Taxonomy Work in Progress ⁵

The commonly-seen sea slugs currently called Coryphella trilineata are likely multiple species, according to the researcher currently working on them. Her work is currently underway and unpublished. As of 2023, she has informally suggested to me that there may be four separate species, each with significant DNA differences and less-obvious morphological differences. Ranges vary, but overlap in some cases.

For now, we are leaving all of these slugs as either Coryphella sp. or Coryphella trilineata, according to the observer's preference. After the paper is published, there will be a significant manual effort to re-identify all of these observations.

Notable Features - For Now (until the split) ⁶

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 lines 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. Look-alikes Flabellina bertschi and Coryphella cooperi are very similar, but lack this feature. The digestive gland is either red or orange in color. Maximum length is about 35 mm.

Diet ⁷

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. Orienthella 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), https://www.flickr.com/photos/30314434@N06/24069745476/
2. (c) Ken-ichi Ueda, some rights reserved (CC BY), uploaded by Ken-ichi Ueda, http://www.flickr.com/photos/18024068@N00/2479383263
3. (c) Robin Agarwal (ANudibranchMom on iNaturalist), some rights reserved (CC BY-NC), https://www.flickr.com/photos/30314434@N06/19115954903/
4. (c) Ken Bondy, some rights reserved (CC BY-NC-SA), http://www.flickr.com/photos/kenbondy/10765366106/
5. Adapted by Robin Gwen Agarwal from a work by (c) Ken-ichi Ueda, some rights reserved (CC BY-SA)
6. Adapted by Robin Gwen Agarwal from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Flabellina_trilineata
7. (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Flabellina_trilineata

More Info

• iNat taxon page
• Animal Diversity Web
• Biodiversity Heritage Library
• BOLD Systems BIN search
• CalPhotos
• Global Biodiversity Information Facility (GBIF)
• NatureServe Explorer 2.0
• SeaLifeBase
• World Register of Marine Species

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