The Fishes

The Fishes Three types of fishes Jawless fish (Class AGNATHA) Cartilaginous fish (Class CHONDRICHTHYES) Bony fish (Class OSTEICHTHYES)

Jawless Fish Jaws are absent Paired fins are generally absent Early species had heavy bony scales and plates in their skin

Jawless Fish In most cases the skeleton is cartilaginous. The embryonic notochord persists in the adult. Seven or more paired gill pouches are present. Hagfish sheds slime layer

Jawless Fish A light-sensitive pineal eye is present. The digestive system lacks a stomach. External fertilization; both ovaries and testes present in individual but gonads of only one sex functional in hagfishes, no larval stage; separate sexes and a long larval stage in lampreys.

Lamprey Dissection External Mouth Head & Pharynx Heart Gonads

Cartilaginous Fish Cartilaginous fishes are jawed fish with: paired fins paired nares scales a heart with its chambers in series skeletons made of cartilage rather than bone

Cartilaginous Fish Chondrichthyes also lack ribs, so if they leave water, the larger species' own body weight would crush their internal organs long before they would suffocate.

Cartilaginous Fish Their tough skin is covered with dermal teeth called placoid scales making it feel like sandpaper.

Cartilaginous Fish Do not have bone marrow red blood cells are produced in the spleen and the epigonal organ

Cartilaginous Fish Breathe through 5-7 gills, depending on the species. Pelagic (surface) species must keep swimming to keep oxygenated water moving through their gills Demersal (deep water) species can actively pump water in through their spiracles and out through their gills.

Cartilaginous Fish YouTube Link Reproduce through internal fertilization. Some sharks have live birth YouTube Link

Cartilaginous Fish Divided into two subclasses: Elasmobranchii (sharks, rays and skates) Holocephali  (chimaeras, sometimes called ghost sharks)

Sharks, Rays, Skates

Chimaeras

Bony Fish A group of fish that have bone, as opposed to cartilaginous, skeletons. The vast majority of fish are Osteichthyes 45 orders 435 families 28,000 species

Bony Fish All bony fish possess gills. some species can respire through their skin, intestines, and/or stomach Primitively ectothermic (cold blooded), meaning that their body temperature is dependent on that of the water.

Bony Fish Bony fish typically have swim bladders, which helps the body create a neutral balance between sinking and floating.

Bony Fish They also are able to see in color, unlike most other fish. Bony fish have no placoid scales. Mucus glands coat the body. Most have smooth and overlapping scales.

Bony Fish Some bony fish are hermaphrodites, and a number of species exhibit parthenogenesis. Fertilization is usually external, but can be internal. Development is usually oviparous (egg-laying) but can be ovoviviparous, or viviparous.

Bony Fish Although there is usually no parental care after birth, before birth parents may scatter, hide, guard or brood eggs with sea horses being notable in that the males undergo a form of "pregnancy", brooding eggs deposited in a ventral pouch by a female. http://www.youtube.com/watch?v=EaOHLQy_bjU

Bony Fish Two types of bony fish Ray-Finned – have rays in their fins Lobe-Finned – have thick chunky fins