Derived Vertebrate Characteristics:
• Backbone, segmental
– (usually surrounding/protecting dorsal nerve cord
• Skull
Figure
34.2
Echinodermata
Chordates
Cephalochordata
Urochordata
Notochord
Common ancestor
of chordates
Vertebrates
Myxini
Petromyzontida
Jaws, mineralized skeleton
Lobe-fins
Actinistia
Lungs or lung derivatives
Dipnoi
Lobed fins
Amniotic egg
Mammalia
Milk
Amniotes
Reptilia
Limbs with digits
Tetrapods
Amphibia
Osteichthyans
Actinopterygii
Gnathostomes
Chondrichthyes
Vertebrae
HAGFISH:
• skull of cartilage
• Rudimentary cartilaginous vertebrae
• Retained notochord that is made of cartilage
at maturity
• Segmented muscles
• Marine
• Bottom dwelling scavengers
• Releases defensive slime
Lampreys
•
•
•
•
•
•
Mostly marine
Ectoparasites
Larvae in freshwater, filterfeeders
Most migrate to sea and mature
Cartilage that lacks collagen
Notochord in adult
– rudimentary cartilage partially protect nerve cord
• Inner ear for dynamic equilibrium
GNATHOSTOMES
• Jawed vertebrates
• Another Hox gene duplication
• developed forebrain
– w/ increased visual and olfactory capabilities
• Lateral line system in aquatic gnathostomes
Dorsal fins
Pectoral fins
Pelvic fins
(a) Blacktip reef shark
(Carcharhinus melanopterus)
(c) Spotted ratfish (Hydrolagus colliei)
(b) Southern stingray (Dasyatis americana)
Chondrichthyes
• Sharks, rays,(elasmobranchs) and chimaeras
(holocephalii)
• Skeletons of cartilage showing some
mineralization.
– Mineralization present in the teeth and scales
• Placoid scales
– Homologous to teeth (in dev and structure)
• Paired appendages
Sharks: model chondrichthyans
•
Powerful swimming poor maneuverability
–
•
Creates and stores massive amounts of oil in liver to help increase buoyancy
–
•
•
•
•
•
Still are negatively buoyant and will sink when not swimming
Swimming helps ventilage gills, but then can also use jaw and pharynx muscle to pump water over
gills
Largest examples are suspension feeders that consume plankton
BUT mostly carnivorous
Rows of teeth that move forward as a conveyor belt
Have a relatively short digestive tract
–
•
•
•
•
•
•
•
Pectoral fins mostly for stability and lift
Spiral valve increases SA and prolongs passage of material in digestive tract (i.e., more digestion and
absorption)
Nostrils are dead ends for olfaction
Entire body conducts sound to the inner ear
Electroreceptors—ampulae of lorenzini
Internal fertilization
Males have claspers
Oviparous, ovoviviparous, & viviparous
Cloaca=digestive, urinary, and reproductive opening
Ampullae of Lorenzini
Osteichthyes=vertebrate clade with calcified
endoskeleton (calcium phosphate)
• Term originally applied to boney fish
– Now to all vertebrates with skeleton of bone
tissue
Bony fish = actinopterygii + actinistia + dipnoi
• Have 4-5 pairs of gills
– covered by a bony operculum
• Swim bladder  buoyancy control
• Gas can be transported in and out of gas bladder from blood
controlling buoyancy
• Skin covered by flat, boney scales
– Grow in size as fish grows
• Slime from glands
– Reduces drag
– Reduces topic infection
• Lateral line system
• Most species are oviparous with external fertilization, but there are
lots and interesting variations
Figure 34.18
Ray—finned fish = Actinopterygii
• Have bony rays that support fins and in some cases connect to deeper
skeleton
• Marine and fresh water
Lobed fin fish
• Rod shaped bones surrounded by thick layers of muscle in pectoral and
pelvic fins
• May have been used to “walk” across substrate under water—some extant
species still do this
• Ceolacanth—actinistia
• Believed to be extinct but re-discovered in 1938
• marine
Dipnoi—lung fish
• Freshwater
• Swamps and stagnant water
• Gulp air into pharynx which connects to lungs—suplements gas exchange
across gils (which are still main gas exchange organs)
Organ systems