San Francisco Bay has been invaded these last two weeks by thousands of fat “sea hares” (Aplysia californica). They’re giant, docile, herbivorous sea slugs that eat red marine algae. When disturbed, they expel vivid purple ink in a cloud. We first found them last week at Crab Cove in Alameda, in a long lagoon cut off on the beach by low tide. Later, we found them right here in Lake Merritt. Aplysia are hermaphroditic, and often mate in so-called “Roman circles,” with each one connected to two others, front and behind. They lay millions of microscopic eggs on long strands of yellow string that looks like spaghetti. Each egg strand can be, if uncoiled, a third of a mile long! That can contain 86 million eggs!

 

It’s always fascinating to find a new species in Lake Merritt.

 

You can find a lot of curious creatures just by sweeping a net in the lake.

You can find a lot of curious creatures just by sweeping a net in the lake.

You never know what will turn up in the net!

You never know what will turn up in the net!

You might find a sea hare. Good thing the ink doesn't stain skin or clothes!

You might find a sea hare. Good thing the ink doesn’t stain skin or clothes!

We first met Aplysia californica on the shore in Alameda.

We first met Aplysia californica on the shore in Alameda.

Aplysia are dubbed "sea hares" because of these ear-like projections.

Aplysia are dubbed “sea hares” because of these ear-like projections.

Aplysia californica up close.

Aplysia californica up close.

The color of the red marine algae they eat shows up in their shocking ink blast.

The color of the red marine algae they eat shows up in their shocking ink blast.

An Aplysia in Lake Merritt this week.

An Aplysia in Lake Merritt this week.

Two sea hares with their tangled string egg mass.

Two sea hares with their tangled string egg mass.

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