Lecture on Gastropods and Cephalopods

Introduction

• Topics Covered: Continuation on gastropods and introduction to cephalopods.
• Key Concepts: Specific adaptations, character states in mollusks, and evolutionary impacts of environment on gastropods and cephalopods.

Gastropods

Recap from Previous Lecture

• Discussed radula, different groups like aplocophrines and monoplacophrines.
• Rediscovery of monoplacophrines using remotely operated vehicles.

Deep Sea Thermal Vent Gastropods

• Example: Scaly foot gastropod, Chrysomelon squamiferum.
  • Uses iron sulfide in its shell and dermal sclerites.
  • Discovered around 1999-2000 in the Indian Ocean.
  • Incorporates metal from the environment into its shell.
  • Relies on bacterial endosymbionts for nutrition.

Adaptations and Feeding

• Evolution from herbivorous browsing to carnivory.
• Development of symbiotic relationships, e.g., with Elysia.
• Diverse feeding strategies including deposit feeders and scavengers.

Shell Adaptations

• Variations include thicker periostracum in hydrothermal vent snails.
• Blue-rayed limpet uses photonic structures for reflection, possibly for camouflage or mimicry.

Movement and Mucus

• Methods of movement involve muscle contractions and wave patterns.
• Mucus functions in water conservation, movement, and predator defense.

Reproduction

• Hermaphroditic snails use "love darts" in mating.
• Various reproductive strategies are seen across different species.

Ecological Importance

• Gastropods in marine, freshwater, and terrestrial habitats.
• Role in ecosystem as feeders and prey.

Cephalopods

Introduction

• Synapomorphies include chambered shell, beaks, tentacles, extreme cephalization, camera-style eyes, and muscular mantle.
• Evolution from an ancestral gastropod form with significant changes in body structure.

Nautiloids

• Oldest lineage with external shells.
• Use siphoncle to maintain buoyancy by osmotic pumping.

Evolutionary Adaptations

• Internalized shells in modern cephalopods (cuttlefish, squid, octopus).
• Predatory adaptations including advanced nervous systems and mobility.

Conclusion

• Highlights of unique gastropod and cephalopod adaptations.
• Mention of their ecological importance and evolutionary diversity.
• Introduction to further cephalopod topics in the next lecture.

Closing Remarks

• Encouragement to continue exploring mollusk diversity and adaptation.
• Reminder to be mindful and take care of oneself and others.