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