SCOTLAND: The Big Picture / Maiden's salp (Thetys vagina) , west coast of Scotland, UK, July.

Alex Mustard / Planktonic pyrosome, drifting in blue sea. Ras Mohammed National Park, Sinai, Egypt. Red Sea

David Fleetham / Pelagic tunicate or salp (Salpa aspera) Hawaii.

Doug Perrine / Rover fish (Emmelichthyidae) juvenile sheltering inside a colonial salp at night in surface waters of deep ocean off Kailua Kona, Hawaii, USA.

Doug Perrine / Pyrosome, a type of pelagic colonial tunicate known for its bioluminescence, photographed at night, Kona, Hawaii, USA.

SCOTLAND: The Big Picture / Amphipods (Amphipoda) living on a salp (Salpidae), Scotland, UK, July.

Pascal Kobeh / Pyrosoma / sea tunicate (Pyrosoma sp) in the open water at night, Palau, Philippine Sea

Aflo / Colonial tunicate (Pyrosoma spinosum) Komodo National Park, Indonesia.

Alex Mustard / A small fish, probably a Driftfish (Nomeidae), sheltering inside a Salp (Salpa sp.) in open water as part of the plankton, Bitung, North Sulawesi, Indonesia, Lembeh Strait.

Russell Laman / Chain of Salps (Thaliacea) floating in front of Pacific sea nettles (Chrysaora fuscescens), Monterey, California, USA, Pacific Ocean.

David Fleetham / Pelagic tunicate (Salpa aspera) floating in the open ocean at night, Yap, Micronesia, Pacific Ocean.

Franco Banfi / Salps (Salpidae) drifting in the open ocean, Antarctic Peninsula, Antarctica, Southern Ocean.