Franco Banfi / Opalescent nudibranch (Hermissenda crassicornis), Alaska, United States, North Pacific Ocean.

Franco Banfi / Opalescent nudibranch (Hermissenda crassicornis) Vancouver Island, British Columbia, Canada, Pacific Ocean

Pascal Kobeh / Opalescent nudibranch (Hermissenda crassicornis), Alaska, USA, Gulf of Alaska. Pacific ocean.

Todd Mintz / Thick horned aeolid / Opalescent nudibranch,(Hermissenda crassicornis) Vancouver Island, British Columbia, Canada, August

Tim Laman / Thick horned aeolid nudibranch (Hermissenda crassicornis) and Sea anemones in the Channel Islands, Pacific, California, USA

Juergen Freund / Opalescent / Thick horned nudibranch {Hermissenda crassicornis} Pacific, Canada

Juergen Freund / Opalescent / Thick horned nudibranch {Hermissenda crassicornis} Pacific, Canada

Juergen Freund / Thick horned aeolid (Hermissenda crassicornis) Canada, Pacific

Juergen Freund / Thick horned aeolid nudibranch, Canada

Jeff Rotman / Thick horned aeolid / nudibranch {Hermissenda crassicorn} California Pacific USA

Jeff Rotman / Thick horned aeolid / nudibranch {Hermissenda crassicorn} Pacific Ocean off California, USA

Alex Mustard / Opalescent nudibranch (Hermissenda crassicornis) crawling over kelp, Vancouver Island, British Columbia, Canada, Queen Charlotte Strait, Pacific Ocean.

Alex Mustard / Kelp greenling (Hexagrammos decagrammus) male, swimming among a kelp forest, Browning Pass, Vancouver Island, British Columbia, Canada, Queen Charlotte Strait, Pacific Ocean.

Shane Gross / Opalescent nudibranch (Hermissenda crassicornis) moving across coral reef, Browning Pass, British Columbia, Canada, Pacific Ocean.

Shane Gross / Opalescent sea slug (Hermissenda crassicornis) on Eelgrass blade (Zostera marina) at night. Nanoose Bay, Vancouver Island, British Columbia, Canada. November.

David Hall / Opalescent nudibranch (Hermissenda crassicornis) which preys upon stinging hydroids. It retains its prey's stinging cells (cnidocytes) which are transported to the colorful cerrata on nudibranch&#...

David Hall / Opalescent nudibranchs (Hermissenda crassicornis) and Mushroom compound ascidians (Distaplia occidentalis). Browning Pass, Queen Charlotte Strait, British Columbia, Canada. September.

David Hall / Opalescent nudibranch (Hermissenda crassicornis) preys upon stinging hydroids. Browning Pass, Queen Charlotte Strait, British Columbia, Canada. September.