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Taxonomy

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									WFB 232 Ichthyology
                          Ichthyology – Introduction to Fishes

Vertebrate classes:                # species      % of vertebrates
   Agnatha                           85              <1%
   Chondrichthyes                    850             2%       > 50% of all vertebrates are fishes
   Osteichthyes                      23,000          50%
   Amphibia                          2,600           6%
   Reptilia                          6,500           14%
   Aves                              8,600           19%
   Mammalia                          4,100           9%

physiological and sensory modalities in fish that are not present in other taxa
        osmoregulation
        buoyancy control
        respiration (air and water)
        mechanosensory – lateral line
        electroreception
        electric generation
        light production

Characteristics and constraints of the aquatic environment
   salinity - must deal constantly with osmoregulation - into or out of body
   temperature - water has high thermal capacity, 4x that of air
   motion - from still water, with little oxygen exchange, to torrential currents
   gas saturation - water contains (relative to air) very little oxygen; methods for withdrawal must be
               specialized;
       too little, fish must achieve oxygen elsewhere; too much results in gas bubble diseases
   pressure - increases 1 atm for every 33’ of depth (= 10 m)
       consequence for buoyancy and gas bladders
       few fish are neutrally buoyant – use air or fat to compensate
       fish need much less skeletal support than terrestrial animals, due to support surrounding body
   viscosity - much higher effort required to swim in water than air
       fastest swimming speed (tuna) - 21m/s in short bursts; killer whale does 15m/s
       little effort required to prevent sinking
   light - attenuates rapidly with depth; thus deep-sea fish may create own light
   sound - propagates rapidly in water (400x as well as in air)
       provides medium of communication by vibration, but with little directionality


Distribution of aquatic habitats
    Salt water                   Fresh water
    oceans      97.10%           ice, snow          2.2%
    salt lakes   0.01            groundwater        0.6
                                 lakes              0.01
                                 atmosphere         0.001
                                 rivers             0.0001
    Total       97.11                               2.81

Fish distribution in habitat:
        freshwater                                       41%
        saltwater                                        58%
        move between (anadromous, catadromous)            1%
WFB 232 Ichthyology



                                                Taxonomy

Objectives:
   Learn how species are defined and named; understand how taxonomic nomenclature is used
   Begin to know the classes, orders, and representative families and species in each order of fishes
   Learn to ‘read’ taxonomic descriptions
   Recognize primitive (older) versus advanced (recent) traits in fishes

Classification = hierarchical grouping of organisms (i.e. a process, an operation)
Systematics = the study of relationships
Taxonomy = the science of biological nomenclature (formal rules for use)

Taxonomic hierarchy: (note standardized endings)
   Phylum: Chordata
        Subphylum: Vertebrata
              Superclass: Gnathostomata
                     Class: Actinopterygii (formerly Osteichthyes)
                           Order: Cypriniformes
                                 Suborder: Cyprinoides
                                         Family: Cyprinidae
                                               Subfamily: Cyprininae
                                                       Genus: Cyprinus
                                                               Species: carpio

standardized endings (well-established in ichthyology)
        Order:         -formes
        Suborder:      -oides
        Family:        -idae
        Subfamily:     -inae
        Tribe:         -ini

Only genus and species are underlined or italicized with only the generic term capitalized.

phylogenetic systematics – objective is to make the classifications non-arbitrary, and informative about
        evolutionary relationships
cladograms: each branch represents monophyletic group - all from common ancestor
                if polyphyletic, then subsequent categories based on false assumption
                all members share one or more derived characters
        problem is to determine whether a given character is homologous or convergent

plesiomorphies – primitive character states
apomorphies – advanced character states
autoapomorphies – specialization unique to one taxon
synapomorphies – shared specializations
WFB 232 Ichthyology
Taxonomic relationships defined on the basis of
      morphometrics - usually measurements as ratio against SL, to account for absolute size
      meristics - counts, with ranges - may vary with environment
      anatomical traits - shape, presence/absence of structures
      color patterns - highly variable, change with maturity, subjective, fade in preservative
      karyotypes - changes in number and shape of chromosomes
      biochemical methods - look directly at genetic material

Authorship of scientific names
      In original genus: Amia calva Linnaeus – usually followed by date
      In new genus: Lepisosteus osseus (Linnaeus)
      right of priority – given to first full written description, usually with type specimen from a type
               locality
      the description makes it a nominal species
      original species name must not be changed, even if genus is changed
      - unless previously used for another animal (nomen praeoccupatum)
      - if previously described, later description becomes junior synonym
      hybrids denoted with an x - Rutilus rutilus x Abramis brama

Nomenclature (International Code of Zoological Nomenclature)
pronounciation:
       ch = k (e.g., ichthyology) – there is no ‘k’ in Latin
       initial c = s (e.g., Cyprinidae)

genus and species always italicized; genus is always capitalized, species name is not capitalized
       Neogobius melanostomus

genus and subspecies can be abbreviated after they have been mentioned once in a text
       N. melanostomus
       N. m. caspia

subgenus is usually in parentheses
       Dreissena (Pontodreissena) polymorpha


Characteristics of the classes of extant fishes

Character                  Primitive                      Advanced
skeleton                   cartilaginous                  ossified (calcified bone) - may be lost
paired fins                absent                         present
gill arches                absent                         present
gill arches                not joined to brain case       firmly joined to brain case
nostril(s)                 1, median                      paired
jaws                       absent                         present
fins with spines           absent (trout)                 present (perches) - but may be lost (killifish)
pectoral fins              horiz. base low on             vert. base high on body (basses)
                               body (minnows)
pelvic fins                far back on belly (pikes)      forward, attached to pectoral girdle (sculpins)
tail                       heterocercal                   symmetrical
scales                     cycloid (herring)              ctenoid (sunfish) - absence is specialization
mouth                      front of head (trout)          up- or down-turned (suckers, killifish)
WFB 232 Ichthyology
                                   Taxonomy of Fishes

Kingdom Animalia
   Phylum     Chordata
      Subphylum Vertebrata

           SUPERCLASS AGNATHA
             Class Myxini
                      Order     Myxiniformes (hagfishes)
             Class Cephalaspidomorphi
                      Order     Petromyzontiformes (lamprey)

           SUPERCLASS GNATHOSTOMATA
             Class (Placodermi)
             Class (Acanthodii)
             Class Chondrichthyes
                Subclass      Holocephali
                       Order      Chimaeriformes (chimaeras)
                Subclass      Elasmobranchii
                       9 orders (sharks, rays, skates)
             Class Sarcopterygii
                Subclass      Coelacanthimorpha
                       Order      Coelacanthiformes (coelacanths)
                Subclass      Dipnoi
                       Order      Ceratodontiformes (Australian lungfish)
                       Order      Lepidosireniformes (S. American, African lungfish)
             Class Actinopterygii - (rayfins, higher bony fishes)
                Subclass      Chondrostei
                       Order      Polypteriformes (birchirs, reedfish)
                       Order      Acipenseriformes (sturgeons, paddlefishes)
                Subclass      Neopterygii
                       Order      Semionotoformes (Lepisosteiformes) (gars)
                       Order      Amiiformes (bowfin)
                     Division     Teleostei
                       35-38 orders        (modern body fishes)
WFB 232 Ichthyology
Example of a taxonomic description (adapted from Berg, 1949)

Round goby, Neogobius melanostomus (Pallas, 1811). D1 VI (V-VII); D2 I + 14-16 (13-16); A I
+ 11-13 (11-14); P 18-19 (17-20). [ = the anterior dorsal fin has 5-7 spines, usually 6, and the
posterior dorsal fin has one spine and 13-16 soft rays. The anal fin has one spine and 11-14 soft
rays, and the pectoral fins have 17-20 soft rays.] Scaled on the parietal region, nape, back (all),
throat (all or most), abdomen, pectoral fin peduncles, and one quarter of the gill covers. Scales
on the middle and anterior nape are cycloid. Head is as wide as or wider than deep; depth is
0.9-1.2 times the width. Head length 4.2-4.5 of total body length. Angle of the jaw below the
anterior quarter of the eye. Lower jaw not prominent. Snout 1.1-1.4 times the orbit diameter.
Upper lip narrows slightly to the rear. Usually 6, rarely 7, transverse suborbital series of pit
organs. Ventral fins reach or almost reach the vent. Pelvic disk is 0.6-0.8 times the abdomen
length. If present, the anterior membrane width is very shallow, with rounded, lateral lobes.
Caudal peduncle depth is about two-thirds its length. Lacks a gas bladder and chemoreceptors.
WFB 232 Ichthyology

                                               Fish Anatomy

Objectives: become acquainted with the general external and internal structures of fishes, and how they
       vary functionally and taxonomically
       become familiar with parts of fish and associated terminology
       learn to recognize fishes by similarities and differences in structure

External anatomy

Head
   mouth
       mouth position – superior, terminal, sub-terminal, inferior
       teeth types and locations;
           mostly on mandible (lower jaw), premaxilla and maxilla (upper jaw) – Bond Fig. 2-20
       generally protrusible in derived bony fishes
       frenum - bridge of skin binding lips to snout or chin in non-protrusible jaw
   additional (or seasonal) structures include barbels, tubercules, kype, cirri
   sensory pores
   nares

Body shapes – which taxa have each, what are the advantages of each type?
   fusiform
   sagittaform
   anguilliform
   compressiform
   depressiform
   filiform

Fins – what are each used for? how does their presence or location vary among taxa?
    paired fins:    pelvic – some modified to disk (gobies) or claspers (sharks)
                         placement may be abdominal, subabdominal, jugular, mental (under chin)
                    pectoral
    single fins:    dorsal - one or two; rarely three; may be modified to disk
       (medial)     anal – may be modified to intromittent organ (gonopodium)
                    caudal – rounded, lobed, truncate, emarginated, forked; homocercal or heterocercal
                    adipose – in only a few orders
    peduncles (base of fin or tail where they attach to body)
    supporting structures:
                    ceratotrichia – cartilaginous elements in elasmobranch fins
                    lepidotrichia – rays (double, segmented elements) sometimes modified to spines
                         (ossified, single)

Skin and scales – which are more advanced, or primitive?
    presence, absence, or partial covering of scales
    functions of scales
    types of scales: placoid, ganoid, cycloid, ctenoid, scutes
    skin pigmentation: melanophores
WFB 232 Ichthyology
Internal anatomy

Internal organs
    GI tract (stomach, intestine, pyloric caecae), reproductive organs, kidneys, liver, gall bladder, spleen
    gas bladder may be present or absent, connected or not to other organs
         physoclistous – closed gas bladder
         physostomus – gas bladder has open connected to esophagus

Body musculature
   hypaxial muscles
   epaxial muscles
   myomeres


Osteology
   Skull
       premaxilla, maxilla, dentary, palatine may all have teeth attached
       operculum: opercle, subopercle, preopercle, interopercle
       otoliths – ear bones
       branchial arches - usually 5 pairs - bear gill rakers on inner surface
                 fifth arch may be modified to pharyngeal teeth
       breathing apparatus (see diagrams in Bond)

    Vertebral column
       Vertebrae composed of centrum, with neural spine, neural arch, neural canal
       zygopophysis, basapophysis – small locking projections add rigidity, connection with ribs
       hemal spine, hemal arch (only near tail), hemal canal
       dorsal ribs, or epipleurals, project from pleurals

    Caudal skeleton
       urostyle – last vertebra, modified into plate
       hypurals - modified from hemal arch, connected to end of vertebral column and caudal elements
       epurals – remnant from hemal spine, one or more free bones above hypurals

    Appendicular skeleton
       pterygiophores articulate with fin rays
       pectoral girdle – cleithrum, scapula, coracoid bones
       pelvic girdle – simple system to support fins
WFB 232 Ichthyology
                           Orders of fishes, with selected families

                                 Number of      Representative        Common            # species
Class/subclass        Order        Families     families              names              in order
Myxini                Myxiniformes        1     Myxinidae             hagfish                  43
Cephalaspidomorphi Petromyzontiformes       1   Petromyzontidae       lamprey                  41
Chondrichythes
  Holocephali         Chimaeriformes       3    Chimaeridae           chimaeras                31
  Elasmobranchii      Heterodontiformes    1    Heterodontidae        bullhead sharks           8
                      Orectolobiformes     7    Rhincodontidae        whale sharks             31
                      Carchiniformes       7                          ground sharks           208
                      Lamniformes          7    Cetorhinidae          basking sharks           16
                      Hexanchiformes       2    Hexanchidae           cow sharks                5
                      Squaliformes         3    Squalidae             dogfish                  74
                      Squantiniformes      1    Squantinidae          angel sharks             12
                      Pristiophoriormes    1    Pristiophoridae       saw sharks                5
                      Rajiiformes          9    Rajidae               skates, rays            456
Sarcopterygii
  Coelocanthimorpha Coelacanthiformes      1    Latimeriidae          coelacanth               1
  Dipnoi            Ceratodontiformes      1    Ceratodontidae        Australian lungfish      1
                    Lepidosireniformes     2    Lepidosirenidae       S. Am., African lungfish 5
Actinopterygii
  Chondrostei       Polypteriformes        1    Polypteridae          birchirs, reedfish       10
                    Acipenseriformes       2    Acipenseridae         sturgeons, paddlefish    26
  Neopterygii       Semionotoformes        1    Lepisosteidae         gars                      5
                    Amiiformes             1    Amiidae               bowfin                    1

Div. Teleostei        Osteoglossiformes   6     Hiodontidae           mooneye                217
                      Elopiformes         2     Megalopidae           tarpon                   8
                      Albuliformes        3     Albulidae             bonefish                29
                      Anguilliformes     19     Anguillidae           eels                   738
                      Saccopharyngiformes 4                           swallowers, gulpers     26
                      Clupeiformes        4     Clupeidae             herrings               357
                      Gonorynchiformes    4                           milkfish                35
                      Cypriniformes       6     Cyprinidae            carp, shiners        2,662
                                                Catostomidae          suckers
                      Characiformes       10    Characidae            hatchetfish          1,343
                      Siluriformes        31    Ictaluridae           catfish              2,405
                      Gymnotiformes        6                          knifefish               62
                      Esociformes          2    Esocidae              pikes                    5
                                                Umbridae              mudminnows               5
                      Osmeriformes        13    Osmeridae             smelt                  236
                      Salmoniformes        1    Salmonidae            salmon, trout, ciscoes 66
                                                                      whitefish, chubs
                      Stomiiformes         9                          lightfish, dragonfish 321
                      Ateleopodiformes     1    Ateleopodidae         jellynose fish          12
                      Aulopiformes        12                          lizardfish             219
                      Myctophiformes       2                          lanternfish            241
WFB 232 Ichthyology
                      Lampridiformes        7                       ribbonfish, oarfish      19
                      Polymixiiformes       1   Polymixiidae        beardfish                 5
                      Percopsiformes        3   Percopsidae         trout-perch               9
                      Ophidiiformes         4                       cusk-eels               355
                      Gadiformes           12   Gadidae             cod, hake               482
                      Batrachoidiformes    17   Batrachoididae toadfish                      69
                      Lophiiformes         16   Lophidae            anglerfish              297
                                                Ogvocephalidae batfish
                      Mugiliformes        1     Mugilidae           mullets                  80
                      Atheriniformes      5                         silversides, grunion 285
                      Beloniformes        5                         needlefish, flying fish 191
                      Cyprinodontiformes 13     Cyprinodontidae livebearers                 807
                                                Poeciliidae         guppies
                      Stephanoberyciformes 9                        whalefish                86
                      Beryciformes       14                         squirrelfishes          123
                      Zeiformes            6                        John Dories              39
                      Gasterosteiformes 11      Gasterosteidae      sticklebacks            257
                                                Pegasidae           seamoths
                                                Syngnathidae        pipefish, seahorses
                                                Indostomidae        I. paradoxus
                      Synbranchiformes      3   Synbranchidae       swamp eels               87
                      Scorpaeniformes      20   Cottidae            scorpionfish, sculpin1,271
                                                Dactylopteridae flying gunards
                      Perciformes         128   Percichthyidae      temperate bass        9,293
                                                Centrarchidae       sunfish
                                                Percidae            perch, bass
                                                Sciaenidae          drum
                                                Mullidae            goatfishes
                                                Cichlidae           cichlids
                                                Mugilidae           mullets
                                                Gobiidae            gobies
                                                (also: bluefishes, remoras, blennies, mackerels,
                                                dolphins, snappers, tunas, swordfish)
                      Pleuronectiformes     6   Pleuronectidae      flounder, flatfishes 570
                      Tetraodontiformes     9   Balistidae          triggerfishes           339
                                                Ostraciidae         cowfish, boxfish
                                                Tetraodontidae puffers
                                                Molidae             molas (ocean sunfish)

Totals: 5 classes     57 orders                 478 families                 ~26,000 species
WFB 232 Ichthyology
                                           Swimming

Objectives
      Understand the physical characteristics of water that affect the ability to swim
      Understand the various modes of fish propulsion, factors that affect their efficiency, and
           representative species that use them

physical properties of water
       density – 830 x more than air
       viscosity – 70 x more than air
       boundary layer
       turbulence

Reynolds number (Re) (dimensionless variable)
      Re = LVr/m
            L = length of object
            V = velocity of object
            r = density of fluid
            m = viscosity of fluid

Examples of Re:
      animal                            speed            Re
      whale                             10 m/s      300,000,000
      tuna                              10 m/s       30,000,000
      copepod                           20 cm/s             300
      sea urchin sperm                   0.2 mm/s             0.03

unavoidable issues when swimming:
      flow changes to turbulent at Re ~ 2,000
      boundary layer changes to turbulent as Re goes from 5x105-5x106
      turbulent flow is a consequence of
              decreasing viscosity
              increasing density of liquid
              increasing speed
              increasing length

for efficient swimming
        avoid separation of boundary layer from surface
        maximize laminar flow in boundary layer
        minimize turbulent flow in wake
solutions:
        streamline body (tapering)
        aspect ratio of about 0.25
        max. thickness of body 1/3 back
        drag reduction - keep body rigid
        slime layer to reduce frictional drag
        rough surface (cteni) keeps boundary layer attached
WFB 232 Ichthyology
Swimming modes
     “kick and glide”
     active - sustained for hours or days
     burst - only for up to 30 secs
     large fishes have greater difference between burst and active than small fishes
     active swimming accomplished using red muscle along sides of fish
             - high myoglobin and mitochondrial enzymes
     burst swimming with white muscle
             - great contractile speeds, low endurance


Body/caudal fin propulsion




Medial/paired fin propulsion




non-swimming locomotion
      burrowing
      wriggling
      ‘walking’
      push-and-hold
      walking on bottom vics
      leaping
      gliding
      hitchhiking
      passive drift
      jet propulsion

								
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