Introduction to Fish

fish Phylum Chordata Subphylum Vertebrata Class Agnatha Class Chondrichthyes Class Osteichthyes Class Amphibia Class Reptilia Class Aves Class Mammalia fish

Class Agnatha - jawless fish: hagfish and lampreys absence of jaws no paired fins cartilaginous skeleton 2-chambered heart

Agnatha

Jaws evolved from gill supports. Jaws developed from gill arches located around the pharynx. cranium mouth gill arches Jaws gave vertebrates a huge advantage as predators.

Only two groups of jawed fish still exist. Cartilaginous fish and bony fish are still in existence. Cartilaginous fish have skeletons made of cartilage.

Cartilaginous fish include the Holocephali and Elasmobranchs Holocephali include ratfish, a small group of deep-sea fish. Elasmobranchs include sharks, rays, and skates.

Class Chondrichthyes - cartilaginous fish: sharks and rays cartilaginous skeleton 2-chambered heart 5+ pharyngeal slits well developed lower jaw bony teeth placoid (tooth-like) scales ventral mouth and nostrils nostrils do not open into mouth

Cartilaginous fish

Chondrichthyes

Bronze whaler

Eagle ray

Chondrichthyes

Class Osteichthyes - bony fish ossified skeleton 2-chambered heart pharyngeal slits covered by single bony operculum (gill cover) membranous fins strengthened with rays presence of a swim bladder (teleost) lateral line sensory receptor

Bony fish

Swim bladder

Fish are vertebrates with gills and paired fins. Fish use specialized organs called gills to breathe underwater. sheets of thick, frilly tissue filled with capillaries take in dissolved oxygen from water, release carbon dioxide water flow

Countercurrent flow is the opposite movement of water against the flow of blood in the fish’s gills.

Circulatory system of fish

Bony fish have skeletons made of bone. operculum protects a bony fish’s gills movements of operculum help bony fish move water over gills

Fins are surfaces that project from a fish’s body. keep fish stable redirect water around fish as it swims help fish maneuver in water dorsal fin caudal fin anal fin pectoral fin pelvic fin

Myomeres – bands of muscle along sides of Myomeres – bands of muscle along sides of body contract pushing against water, forces body forward

Dorsal & anal fins – act as rudders to steer & provide Dorsal & anal fins – act as rudders to steer & provide stability (unpaired) Pelvic fins – to turn, balance, & “brake” (paired) Pectoral fins – steering (paired)

Fish senses

All fish have a lateral line system. sensory system sensitive to small changes in water movement lateral line

Lateral line system

Fish scales Reduce drag and direct water flow

Types of fish scales

General Life Style Categories Fish Adaptations and Life Styles General Life Style Categories a. pelagic cruisers occurring in water column far away from the bottom (benthic) environment often referred to as "blue water" includes tuna, billfish, blue sharks, mackerel sharks (great whites and mako sharks)

b. demersal bottom-associated fishes, but not usually sitting on the bottom rely on the benthic environment as a source of food, place to reproduce, and/or place of refuge, etc. includes most reef fishes (e.g., butterfly fishes, surgeon fishes, wrasses, parrot fishes, etc.)

c. benthic bottom-dwelling fishes that spend the majority of time sitting on the bottom includes flatfishes, lizard fishes, many scorpion fishes, many hawkfishes, gobies, etc.

Body shape tuna 1) fusiform a) = torpedo-shaped b) allows minimal drag while swimming c) best shape for a pelagic cruise

2) compressed laterally flattened (e.g., butterflyfishes & surgeonfishes) allows for maneuverability in surge environments useful for demersal fishes that hover above the reef exception seen in flatfishes that lie on one side of the body as benthic fishes

John Dory: predator in waiting…

3) elongated or attenuated long body (e.g., trumpetfish, cornetfish, eels) seen in demersal fish that either hover motionless in the water) seen also in benthic fishes (e.g., eels) that hide in holes in the reef

4) depressed dorso-ventrally flattened (e.g., frogfishes, scorpionfishes & gobies) broad ventral surface facilitates resting on the bottom seen in many benthic fishes

Body Coloration 1) source of color pigment color - chromatophores for yellows, reds, oranges, browns, & blacks structural color - iridophores (reflection) & light refraction for blues, silvers, & rainbows

2) patterns a) countershading dark blue or black dorsally, white or silvery ventrally results in blue water "camouflage“ observed most frequently in pelagic cruisers

b) camouflage matching the background coloration usually involves having irregular dark blotches and spots typically seen in benthic fishes, especially benthic ambush predators (e.g., frogfishes, gobies, & many scorpionfishes) some fishes (e.g., flatfishes) may exhibit rapid color changes in response to different backgrounds

Cryptic colouration

5) matching downwelling light b) camouflage 5) matching downwelling light Hatchet fish Cookie cutter shark

c) disruptive coloration 1) color pattern breaks up the silhouette of the fish 2) may involve dark bars across the eye and tail region 3) seen in many demersal fishes such as butterfly fishes

d) bars and stripes 1) bars are vertical (e.g., manini) 2) stripes are horizontal (e.g., ta'ape) 3) seen frequently in schooling demersal fishes 4) may confuse potential predators by making it difficult to select individual prey from the school

  e) misdirection 1) false eye spots, etc. 2) observed in many demersal butterfly fishes

f) advertising coloration 1) bright, obvious color patterns 2) possible functions a) advertising a cleaning station (e.g., cleaner wrasses) b) advertising a warning (e.g., nohu) c) advertising for mates (e.g., male parrotfishes) Hawaiian cleaner wrasse Nohu

1) imitating other creatures g) mimicry 1) imitating other creatures 2) seen in a few demersal and benthic fishes 3) examples a) blenny (Aspidontus taeniatus) mimics cleaner wrasses b) shortnose wrasse mimics Potter's angel which sports a defensive spine

g) mimicry 4) leafy sea dragon (Australia)                                      

h) uniform red coloration most often observed in deep-dwelling or night active demersal fishes examples include opakapaka, oweoweo, menpachi, & squirrelfishes

i) noctural versus diurnal color changes j) male versus female color differences k) juvenile versus adult color differences Dragon wrasse Stoplight parrotfish Bluehead wrasse

Sex and social behaviour

Territoriality Black angel fish

Distribution - Anatomy - Circulation - Respiration Chondrichthyes (370) Placoderm (395-345) Ostracoderm (510-=350 mybp)                                                                                                                      (360) Osteichthyes (395) allows. Class Agnatha or Cephalaspidomorphi, the jawless fishes Subclass (or order) Cyclostomata, the lampreys and hagfishes. (In certain classifications, the lampreys and hagfishes are each considered separate superclasses: Cephalaspidomorphi and Pteraspidomorphi, respectively.) Class Chondrichthyes, the cartilaginous-skeleton fishes Subclass Holocephali, the chimaeras, or ratfishes Subclass Elasmobranchii, the sharks, skates, and rays Class Osteichthyes, the bony fishes Subclass (or order) Crossopterygii, the coelacanth Subclass (or order) Dipnoi or Dipneusti, the lungfishes (In some classifications, the above two subclasses are treated as orders of a single subclass, the Choanichthyes or Sarcopterygii, the lobe-finned fishes.) Subclass Actinopterygii, the ray-finned fishes Infraclass (or superorder) Chondrostei, the primitive ray-finned bony fishes: sturgeons, paddlefish, and bichirs (In some classifications, the bichirs are placed in a subclass of their own, the Brachiopterygii.) Infraclass (or superorder) Holostei or Neopterygii, the intermediate ray-finned fishes: gars and the bowfin (In certain classifications, the gars are treated as a separate superorder, the Ginglymodi. The term Ginglymodi also has been used to designate the gars as an order, but this term has been replaced at the ordinal level by the term Lepisosteiformes; orders are now indicated by the ending -formes.) Infraclass (or superorder) Teleostei or Neopterygii, the advanced bony fishes: herring, salmon, perch. Distribution - Anatomy - Circulation - Respiration lamprey & hagfish

Coelacanth

Lungfish

New Zealand Fish Over 1,000 species, many in Indo-Pacific and Australia as well Of the 270 coastal species, approx. 25% are endemic

Triplefins Osteichthyes

Parore: Herbiverous fish feeding on kelps and other algae

Demersal fish live on the sea floor

Pelagic fish live in the water column above

Variations on a theme

Osteichthyes

Blue maomao : plankton feeders

Trevalley : plankton feeders

Snapper

Leatherjacket

Yellow-finned tuna