Alex Mustard / Yellowbelly hamlets (Hypoplectrus aberrans) pair spawning at dusk (artifically backlit). Hamlets are hermaphroditic species. George Town, Grand Cayman, Cayman Islands. Caribbean Sea.

Alex Mustard / Black hamlet (Hypoplectrus nigricans) and Yellowbelly hamlet (Hypoplectrus aberrans) spawning at dusk. As this genus is quite recently evolved hybridization is still possible. Hamlets are one of the...

Alex Mustard / Butter hamlet (Hypoplectrus unicolor) pair spawning at dusk, George Town, Grand Cayman, Cayman Islands, British West Indies, Caribbean Sea.

Stephen Dalton / Edible snails (Helix pomatia) pair prior to mating, UK

Tony Wu / Asian sheepshead wrasse (Semicossyphus reticulatus), two males fighting over territory. Female wrasse in background. Niigata Prefecture, Honshu, Japan. June.

Alex Mustard / Pair of Yellowbelly hamlets (Hypoplectrus aberrans) spawning at dusk. Hamlets are one of the few vertebrate species that are true hermaphrodites, here the fish with the open mouth is acting as a male...

Alex Mustard / Pair of Barred hamlets (Hypoplectrus puella) spawning at dusk . Hamlets are one of the few vertebrate species that are true hermaphrodites, here the fish in the foreground is acting as a male, but thi...

Ingo Arndt / Leopard slug (Limax maximus) mating pair following each other shortly before mating. These slugs are hermaphrodites and can be seen here transferring sperm to one another through their male organs, Sw...

Ingo Arndt / Leopard slug (Limax maximus) mating, hanging from a rope of mucus. These slugs are hermaphrodites and can be seen here transferring sperm to one another through their male organs, Switzerland

Ingo Arndt / Leopard slug (Limax maximus) climbing and eating at the same time a rope of mucus after mating. These slugs are hermaphrodites and can be seen here transferring sperm to one another through their male...

Ingo Arndt / Leopard slug (Limax maximus) climbing and eating at the same time a rope of mucus after mating. These slugs are hermaphrodites and can be seen here transferring sperm to one another through their male...

Ingo Arndt / Leopard slug (Limax maximus) mating, hanging from a rope of mucus. These slugs are hermaphrodites and can be seen here transferring sperm to one another through their male organs.Switzerland. Sequence...