For several weeks now, large “sea hares” (Aplysia californica) have been showing up on beaches in Alameda and here in Lake Merritt. Kieran and I have been catching quite a few and studying them. As I’ve reported before, they squirt out a deep purple ink when stressed. It forms a blood red cloud in water, but retains its dark purple hue in the air. We wondered (as did one of our friends) whether the ink could be used for dyeing cloth or even writing. So this week we “milked” three Aplysiae of their ink, collected it in a cup, and tried it out.

I successfully used the ink to address an envelope (to our curious friend) and sent him a letter. The ink doesn’t write in its lovely deep purple color — it comes out quite faded. But it was good enough for the U.S. Postal Service.

As for dyeing cloth, well, we aren’t going to become 21st century Phoenicians, cornering the market on a rare, royal dye! Aplysia ink is no match for Murex, it seems. Though a test on a bit of white cotton fabric turned it a deep purple, as soon as we rinsed the cloth most of the color washed out.

How long these giant, gentle slugs will remain in our lake is anyone’s guess. But their appearance shows that the opening up of the estuary linking lake and bay has made Lake Merritt a much healthier place for wildlife.

You never know what sort of wildlife you will encounter in Lake Merritt.

You never know what sort of wildlife you will encounter in Lake Merritt.

Sea hares are quite large. Our dog was very curious about them.

Sea hares are quite large. Our dog was very curious about them.

Doodle sniff

We collected the viscous, violet ink of three large sea hares.

We collected the viscous, violet ink of three large sea hares.

The ink was OK, but not great, for calligraphy.

The ink was OK, but not great, for calligraphy.

We tested sea hare ink as a cloth dye...

We tested sea hare ink as a cloth dye…

The ink did color the cloth at first...

The ink did color the cloth at first…

Rinsing the cloth in water, though, quickly removed the color.

Rinsing the cloth in water, though, quickly removed the color.

The color immediately washed out.

The color immediately washed out.

The letter arrived the next day, so Aplysia ink seems to meet U.S. Post Office standards!

The letter arrived the next day, so Aplysia ink seems to meet U.S. Post Office standards!

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