Doug Perrine / Pelagic nudibranch / Blue sea slug (Glaucus atlanticus) along with a much smaller relative, (Glaucilla sp) feeding on a Portuguese man o' war, (Physalia utriculus) Kona, Hawaii, Hawaiian Islands,...

Doug Perrine / Blue dragon / Blue seaslug (Glaucus atlanticus) feeding on a Portuguese man o' war (Physalia utriculus) along with a much smaller relative, Glaucilla sp. (upside down); Glaucus and Glaucilla store th...

Tony Wu / Blue sea slug (Glaucus atlanticus) approaching the venom-filled tentacles of a Indo-Pacific Portuguese man-of-war (Physalia utriculus). Both were washed ashore as part of a mass, multi-day stranding o...

Tony Wu / Blue sea slug (Glaucus atlanticus) that was washed ashore with a mass, multi-day stranding of thousands of Indo-Pacific Portuguese man-of-war (Physalia utriculus). This species predates Portuguese man...

Luis Quinta / Blue sea slug (Glaucus atlanticus) juvenile, portrait, Portugal, Atlantic Ocean.

Luis Quinta / Blue sea slug (Glaucus atlanticus) juvenile, feeding on Blue button hydroid colony (Porpita porpita), Portugal, Atlantic Ocean.

Sergio Hanquet / Blue dragon seaslug (Glaucus atlanticus) feeding on blue button (Porpita porpita), Tenerife, Canary Islands.

Sergio Hanquet / Blue dragon seaslug (Glaucus atlanticus) feeding on Blue button hydroid colony (Porpita porpita) Tenerife, Canary Islands. October

Sergio Hanquet / Blue dragon seaslug (Glaucus atlanticus) swimming,Tenerife, Canary Islands. September

Sergio Hanquet / Blue dragon seaslug (Glaucus atlanticus) on white background,Tenerife, Canary Islands. September

Sergio Hanquet / Blue dragon seaslug (Glaucus atlanticus) with Blue button hydroid colony (Porpita porpita) on which it feeds. Tenerife, Canary Islands. October

Sergio Hanquet / Blue dragon seaslug (Glaucus atlanticus) with blue button hydroid colony (Porpita porpita) on which it feeds. Tenerife, Canary Islands. October