Marine Reptiles & Birds: Evolution and Adaptations in Ocean Environments

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

5. 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

6. 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

7. Marine Crocodiles • 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

8. 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

17. 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

18. 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

19. Sea Turtles • Reproduction • courtship – males court females before mating; males may compete for a female, or 1 female may mate with several males and lay eggs fertilized by several different males thereby increasing genetic diversity of population • nesting – females dig shallow pits on the beach, usually at night, and bury eggs, clutch size is between 80 – 150 eggs • Single female can lay several clutches of eggs at 2 to 3 week intervals • development and hatching • average incubation time is 60 days • temperature determines development time and sex ratio • hatchlings rush for the safety of the sea after hatching

21. 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 af earth’s magnetic field • use sun

22. 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

24. 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

25. 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

26. 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

27. Sea Snakes • 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

28. 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

29. 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

30. 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

31. 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

33. 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 • 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

34. 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

35. Shorebirds • Avocets and Stilts • 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

36. 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

37. Gulls and Their Relatives • 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

38. 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

39. 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

40. 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

41. Gulls and Their Relatives • Puffins • 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

42. 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

43. Pelicans and Their Relatives • Pelicans (Family Pelecanidae) • large birds preferring warm latitudes and estuary, coastal and inland waters • require a large fish population to support colonies of large birds

44. Pelicans and Their Relatives • Boobies • dive into the sea from 18-30 m up to fish • species lay differing numbers of eggs; this is thought to reflect the reliability of the food supply around where they nest • Cormorants • swim along the surface scanning for fish, then plunge deep to pursue them • lacking oil glands, they must periodically dry their wings in order to fly

45. Pelicans and Their Relatives • Frigatebirds (Family Frigatidae) • lightweight body and near 2 m wingspan • lacking oil glands and cannot waterproof their feathers – if forced to settle on ocean surface most likely will drown • hence they feed by skimming surface with their bills • pursue/attack other birds to steal prey

46. Tubenoses • Tubenoses include petrels, albatrosses and shearwaters • Have obvious tubular nostrils on their beaks which join with large nasal cavities within the head • Nasal glands secrete concentrated salt solution

47. Tubenoses • Albatrosses gliders with wings nearly 3.5 m long • most live in the Southern Hemisphere where winds circle the earth without encountering land • usually come to land only to breed • elaborate courtship displays precede mating • 1 egg is incubated by both parents on a volcano-shaped nest, and the young are fed on stomach oil, then regurgitated fish

48. Penguins • Penguins (Family Sphenisciformes) • Bird most adapted to marine lifestyle • Awkward on land, but swift swimmers • flap their wings to swim • torpedo-shaped bodies are streamlined • flat, webbed feet are used for steering • leap from the water to breathe • Eat fishes, squid and krill • Eaten by leopard seals and killer whales

49. Penguins • Adelie penguins lay eggs in summer; emperor penguins in mid-winter • Female emperor penguin lays 1 egg, which the male incubates for 2 months while she visits her feeding grounds • egg sits on his feet, covered by a fold of skin • male can feed the chick a secretion from his crop if it hatches before female’s return

50. Penguins • both parents help to feed the chick once it reaches 6 weeks • by summer, the chick can feed itself, and is ready to enter the sea