Chapter 24: Fishes, Class: Chondrichthyes-> Cartilaginous fishes Flashcards
List some very general characteristics of this class!
- well developed sense organs, powerful jaws and predacious habits
- true bone is completely absent
- nearly all are marine (28 live in freshwater primarily)
- after whales sharks are the largest living vertebrates
What is the subclass that contains Sharks, Skates and rays?
- Elasmobranchii
What type of body do sharks possess?
- fusiform ( spindle-like shape…the middle is wide and tapers at both ends of the body)
What are thrust and lift provided by for sharks?
- asymmetrical heterocercal tail , vertebral column turns upward and extends into dorsal lobe of caudal fin.
List the fins included on a shark! (4)
- paired pectoral and pelvic fins
- one or two median dorsal fins
- one median caudal fin
- sometimes a median anal fin
In males what is the medial part of the pelvic fin modified for?
- copulation, it forms a clasper
Paired nostrils are ___ to the mouth
anterior
Lateral eyes are ___.
lidless
Behind each eye there is a ___. Which is a remnant of what?
- spiracle, remnant of the first gill slit
How do they detect prey at great distances?
- large olfactory organs sensitive to one part blood per 10 billion water
What kind of scales do they have? Function?
- tough leathery placoid scales reduce water turbulence
Nostrils to each side of the hammerhead shark may improve what?
- stereo-olfaction
Prey can also be located from long distances by sensing low frequency vibrations in the ___.
- lateral line
L> consists of neuromasts in interconnected tubes and pores on the side of the body.
At close range when located prey they switch to what detection method?
- vision
L> most sharks have excellent vision even in dimly lit water
Up close sharks are guided by what?
- bioelectric fields that surround all animals
What are ampullae of Lorenzini?
- electroreceptors located on the sharks head
The upper and lower jaws are equipped with sharp, ____ shaped teeth that are constantly being ___.
- triangular
- replaced
The mouth of sharks opens into a large ___, containing openings to ___ and ___.
- pharynx
- gill slits
- spiracles
Sharks have a short ___ which runs to the stomach.
esophagus
The liver and pancreas open up into what?
- straight and short intestine
What in the sharks intestine slows passage of food and increases absorptive area?
- spiral valve
Rectal glands secretes ___ and assists in what?
-NaCl
- assists the opisthonephric kidney
L> Origin of tissues two parts from embryological development
The heart chambers provide what??
- standard circulatory flow through gills and body
Elasmobranchs retain what?
- nitrogenous compounds in the blood
- They raise blood solute concentrations and eliminates the osmotic inequality between blood and seawater….TMAO and Urea
