Chondrichthyes Cartilaginous Fish Characteristics Endoskeleton entirely cartilaginous Fusiform

Chondrichthyes Cartilaginous Fish

Characteristics • • • Endoskeleton entirely cartilaginous Fusiform Body Mouth Ventral Skin with placoid scales 2 chambered heart Separate exposed gill slits No operculum Heterocercal tail Internal reproduction (claspers & cloaca)

Fusiform body • Torpedo shape • Sharks have countershading (Dark on top & light on the bottom)

Placoid Scales • These scales point towards the tail and helps to reduce friction from surrounding water when the shark swims

Shark Anatomy

Shark Anatomy

Shark Senses smell hearing lateral line organ vision ampullae of Lorenzini touch and taste

How a Shark Eats

Two chambered heart

Gill Slits

Lack operculum

Heterocercal vs Homocercal • Sharks have heterocercal caudal fins with the vertebrae extending into the superior region of the caudal fin

Shark Reproduction • • Male claspers are inserted into female cloaca for internal fertilization Ovoviviparous 90% Viviparous (Great whites) Oviparous

Female Reproductive Anatomy

Male Reproductive Anatomy

Chondrichthyes Reproduction • oviparous (laying eggs that hatch outside the mother's body) • ovoviviparous (brooding eggs that hatch within the mother's body, and then releasing the young) • viviparous (young develop within a uterus inside the mother's body, and are nourished prior to birth via a connection with the mother's bloodstream (placenta).

Cat Shark Egg Oviparous Porbeagle embryo viviparous Dogfish Shark embryos Ovoviviparous

Characteristics con’t • • No swimbladder or lung 2 olfactory lobes 2 cerebral hemispheres 2 optic lobes 1 cerebellum 1 medulla oblongata 3 pairs of semicircular canals Ampullary organs of Lorenzini

Swimbladder • Sharks lack a swimbladder • Oil in the liver is used to change buoyancy

Tapetum lucidum Reflects light in the eye

Lateral Line System

Whale Shark Worlds largest fish (46 ft long)

Not many fossils Guitarfish (One of the few chondricthyes fossils) •

Elasmobranchii • Includes the familiar sharks, skates, and rays, as well as some strange fossil relatives. • Elasmobranchs have an upper jaw that is not fused to the braincase and separate slit-like gill openings.

Rays & Skates

Rays & Skates • Rays and Skates, unlike sharks, are not fusiform, but dorsoventrally flattened. • Gill slits open on the ventral surface of the head • Spiracles on the top of the head direct water over the gills, to prevent sludge from clogging these delicate structures • They feed primarily on mollusks and crustaceans, and so have teeth modified for crushing.

Skates vs Rays • • The major difference between skates and rays is the way in which they reproduce. Rays are viviparous (live bearing) Skates are oviparous (egg laying), releasing their eggs in rectangular cases sometimes called "mermaid´s purses".

Mermaid purse

Bradyodonti • Includes forms with an upper jaw fused to the braincase and a flap of skin, the operculum, covering the gill slits. • The Bradyodonti includes the chimaeras and ratfish, which are relatively rare, deep-water, mollusc-eating forms.

Chimaera

Ratfish