Osteichthyes "Bony Fish"

Question 1

What kind of phylum does this group include? what other group does it overlap with?

Answer 1

includes actinopterygii, actinistia, and dipnoi which have lungs and lobed fins

Question 2

What are class osteichthyes? what are their features?

Answer 2

• class of bony fish which is the skeleton of the fish is ossified and there sa replacement of cartilage by calcium phosphate (not present in gnathostomes)
• there are three classes: actinopterygii, actinistia, and dipnoi
• mainly marine and freshwater

Question 3

What is some features of the phylogenic group of bony fish?

Answer 3

• it is paraphyletic (it left out some descendants of common ancestors)
• includes: jawless fishes, cartilaginous fishes, bony fishes and EXCLUDES tetrapods
• in order to make this taxon monophyletic we have to include ALL OTHER BONY VERTEBRATE like tetrapods
• in reality bony fishes should include: reptiles, birds and mammals

Question 4

Describe the evolution of lungs and swim bladders

Answer 4

• bony fish descended from fresh or brackish water ancestors that had simple lungs and gills (had both)
• their simple lung was dorsal out-pocketing of foregut with gas and augmented gas exchange by their gills
• the original lung of the ancestor modified into the SWIM BLADDER
• lungs and swim bladders are homologous
• swim bladders –> provide buoyancy
• lungs –> provide respiration
  both developed from the same embryonic tissue: the lungs developed from the ventral out pocketing of the gut and the swim bladder developed from the dorsal out pocketing of the gut

Question 5

What are some characteristics of bony fish?

Answer 5

• they have an ossified endoskeleton
• they have flat plate-like bony scales (they are not tooth-like the chondrichthyans)
• their lateral line is used to detect movements and vibrations in the water
• gill openings are covered in single protective flap called the operculum
• they also have a swim bladder (most bony fish) that controls buoyancy of fish by adjusting the volume of gas in the swim bladder and degree of inflation
• fish can float at any depth they desire because of this swim bladder (likely evolved from lungs present in extinct ancestor)

Question 6

How do bony fish reproduce and move?

Answer 6

• they reproduce through external fertilization –> gametes are released into the water and fertilized eggs are sometimes cared for (i.e. seahorse)
• move by their flexible fins (not stiff) and used for propolsions

Question 7

What are the features of the Class Actinopterygii?

Answer 7

1. ray finned fish
   - includse most of bony fish
   - named for their long flexible rays that support fins

Question 8

What are features of class sctinistia?

Answer 8

• 1st lineage of lobe-fin fish
• coelacanth –> lobe finned fish which are restricted to deep water
• ## both classes of lobe fins have fleshy, muscular pectoral and pelvic fins and are supported by bony elements

Question 9

What are features of class dipnoi?

Answer 9

• they are the second lineage of lobe fins –> include lungfish –> which live in freshwater in southern hemisphere
• has gills and lungs, and have lobe fins
  they gulp air into their lungs from water surface and lower it raising floor of mouth cavity (use buccal pump to pump h2o into their mouth)

Question 10

What is the economic importance of lobe fins and bony fish?

Answer 10

• overfishing causes collapse of fish stocks
• no catch reserves may allow replenishment of stock outside of reserve
• 95% of saltwater species of bony fish are caught in the wild and put in aquariums