Lecture 16- Chondrichthyes Flashcards
(22 cards)
Define Ichthyology.
The scientific study of the biology of fishes (ex: sharks, stingrays, lampreys, etc.)
What characteristics play into the body form of chondrichthyes?
- External gill openings (5-7 pairs), 1st and 2nd dorsal fins, spiricle, caudal fin
- Clasper
- Lateral line
- Cartilaginous skeleton
- 3 pairs of semi-circular canals (balance and equilibrium)
- Constantly shedding teeth
What is the purpose of the clasper? Purpose of the lateral line?
- Clasper allows males to hold on to females during reproduction
- Lateral line detects movement in water
What is the purpose of an oily liver in sharks?
removes toxins and helps to control buoyancy
Sharks have a 2 chambered heart. The top chamber is called the ___ and the bottom is called the ___.
Atrium; Ventricle
Name the variations in the Caudal fin.
- Heterocercal: sharks; ancestral condition; asymmetrical
- Diphycercal: lung fish; symmetrical to a point; close relation to amphibians
- Homocercal: perch; derived condition; symmetrical
In the class Chondrichthyes, what form of fertilization is used?
Internal fertilization
Name the morphological variation of scales.
- Placoid scales: ancestral condition; feels rough like sand paper; made of dentin and enamel (has sharp ridges)
- Ganoid scales: non shark fish; diamond shaped
- Cycloid scales: spherical shaped
- Ctenoid scales: teleost fishes, sharp ridges at the end of the scales
What type of teeth do sharks have?
Polyphydont teeth (constantly shedding and growing new ones)
What are Neuromast cells?
Found in lateral line; they are mechanoreceptors that detect movement in water (makes it easier to detect prey)
A heightened sense of smell in chondrichthyes is called what? What type of sense of smell to hammerheads have?
Chemoreception; Stereosmell
Define Ampullae of Lorenzini.
Sensory cells that are sensitive to electrical potentials; detecting prey that give off weak magnetic fields; found near rostrum of shark
The two sub-classes of Chondrichthyes are ___ and ___.
Holocephali (ratfish) and Elasmobranchii (sharks and rays)
What are the major differences between skates and rays?
- skates have 2 dorsal fins, rays have 1
- skates are oviparous, rays are viviparous
- skates have no venom, rays have serrated barbs on caudal fin (which is associated wit venom)
In the class Osteichthyes, what are the sub-classes?
Actinopterygii (ray-finned fish) and Sarcopterygii (lobe-finned fish)
Actinopterygii traits?
- Major adaptive radiation in the devonian (300 mya; age of fish)
- Homocercal tail
- Ganoid scales in ancestral forms; cycloid of ctenoid in derived forms
- Fins supported by lepidotrichia (sharp ray-like bones; additional structural support in fins for increased efficiency in moving through water)
Sarcopterygii traits?
- Morphological characteristics similar to amphibians
- Only 8 extant species with 2 orders -> Coelacanthiformes (ancestral) and Dipnoi (derived)
- Diphycercal tail
- Fertilization can be either internal or external
Basic external anatomy of fish?
- Dorsal fin: spiny vs. soft-rayed (both provide support)
- Respiration by gills
- Excretion -> better developed kidneys
- Small cerebrum and small cerebellum
-3 semi-circular canals
The bony structure that protects the gills is called the what?
Operculum
Purpose of the swim bladder/ gas bladder?
Helps with buoyancy
Define counter current exchange.
Mechanism in fish gills that allows fish to extract oxygen from water more efficiently; helps with the efficiency of simple diffusion when blood is moving in a different direction than the water currents
How is buoyancy achieved in Chondrichthyes? Actinopterygii?
- Chondrichthyes: large oily livers; vacuoles in liver cells
- Actinopterygii: gas bladders; adjust w/ water pressure for movement in the water column
