Meet The Locals: Lake Merritt Nudibranch

Nudibranchs are incredibly tiny creatures, only as long as your thumbnail is wide. They float around the shallow waters of oceans all across the world, chomping up hydroids, corals, and anemones, as their gills — long tendrils that line the tops of their back — sway in the wake of their movement. They love to eat anemones, and the Lake Merritt nudibranchs prefer a small introduced species in particular. They have learned to metabolize their prey while not harming the stinging cells which all anemones and corals have. As they digest their meal, their body moves the unharmed cells into their swaying gills, acting as a secondary defense against predators.

However, what makes the Lake Merritt nudibranchs even more peculiar is that Lake Merritt, from which they get their common name, is not their original home. In 1958, these nudibranchs were described on the coast of Brazil, and later found in other parts of the world. They were not discovered at Lake Merritt until 1967, likely arriving in large cargo ships, which use massive amounts of ocean water to help balance the ship, called ballast water. In other words, the Lake Merritt nudibranch is a very modern creature, brought here through the inevitable frenzy of capitalism, which globalized our world like nothing has quite before. Regardless of how they arrived here, the Lake Merritt nudibranch has made Oakland its only California home in the entirety of North America.

So while it is not a native species, it’s worth remembering that the vast majority of species in Lake Merritt are not native in the traditional sense of the word. And yet, in the odd soup-bowl of Lake Merritt, which marine ecologist Jim Carlton described as “an accidental zoo,” the nudibranch has found a home, a new resident in waters carved out and transformed by the driving desire of commerce and the aquatic connection of the human globe.