Georgette Douwma / Harlequin or Ornate ghostpipefish (Solenostomus paradoxus) female carrying eggs in pelvic fins. North Sulawesi, Indonesia.

Alex Mustard / Ornate ghost pipefish (Solenostomus paradoxus) the larger female is above, her pelvic fins are cupping a clutch of eggs, male below, Dauin, Negros Island, Philippines. Bohol Sea, Pacific Ocean.

Pascal Kobeh / Feather star clingfish (Discotrema crinophila) living in crinoid, New Caledonia, Pacific Ocean. This fish perfectly mimics its host and has modified pelvic fins that act as suction cups for attachment...

Alex Mustard / Warty frogfish (Antennarius maculatus) swimming over the seabed, by gulping in water, then closing its mouth and squirting the water out of vents by its pelvic fins. Anilao, Batangas, Luzon, Philippin...

Alex Mustard / Close up portrait of female Lionfish (Pterois volitans) in the late afternoon, when Lionfish are more active. The Alternatives, Sha'ab Mahmood, Sinai, Egypt. Red Sea.

Alex Mustard / A male Lumpsucker (Cyclopterus lumpus) uses his sucker (modified pelvic fins) to attach to this rock in the surge of water moving through this kelp forest. Hallbjarnarstadur near Husavik, north east I...

Alex Mustard / Indonesian speckled carpetshark (Hemiscyllium freycineti) walks across the seabed under the cover of darkness. Rather than swim, this species of epaulette shark walks on its pectoral and pelvic fins....

Alex Mustard / Female ornate ghost pipefish (Solenostomus paradoxus) with eggs clasped between her pelvic fins. Manado, North Sulawesi, Indonesia. Sulawesi Sea.

Alex Mustard / 2020VISION / Juvenile Lumpsucker (Cyclopterus lumpus) attached to a kelp frond with its pelvic fins, which are modified into a sucker. Shetland Islands, Scotland, UK, June

Jane Burton / Pike cichlid {Crenicichla lepidota} resting on rock, 'tripoding' on pelvic fins and tail, captive, from South America

Ian Coleman / Illustration of pelvic fin of Gray reef shark (Carcharhinus amblyrhynchos). Endangered/threatened species.

Ian Coleman / Illustration of pelvic fin of Caribbean reef shark (Carcharhinus perezi). Endangered / threatened species.