Marine Vertebrates

Marine Reptiles, Seabirds & Mammals

Marine Reptiles

Basic Characteristics

  • Air-breathing: Presence of lungs

  • Ectothermic: Mostly cold-blooded (poikilotherms)

  • Scales: Body covered with scales

  • Reproduction: May lay eggs on land

Classification

  • Class Reptilia: Includes marine reptiles and others

    • Order Carnivora: Sea otter, marine otter, polar bear

    • Order Sirenia: Manatees, dugong

    • Order Cetacea:

      • Suborder Mysticeti: Baleen whales

      • Suborder Odontoceti: Toothed whales

    • Order Squamata:

      • Sea snakes, marine iguana

    • Order Crocodilia: Saltwater crocodile, American crocodile

Types of Marine Reptiles

  • Four groups:

    • Sea turtles

    • Sea snakes

    • Marine iguana

    • Saltwater crocodile and American crocodile

Sea Turtles

Conservation Status

  • Threatened/Endangered: All species are threatened or endangered

  • Threats include:

    • Overfishing and hunting for food

    • Egg predation by humans and animals

    • Bycatch in fisheries

    • Pollution, such as plastic ingestion

    • Coastal development affecting nesting sites

Species of Sea Turtles

  • Seven species:

    • Green sea turtle

    • Leatherback sea turtle

    • Loggerhead sea turtle

    • Hawksbill sea turtle

    • Olive ridley sea turtle

    • Kemp's ridley sea turtle

    • Australian flatback sea turtle

Physical Characteristics

  • Shell: Body enclosed by a shell (carapace)

  • Anatomy: Ribs fused to shell, powerful jaws, no teeth

  • Ectothermic: Most sea turtles are cold-blooded; exception is the leatherback sea turtle, which is endothermic

Feeding Habits

  • General diet includes sponges, crabs, and mollusks

  • Exceptions:

    • Green sea turtle is herbivorous

    • Leatherback feeds mainly on jellyfish

Sea Turtles: Reproduction

Breeding

  • Process: Internal fertilization at sea

  • Sperm Storage: Females can store sperm

  • Multiple Paternity: Clutch of eggs may have different fathers

  • Nesting Frequency: Females breed every 2-4 years

  • Egg Laying: Lay eggs above the high tide mark

  • Clutch Size: Up to 100 eggs per clutch, incubation period averages 60 days

Temperature-Dependent Sex Determination

  • Incubation Temperature: Determines gender of hatchlings

    • Higher temperatures produce more females

    • Lower temperatures produce more males

Sea Snakes

  • Body Structure: Laterally flattened with paddle-like tail

  • Species Count: About 70 species, found exclusively in Indian and Pacific Oceans

  • Size: Most adults are 3 to 4 feet long

  • Breeding: Most species are ovoviviparous, though some lay eggs on land

  • Diet: Carnivorous, feeding primarily on fish and fish eggs

  • Human Interaction: Sea snake bites can be fatal due to neurotoxin, but are generally not aggressive

Saltwater Crocodile

  • Habitat: Found in Australia, Indian Ocean, and Western Pacific

  • Habitat Variety: Estuaries, mangrove forests, rivers, and oceans

  • Diet: Predaceous, feeds on various prey including humans

  • Size: Can exceed 30 feet in length

American Crocodile

  • Habitat: Coastal regions, lagoons; widely spread in Florida, Caribbean, and Central America

  • Diet: Primarily fish

  • Size: Males can reach lengths of 20 feet

Marine Iguana

  • Endemic to: Galapagos Islands

  • Behavior: Spend part of life in water feeding on seaweeds, and sunbathe on shore

Seabirds

Definition

  • Birds that nest on land but feed on marine organisms

Metabolism

  • Homeothermic: Maintain constant body temperature through metabolic processes

  • Adaptations: Oil-coated feathers for waterproofing

Reproduction and Behavior

  • Egg Protection: Hard-shelled eggs for protection

  • Nesting Habits: Nesting in colonies on cliffs or isolated areas

  • Complex Behaviors: Includes mate selection, parental protection, and migration

Pinnipeds

  • Classification: Order Pinnipedia, includes seals, sea lions, and walrus

  • Feeding: Mostly predatory, feeding on fish, squid, shellfish

  • Breeding Behavior: Breed on land, timing births with availability of food

  • Physical Features: Adapted flippers and a thick layer of blubber for cold water

Marine Mammal Characteristics

General Features

  • Hair or Fur: Presence of hair, although reduced in some species

  • Mammary Glands: Produce milk for young

  • Insulation: Layer of blubber for temperature regulation

  • Complex Behavior: Capable of migrations and learning

Groups of Marine Mammals

  • Pinnipeds, Sirenians, Cetaceans (whales, dolphins)

  • Key characteristics vary across groups

Adaptations

Diving Adaptations

  • Breathing: Rapid breathing prior to dives

  • Oxygen Use: Lungs extract 90% of oxygen, more blood for oxygen storage

  • Heart Rate: Slows during dives, reducing blood flow to non-vital organs

Echolocation in Toothed Whales

  • Sound Production: Emitted clicks used for navigation and hunting

  • Melon Structure: Directs and receives echoes

Conclusion

Summary of Key Characteristics

  • Comparison of marine reptiles, seabirds, and marine mammals including reproductive strategies, physical adaptations, and ecological roles

  • Importance of conservation efforts for various species due to threats from human activities and environmental changes

  • Notable adaptations that allow survival in marine environments.