The bright dark blue and silver body distinguishes this species. The cerata are elevated on three cushions per side of the body.

Glaucus Atlanticus Forster (1777):


Identification: The bright dark blue and silver body distinguishes this species. The cerata are elevated on three cushions per side of the body. The rhinophore and oral tentacle are short.

Size: 20-40mm

Location: Worldwide Tropical Oceans

Glaucus Marginatus (1860)

Identification: Similar to Glaucus Atlanticus, has multiple rows of cerata in each cluster

Size: 20mm

Location: Tropical and subtropical oceans

The main differences between these two species are:

  • Glaucilla marginata has more cerata than Glaucus atlanticus, up to 137 in total
  • the tail (metapodium) of Glaucus atlanticus is much longer than that of Glaucilla marginata
  • Glaucus atlanticus is the larger of the two species – Glaucilla marginata only reaches 12mm in length
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