Transcript Chapter 11
Chapter 11 Marine Reptiles and Birds Karleskint Turner Small 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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, verticallyflattened orange bills to slice through adductor muscles of bivalve molluscs – use bills to pry limpets off rocks, crush crabs and probe mud 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 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 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 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 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 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 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 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 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 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 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 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 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 – feed just under the water’s surface using gular (throat) pouches as nets • gular pouch: a sac of skin that hangs between the flexible bones of the bird’s lower mandible 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 Pelicans and Their Relatives • Cormorants (continued) – most are strong fliers, but the Galápagos Island species is flightless – guano cormorant of the coast of Peru valued for its guano (bird manure) • 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 Tubenoses • Tubenoses (Order Procellariiformes) 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 • Stomachs contain a large gland that produces a yellow oil composed of liquefied fat and vitamin A, used for feeding hatchlings and defense Tubenoses • Albatrosses (Family Diomedeidae) – 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 Tubenoses • Petrels (Family Hydrobatidae) – storm petrels are small birds with long legs with a characteristic, fluttering flight • feed with legs extended and feet paddling rapidly just below the surface • form long-term pair bonds for breeding – diving petrels resemble auks • live only in the Southern Hemisphere in year-round cold water • spot prey from the air, perform a headlong dive, and pursue prey by “flying” underwater 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 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 – crop—a digestive organ that stores food before it is processed Penguins – female returns with food in her crop for the chick, and male can feed – 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