Overview
This lecture explores a variety of survival strategies and adaptations in ocean animals, detailing their interactions, breeding behaviors, and unique habitats.
Drifters of the Open Ocean
- Over half of open ocean animals drift in currents, including common jellyfish.
- Jellyfish feed on prey that encounters their tentacles and can grow up to 2 meters across.
- When jellyfish find plankton-rich water, their populations rapidly increase.
- Portuguese man-of-war uses a gas-filled bladder and sail to drift and hunt with its long, venomous tentacles.
Predator-Prey Interactions
- The Portuguese man-of-war can kill fish or, rarely, humans with its tentacles.
- Some fish, like the man-of-war fish, have partial resistance to the stings and feed among the tentacles.
- Specialized tentacles digest paralyzed prey.
Crab Behaviors and Survival
- Australian spider crabs gather in huge numbers annually to molt safely.
- Safety in numbers helps protect vulnerable crabs from predators like stingrays during molting.
- Sally Lightfoot crabs in Brazil race to seaweed-covered rocks at low tide, avoiding predators like moray eels and octopuses.
Coral Reefs and Competition
- Coral reefs, such as those in the Coral Triangle, support high biodiversity and competition.
- Cuttlefish hunt crabs using color-changing skin to hypnotize prey.
- Reef dwellers face numerous predators and must adapt to survive.
Breeding and Nesting Strategies
- Birds like terns use lagoons for chick flight training, facing predation from giant trevally.
- Clownfish live among sea anemones for protection, mutual cleaning, and egg-laying.
- Male clownfish prove themselves by preparing safe egg-laying sites.
Oceanic Hunters and Scavengers
- Blue sharks travel thousands of kilometers, locating food by scent, and feed on whale carcasses.
- Great white sharks dominate whale carcasses before blue sharks get access.
Mating Adaptations
- Giant Australian cuttlefish males compete for mates using color displays; smaller males use mimicry to sneak matings.
- Japanese cobodai wrasse: largest females transform into males to increase reproductive success.
Seabird Parenting Challenges
- Puffins raise chicks on remote arctic cliffs, alternating long fishing trips while avoiding predators like arctic skuas.
- Declining fish stocks create challenges for seabird parents.
Deep Sea Life and Adaptations
- Deep ocean hosts bioluminescent life forms for communication and hunting.
- Siphonophores clone themselves and may exceed the length of a blue whale.
- Marine snow provides food for deep-sea filter feeders; leftovers form thick mud layers.
- Deep-sea creatures like the sea toad and flapjack octopus are adapted to the muddy seafloor.
- Brine lakes on the seafloor create unique habitats, supporting life like giant mussels and scavenging cutthroat eels; brine is toxic to many organisms.
Key Terms & Definitions
- Jellyfish — drifting ocean animals with stinging tentacles.
- Portuguese man-of-war — colonial organism using a gas bladder to float; has long, venomous tentacles.
- Molting — process where crabs shed old shells to grow.
- Cuttlefish — mollusk with color-changing skin for hunting/hypnosis.
- Coral Triangle — region with the world’s richest coral reefs.
- Marine snow — organic debris drifting down in the deep ocean.
- Brine lake — dense, salty water pools forming unique deep-sea habitats.
Action Items / Next Steps
- Review key terms and animal adaptations described.
- Prepare for discussion on ocean animal survival strategies.