Chapter 9

Basic characteristics of marine reptiles

- Air-breathing: presence of lungs - Mostly "cold blooded" (ectotherms, poikilotherms; see Table 4.2) - Body covered with scales - May lay their eggs on land

Sea Turtles • Seven (or eight) species of living sea turtles :

- Green sea turtle (some biologists recognize two species, the Pacific and the Atlantic green turtles) - Leatherback sea turtle - Loggerhead sea turtle - Hawksbill sea turtle - Olive ridley sea turtle - Kemps ridley sea turtle - Australian flatback sea turtle

Groups of Marine Mammals

1. Pinnipeds (Order Pinnipedia) - seals, sea lions, and walrus 2. Carnivores (Order Carnivora) - sea otter, marine otter, and polar bear 3. Sirenians (Order Sirenia) - dugong and manatees 4. Cetaceans (Order Cetacea) - whales, dolphins, and porpoises

Four groups of marine reptiles:

1. sea turtles 2. sea snakes 3. marine iguana 4. saltwater crocodile 5. American crocodile

Walrus (Order Pinnipedia)

• Odobenus rosmanus • Absence of external ears • Both males and females possess large tusks, but adult males are slightly larger than females, with longer and stouter tusks • On land, walruses are capable of rotating their hind flippers to walk on all fours as in sea lions. • Food: mainly bivalve mollusks (clams); also other benthic invertebrates like worms, snails, sea cucumbers, squids, and crabs. May occasionally prey on fishes such as polar cod and scavenge on seal carcasses. • Arctic Sea - both Pacific and Atlantic • In relatively shallow water. Migrates with pack ice, some aggregating in small rocky islands and coasts in summer • Delayed implantation; females give birth every 2 years • Copulation and nursing in the water

Sea Turtles

• All species of are threatened or endangered •Endangered - a species that is in danger of becoming extinct •Threatened - a species that may become endangered because of low numbers • Threats: use a food by humans; eggs eaten by humans and other animals; individuals getting caught in drift, gill, and shrimp nets; swallowing plastic bags; development of beaches used as nesting areas

Order Cetacea

• Baleen whales (Suborder Mysticeti) - baleen for filter feeding, two blowholes, smaller size • Toothed whales (Suborder Odontoceti) - teeth, single blowhole, larger size

Sea Snakes

• Breed at sea; most species are ovoviviparous • A few species still return to land to lay eggs • Carnivorous and mainly feed on fishes and fish eggs • Bites from sea snakes can be fatal for humans (sea snakes are related to the cobra and have a powerful venom) but sea snakes are not known to be aggressive and have small mouths

American Crocodile

• Considered a marine species because it tolerates seawater and can be found in lagoons and other coastal regions • Widely distributed in Florida, the West Indies, and Pacific and Atlantic coasts of Central America and northern South America • Males have been recorded as long as 20 ft but average is 14 ft • Feed mostly on fish

Baleen Whales

• Filter feeders: Take in huge mouthfuls of water containing krill or small fishes. The baleen traps the prey, and water is forced back out of the mouth • 13 species, including the right, gray, blue, and humpback whales

Sea Otter (Order Carnivora)

• Fine, dense fur coats for insulation, no blubber • Smallest true marine mammal • Anterior feet small with retractile claws; posterior feet broad and webbed • Metabolic rate higher than most mammals of similar size so must consume large quantities of food. Adult sea otters may eat as much as 9 kg (20 lb.) of food each day: sea urchins, crabs, abalone, clams, mussels, octopuses, and fishes. Typically found in waters close to shore. The Alaskan sea otter has a greater tendency to come to shore than the California sea otter

Saltwater Crocodile

• Found in Australia, the Indian Ocean, and some Western Pacific Islands • It can be found in estuaries, mangrove forests, rivers, and the open ocean • It is a predatory species that eats all types of prey, including humans • Reaches to over 30 feet (although individuals over 20 feet are rare)

Manatees, Dugong (Order Sirenia)

• Front flippers but no rear limbs; paddle-like horizontal tail • Primarily herbivores (seagrasses, freshwater vegetation). Manatees consume about 4% to 9% (15 to 49 kg or 32-108 lb. for an average adult manatee) of their body weight in wet vegetation daily. • Manatees may reach 4.5 m (15 ft), 600 kg (1,320 lbs) • All four species endangered or threatened, particularly dugong • Slow reproduction, mature after about five years and giving birth to a single calf every two to five years after a gestation period of about a year. 29

Marine Mammals

• Homeotherms, endotherms: hair (reduced in some species) and layer of blubber for insulation • Viviparous with placenta to provide nutrients to embryo • Mammary glands • Large brain in relation to body size • Complex behaviors

Marine Mammals

• Homeotherms, endotherms: hair (reduced in some species) and layer of blubber for insulation • Viviparous with placenta to provide nutrients to embryo • Mammary glands • Large brain in relation to body size • Complex behaviors

Sea Otter

• Important predator in giant kelp beds regulating the number of sea urchins that graze on the kelp (see Fig. 13.27) • Similar role in seagrass meadows (see Fig. 13.28) • Endangered species, brought almost to extinction by hunters of their valuable pelts

Sea Snakes

• Laterally flattened body with a paddle-like tail for propulsion through the water • 70 species of sea snakes • Found only in the Indian and Pacific oceans • Most species are 3-4 feet in length as adults

Manatees, Dugong (Order Sirenia)

• Manatees -Three species: • Trichechus manatus - West Indian manatee (Florida and West Indies); often enters freshwater waterways along coast • Trichechus senegalensis - the West African manatee); also enters freshwater waterways along coast • Trichechus inunguis - Amazonian manatee (strictly fresh water) • Dugong ( Dugong dugon ) - East Asia to western Pacific islands

Penguins

• Most radically adapted of all seabirds: flightless with flipperlike wings • Spend a great deal of their time searching for prey at sea • Most species live in Antarctica or sub-Antarctic regions • Adapted to cold water with a layer of fat and the trapping of air in the feathers • Males and females share parenting responsibilities

Marine Iguana

• One species found only on the Galapagos Islands • While they are called marine, they only spend a portion of their time in the water • They dive to feed on seaweeds and seagrasses near shore • A large portion of their day is spent basking on the shore to warm up from their dives in the cold water surrounding the Galapagos

Pinnipeds (Order Pinnipedia)

• Predators, feeding mostly on fish, squid, shellfish • Breed on land and return to sea after giving birth ( delayed implantation of embryo in many species so that birth of calf is timed with the return of females to land) • Prefer breeding near shallow water near abundant food • Mostly living in cool or cold water: presence of blubber • Monk seals are the exception: Hawaiian and Mediterranean monk seals are endangered; Caribbean monk seals have not been seen since the 1950's • Fore and hind limbs adapted as flippers for swimming • 35 species

Adaptations: Diving

• Rapid breathing prior to dive ( apneustic breathing ) • Lungs remove 90% of O2 from air (as opposed to 20% for humans) • Elastic tissue in lungs helps temporarily expand lungs during apneustic breathing • Marine mammals have more blood than non-diving mammals for their size (means more hemoglobin to carry oxygen) • Muscles contain more myoglobin to hold oxygen in tissues • The heart rate slows dramatically during a dive ( bradycardia ) • Blood flow is reduced to extremities and digestive system • Muscles employ anaerobic respiration as necessary (needs less O2 but results in lactic acid build-up) • Marine mammals can tolerate more lactic acid than other mammals • Rib cage and lungs collapse during dive to force air into tissues and prevent decompression sickness (" bends ")

Pinnipeds

• Sea lions, fur seals, and seals

Sea Turtles: Reproduction

• Sea turtles breed at sea: internal fertilization (copulation) • Females can store sperm • One clutch (group) of eggs can have multiple paternity: males and females are not monogamous • Females normally breed every 2-4 years • Females must return to land to deposit their eggs above the high tide • Females dig a hole in the sand using only the back flippers • During their breeding year, females may lay up to 7 clutches of eggs

Sea Turtles: Feeding Habits

• Sea turtles feed on sponges, crabs, molluscs, and other invertebrates • Exceptions: Green sea turtle - vegetarian (seaweeds, seagrasses) Leatherback (largest of all sea turtles: up to 9 ft, 2,000 lbs; see Fig. 9.2 b ) - mostly jellyfishes but can dive to depths of at least 2,000 ft in search of other prey

Sea Turtles: Reproduction

• Sea turtles, like many reptiles, show temperature - dependent sex determination • The gender of the hatchling is not genetically predetermined but determined by the temperature in which the eggs are incubated • For each species, there is a temperature that will produce 50% males and 50% females; temperatures higher than this temperature will produce more females, lower temperatures more males • Potential problem: global warming!

Seabirds

• Seabirds = birds that nest on land but feed exclusively or in part on marine organisms • Like mammals, seabirds are able to maintain a constant body temperature ( homeotherms ) derived through metabolic means ( endotherms ) • Feathers are coated with an oil from glandular secretions to waterproof the body

Toothed Whales

• Simple, peg-like teeth, which vary considerably in number and size among species. Dolphin teeth are conical and interlocking, those of porpoises are spade-shaped. Teeth are adapted for grasping and tearing, not chewing. • Diet: fishes, squids, bottom invertebrates (see Table 9.1) • Include dolphins, porpoises, belugas, narwhals, sperm, orcas (killer whales), river dolphins, and beaked whales • Many threatened with extinction as a result of whaling (see section "Whaling")

Sea Turtles

• The body of sea turtles is enclosed by a shell , or carapace • The ribs are fused to the shell • All have powerful jaws with no teeth • Like other reptiles, sea turtles are poikilotherms and ectotherms (exception: leatherback sea turtle is an endotherm because it keeps a body temperature that is higher than that of the water so it can venture into cold water in contrast to the other sea turtles, which are restricted to the tropics)

Order Cetacea

• Whales, dolphins, and porpoises. • Fore limbs are modified into flippers. • Fin-like tail ( fluke ) • Nostrils are located on the top of the head as a single or double opening (blow hole)