Marine Biology Notes

Marine Mammals

  • The term "marine mammal" is a general term, not a strict classification.

  • Includes freshwater animals like river dolphins.

  • It is a polyphyletic, meaning it involves multiple origins and is not a single lineage classification.

Orders of Marine Mammals

  • Three main orders:

    • Order Sirenia: Sea cows (e.g., Florida manatee).

    • Order Carnivora: Includes dogs, bears, wolves, cats, and pinnipeds (seals, sea lions, otters).

    • Order Cetacea: Whales, including dolphins. Dolphins are toothed whales.

Defining Marine Mammals

  • Live in the water and are mammals.

  • River otters are not considered marine mammals, even though some dolphin species are exclusively freshwater.

Order Sirenia: The Sea Cows

  • The name "Sirenia" comes from sirens or mermaids.

  • Europeans supposedly mistook manatees for mermaids.

  • Species include:

    • West Indian manatee (found in Florida)

    • Amazonian manatee

    • West African manatee

  • West Indian manatees can be found in the ocean for faster travel.

  • Dugongs are exclusively marine species with dolphin-shaped tails.

  • Stellar sea cows are now extinct and were much larger than manatees, hunted to extinction.

Families within Sirenia

  • Dugongidae: Saltwater sea cows, including dugongs and the extinct Steller's sea cow.

  • Trichechidae: Manatees, including Florida/West Indian manatees, Amazonian, and West African manatees.

Species Account: Florida Manatee

  • Subspecies: Trichechus manatus latirostris

  • Moved from "endangered" to "threatened" status due to reduced boat strike deaths.

  • Boat strikes were a major issue because of the U-shaped riverbeds, which made it difficult for manatees to locate the direction of boat engines.

  • Current leading cause of death is cold.

  • Manatees avoid cold by swimming near warm springs (72°F) or near the exhaust canals of nuclear power plants.

  • SeaWorld does manatee rescues and rehabilitation with public viewing.

  • False floors in tanks allow for diagnostics without fully removing them from the water.

Order Carnivora: Carnivores

  • Includes vegetarian (pandas) and omnivorous (most bears) members.

  • Marine mammals: polar bear, California sea lion, sea otter, walrus, leopard seal.

Family Ursidae: Bears

  • Polar bear (Ursus maritimus) is the only marine representative.

  • Polar bears spend more time swimming than on land/ice.

  • Behavior rhyme: "Black bite back, brown lay down, white good night."

  • Polar bears have interbred with grizzly bears (brown bears) to create hybrid polar-grizzly bears.

Pinnipeds: Seals, Sea Lions, and Walruses

  • Taxonomy is debated (clade or suborder?).

  • Pinnipeds are difficult to study due to their marine habitat.

  • Question: Did they descend from a common ancestor (monophyletic origin) or independently evolve similar traits (polyphyletic group)?

Families within Pinnipedia

  • Phocidae: True seals, lacking an external ear (pinna).

  • Otobinidae: Walruses, with only one extant species and 11 extinct species.

  • Otariidae: Sea lions, with external ear pinna and are noisy.

Species Account: Leopard Seal (Hydrurga leptonyx)

  • Antarctic predator, very vicious.

  • Known to have killed people.

  • Favorite meal is penguins.

  • No external ear pinna, just a hole for the ear canal.

Walruses (Odobenus rosmarus)

  • Known for tusks and mustaches (whiskers for feeling).

  • 11 known extinct species.

California Sea Lion (Zalophus californianus)

  • Males have a bump on their heads and are very vocal.

  • External ear pinna.

  • Sea lions are noisy.

  • Native to California waters; gather on rocks off the coast.

  • Common prey for great white sharks and orcas.

Clavistics of Seals, Sea Lions, and Walruses

  • Shared traits: Lack of ear pinna (seals and walruses).

  • Seals and sea lions have free tails, whereas walruses have webbed tails.

  • Varied tongue shapes.

  • External scrotum only in sea lions.

  • Teeth: 2 for seals, 4 for walruses and sea lions.

  • Locomotion: Seals and walruses use two limbs, while sea lions are quadrupeds on land.

  • Lactation: Females feed during lactation by viruses and sea lions, while seals fast during lactation.

  • No clear evolutionary pattern emerges, suggesting a complex, possibly polyphyletic origin.

  • Graduate research focused on reproductive physiology and hormones of these animals.

Delayed Implantation

  • Breeding window for northern elephant seals is three months.

  • Females pregnant at the beginning or end of the season give birth within two weeks of each other.

  • Delayed implantation occurs due to the uterus not allowing implantation until the correct concentration of progesterone is present.

  • Progesterone is present when the pineal gland detects the appropriate amount of daylight.

  • This ensures that after breastfeeding, pups have enough fish to hunt because fish populations vary seasonally.

  • Avoids predators and maximizes body heat retention.

Pinniped Evolution

  • Some papers suggest delayed implantation evolved independently 17 times (convergent evolution).

  • Pinniped evolution is complex, with no easily defined evolutionary patterns.

  • Monophyletic origin suggested if evolution explains current state.

Family Mustelidae: Weasels

  • Sea otter (Enhydra lutris) is the only marine otter species.

  • Uniquely uses tools: uses its tummy as a table where they grab sea urchins and rocks, using the rock to clobber the sea urchins open and eat their soft insides.

Order Cetacea: Whales

  • Three suborders:

    • Archaeoceti: Extinct whales. This is a bad taxonomy because it is not meant to show interrelatedness.

    • Mysticeti: Baleen whales (filter feeders with baleen in their mouths).

      • Misty means mustache, so the name means mustache whales.

    • Odontoceti: Toothed whales (predators include dolphins and porpoises).

Whale Series

  • Illustrates the supposed descent of whales.

  • Includes Pakicetidae, which had four legs and hoofs.

  • Shows the progression from land animals to water-based animals with wide paws and eventually long tails with flukes.

  • Each point on the family tree represents a hypothetical common ancestor (missing link).

  • All of the missing links are missing for all animals, for all of life. There are no intermediate forms.

Suborder Mysticeti: Baleen Whales

  • Most are great whales, except for the sperm whale.

  • Four families are all baleen whales.

  • Feeding styles:

    • Gulpers: Have throat pleats to expand mouth with water and food (krill, plankton). Expel water through baleen, trapping food.

    • Skimmers: Swim along the surface with mouths open, collecting plankton.

  • Two slits on their blowholes compared to one opening for odontocetes.

Species Account: Blue Whale (Balaenoptera musculus)

  • Family Balaenopteridae (Rorquals).

  • Largest animal ever to live on Earth.

  • Gulpers with throat pleats.

  • Can be 100 feet long.

  • Inhabit cold waters due to blubber and high body mass to surface area ratio, which allows it to conserve more heat.

Suborder Odontoceti: Toothed Whales

  • Most use echolocation.

  • Hear with the mandible bone that transfers sound to the temporal lobe where the ear is.

  • Only freshwater cetaceans are in this suborder.

  • Very intelligent.

  • Inhabit all marine environments except the abyssal depths.

Characteristics

  • Fusiform bodies (narrow at both ends, bulk in the middle).

  • Single blowhole opening, no path to lungs through the mouth.

  • Predators eating fish, squid, and pinnipeds.

Superfamilies within Odontoceti

  • Physeteroidea: Sperm whales.

  • Ziphiioidea: Beaked whales.

  • Delphinoidea: Dolphins and dolphin-like creatures.

Families within Physeteroidea

  • Physeteridae: Regular sperm whales.

  • Kogiidae: Pygmy and dwarf sperm whales.

Families within Ziphiioidea

  • Ziphiidae: Beaked whales (hard to observe).

  • Platanistidae: Ganges and Indus River dolphins.

Species Account: Strapped-Toothed Whale (Mesoplodon layardii)

  • Males have tusks that grow over their rostrum, potentially hindering feeding.

Superfamily Delphinoidea: Dolphins and Dolphin-like Creatures

  • Families:

    • Monodontidae: Narwhal and Beluga (one-tooth family).

    • Phocoenidae: Porpoises.

    • Delphinidae: Proper dolphins.

Family Monodontidae

Species Account: Beluga (Delphinapterus leucas)

  • Known as the "canaries of the sea" due to vocalizations.

  • Inhabit Arctic Ocean, North Atlantic, North Pacific.

  • Abundance estimates vary widely (50,000-150,000) due to diving behavior; and the fact that they are big and white and swimming.

Family Phocoenidae: Porpoises

Species Account: Harbor Porpoise (Phocoena phocoena)

  • Separated from dolphins by tooth shape.

  • Porpoises have spade-shaped teeth, while dolphins have conical teeth.

  • Generally smaller than dolphins.

Family Delphinidae: Dolphins

  • Genus Cephalorhynchus dolphins live along the coast of land masses in the Southern Ocean.

  • Commerson's dolphin (Cephalorhynchus commersonii) found off the East Coast of South America and the Kirkcalan Islands swim upside down.

Species Account: Hector's Dolphin (Cephalorhynchus hectori)

  • Found only in waters off the coast of New Zealand.

  • Dorsal fin shaped like a Mickey Mouse ear.

  • Endangered due to accidental capture in fishermen's nets.

  • Conservation efforts in place in New Zealand.

  • You can adopt one through WWF.

Orca/Killer Whale

  • Also a dolphin, is a member of Family Delphinidae.

  • Largest species of dolphin.

  • Ecosystems with orcas have an extra trophic level because they eat top predators also known as tropic cascades.

  • Highly intelligent, with unique hunting strategies.

  • Exhibit coordinated hunting and teaching behaviors to their young.

  • In New Zealand, they flip over rays, causing tonic immobility.

  • Off the coast of California, they kill great whites and eat their livers.

  • Bottlenose dolphins in Florida Bay kick up sediment to trap fish.

Odontoceti Hybrids

  • Hybrids are written as species A x species B (e.g., Tursiops truncatus x Pseudorca crassidens).

  • Hybrids can occur between different genera.

  • Offspring can be viable and fertile.

  • Bottlenose dolphins hybridize with various other dolphin species.

  • Hybridization challenges the traditional concept of speciation because they can all interbreed.