marine fishes phylum chordata subphylum vertebrata
TRANSCRIPT
Marine FishesPhylum Chordata
Subphylum Vertebrata
Characteristics• Backbone• Bilateral symmetry• Endoskeleton• Fish-simplest & oldest of all living vertebrates
(Fossils date back to 400 million years ago)• Most abundant-over 22,000 species of fish in
world• 58% are marine
Jawless Fishes
• class Agnatha• Most primitive• No jaws- feed by
suction
Cartilaginous Fishes
• class Chondrichthyes (Con-dric-thees)
• Sharks, rays, skates, & ratfishes
• Skeleton is made of cartilage – Lighter & more flexible
than bone
Mouth is ventral (underneath head)• Sandpaper like skin• May have well developed teeth– Constantly are replaced
Movement• Fins more rigid than bony fish• Rely on pectoral fins to “lift” them in order to
prevent sinking (no air bladder)• Large, oily liver that increases buoyancy• Streamline body shape – moves quickly b/c of
large muscles in the caudal fin.• Asymmetric caudal fin improves stability
Sharks
• Smallest = pygmy shark (25cm)• Largest = whale shark (15 meters)! These are
filter feeders.• Bottom dwellers = nurse & leopard• Most aggressive = Great White• Other dangerous sharks = Tiger and
Hammerhead
http://www.youtube.com/watch?v=_DbCcMbOL3M&safety_mode=true&persist_safety_mode=1&safe=active
Sensory
• Sensitive receptors to detect stimuli: Lateral Line organ– Hair-like sensors that pick up sound vibrations
up to ½ km away
• Ampullae of Lorenzini in the snout – senses electric fields generated by the muscles of potential prey.
• 2/3 of the sharks brain is devoted to sense and smell
Reproduction• Internal fertilization• Male sharks = Claspers that hold onto female for transfer
of sperm into reproductive tract.• Some (mostly aggressive) have internal development and
live births (viviparous) - -hammerheads• Some start predation early by devouring their siblings
before they hatch!• Other sharks and skates have external development –
develop in a black, leathery case called a “mermaids purse” – take over a year to develop. (oviparous)
Whale Shark- largest fish in existence
Bull Sharks
Very AggressiveFresh and Saltwater
• Sharks must swim to force water over their gills– If caught in nets they will drown
• Some exceptions: nurse sharks- gills can contain enough oxygen w/o swimming
Bony Fishes• class Osteichthyes (Osti-ich-thees)• Skeleton partially bone• Have an operculum-gill cover to protect gills• Caudal fin usually same size (top & bottom)
• Bony fish have fin rays vs. cartilaginous fins
• & a swim bladder
Sunfish-largest Bony fish1996, Japan9.6 ft long
Biology of Fishes
• Study of fishes: Ichthyology• Body Shape• Directly related to lifestyle• Fast swimmers=streamlined
• Coral reef fish=laterally compressed
• Elongated bodies fit into rocks & other narrow spaces
• Truncate, short-
Laterally compressed-at Laterally compressed-at beginning of life one eye beginning of life one eye on each side then on each side then migrates to same sidemigrates to same side
• Irregular shapes help with concealment-
Countercurrent exchange Heat exchange:
legs of birds, body heating of fish such as Tuna and Mako shark
Fins
• Pairs = Pectoral & Pelvic• Single = Dorsal, Anal & Symmetric Caudal
(have air bladder for stability)• Skin – slimy mucus coating acts as a barrier
against infection and friction
Pelvic Fin Anal Fin
1st Dorsal Fin
2nd Dorsal Fin
Pectoral Fin
Caudal Fin