Chondrichthyes Flashcards
What are the two groups of Chondrichthyes?
Elasmobranchs and the Holocephali.
Give characteristics of the Holocephali.
- Chimaeras and ratfish.
- Single gill opening.
- Cartilaginous skeleton.
- Whip-like tail.
- Bottom feeder.
- Large flat plates for teeth.
What are the three groups of Elasmobranchs?
- Squaloid sharks - dogfish, no anal fin.
- Galeoid sharks - great white etc, anal fin.
- Batoidea - skates and rays.
Give characteristics of the Elasmobranchs.
- Dorso-ventrally depressed.
- Caudal fin = tail.
- Male has clasper for reproduction.
- Ventral mouth.
- Placoid scales.
- Cartilaginous skeleton.
- Internal fertilisation.
- High concentration of urea and trimethylamine oxide in blood.
- Negatively buoyant, must keep swimming to stop from sinking.
What fins provide control of pitch?
- The paired pectoral and pelvic fins.
What fins provide thrust/yaw?
- Caudal fin.
What fins provide roll?
- Dorsal and anal fins.
How do predatory sharks search for prey?
- Chemoreception (highly sensitive olfactory system).
- Vision.
- Mechanoreception.
- Electroreception.
Explain shark electroreception.
- Sharks have electroreceptors (modified hair cells) on their head.
- Consists of a pore, a jelly filled canal, the Ampulla of Lorenzini and the nerve.
What sharks and rays are known as filter feeders?
- Basking sharks.
- Whale sharks.
- Manta rays.
How do small sharks reproduce?
Male wraps around female.
How do large sharks reproduce?
Male bites onto back or fin of female.
What is lecithotrophy?
Yolk supplies most of nutrients, oviparous egg is deposited out of body.
What is matrotrophy?
Female reproductive tract supplies nutrients. Ovoviviparous and viviparous young is born fully formed.
What are three different matrotrophic methods?
Embryos feed on their siblings (embryophagy).
Nutrients delivered to mouth of embryo by oviduct.
Yolk sac placenta direct from female blood stream via vascularised yolk sac (placentotrophic).
