Download Marine Fishes

Marine Fishes
Phylum Chordata
Subphylum Vertebrata
Characteristics
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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
tp://www.youtube.com/watch?v=_DbCcMb
L3M&safety_mode=true&persist_safety_mo
e=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 Aggressive
Fresh 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
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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
Sunfishlargest
Bony fish
1996,
Japan
9.6 ft long
Biology of Fishes
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Study of fishes: Ichthyology
Body Shape
Directly related to lifestyle
Fast swimmers=streamlined
• Coral reef fish=laterally
compressed
Laterally compressed-at
beginning of life one eye
on each side then
migrates to same side
• Elongated bodies fit into rocks & other narrow
spaces
• Truncate, short-
• 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
1st Dorsal Fin
2nd Dorsal Fin
Caudal
Fin
Pectoral Fin
Pelvic Fin
Anal Fin