Jeff Rotman / Symbiotic emperor shrimp (Periclimenes imperator / Zenopontonia rex) living in the gills of a spanish nudibranch (Hexabranchus sanguineus) Red Sea, Egypt

Jeff Rotman / Emperor Shrimp (Periclimenes imperator / Zenopontonia rex) living inside gills of Spanish Dancer Nudibranch (Hexabranchus sanguineus). Egypt, Red Sea.

Doug Perrine / Spanish dancer nudibranch (Hexabranchus sanguineus) defecating whilst swimming. Gato Island, off Malapascua, Cebu, Philippines.

Magnus Lundgren / Wild Wonders of China / Free swimming juvenile spanish dancer (Hexabranchus sanguineus) in the night, Kenting National Park, Hengchun Peninsula, Taiwan

Magnus Lundgren / Wild Wonders of China / Free swimming juvenile spanish dancer (Hexabranchus sanguineus) in the night, Kenting National Park, Hengchun Peninsula, Taiwan

David Fleetham / Imperial commensal shrimp (Periclimenes imperator / Zenopontonia rex) on Spanish dancer nudibranch (Hexabranchus sanguineus) at night. Philippines.

MYN / Dirk Funhoff / Click beetle (Ampedus sanguineus), Staudernheim, Pfalz, Germany. June. Meetyourneighbours.net project

MYN / Dirk Funhoff / Click beetle (Ampedus sanguineus), Staudernheim, Pfalz, Germany. June. Meetyourneighbours.net project

Tony Wu / Spanish dancer nudibranch (Hexabranchus sanguineus) scavenging the reef at night in Ambon, Indonesia

Pascal Kobeh / Diver in front of two mating Spanish dancers (Hexabranchus sanguineus) Madagascar. Indian Ocean. September 2012.

Alex Mustard / Spanish dancer nudibranch (Hexabranchus sanguineus) moves across coral reef in daylight. It is unusually to see this large nudibranch during daylight. Nuweiba, Sinai, Egypt. Gulf of Aqaba, Red Sea.

David Tipling / Trumpeter Finch (Rhodopechys githaginea) vagrant to Cley, Norfolk, UK, June