Figure 34.14 The origin of tetrapods Return to the sea: Marine birds, reptiles and pinnipeds Phylum Chordata Free swimmers Nekton Now we move to reptiles (Class Reptilia) and birds (Class Aves), then on to marine mammals (Mammalia). These are all re-entry animals they reentered the marine environment to exploit niches there. With birds we see the advent of true endothermy. We call most of these organisms (as well as the large fish) nekton Tend to be large The birds, reptiles and mammals breathe air, and are all re-entry animals They have various adaptations for thermoregulation, breeding, osmoregulation, and movement that evolved in response to their re-entry into an aquatic environment MANY are K selected, which makes them susceptible to exploitation, invasive species etc. Genetic bottlenecks 1
Nekton adaptations Sea Turtles r vrs. K selection reproductive strategies Breeding on land many still rely on land (but not cetaceans and some others) Migrations often long Staying warm (endotherms) Osmoregulation (salt and water balance) Salt glands in marine birds remove excess salt from the blood 8 species, all threatened or endangered all lay eggs on land and depend on beaches for reproduction LeatherBack Green Sea Turtle Strong Swimmers who spend most of their lives in the open water. Front flippers used for swimming, back flippers used for steering 2
Sea Turtles Illness Papilloma virus is affecting many sea turtles (especially greens). We don t know why Take a look at the SWOT website: http://seaturtlestatus.org/ Sea Turtles Re-entered the sea about 150 MYA Have a very long generation time and life span (in excess of 80 years) Reproduce late (often not until they are 20-40 years old) K selected! They live throughout the tropics and suptropics Can stay underwater up to 50 minutes! They undertake extensive migrations from breeding to feeding areas Females have breeding site fidelity Sea Turtle diet Depends on the species. Many juveniles are omnivorous (eat algae, plants and other animals) They are largely all carnivores and eat Sponges - esp. Hawksbill turtles Jellies and salps (leatherbacks) Crabs Fishes Urchins Gastropods Cephalopods Adult green turtles eat sea grasses and algae 3
Food Leatherbacks eat jellyfish and other soft-bodied animals. A floating plastic bag looks just like a jellyfish, but it will choke a sea turtle. Food Leatherbacks eat jellyfish and other soft-bodied animals. A floating plastic bag looks just like a jellyfish, but it will choke a sea turtle. Loggerheads heat hard shelled organisms. Nesting and breeding: Females nest every few years once reproductive They will return to the beach where they were born approx. every 2 weeks (up to 7 times) during the breeding season to lay up to 130 eggs Males remain in the water mating happens there Hatching happens after 9-10 weeks Green Turtle nesting sites 4
Nesting The female leatherback comes ashore to nest. She crawls up at night, digs a hole in the sand, and lays 80 to 100 eggs. At dawn, she returns to the sea. Eggs The eggs look like billiard balls. Their shells are soft and leathery. Scientists move nests that are too close to the water to safer areas or to hatcheries Hatching The eggs hatch in about two months. Scientists can tell if the hatchlings will be male or female by the temperature of the nest. Colder temperatures produce males. Warmer temperatures produce females. 22.5-27 deg C = males, >30 def. C= females Hatching Hatchlings wait until night to leave the nest. Predators, like sea gulls, would eat them during the day. The new hatchlings head for the water. When they get there, they ride out to the sea. 5
Conservation Poaching food and products CITES controlled International treaties and some local regulations TED devices Light ordinances Protected beaches Controlled harvesting Plastics!! Habitat destriution: building on beaches Erosion and sea level rise Other Marine Reptiles Sea Snakes Other Marine Reptiles Salt Water Crocodile Other Marine Reptiles Marine Iguana - Galapagos Special salt glands in the nose for salt excretion Size: Where They Live: What They Eat: Special Facts: length of crocodile- 5 to 15 feet. coastal areas, tidal and nontidal near saltwater snails, frogs, fish turtles, snakes, waterfowl, small mammals the crocodile will swallow its prey whole. Crocodiles have been around since the dinosaurs 6
Seabirds Like the reptiles, pinnipends and cetaceans these are re-entry animals - they went from land back into the water. Why? Sphenisciformes Porcellariiformes Charadriiformes Anseriformes Ciconiiformes Pelicaniformes Something about seabirds 28 orders of birds (8600 species) - 4 true orders of seabirds Approx. 250 species All seabirds still breed on land - many on islands Many migrate long distances Many are threatened or endangered Many serve as harbingers of ocean conditions Endotherms (higher body temperatures than us!) Adaptations Webbed feet Countercurrent heat exchangers Oil in feathers (some) Air in feathers (some) Salt secreting glands Variety of lifestyles Seabird lifestyles Shorebirds: Waders Long legs (some) Specialized bills Countercurrent heat exchangers in legs Avocets, stilts, curlews, sanderlings, plovers Seabird lifestyles Divers: Pursuit divers Webbed feet Low oxygen consumption Fusiform No oil in feathers 7
Plunge divers Skimmers and wanderers Scavengers Kleptoparasites! Seabirds stay warm: By using countercurrent heat exchangers By having air in their feathers Some have fat (penguins!) Some have oil in feathers High metabolism Seabirds osmoregulate: By having a salt secreting gland (to get rid of excess salt) By producing uric acid instead of urea (helps retain water) By having efficient kidneys They can drink seawater! Counter current heat exchangers revisited Blood in the arteries runs deep (not near the surface) As it passes by cooler veins, it gives up some of its heat, warming up the veins. In this way, heat can be trapped within areas where it is needed Breeding on islands Most seabirds breed on islands or in large colonies What are the conservation implications? Introduced rats, cats on islands where birds are ground nesters Destruction of colony site = destruction of huge percentage of the population 8
Long migrations Seabirds undertake some of the longest migrations of any animal: the arctic tern migrates 10,000 miles from the Arctic to the Antarctic! These migrations are to and from feeding and breeding grounds. Seabirds are highly dependent on oceanographic conditions and food availability 9