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Chapter 11 Marine Reptiles and Birds

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  1. Chapter 11 Marine Reptiles and Birds

  2. Marine Reptiles • Ancestors of modern reptiles appeared about 100 million years ago. • Reptiles adapted for success on land, then used the same characteristics to return to the sea and gain success there as well • Modern-day reptiles include: • crocodilians • turtles • lizards • snakes • All are represented in the marine environment

  3. Amniotic Egg • An amniotic egg is covered by a protective shell and contains: • amnion: a liquid-filled sac in which the embryo develops • yolk sac: sac where yolk (food) is stored • allantois: an additional sac for disposal of waste • chorion: membrane lining inside of the shell providing a surface for gas exchange during development • Evolution of amniotic egg allowed longer development (within egg) eliminating predator prone larval stage and because eggs are laid in dry places, aquatic predators are avoided • Copulatory organs allow efficient internal fertilization

  4. Physiological Adaptations • Other adaptations helping reptiles survive on land and in the ocean include: • Advanced circulatory system in which circulation through the lungs is nearly completely separate from circulation through the rest of the body • more efficient method of supplying oxygen to animal’s tissues • Kidneys are efficient in eliminating wastes while conserving water, allowing reptiles to inhabit both dry regions and the salty ocean • Skin covered with scales and lacking glands decreases water loss

  5. Marine Crocodiles • Best adapted to the marine environment is the Asian saltwater crocodile (Crocodylus porosus) • Largest living reptiles (males can grow up to 6 to 7 m long) • Feed mainly on fishes • Drink salt water and eliminate excess salt through salt glands on their tongues • Lives along the shore, where it nests

  6. Marine Crocodiles • Females reach sexual maturity at 10 – 12 years of age, males mature at ~ 16 years. • Elevated nests contain 40 – 60 eggs, incubation period is ~ 90 days • Communicate with calls or barks • Good navigational skills, can return to home estuary after being displaced long distances, using clues from sun and earth’s magnetic field

  7. Sea Turtles • Seven species inhabit world’s oceans • Adaptations to life at sea • protective shells that are fused to the skeleton and fill in the spaces between the vertebrae and the ribs • outer layer of shell composed of keratin • inner layer composed of bone • carapace: dorsal surface of the shell • plastron: ventral surface of the shell • leatherback turtle lacks shell and has a thick hide containing small bony plates

  8. Sea Turtles • Adaptations to life at sea (continued) • shell is flattened, streamlined, reduced in size and weight, for buoyancy/swimming • large fatty deposits beneath the skin and light, spongy bones add buoyancy • large fatty deposits beneath skin and spongy body also aid in buoyancy • front limbs are modified into large flippers • back limbs are paddle shaped and used for steering and digging nests

  9. Sea Turtles • Behavior • generally solitary, interact for courtship and mating • remain submerged while at sea; breathe air but can stay under water for as long as 3 hours • alternate between feeding and resting during the day • sleep on the bottom under rocks or coral, in deep water, sea turtles can sleep on surface

  10. Sea Turtles • Feeding and nutrition • have a beak-like structure instead of teeth • green sea turtle is the only herbivore, others are carnivorous • leatherback sea turtles eat jellyfish • pharynx is lined with sharp spines to hold slippery prey • digestive system adapted to withstand stings • large amounts of salt consumed with food and water are eliminated as concentrated tears through salt glands above the eyes

  11. Sea Turtles • Turtle migrations • migrate hundreds to thousands of kilometers from feeding grounds to nesting beaches • females return repeatedly to beaches where they were born to nest • green sea turtles feed on grasses in warm, shallow continental waters, but breed on remote islands thousands of kilometers away • some breed on a 2- or 3-year cycle • many hypotheses explaining method for sea turtle navigation over long distances: • utilize smell and taste as well as auditory cues • sense angle intensity of earth’s magnetic field • use sun

  12. Sea Turtles • Sea turtles in danger • beach erosion/alteration • artificial lighting near nesting beaches • sea turtles are killed when trapped in fishing nests, especially those used for shrimpers • turtle exclusion devices can reduce turtle mortality by as much as 95% when used for shrimp nets • turtles are hunted by humans for meat, eggs, leather and shells • Dogs, cats and raccoons dig up nests and prey on eggs

  13. Marine Iguana • The marine iguana of the Galápagos Islands off Ecuador is the only marine lizard • Most are black, but some are mottled red and black • dark coloration is thought to allow more absorption of heat energy • raising body temperature allows them to swim and feed in cold Pacific waters • few natural predators but vulnerable to feral predators such as rats, dogs and cats

  14. Marine Iguana • Feeding and nutrition • herbivores with a short, heavy snout for grazing on dense mats of seaweed • larger animals dive at high tide to feed on deep water algae, smaller animals feed in the intertidal • excess salt from consumed seawater is extracted and excreted by specialized tear and nasal glands

  15. Marine Iguana • Behaviors • good swimmers, using lateral undulations of the body and tail • each male occupies a small territory on the rocks, usually with 1 or 2 females • intruders or challengers are attacked when they enter the male’s territory • fights between male iguanas rarely result in serious injury and population remains unaffected

  16. Sea Snakes • Descendants of lizards that have lost their limbs as an adaptation to a burrowing lifestyle • Adaptations to life in the sea • scales are absent or greatly reduced for streamlining • tail is laterally compressed into a paddle • nostrils are higher on the head • valves in the nostrils prevent water from entering when the snake is submerged • single lung reaches to the tail, and trachea is modified to act as an accessory lung by absorbing oxygen

  17. Sea Snakes • Adaptations to life in the sea (cont.) • can exchange gases through the skin while under water • can lower metabolic rate to use less O2 • Feeding and nutrition • eat mainly fish, fish eggs and eels • most ambush prey and strike with venomous fangs • can swallow prey more than twice their diameter • eliminate excess salt by way of a salt excreting gland located posteriorly under the tongue

  18. Sea Snakes • Reproduction • 3 oviparous species lay eggs on land • others are viviparous, with females retaining the eggs within their bodies until they hatch • congregate in enormous numbers to mate • male sea snakes have two penises called hemipenes • gestation period ranges from 4 to 11 months, young can swim at birth • Sea snakes and humans • sea snake venom is toxic to humans • being timid, sea snakes rarely bite humans; people eat them in Japan

  19. Sea Snakes • Sea Snakes and Humans • toxin can be highly toxic to humans • sea snakes timid by nature, rarely bite humans, no accounts of attacking swimmers • in Japan, sea snake consumption supports a major fishery

  20. Seabirds • 250 of 8,500 bird species are adapted to live near or in the sea • Seabirds feed in the sea • Some spend months away from land, but all must return to land to breed • Types of seabirds: • shorebirds • gulls and their relatives • pelicans and their relatives • tubenoses • penguins

  21. Adaptations for Flight • Homeothermic—maintaining a constant body temperature • Feathers aid in flight and insulate • High rate of metabolism to supply energy for active flight/nervous system • Strong muscles, quick responses and great deal of coordination aid birds in flight • Advanced respiratory system with 4-chambered heart provides more oxygen to active muscles • Keen senses (especially sight and hearing) and relatively large brain to process sensory information effectively

  22. Adapting to Life in the Sea • Large amounts of salt are consumed with food and salt water • salt glands above the eyes produce tears to remove excess salt • these tears have twice the salt concentration of seawater

  23. Shorebirds • Waders that feed on an abundance of intertidal marine life • Include oyster catchers, plovers and turnstones, sandpipers and curlews, avocets and stilts and herons • Oystercatchers (Family Haematopodidae) • oystercatchers use long, blunt, vertically-flattened orange bills to slice through adductor muscles of bivalve molluscs • use bills to pry limpets off rocks, crush crabs and probe mud

  24. Shorebirds • Plovers and Turnstones (Family Charadriidae) • Plovers • have short, plump bodies with bills resembling a pigeon’s, and are shorter than other waders • have nests characteristic of waders, built in depressions or hollows on the ground • Turnstones • heavyset birds, use slightly upturned bills as crowbars to turn over stones, sticks and beach debris in search of food

  25. Shorebirds • Sandpipers and Curlews (Family Scolopacidae) • Sandpipers • are relatives of plovers and oystercatchers • feed on small crustaceans and molluscs in sand as tide recedes • Curlews • long-billed curlew uses bill like a forceps to extract shellfish from their burrows

  26. Shorebirds • Avocets and Stilts (Family Recurvirostridae) • avocets and stilts have very long legs, elongated necks, and slender bodies • avocets wade through shallow water, moving a partially opened beak from side to side through the water, to feed • stilts probe the mud for small animals (e.g. insects, crustaceans) with their bills

  27. Shorebirds • Herons (Family Ardeidae) • include egrets and bitterns • widespread, represented on every continent • skinny legs and long necks aid in hunting • most stand still and wait for prey to come in range to feed • some stalk prey or stir up the bottom to frighten prey into motion so it can be caught

  28. Gulls and Their Relatives • Family Laridae • Gulls have webbed feet and oil glands to waterproof their feathers • They are not true ocean-going birds, and do not stray far from land • Have enormous appetites but are not selective feeders • Relatives of gulls include terns, skuas, jaeger birds, skimmers and alcids

  29. Gulls and Their Relatives • Gulls • herring gulls are the most widespread, and are vocal, gray and white, and travel in large groups • feeding • noisy, aggressive, efficient predators and scavengers • may drop prey with hard shells on rocks or parking lots to break the shell open • highly successful at finding food and surviving, in some areas have reached nuisance proportions

  30. Gulls and Their Relatives • Gulls (continued) • nesting • highly gregarious; gather in large colonies • not picky about nesting sites or materials • both sexes assist in incubating 2-3 eggs • chicks hatch in 3-4 weeks, and remain in the nest until almost fully grown, camouflaged by speckled down • female can lay another clutch of eggs immediately if first one is lost • chicks are vulnerable to predation by other animals and by other gulls, not uncommon for only 1 out of every 5 hatchlings to survive

  31. Gulls and Their Relatives • Terns • small, graceful birds with brightly-colored and delicately-sculpted bills, forked tails • hunt by plunging into the water for fish and invertebrates; will steal food • usually gregarious nesters • Skuas and Jaegers • very aggressive omnivores and predators • “hawks” or “vultures” of the sea • jaegers will pursue other birds to steal their prey

  32. Gulls and Their Relatives • Skimmers (scissorbills) • small birds with pupils that are vertical slits and a flexible lower jaw protruding much farther than the upper bill • fly over water and use the lower bill to create ripples at the water’s surface that attract fish • fish are then collected by flying along the same path over the water a second time

  33. Gulls and Their Relatives • Alcids (Family Alcidae) • Include auks, puffins and murres • look like penguins but are related to gulls • convergent evolution: similar selective pressures brought about similar adaptations in unrelated groups of animals • ecological equivalents: different groups of animal that have evolved independently along the same lines in similar habitats, and therefore display similar adaptations • major difference is that alcids can fly

  34. Gulls and Their Relatives • Alcids (continued) • nesting and reproduction • alcids gather in dense, noisy colonies in the cliffs along the northern Atlantic and Pacific oceans in early spring • both parents care for 1 pear-shaped egg • parental care of the young • young murres plunge into the water to be joined by the parents, and swim out to sea • alcid parents spend most of their time gathering food for hungry chicks • adult puffins abruptly leave chicks to learn to swim and survive by themselves after 6 weeks of constant care

  35. Pelicans and Their Relatives • Pelicans (Order Pelecaniformes) include gannets, boobies, cormorants, darters, frigatebirds, tropicbirds • Have webs between all 4 toes • Upper mandible is hooked in pelicans, cormorants and frigatebirds • Many are brightly colored, or have head adornments