Class Chondrichthyes “Cartilage Fish”

Class Chondrichthyes Two sub-classes Elasmobranchii Holocephali Sharks Rays Skates Holocephali Rat fish Rabbit fish Parrot fish

Class Chondrichthyes Most are marine Most are active predators Few plankton eaters (whale & basking sharks)

Relationship to Humans Used for food Liver oil Clothing Jewelry Competition fishing

Characteristics Paired Fins Tough placoid scales: “placoderms” Provide protection Aid in streamlining Some species secrete mucous

Characteristics Powerful jaws, multiple rows of replaceable teeth Great white bites with force greater than a shot from 30-06 rifle Mouth is ventral Heterocercal tail – unequally divided

Characteristics Skeleton – cartilaginous, with no true bones Notochord present in young No ribs – larger species die when taken from water due to body weight on organs 2 chambered heart (atrium & ventricle) Closed circulatory Heart is ventral, in head region Blood pumped through aorta to gills, then to body tissues, back to heart through veins

Characteristics Cold blooded – “poikilothermic” – internal body temp. can have wide range Body temp matches the environment Reproduction Dioecious, with internal fertilization Dogfish & rays are oviparous Most species are viviparous

Characteristics Wide range of sizes Dogfish= 3ft Great white= 20 ft Basking shark= 40 ft Whale shark= 45+ft (largest fish)

Characteristics Nervous system: well developed brain Olfactory – 2 nostrils for taste/smell Optic – well developed eyesight Auditory – Ears inside body, well developed; works with… Lateral line – sensory openings along length of body, pick up low frequency vibrations

Characteristics Nervous system cont… Electromagnetic receptors= “ampullae of lorenzini” Detects electric currents given off by any living thing May help orient animal to earths electromagnetic field

Characteristics Respiration 5-7 gill pairs Most species have spiracles just behind eyes Provide direct oxygen supply to eyes