Andy Rouse / Mountain gorilla (Gorilla beringei) baby held by mother, Rwanda

Tim Fitzharris / Whale Shark (Rhincodon typus) eating with attendant Remoras (Remora remora), Philippines

Flip Nicklin / Manta Ray (Manta birostris) with two Remora (Remora remora) attached to it, Hallcion Reef, Cocos Island, Costa Rica

Flip Nicklin / Sperm Whale (Physeter macrocephalus) adult with attached Remoras skimming ocean surface, Dominica

Norbert Wu / Remora (Remora remora) top of head modified with plates to stick onto animals, worldwide

Bence Mate / Night Heron (Nycticorax nycticorax) with small mosquito on beak, Kiskunsagi National Park, Hungary

Mark Carwardine / Blue Whale (Balaenoptera musculus) dorsal fin with two remoras and barnacles, Gulf of California, Baja California, Mexico

Pete Oxford / Whale Shark (Rhincodon typus) and Remoras (Remora sp), Cenderawasih Bay, West Papua, Indonesia

MYN / Paul van Hoof / European medicinal leech (Hirudo medicinalis) adult showing sucker at one end, The Netherlands, June.Meetyourneighbours.net project

Fred Bavendam / Manta Ray (Manta birostris) with attached White Suckerfish (Remora albescens), Milne Bay, Papua New Guinea

Nick Upton / Duck Leech (Theromyzon tessulatum) waiting and ready to crawl up the nostrils of a duck to suck blood from its respiratory tracts, reaching out from a Delicate stonewort (Chara virgata) alga in a shal...

Pete Oxford / Remora (Remora remora) showing sucker-like first dorsal fin, Umkomaas, Kwazulu Natal, South Africa