing.

   2. Saltwater: Concentration of water in seawater is less than in your blood. Lose water through the gills. Drink lots of water and actively excrete the salt.

3. Oxygen derivation: O2 concentration is less in water than in air, so have to pass much more water than you would with air.

4. Movement: Water is very viscous compared to air. Fish are hydrodynamically shaped so can slip through water with least resistance.

   1. 2 types of drag: compression drag (moving water out of the way in front) vs pressure drag (on the sides)

5. Habitat dimensions → live in 3D habitat.   

What are the characteristics of Class Myxini?

Class myxini – Hagfishes (jawless)

•  

  • Mouth is surrounded by barbels, external gill openings and pores that exude slime (from slime pores).

  • Teeth on tongue

  • scavengers.

  • They can tie themselves into knots and then cinch knot against the surface of the corpse (or whatever) to give traction in order to chew through

What are the characteristics of Class Cephalaspidomorphi?

Class Cephalaspidomorphi - Marine lampreys (jawless)

•  

  • Native to eastern seaboard. Also in Gulf by Florida

  • Larval form is in freshwater.

  • Seaway to Great Lakes allowed marine lampreys to spread to them

  • Lifecycle:

    1. Adults spawn in freshwater streams.

    2. Ammocoete larvae buries itself in sediment and filter feeds. Goes through metamorphosis while buried in.

    3. Migrates towards lakes

    4. Parasitic stage in lakes.

  • Attaches to fish with keratinized teeth and suction. Tongue protrudes and rasps flesh (has teeth on tongue)

What are the characteristics of Class Chrondrichthyes?

Species: Sharks, skates, rays, ratfish

•  

  • Paired fins

•  

  • Males have claspers (modified fins for internal fertilization)

  • Thresher sharks have very asymetrical tail fins

  • Eat: some are filter feeders, predators,

What specialized senses do members of Class Chrondrichthyes have?

1.  
   1.  

      1. Lateral line is very complicated and effective.

      2. Has ampullae of Lorenzini: (jelly-filled areas in the face). They detect electrical activity.

How is the digestive system of members of Class Chrondrichthyes made more efficient?

•  

  • increase surface area of digestive tract by making food rotate through intestine like a corkscrew

    • Called the spiral valve (for whole intestine)

How do torpedo rays and others generate electricity?

•  
  •  

    • Cause depolarization of nerve cells on a mass scale, then let current out. Usually strongest from ventral side.

    • Burst is ~200 volts (but low amps)

How is the ratfish different from other chrondrichthyes?

Have smooth skins rather than scales.

What are the different divisions of Class Osteichthyes?

 Class Actinopterygii: ray-finned fishes

•  

  • Most fish

  • Fins are supported by fin rays.

  • Example: salmon

Class Sarcopterygii: lobe-finned fishes

•  

  • Coelocanth and lungfish

  • Viewed as ancestors to amphibians

  • Lungfish: lung is modified swim bladder

How do salmon spawn? What are the stages of their lifestyles?

Pacific Salmon: mostly adults that move up into natal streams (place of their birth), spawn, then die.

Juveniles go down stream, spend some time in ocean, then go back to mate. Alevins (eggs) hatch into fry, which become parr, then smolts. Become adults by time transition from freshwater streams to saltwater rivers.

Define: anadromous. Give an example

Anadromous: live in saltwater and migrate to freshwater to spawn. Pacific Salmon

Define: catadromous. Give an example

Catadromous: Live in freshwater and migrate to saltwater to spawn. American eel.

Define: semelparous and iteroparous

Semelparous: Reproduce once and only once.

Iteroparous: Reproduce more than once.