CORRECTION! Amiiformes – (bowfin) • “cycloid” scale • no ganoine layer, just particles • analogous to teleost

• spiral valve Lecture 7- Form and Function

1. General concepts on fish body forms 2. General fin pattern 3. Fins as preadaptations 1. -Pectoral fins 2. -Pelvic fins 3. -Caudal fins 4. -Anal fins 5. -Dorsal fins 4. Other preadapations 5. Swimming principles 6. Swimming performances and modes Fish body form

Posterior Anterior Fish body form

- maneuverability

- benthic lifestyle "An eel-like body Fish body form facilitates forwards and backwards movements into and out of tight places and soft bottoms" - The Diversity of Fishes: Biology, Evolution, fusiform bodies are and Ecology undoubtedly the result of energetic advantages

ovate bodies can deter predation among other things Fish body form Fish body form Fish body form

finlets and keels

…the need for speed Fish body form

Mouths • position correlates with trophic ecology in many fishes

• superior

• terminal

• inferior Fish body form Dentition reflects diet … we often see convergence Fish body form Fish body form

Gill rakers • morphology large prey corresponds quite closely with diet

intermediate prey

filter feeder/zooplankton Fish body form 1st gill arch (most anterior)

Number of gill rakers can be diagnostic in taxa identification Fish body form ram

suction Fish body form

cirri: fleshy flaps - camouflage - chemoreceptors

great for ID Fish body form

Roll Pitch

Yaw

• fishes are subject to 3 different movements • fins and bodies are adapted to control these movements Fish body form Lepomis spp. (Centrarchid sunfishes) Preadaptations • a trait can evolve because it served one particular function but subsequently it may come to serve another • results in shift of trait function during evolution gurnards (Triglidae) Fins as preadaptations Pectoral fins

• modified pectoral fin rays • touch and taste

• run length of their body

• generate lift Fins as preadaptations clingfishes (Gobiesocidae) Pelvic fin Chondrichthyans

• adhesion pelvic + pectoral

• internal fertilization

• generate lift Fins as preadaptations Caudal fin

• stunning prey livebearers (Poecillidae) Fins as preadaptations Anal fin • internal fertilization intromittent organ: male organ speciliazed for sperm delivery

gonopodium

surfperches (Embiotocidae) • adhesion Fins as preadaptations Dorsal fin

• defensive locking mechanism esca

ilicium

• lure Other preadaptations

• stereo-chemoreception Swimming efficiency

Water

• 800x denser than air

• 50x more viscous than air

• 95% reduction in O2 carrying capacity Swimming efficiency

Chief cause of added energetic cost is drag • viscous or frictional drag: involves friction between fish’s body and surrounding water • not affected greatly speed • affected by surface smoothness & SA

• inertial or pressure drag: caused by pressure differences resulting from displacement of water as the fish moves through it • increases with speed • intimately linked to body shape Swimming efficiency -the need for speed

Most fast-swimming fishes have streamlined shape that minimizes both inertial and viscous drag • round in cross section • maximal width = 25% of length

For example: - pelagic sharks ~ 0.26 - swordfish 0.24 - tuna 0.28 Swimming efficiency characteristic of chondrichthyes aka dermal denticle

reduced turbulence and viscous drag

• Scales in the mouths of some of the earliest known vertebrates evolved into teeth Swimming efficiency

White shark Swimming efficency

surface covered in ganoine (mineralized tissue)

loss of ganoine Swimming efficiency cycloid

many teleost taxa have cycloid & ctenoid scales ctenoid Swimming modes - most of body Anguilliform Swimming modes - via tail Carangiform Swimming modes - via tail Thunniform Swimming modes - via fins Tetraodonitiform Swimming modes - via fins Rajiform Swimming modes - via fins Gymnotiform Swimming modes - via tail Amiiform Swimming modes - via fins Labriform