Three-lined Aeolid

Orienthella trilineata

Summary 5

A relatively common sea slug along most of our coast. The most distinguishing feature are the three white lines running down the back. The two on the sides can be a bit tricky to see from certain angles, particularly in photos. Also make sure to check for the annulate rhinophores. Flabellina bertschi is a very similar rarity in our area that lacks this feature.

Description 6

Flabellina trilineata is a flabellinid nudibranch with a translucent body and three longitudinal white lines on the back and sides. The line down the middle of the back passes between the rhinophores where it splits and continues to the tips of the oral tentacles. The rhinophores are perfoliate and coloured white at the base but orange in the outer third. The digestive gland is either red or orange in colour. Maximum length is about 35mm.

Diet 6

This species feeds on hydroids, especially Tubularia spp. and Eudendrium californicum.

Distribution 6

This species was described from Nanoose Bay, Regional District of Nanaimo, Vancouver Island, British Columbia, Canada. Flabellina trilineata is a seasonally abundant aeolid ranging from Baja California, Mexico to Alaska.

Sources and Credits

  1. (c) Robin Agarwal (ANudibranchMom on iNaturalist), some rights reserved (CC BY-NC),
  2. (c) Ken-ichi Ueda, some rights reserved (CC BY), uploaded by Ken-ichi Ueda,
  3. (c) Robin Agarwal (ANudibranchMom on iNaturalist), some rights reserved (CC BY-NC),
  4. (c) Ken Bondy, some rights reserved (CC BY-NC-SA),
  5. (c) Ken-ichi Ueda, some rights reserved (CC BY-SA)
  6. (c) Wikipedia, some rights reserved (CC BY-SA),

More Info

iNat Map

Color red, white