Top 10 Most Popular Nudibranchs

It's been six months since SEASLUG.WORLD launched. Starting with 551 species, we've grown to 943 — and to celebrate, here's our most popular nudibranch ranking!

1st Place: Hypselodoris festiva (Ao-umiushi)

Commonly seen throughout Japan (except Okinawa), but actually quite rare worldwide. Divers in Izu often swim right past them, but their blue-and-yellow coloring is truly beautiful.

2nd Place: Verconia simplex (Shirousagi-umiushi)

This bunny-like nudibranch gained popularity after being featured as a rabbit-esque sea slug. It even has its own LINE sticker set!

3rd Place: Aplysia japonica (Kuroheri-amefurashi)

A surprising 3rd place goes to this sea hare. It sometimes appears in massive numbers in Izu, so many divers have encountered them.

4th Place: Halgerda okinawa (Internet Umiushi)

Named "Internet Nudibranch" for the web-like pattern on its back. Often cited as one of the strangest Japanese species names.

5th Place: Goniobranchus preciosus

A nudibranch without a standard Japanese name takes 5th place. Formerly known as Chromodoris preciosa, the genus change also changed the species name ending due to Latin gender rules.

6th Place: Sagaminopteron ornatum (Murasaki-umikochou)

Famous as a 'swimming nudibranch' — though technically a cephalaspidean, not a true nudibranch.

7th Place: Hypselodoris apolegma (Cinderella Umiushi)

Well-known enough to appear as a book title. However, it's frequently misidentified.

8th Place: Nembrotha chamberlaini (Seguro-ryugu-umiushi)

The Japanese common name 'Seguro-ryugu-umiushi' is technically a nickname. Rarely seen in Japanese waters.

9th Place: Costasiella sp. (Leaf Sheep)

An unnamed species takes 9th place! Also known as the "leaf sheep," it went viral for its adorable appearance resembling a tiny cartoon sheep.

10th Place: Siphopteron sp. (Lemon Umikochou)

The lemon-colored sea butterfly rounds out our top 10.

Notable absentees include Jorunna sp. (the "sea bunny") and Mexichromis aurora (Strawberry Milk Nudibranch). Surprising results! We're aiming for 1,000 species — if you have nudibranch photos, please contribute!