Slug Highway | Nature Lookings

Sea slugs don’t follow rules—they follow opportunity.

The Slug Highway is a shifting, seasonal route stretching up and down the Pacific Coast, where species appear, disappear, and reappear across surprising zones. This project tracks those movements: range expansions, urban invasions, cryptic boom cycles, and possible reintroductions of long-lost species.

This isn’t just data—it’s a resurrection map.

Pacifia amica ⭐ The Ghost of Tacoma I’ve only ever found this slug in one place: a floating dock in Tacoma, Washington. And even there, it’s rare—blink-and-you’ll-miss-it rare. Pacifia amica has a handful of sightings in all of North America, and for some reason, this one dock seems to be its little haunted harbor. They’re tiny, white, and absolutely easy to overlook, hiding in tangled hydroids. I usually spot them by slowing way down and looking for movement or texture changes on the hydroid.	Tenellia spadix ⭐ The Flame-Tipped Phantom I found this tiny burner of a nudibranch on the outer Olympic Coast, nestled in a patch of red algae. It had only ever been documented in California, and never in Washington—not until this moment. That makes it a range extension, but it also feels like a message. These fragile, flame-tipped ghosts might be quietly expanding north, and we just haven’t been looking close enough. If you’re out on the outer coast, especially in high-energy red algal zones	Dirona picta ⭐The Psychedelic Dirona This was the first and only record of Dirona picta in Washington—spotted drifting midwater at Olympic National Park like it had slipped through a portal. It’s a species mostly known from California and Oregon, but here it was, golden and ghostlike in the surge. It’s a reminder: look where you don’t expect. Some slugs don’t crawl into the record—they float in sideways.
Hermissenda opalescens ⭐The Subtle Invader I found Hermissenda opalescens in Olympic National Park—well north of its usual range. It’s nearly identical to the common horned nudibranch (H. crassicornis), but if you look closely, it lacks the white lines on the cerata. Some locals have faint striping, so it takes practice and sharp eyes to tell them apart. If you’re in the northern zones, check your photos. It might not be who you think it is.	Dendronotus robilliardi ⭐The Delicate Stranger I found this slender, frilly Dendronotus on the outer Olympic Peninsula—far from where it’s usually seen. Most records are from deeper waters or more northern coasts, so this intertidal sighting might be a sign it’s creeping farther south or shallower than we thought. It looks like a small, transparent feather with delicate white lines—easy to overlook, but unforgettable once seen.	Suborder Cladobranchia ⭐The Berkeley Glitch I found this slug on a public dock in Berkeley—fully exposed and no one has been able to ID it. It’s not Catriona rickettsi or known eubranchus. Several experts now believe it may be an undescribed species. It’s a reminder that even in the most obvious places, life hides in plain view. If something looks off, don’t scroll past it. Document it. You might have just met something new.
Tenellia willowsi ⭐ Willow’s Aeolid I found this tangled-looking aeolid on red algae at Point Defiance, and it stopped me in my tracks. It was Zelenzia willowsi—a species that's rarely recorded and easy to miss. Its cerata looked like messy dreadlocks to the naked eye, but under light, the structure was wild. These slugs live deep in the hydroids. If you're scanning red algae or fouling zones, slow down and let your eyes adjust—you might see one where it looks like nothing is there.	Coryphella cf. trilineata ⭐The Spicy Three-Lined Aeolid I found this bright orange-mouthed Coryphella variant at two different sites in Olympic National Park—far north of where it’s usually seen. This spicy morph, with orange rhinophores and oral tentacles, is typically Oregon and south. These might be the first sightings of it in Washington. If you think you’ve found a regular trilineata, look again. The spice might be hiding in plain sight.	Tenellia viridis ⭐The Tacoma Glowstick This bright green nudibranch showed up on a public dock in Tacoma—Tenellia viridis, a species that’s rarely reported in Washington and easy to miss. It was feeding on hydroids, glowing like someone dropped a highlighter into the sea. It’s small, flashy, and usually tucked deep in the fouling. Get low, use a light, and don’t assume you’ve seen everything.