What is a fish?? Classic definition: -Any of numerous cold-blooded aquatic vertebrates of the superclass Pisces, characteristically having fins, gills, and a streamlined body and including specifically, and... -Any of the class Osteichthyes, having a bony skeleton, and... -Any of the class Chondrichthyes, having a cartilaginous skeleton and including the sharks, rays, and skates. Although this is all accurate...we will find that fish are considerably MORE!!
Fish similarities... • Vertebrate ( chordate) • Gills • Poikilothermic • Fins • Scales
Drag Reduction Features in Fish • “Fusiform” body shape • Reduction of body wave amplitude • Reduction of surface area • Boundary layer modifications
What is a fusiform body shape? • pointed leading edge • maximum depth 1/3 body length back from head • posterior taper • caudal fin interrupts ideal fusiform shape
Ostracoderms • Class Pteraspidomorphi (sp. diplorhina = “two nares”) • they literally had two separate olfactory bulbs in the brain. • those with a different shell, i.e. dermal armor
Placoderms - earliest gnathostomes(jawed vertebrates) • True jaws = more food! • Paired fins = more food!
Lamprey • Predatory/parasitic • Rasping teeth
Distinguishing Elasmobranch Traits • cartilaginous skeleton • no swim bladder • heterocercal tail • placoid denticles - scales and teeth • spiracles present with 5-7 gill slits (no operculum) • urea retained for osmoregulation • spiral valve in intestine • males have claspers, internal fertilization • oviparous, ovoviviparous, viviparous • teeth in rows, are constantly replaced Elasmobranch… plate or strap gill
Cetorhinus maximus Carchariniformes – basking sharks, filter feeder
Mako Great White Isurus oxyrinchus Lamniformes - mackerel, mako, white sharks -carnivores Great White, Carcharodon carcharias
Skates and rays spend most of their lives near (on) the ocean floor eating molluscs, squid, and small fish. Yellow stingray, Urolophus jamaicensis
Like sharks, skates and rays come in many shapes and sizes.
Spotted ratfish Hydrolagus colliei Family: chimaeridae • Identification: Broad, flat, duckbill shaped snout containing incisor shaped teeth. Prominent, venomous spine at leading edge of dorsal fin. Tapering tail constitutes almost half overall length. Coloration brown or grey with white spots. Skin smooth and scaleless. Can give off an iridescent, silvery sheen. Fins grey or dark. • Size: up to 97cm in length.
Placoid scales Found in sharks and rays, and can vary greatly in external appearance. They do not increase in size as the fish grows, instead new scales are added. Placoid scales are often referred to as denticles. Placoid scales consist of a flattened rectangular base plate which is embedded in the fish, and variously developed structures, such as spines, which project posteriorly on the surface. The spines give many species a rough texture. Placoid scales of the Broadnose Sevengill Shark.
Cycloid and Ctenoid Scales Found in bony fishes (the Teleostei). Overlapping = flexibility, over cosmoid or ganoid scales. Cycloid scales—smooth posterior margin, no ctenii. (Greek "cyclo“ or circle.)
Coloration is also veryimportant in fish.Here a stonefish “disappears”amid the coral background.Chromatophores, specializedpigment cells within itsskin provide protective coloration.
Disruptive Coloration (Camo!) • Disrupt the outline of the fish
Countershading • Being dark on top, light on bottom – Look like substrate from above – Look like water surface from below
Fish Locomotion Primary forces involved in fish swimming: Thrust - force that propels forward Drag - friction produced from passing an object through a medium Gravity – force from earth’s magnetic pull (partially counterbalanced by density of water) Lift - upward force that counteracts gravity
Skeletal Fish Muscle: • Essentially three types of fish muscle: red, white, pink. • Red muscle (oxidative): Highly vascularized, myoglobin containing tissue used during sustained swimming. Small diameter and high blood volume = rich O2 supply! Presence leads to strong flavor in some fishes (tuna). • White muscle (glycolytic): Little vascularization. Used during “sprint” swimming. Large diameter fibers. • Pink muscle: This one is sort of in between red and white. Serves in sustained swimming, but not to the extent that red muscle is used.
Swimming Styles Body wavesAnguilliform (eel-like) Lateral curvature in spine and musculature that moves in a posterior direction Start: lateral displacement of head, and then passage of this displacement along the body axis to the tail Result: backward-facing “wall” of body pushing against the water
Swimming Styles Partial body waves(Sub) Carangiform, Thunniform (tuna-like) • Body wave begins posterior to head and increases with amplitude as it moves posteriorly • Reduced drag compared to full body wave swimming • Wave STARTS at the caudal peducle (deeply forked, lunate)
Swimming Styles Caudal peduncle/fin beats Ostraciform (boxfish-like and puffer-like) Sculling action of caudal fin—like rowing No body waves - body remains rigid - useful for odd-shaped fishes
Swimming Styles Medial fin wavesAmiiform - bowfin-like Body rigid, but medial fins generate posterior waves (forward) or anterior (reverse) Good for stalking or moving without disrupting body musculature that serves as electric organ (knifefish) Also used for sculling - triggerfish & others
Swimming StylesPectoral fin beatsLabriform wrasse-likeSimilar to rowing laterally-positioned pectoral fins- often includes feathering as wellEspecially useful for fine maneuveringe.g. by deep-bodied fishes
Fish Feeding - function • Herbivores • < 5% of all bony fishes, no cartilaginous fishes • browsers - selective - eat only the plant • grazers - less selective - include sediments • Detritivores • 5 - 10% of all species • feed on decomposing organic matter
Fish Feeding - function, cont. • Carnivores • zooplanktivores • suction feeding • ram feeding • benthic invertebrate feeders • graspers • pickers • sorters • crushers
Fish Feeding - function, cont. • Carnivores, cont. • fish feeders • active pursuit • stalking • ambushing • luring
Fish feeding behavior • Fish feeding behavior integrates morphology with perception to obtain food: • Search • --> Detection • --> Pursuit • --> Capture • --> Ingestion
Feeding behavior • Fish show versatility in prey choice and ingestion • Behavior tightly linked to morphology (co-evolution)
Similar to Darwin’s finches, different shaped mouths permit specialization on many prey items.
Fish circulation is a closed system. Heart pumps blood through a loop of arteries, veins, and capillaries.