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© 2006 Thomson-Brooks Cole Chapter 10 Fishes

© 2006 Thomson-Brooks Cole Chapter 10 Fishes. © 2006 Thomson-Brooks Cole Key Concepts Hagfishes and lampreys are jawless fishes. Sharks, skates, and rays

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Text of © 2006 Thomson-Brooks Cole Chapter 10 Fishes. © 2006 Thomson-Brooks Cole Key Concepts Hagfishes...

  • Chapter 10Fishes

  • Key ConceptsHagfishes and lampreys are jawless fishes.Sharks, skates, and rays have skeletons composed entirely of cartilage.Sharks have streamlined bodies and highly developed senses that help them to be efficient predators.Most marine fishes have skeletons composed primarily of bone.

  • Key ConceptsThe shape of a fishs body is primarily determined by the characteristics of its environment.Many fishes exhibit coloration and color patterns that help them blend in with their environment.Color in fishes functions in camouflage, species recognition, and communication.

  • Key ConceptsMost bony fishes have a swim bladder that helps them maintain neutral buoyancy.Most marine fishes are carnivorous, but herbivores, omnivores, and filter feeders also exist.Most marine fishes are oviparous and produce large numbers of eggs.Fishes such as salmon and eels migrate long distances sometime during their life cycle.

  • FishesFishes are vertebratesanimals that possess vertebrae, a series of bones or cartilages that surround the spinal cord and help support the bodyPrimitive fishes lacked paired fins and jawsAdaptation of jaws and paired fins allowed fish to more efficiently obtain food

  • Jawless FishesClass Myxini (hagfish) and class Cephalospidomorphi (lampreys)Lack both jaws and paired appendagesHave skeletons of cartilage (no bone)Lack scalesHagfish also lack vertebrae (some scientists consider them invertebrates)

  • HagfishesBottom dwelling slime eelsSkins are used to make leather goodsHagfish feeding apparatus is composed of two dental plates containing horny cusps, used to grasp the preys fleshfeed on live prey and scavengeSlime glands produce abundant milky, gelatinous fluid if hagfish is disturbedSexes are normally separate

  • LampreysHave oral disk and rasping tongue covered with tooth-like keratin platesReproductionmales migrate up rivers and build nestsfemales arrive and they spawn; eggs attach to stones of the nestlarvae are benthic filter feedersafter 3-7 years, they metamorphose into adults and return to the sea

  • Cartilaginous FishesClass Chondrichthyese.g. sharks, skates, rays, chimaerasSkeleton of cartilagePossess jaws and paired finsHave placoid scales2 major groups:holocephalans (chimaeras or ratfish)elasmobranchs (2 body forms: streamlined or dorsoventrally flattened)

  • SharksExcellent swimmers with streamlined bodiesswim with powerful, sideways sweeps of the caudal fin (tail)heterocercal tailcaudal fin in which the dorsal lobe is longer than the ventralMales have claspersmodified pelvic fins which transfer sperm from the male to the female

  • SharksMaintaining buoyancysharks sink if they stop swimminglarge livers produce squalenean oily material with a density less than seawatersqualene offsets the sharks higher density to help maintain buoyancy

  • Shark Sensory SystemsVisiona clear nictitating membrane covers and protects each lidless eyemany species seem to have color visionOlfactionmore important than vision almost 2/3 of the sharks brain cells are involved in processing olfactory informationsharks are sometimes referred to as swimming noses

  • Shark Sensory SystemsLateral line systemconsists of canals running the length of the animals body and over the headcanals open to the outside at regular intervals, allowing free movement of water over the neuromasts (sensory receptors) withinneuromasts detect vibrations in the fluid which alert the shark to movements in the water, possibly made by prey animals

  • Shark Sensory SystemsAmpullae of Lorenziniorgans scattered over the top and sides of the animals head sense electrical currents in the water

  • Digestion in SharksBlade-like, triangular teeth in the mouth grasp prey and tear off chunksFood is swallowed whole (sharks cannot move their jaws back and forth to chew)Food passes through stomach to a short intestine containing a spiral valvespiral valvea structure which aids in absorption by slowing the movement of food and increasing the surface area

  • Osmoregulation in SharksMaintain an internal solute concentration > or = to the seawaterretain large amounts of nitrogenous wastes, mostly urea and trimethylamine oxide (TMAO)Gills and rectal gland (a large structure that empties into the intestine) work to excrete excess sodium chlorideKidney excretes other salts

  • Reproduction in SharksSperm produced in paired testes are transferred to the female through grooves in the claspersOviparitymost primitive modeeggs are laid outside the body and the embryos develop in a protective casee.g. whale sharks, bullhead sharks

  • Reproduction in SharksOvoviviparitymost common modeeggs hatch within the mothers uterus but no placental connection is formedyoung are nourished by yolk from the egge.g. basking sharks, thresher sharks, saw sharks, sand tiger

  • Reproduction in SharksViviparitymost recent mode to evolveeither the young directly attach to the mothers uterine wall or the mothers uterus produces uterine milk that is absorbed by the embryoe.g. requiem sharks, hammerhead sharks

  • Skates and RaysHave flattened bodies adapted to a bottom existenceGreatly enlarged pectoral fins that attach to the headReduced dorsal and caudal finsEyes and spiracles (openings for the passage of water) on top of the headGill slits on the ventral sideSpecialized pavement-like teeth are used to crush prey (e.g. invertebrates)

  • Differences between Skates and Rays

  • Defense MechanismsElectric rays have electric organs that can deliver up to 220 VStingrays have hollow barbs connected to poison glandstreatment for stingray wounds: submerge in hot water to break down protein toxinSawfishes and guitarfishes have a series of (non-venomous) barbs along their pointed rostrums

  • ChimaerasSubclass Holocephalie.g. ratfish, rabbitfish, spookfishLarge pointed heads and long, slender tailsGills covered by operculum; water inhaled through the nostrilsMales have claspers on their heads and pelvic fins

  • ChimaerasOviparous produce large eggs in a leathery caseHave flat plates for crushing prey instead of teethGenerally bottom dwellersLittle commercial valuemarketed as food in parts of China and New Zealandtheir oils can be used as a lubricant

  • Bony FishesClass OsteichthyesVery diverse 25,000 speciesMost forms have: swim bladder (or lung), bone, bony scales, and fin rays2 major lineages:lobefins (subclass Sarcopterygii) coelacanths, freshwater lungfishray-finned fishes (subclass Actinopterygii)

  • CoelacanthsCharacterized by lungs and lobed, paired fins resembling tetrapod limbsKnown from fossils only before live specimen was discovered in 1938Skeletons are bone + cartilageFat-filled swim bladder for buoyancyNearly isotonic to seawater like sharksOvoviviparous

  • Ray-Finned Fishes2 major groups:subclass Chondrostei primitive forms with heterocercal tails, primarily cartilage skeleton, ganoid scalesganoid scalesthick, heavy scales which give the fish an armored appearance

  • Ray-Finned Fishessubclass Neopterygii homocercal tails, cycloid or ctenoid scales, more maneuverable finshomocercal tailstails with dorsal and ventral flanges nearly equal in size; vertebral column usually does not continue into the tailcycloid & ctenoid scalesscales that are thinner and more flexible; less cumbersome for active swimmers

  • Ray-Finned FishesPossess unpaired median fins and paired fins, providing better control of movementsMedian fins consist of 1 or more dorsal fins, caudal fin, and usually anal finhelp maintain stability while swimmingPaired fins consist of pectoral and pelvic finsboth used in steeringpectoral fins also help to stabilize the fish

  • Body ShapeFusiform body shapestreamlined shape with a very high and narrow tailefficient movement for active swimmers

  • Body ShapeLaterally compressed or deep bodyallows navigation through grass or corals

  • Body ShapeDepressed or flattened bodiesbottom-dwelling fishes

  • Body ShapeGlobular bodies, enlarged pectoral finsappropriate for sedentary lifestyle

  • Body ShapeLong, snake-like bodies, absent or reduced pelvic and pectoral finsuseful for burrowing, living in tight spaces

  • Fish Coloration2 basic types of fish colors:pigments (biochromes)structural colorsPigmentscolored compounds found in chromatophores chromatophoresirregularly-shaped cells, usually appearing as a central cell body with radiating processesfish can alter color by moving pigments between the central core and processes

  • Fish ColorationStructural colorscolors produced by light reflecting from crystals located in specialized chromatophoresiridophoreschromatophores used to produce structural colorscolorless, relatively immobile crystals produce mirror-like silver or iridescence

  • Fish ColorationCountershading is seen in open ocean fishobliterative countershadingcoloration in which the back (dorsum) is dark green, dark blue or gray, and the shades grauate on the sides to the bellys pure whiteDisruptive colorationbackground color of the body is usually interrupted by vertical lines; may be an eyespotmore difficult for predators to see the fish

  • Fish ColorationCryptic colorationcoloration which blends with the environmentused for camouflage

  • Fish ColorationPoster colorsbright, showy color patternsmay advertise territorial ownership, aid foraging individuals to keep in contact, or be important in sexual displaysaposematic (warning) colorationbright coloration to warn predators that the fish is too venomous or spiny to eat

  • Locomotion in Bony FishesIn swimming, the trunk muscles propel the fish through the watertrunk muscles are arranged in a series of muscle bandsmuscles contract alternately from one side of the body to the othercontractions originate at the anterior end and move toward the tail, flexing the body and pushing against the water

  • Locomotion in Bony FishesFish with different body forms swim in different wayselongate fish undulate the entire bodyswift swimmers flex only the posterior portion of the bodyother fish are somewhere in betweenfish with a dermal skeleton can only flex the area before the caudal finsome fish swim using their fins alone

  • Respiration and OsmoregulationGills often used to extract O2, eliminate CO2, and aid in salt balancegill filamentshighly vascularized, rod-like structures which compose the gillscountercurrent multiplier systemblood flows in the opposite direction from the incoming water, maintaining a stable gradient that favors the diffusion of O2 in and CO2 out of the body

  • Respiration and OsmoregulationWater must be continuously moved past the gills to keep blood oxygenatedmost bony fish ventilate gills by pumping water across themvery active fishes use ram ventilationcontinuously swimming forward at high velocity with the mouth open

  • Respiration and OsmoregulationBloods salt concentration is about 1/3 that of seawater, so water is lostFish drink seawater to compensatechloride cellsspecialized cells on the gills which eliminate most of the excess saltkidneys and digestive tract remove other excess saltmarine fish excrete negligible amounts of urine in order to retain maximum water

  • Cardiovascular SystemConsists of heart, arteries, veins, and capillariesPath of blood:deoxygenated blood collected from veins by sinus venosus (thin-walled chamber)passed to atrium, then ventricleventricle propels blood to gill capillaries where it is oxygenatedcollected from gills by dorsal aorta and passed to body via arteries and capillaries

  • Cardiovascular SystemMany active swimmers have a countercurrent arrangement of blood vesselsmaintains body-core temperature at 2-10o C above seawater, increasing efficiency of swimming musclesheat is transferred from arteries coming from the body core to veins near the outside, so that venous blood is warmed before flowing toward the core

  • Buoyancy RegulationMost fish use a swim bladdera gas-filled sac that helps offset the density of the body and regulates buoyancythe fish can adjust the amount of gas in the swim bladder to maintain depthgas is added as the fish descends and removed as it ascends

  • Buoyancy Regulation2 methods for adjusting the amount of gas in the swim bladdergulping air from the surface or spitting air out as neededgas glanda specialized gland which fills the swim bladder from gases dissolved in the bloodfish with a gas gland empty gas from the swim bladder through diffusion into the bloodActive swimmers do not have swim bladders, and must keep swimming

  • Nervous System and SensesNervous system consists of: brain, spinal cord, peripheral nerves, and various sensory receptorsOlfactionolfactory pitsblind sacs opening to the external environment that contain olfactory receptorssize varies with dependence of fish on olfaction

  • Nervous System and SensesTaste and hearingtaste receptors may be located on the surface of the head, jaws, tongue, mouth and barbels (whisker-like processes about the mouth)bony fishes have a lateral line system for detecting movement in the waterears are internal and have a detection range of 200 to 13,000 hertzhuman range = 20 to 20,000 hertz

  • Nervous System and SensesVisionno eyelidsusually dont need to adjust pupil size because of the low quantity of lightentire lens moves back and forth to focuseyes are usually set on the sides of the headmost have monocular visionshallow-water species can perceive color

  • Feeding TypesCarnivores (e.g. pufferfish, groupers)most bony fishes are carnivoresprey are usually seized, swallowed wholechewing would block water flow past gillsHerbivores (e.g. surgeonfish, parrotfish)feed on a variety of plants and algaeteeth often broad and flat with a sharp edge to scrape food from surfacesmay have gizzard-like stomach to grind vegetable matter

  • Feeding TypesFilter feeders (e.g. anchovies, larvae)feed on planktontypically use gill rakersprojections from the gill arches which filter phyto- and zooplankton from seawatermost travel in large schools, and are an important food source for larger carnivores

  • Adaptations to Avoid PredationMany exhibit elaborate camouflagePufferfishes and porcupinefish inflate their bodies to deter predatorsFlying fishes use enlarged pectoral fins to glide through the air and escapePearlfish hide in other organismsParrotfish secrete a mucus cocoonSurgeonfish are armed with razor-sharp spines

  • Adaptations to Avoid PredationClingfishes use a sucker to attach to rocks so predators cant dislodge itTriggerfish projects spines to deter predators or wedge itself into cracksScorpionfish and stonefish have venom glands for self-protection

  • Reproduction in Bony FishesGonads are paired structures suspended from the roof of the body cavity by mesenteries (membranes)Sperm and eggs pass to the outside through ducts, except in salmonEgg and sperm development is usually seasonalVariation in the level of pituitary and gonadal hormones controls the reproduction process

  • Reproduction in Bony FishesPelagic spawners (e.g. tuna, wrasses)release vast quantities of eggs into the water for fertilization by malesfertilized eggs drift with the currentsno parental careBenthic spawners (e.g. smelt)non-buoyant eggs with large yolksno parental carepelagic or benthic embryos/larvae

  • Reproduction in Bony FishesBrood hiders (e.g. grunion)species that hid their eggs in some way but exhibit no parental careGuarders (e.g. damselfish)species that care for their offspring until they hatch and, frequently, through their larval stagesBearers (e.g. jawfish, seahorses)species that incubate their eggs until they hatch (in the mouth or a special pouch)

  • Reproduction in Bony FishesLarval developmentmany larvae are zooplanktoninitially nourished by a yolk sac attached to the abdomen; absorbed once mouth and digestive tract have developedlarva grows into juvenile, leaves the planktonic community to become adultfishes grow for as long as they live

  • Reproduction in Bony FishesHermaphroditismindividuals have both testes and ovaries at some time in their livesoccurs in at least 14 bony fish familiessynchronouspossessing functional gonads of both sexes at one timesequentialchanging from one sex to anotherprotogynychanging from female to maleprotandrychanging from male to female

  • Fish MigrationsDaily migrations usually associated with feeding and predator avoidanceSeasonal migrations usually associated with spawning, changing temperatures or feedingMigrations may occur within seawater or between seawater and fresh watercatadromousfishes that move from fresh water to seawater to spawnanadromousfishes that move from seawater to fresh water to spawn

  • Fish MigrationsFreshwater eelsbest-studied catadromous fishesmigrate down coastal rivers to the sea during the falladults spawn and then dieyoung hatch, develop into leaf-like leptocephalus larvae, and migrate back to riversafter arrival, young metamorphose into juveniles (elvers) that migrate into streams and estuaries

  • Fish MigrationsSalmonAtlantic/Pacific species are anadromousPacific species return to spawning grounds once, reproduce, and die; Atlantic species may spawn more than oncelay eggs in a redda shallow depression in the gravel of a fresh water streamsalmon navigate upstream by the characteristic odor of the stream; there is not agreement on how they locate the correct rivers mouth from the open sea