Guy Edwardes / Black-bellied Bustard (Lissotis melanogaster) calling, Serengeti National Park, Tanzania, Africa February

Doug Perrine / Female Bull sharks (Carcharhinus leucas) in seasonal breeding aggregation with Sharksuckers (Echeneis naucrates) Playa del Carmen, Cancun, Quintana Roo, Yucatan Peninsula, Mexico (Caribbean Sea)

Alex Mustard / A lemon shark (Negaprion brevirostris) drags its pectoral fin through the sand as it swims accompanied by Remoras / Sharksuckers (Echeneis naucrates). Little Bahama Bank. Bahamas. Tropical West Atlant...

Alex Mustard / Male Lemon shark (Negaprion brevirostris) portrait with Remoras / Sharksuckers (Echeneis naucrates). Little Bahama Bank. Bahamas. Tropical West Atlantic Ocean.

Alex Mustard / Lemon shark (Negaprion brevirostris) accompanied by Remoras / Sharksuckers (Echeneis naucrates). Little Bahama Bank. Bahamas. Tropical West Atlantic Ocean.

Doug Perrine / Female Bull sharks (Carcharhinus leucas) in seasonal breeding aggregation with Sharksuckers (Echeneis naucrates) Playa del Carmen, Cancun, Quintana Roo, Yucatan Peninsula, Mexico (Caribbean Sea)

Doug Perrine / Female Bull sharks (Carcharhinus leucas) in seasonal breeding aggregation with Sharksuckers (Echeneis naucrates) Playa del Carmen, Cancun, Quintana Roo, Yucatan Peninsula, Mexico (Caribbean Sea)

Doug Perrine / Sharksuckers (Echeneis naucrates) with Bull sharks (Carcharhinus leucas) Playa del Carmen, Cancun, Quintana Roo, Yucatan Peninsula, Mexico (Caribbean Sea)

Doug Perrine / Female Bull sharks (Carcharhinus leucas) in seasonal breeding aggregation with Sharksuckers (Echeneis naucrates) Playa del Carmen, Cancun, Quintana Roo, Yucatan Peninsula, Mexico (Caribbean Sea)

Doug Perrine / Female Bull sharks (Carcharhinus leucas) in seasonal breeding aggregation with Sharksuckers (Echeneis naucrates) Playa del Carmen, Cancun, Quintana Roo, Yucatan Peninsula, Mexico (Caribbean Sea)

Jeff Rotman / Diver observing Giant Napolean Wrasse (Cheilinus undulatus) with symbiotic Sharksuckers / Remoras (Naucrates ductor). Egypt, Red Sea. Model released.

David Fleetham / Two Sharksuckers / Remora (Echeneis naucrates) clinging to the shell of a resting Green sea turtle (Chelonia mydas), Sipadan, Malaysia, Celebes Sea. Endangered.