John Cancalosi / Snapping turtle (Chelydra serpentina) and Bluegill (Lepomis macrochirus) fish attempting to feed on algae on turtle's shell. Maryland, USA. August.

Georgette Douwma / Kaleiscopic Banggai cardinalfish (Pterapogon kauderni). Lembeh Strait, North Sulawesi, Indonesia.

Nick Upton / Great pond snail (Lymnaea stagnalis) grazing aquatic vegetation in a garden pond, Wiltshire, UK, February.

Nick Upton / Great pond snail (Lymnaea stagnalis) grazing aquatic vegetation in a garden pond, Wiltshire, UK, February.

Nick Upton / Great pond snail (Lymnaea stagnalis) grazing aquatic vegetation in a garden pond, Wiltshire, UK, May.

Cyril Ruoso / Signal crayfish (Pacifastacus leniusculus), non-native invasive species. On riverbed in woodland. La Cure river, Morvan, Bourgogne-Franche-Comte, France. May.

Cyril Ruoso / Signal crayfish (Pacifastacus leniusculus), non-native invasive species, on riverbed. La Cure river, Morvan, Bourgogne-Franche-Comte, France. May.

Cyril Ruoso / Signal crayfish (Pacifastacus leniusculus), non-native invasive species, on riverbed in woodland. La Cure river, Morvan, Bourgogne-Franche-Comte, France. May.

Robin Chittenden / River crab (Potamon potamios) on sand. Cyprus. April.

Magnus Lundgren / Wild Wonders of China / Arc-eye hawkfish (Paracirrhites arcatus) often found perched on corals like Acropora, Stylophora, and Pocillopora, Xiaoliuqiu Island, Taiwan

Pascal Kobeh / Zander / Pike-perch (Sander lucioperca) on the bottom of the river, Cher River, Loir-et-Cher Department, France

Pascal Kobeh / Yellowmouth barracuda (Sphyraena viridensis) with a white / silver trevally / guelly jack (Pseudocaranx dentex), Canary Islands