Fishes Flashcards
(24 cards)
What were the early fish that lacked jaws known as?
Agnatha (includes hagfish and lampreys, as well as extinct ostracoderms)
What are the jawed fish known as, and what are their characteristics?
paired appendages, include chondrichthyes and osteichthyes, were formed from a group of ostracoderms
How did the jaws of fish evolve?
Through modifications of the cartilaginous gill arches of jawless fish (these arches are derived from neural crests)
What do jaws allow for?
more efficient predation
What do jaws eventually lead to?
led to stronger structural support when transitioning from cartilage to bone, as well as the appendages allowing animals to walk on land
What other characteristic are jaws associated with?
paired pectoral and pelvic appendages, which allow for more control while swimming
What class of gnathostomata is characterized by the cartilaginous structure?
chondrichthyes
What is cartilage composed of?
avascular tissue made up of special cells called chondroblasts that secrete the extra-cellular matrix (water and collagen fibers) and mature into chondrocytes
What are some examples of fish in the class chondrichthyes?
sharks and rays
What class of gnathostomata is characterized by bony structures?
osteichthyes
What is bone composed of?
vascular tissue made of special cells called osteoblasts that mature into osteocytes, which secrete the extra-cellular matrix (water, collagen fibers, proteins and calcium salts that leads to calcification).
What are the two subclasses of osteichthyes?
actinopterygii (ray-finned fishes) and sarcopterygii (lobe-finned fishes)
How are ray finned fishes characterized?
fins supported by spines, fins moved by muscles that do not extend into the fins, pair of pectoral, pair of pelvic, as well as dorsal, anal, and caudal fins. body tapers at end
How are lobe-finned fishes characterized?
rounded fins (like earlobes), fins supported by muscles and articulable bones at the base. the end of each fin has thin bony structures that fan out. precursors to amphibian legs and feet
What are some examples of lobe-finned fish?
There are only seven extant species, some examples include the coelacanth and the lungfish
What are the main fins that have functional differences in bony fishes and cartilaginous fishes?
the pectoral fins function for lift in cartilaginous fish, but have many functions in bony fish. the pelvic fins are used for lift and reproduction in cartilaginous fishes while used for braking and steering in bony. the dorsal and anal fins are used for steering in both fish types. the caudal fin is used for propulsion in both types, yet in cartilaginous fish it is heterocercal (different sized) while in bony fish they are homocercal (symmetrical).
What fish lacks a swim bladder?
Sharks
How do sharks account for their lack of a swim bladder?
their livers are filled with squalene, a lipid with a density lower than that of water. to float and maintain their position, they use dynamic lift (always in motion)
How do most bony fish control their buoyancy?
most control their buoyancy by adjusting the amount of gas in the swim bladder. pressure is inversely related to volume, so in deeper water a fish would expel gas to maintain neutral buoyancy
What are the 2 main ways fish control the gas entering the swim bladder?
physostomous fish suck or expel air by mouth. physoclistous fish allow gas to enter the swim bladder through the gas gland from blood flow. This is accomplished by keeping a gradient that favors the diffusion of oxygen into the swim bladder, known as rete mirable.
Describe the process of rete mirable.
- gas gland secretes lactic acid into blood
- high acid concentrations cause hemoglobin to release oxygen
- countercurrent multiplier increases o2 to higher levels
How do freshwater and marine fish differ in their osmotic regulation?
freshwater fish use hyperosmotic regulation, pumping out excess water and absorbing as much salt as possible. marine fish use hypo-osmotic regulation, replacing water loss due to osmosis and excreting excess electrolytes through the gills by salt secretory glands
How is osmotic regulation accomplished in chondricthyhes?
they are iso-osmotic, which is slightly hyperosmotic to surrounding water. excess salt is eliminated in fluid made by rectal gland.
