CALCIUM METABOLISM IN EMBRYOS OF THE OVIPAROUS SNAKE COLUBER
Class Agnatha, Osteichthyes - Jutzi-ZoologyLecture.pdf · Vertebrate Reproduction Oviparous Lay...
Transcript of Class Agnatha, Osteichthyes - Jutzi-ZoologyLecture.pdf · Vertebrate Reproduction Oviparous Lay...
Fish
Class Agnatha, Chondrichthyes, &
Osteichthyes
Subphylum Vertebrata
● All vertebrates are divided into two Superclasses
● Superclass Agnatha - Jawless vertebrates (2 living species)
● Superclass Gnathostomata - Jawed vertebrates (all other vertebrates)
Vertebrate Reproduction
● Oviparous ○ Lay eggs outside the body
so they may develop and hatch
● Ovoviviparous○ Egg remains in mother until
offspring hatch○ The offspring are born alive
● Viviparous○ Embryo receives
nourishment from mother○ The offspring are born alive
Placoderms
Ostracoderms
Hagfish & Lampreys
Cartilaginous Fish Bony Fish
Lobe-Finned Fish
Ray-Finned Fish
Coelacanths
LungfishEarly Amphibian
(Ancestor of all Tetrapods)
Superclass Agnatha● First appeared in the Cambrian
Period about 500 mya
● No jaws
● No paired appendages
● Notochord provides primary protection and support for nerve cord
● Fertilization & development are carried out externally
Ostracoderms
● Earliest vertebrates
● Evolved just after the Cambrian explosion
● Jawless - fed by filter feeding
● Covered in armor made of bony plates
● Totally extinct group of fish (P-T extinction)
Hagfish and Lampreys
Lampreys
● Live mostly in coastal and fresh waters
● Always return to freshwater to reproduce
● Though jawless, the mouth is lined with sharp teeth able to tear flesh
● Ectoparasitic
Lampreys
● Begin life as burrowing, toothless larvae
● After 5 to 7 years, they undergo an incredible metamorphosis to turn into pelagic, adult parasites
● Attach to fish, secrete an anticoagulant, and feed on blood
Hagfish● Jaw is partially movable
horizontally, but still considered Agnathans
● Entirely marine - never found in freshwater
● Able to change sex to meet population needs - many species exist in a 100:1 female-to-male ratio
● No larval stage
Hagfish
● Able to secrete copious amounts of thick slime to deter or evade predation
● Clean off the slime by tying themselves in knots
● Endoparasites - feed by burrowing into the mouth, gills, or anus of a host fish and consuming their prey from the inside out
Superclass Gnathostomata
● Jaws● Paired appendages
Placoderms
Ostracoderms
Hagfish & Lampreys
Cartilaginous Fish Bony Fish
Lobe-Finned Fish
Ray-Finned Fish
Coelacanths
LungfishEarly Amphibian
(Ancestor of all Tetrapods)
Class Placodermi
● Among the first jawed fish along with the ancestors of Class Chondrichthyes
● Went extinct along with the Ostracoderms
● Head and thorax were covered by bony plates
● 320 mya fossil shows earliest example of viviparous birth
Class Chondrichthyes
● Cartilaginous skeleton
● Notochord provides a large portion of back support
● No operculum○ Must swim constantly
to allow oxygenated water to move across gills
● No swim bladder ○ They are unable to
regulate their buoyancy levels
Buoyancy
● Cartilaginous fish must also constantly swim to keep from sinking. They use dynamic lift to maintain a constant level in the water column
● Liver oil and the ability of some sharks to swallow air allow them to obtain some level of buoyancy
Class Chondrichthyes● Respire with the use of 5 to
7 exposed gill slits
● Skin covered with dermal denticles - tooth-like structures that protect the skin and cause it to feel like sandpaper when rubbed against the grain
● Denticles also reduce small vortices produced during movement that cause hydrodynamic drag - increase swimming efficiency
Sharks
● The largest of all fish is the whale shark. It is a filter feeder
● Most sharks are simple carnivores
● Teeth are anchored into flesh rather than bone and they rip out and are replaced very rapidly
Shark Anatomy
Sexual Dimorphism in Sharks
Sharks
● Although most fish are exothermic, the shortfin mako shark and the great white shark are slightly endothermic
● Most sharks are ovoviviparous. They carry their eggs internally until the young hatch and are born alive and fully functional
Sharks
● Sharks have electroreceptor organs called the Ampullae of Lorenzini that detect the electromagnetic fields that all living things produce. This assists sharks in hunting and in navigation
● Sharks also have a very keen sense of smell and can detect 1:1,000,000 blood in water
Skates & Rays
Skates & Rays● Possess 5 gill slits that are
located underneath the pectoral fins rather than on the side of the head as in sharks
● Eggs laid in little pouches you may find on the beach
Skates & Rays● Wide distribution of group
members. Tropical to cold-water species exist
● Most are benthic (live on the seafloor) and respire by moving water in through their spiracles towards their gills
● Manta ray is an example of a rare pelagic ray
Skates & Rays·Skates and rays are very similar. However, skates tend to have a
more shovel-shaped head than rays and they lack spines in their tails.
Placoderms
Ostracoderms
Hagfish & Lampreys
Cartilaginous Fish Bony Fish
Lobe-Finned Fish
Ray-Finned Fish
Coelacanths
LungfishEarly Amphibian
(Ancestor of all Tetrapods)
Class Osteichthyes
● Boney fish - Actually called endochondral bone because it is formed by the ossification of cartilage
● Comprise the most various and largest class of vertebrates on Earth today
● Includes the vast majority of all
fish
Class Osteichthyes
● Swim bladder present - Allows a fish to adjust its buoyancy and thus its position in the water column
● Operculum present - Allows fish to pump water across the gills without having to physically move through the water
● Lateral line – senses vibrations in the water
Oxygen Exchange at the Gills
Countercurrent Exchange
Osteichthyes Evolution
Osteichthyes Classification
Subclass Actinopterygii
● Ray-finned fish
● Comprised of most members of class Osteichthyes
● Fins attach to body of the fish with multiple, small bones
● All members have homocercal tails
Caudal Fins
General Osteichthyes Anatomy
Subclass Actinopterygii
● Bichirs
● Also known as ropefish
● Live in freshwater environments in Africa and around the Nile delta
● Identified by noting the unique 12+ dorsal fins
● Sister group of all other ray-finned fish
● Sturgeon & Paddlefish
● The most ancient living bony fish with shark-like heterocercal tails & partially cartilaginous skeletons
● Sturgeons lack normal scales seen on other bony fish but they have armor plates along their sides
● Paddlefish lack the armor plating but have paddle-like rostrums the detect electromagnetic fields
Subclass Actinopterygii
Subclass Actinopterygii● Gar
● Fresh, brackish, & marine fish of the Americas
● Almost as old and primitive as the sturgeons & paddlefish
● Thicker scales than other bony fish but not as heavily armored as the sturgeons
● Identifiable by noting the long, skinny snout
Subclass Actinopterygii● Bowfin
● Only a single surviving species in this entire family of fish is native to eastern US & Canada
● Closest relative to the teleost fish
● Known for their long dorsal fins that cover most of their back
● Considered a trash fish - not very edible
Subclass Actinopterygii
● Teleost Fish
● The most advanced of all fish
● Almost 30,000 species - more than all other vertebrate species combined
● Almost any fish you can name belongs to this group
● Extremely important as food sources for humans and many other animals
Subclass Sarcopterygii
● Lobed fins joined to the body at a single bone
● Two dorsal fins with separate bases and diphycercal caudal fins
● There are only 8 living species in this subclass
●● These include lungfish and
coelacanths
Subclass Sarcopterygii
● Sauropterygians are able to utilize a primitive lung to breathe air when their ponds dry out or the water becomes anoxic
● Lungfish are known to use their fleshy pectoral fins like legs and crawl to new ponds when their previous ponds dry out
Structure of Lungs
● The Trachea leads down to the lung
● Separates into two bronchi leading to each lung
● Tubing terminates into little sacks called ALVEOLI that allow for gas exchange
Subclass Sarcopterygii
● ·The subclass split into two main groups long ago with the coelacanths staying in the ocean and the lungfish & tetrapodomorphs moving to freshwater environments
● Tetrapodomorphs further evolved into land vertebrates
Fish Scales
The End!