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Lungfishes and Ancestral Tetrapods. Lecture 8a. Take your time, I can do this all day. Superclass Gnathostomata. Class Placodermi. Class Chondrichthyes. Class Sarcopterygii. Subclass Elasmobranchii. Subclass Holocephali. Sublass Dipnoi. Lungfish. Placoderms. Coelacanth. Rays.

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lungfishes and ancestral tetrapods
Lungfishes and Ancestral Tetrapods

Lecture 8a

Take your time, I can do this all day.

slide2

SuperclassGnathostomata

Class Placodermi

Class Chondrichthyes

Class Sarcopterygii

Subclass

Elasmobranchii

Subclass

Holocephali

SublassDipnoi

Lungfish

Placoderms

Coelacanth

Rays

Sharks

Chimaeras

Tetrapods

subclass dipnoi lungfishes
Subclass Dipnoi: Lungfishes
  • Originated ~400 mya
    • Common until ~225 mya
    • Most were marine
  • Six extant species
subclass dipnoi lungfishes1
Subclass Dipnoi: Lungfishes
  • Originally classified as amphibians
    • “The lungfishes have singularly embarrassed taxonomists!” – Duvernoy 1846
  • Have paired lungs—obligate air breathers
    • Extend ventrally off pharynx
    • Extend most of body length
    • Composed of many air sacs
    • Gills are reduced structures
  • Naso-pharyngeal connection

Why would a fish need to evolve air breathing?

subclass dipnoi lungfishes2
Subclass Dipnoi: Lungfishes
  • Estivation—up to 4 years (usually ~7 months)
    • Fills chamber with mucus  forms cocoon
    • Metabolism slows
    • Convert ammonia  urea
the transition to land
The Transition to Land
  • Tiktaalik—biggest fossil discovery in decades
    • Findings published in 2006
  • Fossils from 380 mya, 12 million years before first tetrapod (amphibian) fossils
    • Found in alluvial deposits
the transition to land1
The Transition to Land
  • Shared common ancestor with lungfishes
    • Lobed fins with rays
      • Loss of dorsal/anal fins
      • Transition pectoral skeleton
    • Up to 9 feet long
    • No bony operculum
      • Mobile neck
    • Functioning wrist joint
      • Primitive digits
sea turtle anatomy
Sea turtle anatomy
  • Carapace—fused to backbone
    • Fused-bony scutes
    • Keratin coating
  • Ventral plastron
  • Limbs modified  flippers
  • No true teeth—keratin beak
evolutionary history
Evolutionary history

Originated 120 mya

  • Evolved from more terrestrial form

Five major lineages existed—three went extinct 65 mya

Seven living species

Leatherbacks diverged >100 mya

diversity diet
Diversity & Diet
  • Carapace covered by leathery skin
    • Thousands of tiny bones beneath
  • Jellyfish diet—dive up to 4,000 ft.
    • Weigh up to 2,000 lbs.

Leatherback

  • Average adult weight—300 lbs.
    • 2nd largest
  • Adults nearshore—herbivorous
    • Mostly south of Carolinas

Green

  • Average adult weight—250 lbs.
  • Adults nearshore—carnivorous
    • Bigger head/jaws
  • Migrate up east coast

Loggerhead

osmoregulation
Osmoregulation
  • Keratin in skin (scales)—water tight
  • Salt gained when feeding
    • Papillae—
    • Muscular esophagus—
  • Kidneys have no water re-absorption ability
    • Tear gland modified into salt gland
    • Urine consists of NH3 and urea
slide15

What are some issues a deep diving sea turtle faces?

What adaptations might sea turtles possess to equip them for deep diving?

diving breathing
Diving & Breathing
  • Only spend 5% of time at surface
    • Dive duration—20 to 50 minutes
    • Basking—
    • Surface interval < 5 sec.
  • High tidal volume of lungs—
    • Up to 10x other reptiles
    • Large airways—networked
  • Breathing is active
    • Body muscles ventilate lungs

http://www.youtube.com/watch?v=8nmmYAtmag0

diving breathing leatherbacks
Diving & Breathing—leatherbacks
  • Dive > 5x the depth of other species
      • Flexible plastron
  • > 50% of O2 is stored in blood & tissue
      • Much higher concentration of blood cells
      • Other species store most O2 in lungs
  • Dive duration shorter
can sea turtles get the bends
Can sea turtles get the bends?
  • The bends—N2 under pressure dissolves into blood
    • Comes out of solution during rapid ascent
  • Sea turtle lungs collapse at depth
    • Compressed air restricted to fortified airways
      • non-respiratory surfaces
  • Pulmonary artery constricts
    • Blood flow to lungs restricted

Reptiles have 3-chambered heart

with incomplete partition

reproduction
Reproduction

Age at maturity varies by species

  • 15 to 40 years
  • Max lifespan 50 to 80 years
  • Females do not reproduce annually
    • 2-3 year intervals
      • Replenish fat
    • Males more often

Aging sea turtles

reproduction mating behavior
Reproduction—Mating behavior
  • Males are aggressive with females
    • Also bite each other
  • May remain coupled > 1 hour
  • Males well endowed—bifurcated penis
  • Females mate with

multiple males

    • Sperm stored
reproduction nesting
Reproduction—Nesting
  • Foraging & mating/nesting typically in different locations
  • Most species nest in Florida or Caribbean
    • Loggerheads more widespread
  • Nesting occurs during warmer half of year
    • 1 to 2 hours
  • Females nest innatal region
      • Advantage?

Arribadas!

reproduction nesting1
Reproduction—Nesting

Females produce multiple clutches in a breeding year

    • Leatherbacks—6 times; Kemp’s Ridley—2 times
    • Resting interval 10 to 30 days
  • Number and size of eggs varies by species
    • Leatherback—80 eggs, 75 g each
    • Hawksbill—130 eggs, 25 g each
  • Eggs hatch after 45 to 75 days
    • Depends on species and temperature
reproduction hatching
Reproduction—Hatching
  • Clutch hatches together
    • Early evening—cooler & tougher for predators
  • “Hatchling Frenzy”—
  • Hatchlings orient towards brightness
    • In coastal water orient into waves
    • Offshore use magnetic orientation
migration
Migration
  • Populations have common nesting grounds
  • Foraging areas differ
  • Population mixing on foraging grounds

Loggerheads

migration1
Migration
  • International cooperation important for sea turtle recovery

Leatherbacks

threats to sea turtles
Threats to sea turtles

Low reproductive output & low offspring survival

Natural mortality

Fisheries bycatch

threats to sea turtles1
Threats to sea turtles

Legal harvesting

Poor nesting areas

Poaching

Boat strikes

Tortoiseshell