Shane Gross / Unknown species of pelagic swimming crab, covered in barnacles swimming in the open ocean at night. She is tending to her eggs in a pouch. Anilao, Philippines.

Constantinos Petrinos / Harlequin ghost pipefish (Solenostomus paradoxus) female with eggs in the brood pouch. Lembeh Strait, North Sulawesi, Indonesia.

Ingo Arndt / Netted slug (Deroceras reticulatum) hatching from egg pouch, Germany

Pete Oxford / Marsupial Frog (Gastrotheca riobambae) female with eggs in dorsal pouch, native to South America

Alex Mustard / Pair of Rough snout ghostpipefish (Solenostomus paegnius), with female with egg pouch in front of male. Anilao, Batangas, Luzon, Philippines. Verde Island Passages, Tropical West Pacific Ocean.

Frederique Olivier / Procession of male Emperor penguins (Aptenodytes forsteri) shuffling with egg (or chick) in brood pouch, with female looking for her mate, Antarctica, July.

Frederique Olivier / Procession of male Emperor penguins (Aptenodytes forsteri) shuffling with egg (or chick) in brood pouch, with female looking for her mate, Antarctica, July.

Juan Manuel Borrero / Illustration of Daphnia and egg pouch. Pencil and watercolor painting.

Ingo Arndt / Christmas Island Red Crab (Gecarcoidea natalis) female with eggs shortly before spawning, Christmas Island, Indian Ocean, Territory of Australia

Ingo Arndt / Christmas Island Red Crab (Gecarcoidea natalis) eggs in females opened brood pouch shortly before spawning, Christmas Island, Indian Ocean, Territory of Australia

Juergen Freund / Female Christmas island red crab's full egg pouch. {Geocarcoidea natalis} Christmas Island

Chris Newbert / Harlequin Ghost Pipefish (Solenostomus paradoxus) female carrying eggs in her pouch, 30 feet deep, Solomon Islands