550 likes | 637 Views
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). Characteristics con ’ t.
E N D
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)
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
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 Senses smellhearinglateral line organ visionampullae of Lorenzinitouch and taste
Tapetum lucidum Reflects light in the eye
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
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
Swimbladder • Sharks lack a swimbladder • Oil in the liver is used to change buoyancy
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 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".