Overview
This lecture introduces sea slugs, especially nudibranchs, describing their unique features, biological abilities, and notable species that exemplify their diversity and evolutionary marvels.
Introduction to Sea Slugs
- Sea slugs are marine invertebrates, often vibrant and colorful, found mostly in shallow tropical waters.
- The term "nudibranch" refers to a subgroup of sea slugs with exposed gills; not all sea slugs are nudibranchs.
- Most sea slugs are small, around 2 inches long; a few rare ones reach up to 2 feet.
- Their bright colors can serve as camouflage or as aposematism, a warning of toxicity.
- Their fossil record is virtually non-existent due to their small and soft bodies.
- Nudibranchs are hermaphroditic, possessing both male and female reproductive organs.
Unique Abilities and Defense Mechanisms
- Many nudibranchs sequester toxins from what they eat, becoming toxic themselves (e.g., by eating toxic sponges or cnidarians).
- Aeolid nudibranchs feed on creatures like jellyfish and store their stinging cells (nematocysts) for their own defense.
- Some species, like the blue dragon, consume Portuguese man o’ war and become highly venomous.
Notable and Unique Species
- Sea Bunny: Small, fluffy-looking nudibranch with sensory structures that look like ears and a tail, becoming toxic by eating toxic sponges.
- Aeolid Nudibranchs: Have cerata (extensions on their bodies) and display impressive predatory and defensive adaptations.
- Blue Dragon (Glaucus atlanticus): Eats Portuguese man o’ war and stores its stinging ability for self-defense.
- Leaf Sheep: Belongs to sacoglossan group, not technically a nudibranch; steals chloroplasts from algae (kleptoplasty), enabling photosynthesis for days.
- Other examples include chocolate aeolid, "C snowflake" (suggested name), Undertaker nudibranch, Lion’s mane nudibranch (smells like watermelon candy), Spanish dancer (large, flamboyant nudibranch), donut nudibranch, and disposable penis nudibranch.
Evolutionary and Genetic Insights
- Kleptoplasty in sacoglossans like Elysia chlorotica allows them to photosynthesize by incorporating plant genes, possibly via horizontal gene transfer.
Key Terms & Definitions
- Nudibranch — A subgroup of sea slugs with exposed gills, known for bright coloration and diverse adaptations.
- Aposematism — The use of bright coloring to signal toxicity or unpalatability to predators.
- Hermaphroditic — Possessing both male and female reproductive organs.
- Cerata — Extensions on some nudibranchs used for digestion, respiration, or defense.
- Kleptoplasty — The ability of some sea slugs to steal and use chloroplasts from algae for photosynthesis.
- Nemacyst — A stinging cell used by cnidarians and some nudibranchs for defense.
Action Items / Next Steps
- No direct homework assigned; for deeper understanding, consider further reading on kleptoplasty and horizontal gene transfer in sea slugs.
- Watch the next lecture on the history of life on Earth as announced.