Gary Bell/ Oceanwide / Scarlet Cleaner Shrimp (Lysmata amboinensis) cleaning mouth of Tomato Grouper (Cephalopholis sonnerati), Great Barrier Reef, Australia

Gary Bell/ Oceanwide / Scarlet Cleaner Shrimp (Lysmata amboinensis) cleaning mouth of Tomato Grouper (Cephalopholis sonnerati), Great Barrier Reef, Australia

Gary Bell/ Oceanwide / Scarlet Cleaner Shrimp (Lysmata amboinensis) cleaning female Stocky Anthias (Pseudanthias hypselosoma), Tulamben, Bali, Indonesia

Gary Bell/ Oceanwide / Scarlet Cleaner Shrimp (Lysmata amboinensis) cleaning Yellow-edged Moray (Gymnothorax flavimarginatus), Tulamben, Bali, Indonesia

Gary Bell/ Oceanwide / Scarlet Cleaner Shrimp (Lysmata amboinensis) cleaning Honeycomb Moray Eel (Gymnothorax favagineus), Tulamben, Bali, Indonesia

Gary Bell/ Oceanwide / Scarlet Cleaner Shrimp (Lysmata amboinensis) cleaning mouth of Goldbelly Cardinalfish (Apogon apogonides), Tulamben, Bali, Indonesia

David Fleetham / Cleaner wrasse (Labroides dimidiatus) swimming alongside Golden damsel (Amblyglyphidodon aureus) looking for parasites, Fiji, Pacific Ocean.

Alex Mustard,Alex Mustard / A portrait of a small Candy stripe shrimp (Lebbeus grandimanus) in front of its host pink anemone (out of focus because of the magnification). Browning Wall, Browning Pass, Port Hardy, Vancouver Islan...

Georgette Douwma / White banded/ Scarlet cleaner shrimp (Lysmata amboinensis) on Coral hind (Cephalopholis miniata) Rinca, Komodo National Park, Indonesia, October

Chris Newbert / Scarlet Cleaner Shrimp (Lysmata amboinensis) pair cleaning a Moray Eel (Gymnothorax ocellatus) 80 feet deep, Solomon Islands

Fred Bavendam / Scarlet Cleaner Shrimp (Lysmata amboinensis) working on a Tomato Grouper (Cephalopholis sonnerati), Milne Bay, Papua New Guinea

Sergio Hanquet / Shrimp (Trachycaris restricta), close up. Tenerife, Canary Islands.

Inaki Relanzon / Elm tree (Ulmus) in Gobi desert, South Mongolia.

Colin Varndell / Fresh Wych elm (Ulmus glabra) leaves in spring. Dorset, UK May

Loic Poidevin / Siskin (Carduelis spinus) on Elm (Ulmus minor) branch, Vendee, Pays-de-la-Loire, France. March.

Andres M. Dominguez / Frost covered Elm (Ulmus minor) and Pear tree (Pyrus sylvestris) tree leaves, Sierra de Grazalema Natural Park, southern Spain, December.

Andres M. Dominguez / Frost covered Elm (Ulmus minor) and Pear tree (Pyrus sylvestris) tree leaves, Sierra de Grazalema Natural Park, southern Spain, December.

Andres M. Dominguez / Beetle (Scolytus sp) galleries in Field elm (Ulmus minor). Sierra de Grazalema Natural Park, southern Spain.

Pascal Tordeux / Elm tree (Ulmus sp) in mist / fog, Picardy, France, December 2014.

Kim Taylor / Developing Elm (Ulmus sp) seeds. Gloucestershire, England, April.

Andres M. Dominguez / Field elm (Ulmus minor) leaf litter covered in frost in winter, Sierra de Grazalema Natural Park, southern Spain, November.

Mike Read / English elm (Ulmus procera) leaves on white background.

Fabrice Cahez / Frost on Elm (Ulmus) branches, Vosges, France, January.

Alex Hyde / Wych Elm (Ulmus glabra) bark on a mature tree. Peak District National Park, Derbyshire, UK. May.