A couple of weeks ago, Jason and Matt mentioned they'd been seeing these nudibranchs at the Spud Point Marina docks. I've been saving the pictures because they seemed perfect for Halloween!
This is Polycera atra. I've seen it called a Black Dorid, or an Orange-spike Polycera. (Halloween Nudibranch wouldn't be such a bad name either!)
Although there is a consistent color theme, individuals are variable. In contrast to the first individual, others are quite dark — see below:
The combination of black and white longitudinal stripes with yellow-orange spots is quite striking. The next image is a close-up of one individual's head, showing the frontal veil with spiky processes and two spiraled rhinophores (sensory organs) extending upward.
Polycera atra feeds on Bugula, a common bryozoan growing on the docks. Although the nudibranchs can blend in with their dark bryozoan prey, their eggs ribbons are bright white. The easiest way to find the nudibranchs was to look for the egg ribbons and then to search for a nudibranch nearby. [These nudibranchs were about 2 cm (3/4 inch) long.]