• ~350 million years ago, terrestrial vertebrates evolved from fish-like vertebrates
– Two pairs of fins adapted for walking (“tetrapods”)
– Tetrapods have internal air sacs called lungs
– First land vertebrates were the amphibians

• Amphibians are thin-skinned animals that require moisture to keep from drying out
• “Amphibian” literally translates to “double life”
– Larval form uses gills for breathing
• There are NO marine amphibians; saltwater would result in rapid desiccation

• Having adapted to land, various groups of reptiles, birds and mammals returned to the ocean
• Some, like sea turtles and marine birds, have not fully made the transition and return to land to lay eggs
• Others spend their entire lives at sea, never returning to land

• Reptiles are cold-blooded, air-breathing animals with tough, scaly skin
• Marine reptiles include:
– Sea turtles (7 species)
– Sea snakes (55 species)
– Marine crocodiles (1)
– Marine lizards (iguanas; 1)

• Like most fish, marine reptiles are ectothermic and poikilothermic; “cold-blooded”
• Marine reptiles breath air; they have internal lungs, not gills
• Marine reptiles are equipped with special salt glands to concentrate and excrete salts
• Leathery shells prevent eggs from drying out

• Sea turtles belong to an ancient group of reptiles
• Their body is enclosed by an armor-like shell, or carapace that is fused to their backbone
• All are streamlined and adapted for life in the water
– Forelimbs are modified into flippers
– Hindlimbs act as rudders
– Cannot retract head or limbs

http://fwie.fw.vt.edu
scienceblogs.com
www.underwater.com.au
Leatherback Green Loggerhead
Hawksbill http://www.costaricaturtles.com/costa_new_seaturtles.html
Kemp’s Ridley www.dnr.state.md.us/ fisheriesoxford/ research/fwh/ seaturtles.html

• Sea turtles spend their entire lives at sea; only females come ashore to lay eggs
– Homing (return to same beach where they were born to lay eggs) http://www.colbertnation.com/the-colbert-reportvideos/85965/april-26-2007/stephanie-loses http://www.conservation.org/great_turtle_race/Pages/main.aspx

• When female sea turtles come ashore to lay their eggs, the depth of the burrow she digs affects the temperature of the eggs that are laid
• Temperature (not genetics) determines the sex of the offspring
– Warmer nests  females
© Aqua Image/age fotostock

• Female sea turtles aggregate on the beach in mass nestings called arribadas http://www.youtube.com/watch?v=W4u3GL9SyyM

• Most of the world’s sea turtles are threatened or endangered with extinction
• Dangers include:
– Shrimp trawling; Long-line fishing
– Beach destruction, hardening of shorelines, vehicles and dogs on beaches
– Bright beach lights
– Marine debris; Ghost netting
– Global warming
Credit: © James Watt/Visuals Unlimited

Trends in nesting leatherback turtles in the Pacific
Lewison, R., S. Freeman & L.B. Crowder. 2004

Map of
Reported
Longline
Effort, inc. all Tuna &
Swordfish for 2000
1.4 Billion Hooks Deployed Every Year
Lewison, R., S. Freeman & L.B. Crowder. 2004. Quantifying the effects of fisheries on threatened species: the impact of pelagic longlines on Loggerhead and
Leatherback Sea Turtles

Swordfish fisheries incidentally catch the majority of
Leatherbacks; Bycatch rates 10x higher than tuna fisheries
Pelagic Longline Swordfish Fishers deploy hook sets at night with chemical lightsticks to attract or illuminate baits to hooks

• Every fall and winter, the local sea turtles off
Long Island need to return south to the warmer waters of the Caribbean and the Gulf of Mexico
• Sea turtles that remain can become “cold stunned”
– <50°F
– Call the Riverhead
Foundation: 369-9840

• Approximately 55 species of sea snakes are found in the tropical Indian and Pacific oceans
• The tail end of sea snakes is flattened into a paddle-shape for swimming
• A few species return to land to lay eggs, but most give birth to live young underwater
– ovovivipous

• Sea snakes are closely related to cobras; the most venomous of all snakes
• Sea snake bites can be fatal to humans; extremely venomous
– Why?

• The marine iguana is found on the Galapagos
Islands, off the coast of South America
• Marine iguanas survive in the cold, upwelled waters off the Galapagos by frequently basking on the rocks to raise their body temperature
• Feed on algae
• Efficient swimmers

• The saltwater crocodile inhabits mangrove swamps and estuaries in the eastern Indian
Ocean, Australia, and some of the western
Pacific islands
• Very aggressive; fatal attacks on humans
• Commonly 20ft long
• Inhabits coast, rivers and open sea
© Susan Flashman/ShutterStock, Inc.