7. Actinopterygii Flashcards
Osteichthyes “bony fish”
32,000 species (most living fishes belong to this group)
Marine and freshwater
The class is divided intro two subgroups
- Actinopterygii (ray - finned fishes)
- Sarcopterygii (lobe - finned fishes)
Actinopterygii
“ray - finned fishes”
99 % of all living species of fish (ca. 32,000)
Subclass
Chondrostei
Most of them are instinct. Only 27 species is alive today.
Polypterifirmes
One of the species of Chondrostei
Bichirs (polypterus)
The only vertebrate who have lungs, but no throat
Instead they inhale water through their spiral.
Acipenserriformes
One of the species of Chondrostei
Acipenseridae (sturgeons and paddlefish)
Paraphylistic group, with cartilage skeletons, heterocercal tail, no scales
Some fossils and some are alive today. Fossils suggest they were closer to bony fish.
They sturgeon produce caviar and is really big, which means that they are famous.
They do not use their vestigial spiracles.
The paddlefish has a spiracle and a wierd structure on the forehead, which uses ampullae of Lorenzini to find prey. Normally it just opens its mouth and eat.
Subclass
Neopterygii
Includes the Holostei and the teleostei.
Holestoi is a group of ray-finned bony fish which include gars and bowfins.
They are a mix between telost fishes and sharks.
Teleostei consist of 96% of all extant fishes including humans.
What is the characteristics of teleost fishes
They are found everywhere, from the tropics to the poles. In water temperature from 0 to 35 degrees.
Freshwater ponds, lakes, streams and rivers, surface to deep oceans. Everywhere
Bony skeletons
Operculum, helps the fish to pump water across the gills. It’s kind of some bony plates with muscles.
A gass-filled pouch, whichs helps them
- respire in oxygen poor water
- regulate boyancy
How do a fish regulate buoyancy?
Some other fishes has a swimblather, where they control their boyancy whitout using energy. The bloodvessels on the sides of the sacks can control the amount of gas in the sacks. The blodvessels can pum gas in and out.
Does fish have lungs
Yessss the original fish had lungs, but evolution has found different use for them.
Fx the swim blader, which is a gas-filled pouch (pocket), there help them control buoyancy.
Some fish still have lungs, which they use in ocygen-poor waters.
Whats the different type of scales?
Placoid
- looks like tooth (Chondrichthyes, sharks and rays)
Ganoid
- Silvery enamel on the outside and bone on the inside of the scale.
Cycloid and ctenoid (modern fish)
- Thin and flexible, arranged so they overlap.
What is a Premaxilla
A bone which help fish open their mouth enven more, so they could eat more effectively. Bigger preys.
The Tpremaxilla is so important, because it makes sucking things so much easier.
The homocercal cadual fin
When the fin is more ore less symmetrical, in contrast to sharks.
How do theleost fishes reproduce
Thelost fishes lay eggs in large numbers, and most of them die.
Externatl fertilization
The rare things:
- Few species protects the eggs in the body, fx the seahorse male.
- Few fishes have internal fertilization. The male fertiliz the eggs inside the female, whereafter she lay the eggs. A fish penis.
The fish egg
Structure of teleost fish egg.
The jelly around protects the fish and the yolk. There is a membrane there keeps everything together.
If it’s not surrounded by lots of water, nothing will keep it drying out. The waste products go through the membrane and out into the water, but if there was no water, the embryo will poison itself.
What is Sequential hermaphroditism?
Some fish can change sex, if there is missing a male or female. They do it regulary.
