California Seahare

• utilidadIt can release a deep purple ink in defence, and has been widely used as a model organism in neuroscience to study the basic mechanisms of memory.
• This is the animal in which the workings of memory were discovered. Eric Kandel received the Nobel Prize in Medicine in 2000 for his work with this sea hare.
• He chose it because its nervous system is astonishingly simple: some 20,000 neurons, against the 86 billion of the human brain. And some of those neurons are giants, up to a millimetre across, visible to the naked eye and identifiable one by one.
• The key experiment was the gill-withdrawal reflex: brush its siphon and it retracts the gill; after several harmless brushes it stops doing so. That is learning, and it allowed its molecular basis to be traced neuron by neuron.
• It defends itself with two secretions: purple ink and opaline, a whitish, highly viscous fluid. The opaline sticks to the antennae and mouthparts of lobsters and blocks their sense of smell, which buys it time to escape.
• It is hermaphrodite: each individual functions as both male and female, and they sometimes mate in chains of several animals.
• It owes its name to its two front tentacles, which recall a hare's ears.

Habitat and environment

Shallow rocky bottoms and intertidal pools of California and Baja California, among the algae it feeds on; its colour depends on which alga it eats

Sexual maturity

6.3 months

Sources consulted: Wikipedia (es): Aplysia californica

The pins mark the parks and dive sites where its presence is documented.