#aplysiomorpha

This poor, battered, rubbery lump is a Sea Hare, large Aplysiomorph molluscs well known since ancient times - indeed, the current common name is a direct translation of lepus marinus, as the animal was known to the Romans.

When they’re not traumatised by winter storm bashing them repeated against a rocky beach, sea hares have a pair of tubular rhinophore sticking up from their heads, like the ears of a rabbit or hare. Hence the common name.

Sea Hares eat algae,and are so good at it that some aquarium clubs share a sea hare around to control nuisance algae in their tanks. Back when I lived in Sydney, and before the sewerage outfall at Long Bay was replaced with a deep-ocean outfall, the entire bay was heavily polluted. There was a preexisting ocean pool on the edge of the bay (built before the entire bay was off-limits to swimming - 1950 to 2000) and naturally the extra nutrients promoted massive algae growth. Sea Hares had somehow gotten into the pool, and you could watch from the bus stop as giant sea slugs gorged themselves on the growth, floated up to the top of the pool as the bubbling algae got detached, then descend again as the bubbles popped.

Sea Hares are hermaphrodites, and form long chains of amorous molluscs when breeding. They can also defend themselves with acids and foul-tasting chemicals in their skin and mucus, and as a last resort with poisonous inks derived from their diet. The ink has some very interesting properties - for one thing it can paralyse the sense of smell of lobsters.

The Californian Sea Hare has also been very useful in the study of neurobiology - their nerve cells are so large that scientists could insert electrodes and so on into them, to study electrical impulses and the like.