Download Chapter 11 - marine reptiles and birds

Chapter 11
Marine Reptiles and Birds
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:
–
–
–
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crocodilians
turtles
lizards
snakes
• All are represented in the marine environment
Amniotic Egg
• An amniotic egg is covered by a protective shell
and contains:
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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
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
• 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
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•
•
•
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
• 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
• 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
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
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
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
• Feeding and nutrition
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–
–
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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
• 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:
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–
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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
– 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
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
• 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
• 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
•
Terns
– small, graceful birds with
brightly-colored and delicatelysculpted bills, forked tails
– hunt by plunging into the water
for fish and invertebrates; will
steal food
– usually gregarious nesters
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
• 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
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
Pelicans and Their Relatives
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•
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
•
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 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
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
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
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