#4582 · 🐌 snails, slugs & other molluscs
Four-lined Polycera
🇳🇱 Harlekijnslak ·Polycera quadrilineata
🐌 Snails, slugs & other molluscs 📍 in the Netherlands
9 photos from iNaturalist (Creative Commons) · credits & licences
- 1. © Nathan Jackson · CC BY-NC 4.0
- 2. © elegaer · CC BY-NC 4.0
- 3. © Jørn Ari · CC BY-NC 4.0
- 4. © Heine Jensen · CC BY 4.0
- 5. © Heine Jensen · CC BY 4.0
- 6. © Bianca Bahlert · CC BY-NC 4.0
- 7. © Heine Jensen · CC BY 4.0
- 8. © Heine Jensen · CC BY 4.0
- 9. © Heine Jensen · CC BY 4.0
what is it?
Polycera quadrilineata , is a sea slug, a species of dorid nudibranch. It is a marine gastropod mollusc in the family Polyceridae. The specific epithet quadrilineata means four-lined and refers to the four longitudinal black lines present on the original specimen. This species is sometimes called the fourline nudibranch.
base stats
Bars compare against all animals on log scales: up to 300,000 Dutch and 600,000 worldwide sightings (the most-seen species), 150 t (blue whale), 30 m and 400 years (Greenland shark).
fun facts
- Spotted 282 times in the Netherlands on iNaturalist: the #14 most seen of the snails, slugs & other molluscs in NL.
- 2,497 observations worldwide on iNaturalist.
- Scientifically named by Otto Friedrich Müller in 1776 (250 years ago).
fact sheet
- English
- Four-lined Polycera
- Nederlands
- Harlekijnslak
- scientific name
- Polycera quadrilineata
- class
- Gastropoda
- order
- Nudibranchia
- family
- Polyceridae
- sightings in NL
- 282
- sightings in Europe
- 2,275
- sightings worldwide
- 2,497
- GBIF records in NL
- 1,959
- weight
- —
- length
- —
- lifespan
- —
- named
- 1776 by Otto Friedrich Müller
relatives· Polyceridae
Sources: iNaturalist taxon 425249, Wikidata Q1519574, GBIF 2291758, Wikipedia (EN), Wikipedia (NL). Intro text from Wikipedia (CC BY-SA 4.0).Updated 2026-10-24.