Lecture 13: Marine Reptiles

• Fish sensory systems: Chemoreception
• Regional Endothermy

  Some active swimmers use countercurrent heat exchanges

  As blood moves deeper into the body it warms up
• Defensive Mechanisms:

  Spikes/spines

  Venomous spines

  Flying fish

  Defensive coloration
• Oviparity: external fertilization (most common)
• Ovovivipartiy: internal fertilization with laying eggs
• Viviparity: live birth
• Pelagic spawners: fertilized eggs drift with the currents (no parental care)
• Benthic spawners: fertilized eggs are spread over vegetation or rocks (no parental care)
• Brood hiders: hides eggs in some way (no parental care)
• Guarders: care for offspring until they hatch and often through their larval stage
• Bearers: incubate eggs (often males)
• Oceanandromous: entire life cycle is spent in the marine environment
• Anadromous: life spent in marine but reproduce in freshwater areas
• Catadromous: spend most life in freshwater and reproduce/spawn in marine environments
• Marine reptiles and the evolution of the amniotic egg

  Decreases predation risk due to:

  • loss of free-larval swimming stage
  • terrestrial eggs (marine species unable to prey on)
  • internal fertilization (increased probability of successful fertilization)
• Circulatory system is more developed in reptiles than in fish

  Kidneys are efficient waste removal organs and water retention

  Scaly skin for minimal water loss
• Marine crocodiles

  Asian saltwater crocodile (only croc well adapted to marine environment)

  Strong swimmers

  Good navigators

  Largest extant marine reptile
• Marine crocodiles distribution in Northern Australia and the towards Asia

  Osmoregulation through tongue salt glands (ingestion of salts through foods)
• Marine crocodile reproduction: temperature sex-dependent (pivotal temperature 31.6 C with females born at above and below those temperatures)
• Marine turtles have two groups with 7 extant species
• Leatherback and Kemp's Ridley turtles are the most common in the Chesapeake Bay
• Marine turtles exist in shallow tropical and subtropical coastal waters (except for leatherbacks that live in pelagic and cold waters)
• Marine turtles have two layer shell made out of keratin and bone (except for leatherbacks that have a thick hide)
• Marine turtles osmoregulate though salt glands above the eyes by "crying" out salt
• Turtles can sense the angle and intensity of the earth's magnetic field and olfaction as a way for returning to the beaches where they hatched from
• Marine turtle reproduction

  TSD with pivotal temperature of 29.9 C with females born above the temperature
• Marine iguanas are the only marine lizard

  They do not live in the water, only graze for food in water
• Sea snakes: true sea snakes and sea kraits
• Sea snake adaptations for swimming where scales are absent or greatly reduced

  Gas exchange through skin while submerged
• True sea snakes are the largest snake group, have fixed front fangs equipped with vemon
• Sea Kraits have bold banding patterns and fixed fangs with highly toxic venom

  They are the only oviparous sea snake, all others are ovoviviparous
• Sea snakes osmoregulate through salt glands located under the tounge