Molecules and Memories: Sea Hares’ Twin Treasures
I’m sure you’ve heard of the story of the hare and the tortoise — the arrogant hare challenging the mellow tortoise to a race, tortoise wins, and the moral of the story is “slow and steady wins the race.” Congratulations tortoise, but what about the hare?
Don’t know; never met him. Heard about his cousin though — that guy’s a winner, a Nobel-prize winning one!
Okay, I may have exaggerated calling our species for today a cousin to the hare — about the only thing they have in common is their name, and that they both eat plants but that’s all the similarities I can think of right now.
Members of Family Aplysiidae are commonly referred to as sea hares by virtue of their appearance. Species from this family revolutionized our understanding of not just marine biology, but human consciousness itself. The work of Dr. Eric Kandel led to one of neuroscience’s greatest breakthroughs thanks to his fascination with these creatures. In 2000, Dr. Kandel was awarded the Nobel Prize in Physiology or Medicine for his research on memory using Aplysia californica. He identified three key characteristics of the species that made it a suitable candidate for his study: the size of their nerve cells (they can reach up to 1000 µm, which is big in nerve cell terms!), being relatively few in number (A. californica only has 20,000 cells versus the trillions(!) of a mammalian brain), and that basic learned behaviors can be isolated in the movement of less than 100 neurons².
Dr. Kandel unveiled fundamental principles about how memories are formed and stored in the brain³. In essence, weak stimuli cause more calcium ions to move towards the affected area and that establishes a link between the two, which is what we fondly call short-term memory. Stronger stimuli will activate the synthesis of new proteins that compound that link, and that’s how we make long-term memory. These discoveries transcend species boundaries, providing crucial insights into human memory formation and potential treatments for memory-related disorders.
But the wonders of sea hares don’t stop at neuroscience. These remarkable mollusks are living pharmacies, producing a fascinating array of secondary metabolites that humans can harvest as marine natural products (MNP). A study by Pereira et al. (2016)⁴ enumerates a fraction of the compounds isolated from Aplysia species, which all show potential uses from anti-cancer treatment to novel antimicrobial agents. It’s a powerful reminder that nature’s solutions, refined over millions of years of evolution, often hold the key to human medical advancement.
If you’re ever lucky enough to spot a sea hare, remember: you’re not just looking at a random water animal— you’re witnessing a creature that has helped us understand our own brains better and continues to inspire groundbreaking research across multiple scientific disciplines.
At the moment, SeaLifeBase has information on 41 species belonging to family Aplysiidae. While our team does its best to update species records whenever we acquire new information, there’s still plenty of work to be done as new research comes to light.
Written by: Jasper Mendoza, Research Assistant
[1] Wilson, E. M. (2013, May 14). A Nobel Prize with help from sea slugs. CNN. https://edition.cnn.com/2013/05/14/health/lifeswork-eric-kandel-memory/index.html
[2] Kandel, E. R. (2001). The molecular biology of memory storage: a dialogue between genes and synapses. Science, 294(5544), 1030–1038.
[3] Press release. NobelPrize.org. Nobel Prize Outreach 2025. Tue. 4 Feb 2025. https://www.nobelprize.org/prizes/medicine/2000/press-release
[4] Pereira, R. B., Andrade, P. B., & Valentão, P. (2016). Chemical diversity and biological properties of secondary metabolites from sea hares of Aplysia genus. Marine Drugs, 14(2), 39.
If you have more information on sea hares and other non-fish organisms, we’ll be happy to have you as one of our collaborators. Let us know by sending us an email or visiting our Facebook page.
