Marine Fishes Phylum 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

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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 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 fish 1996, Japan 9.6 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 beginning of life one eye on each side then migrates 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 1 st Dorsal Fin 2 nd Dorsal Fin Pectoral Fin Caudal Fin