Gasterosteiform

stickleback

gasterosteiform, (order Gasterosteiformes), any member of a group of fishes characterized generally by tubular mouths, soft fin rays, pelvic fins located on the abdomen, an air bladder without a duct to the gut, and a primitive kidney. Gill structures are somewhat degenerate. Most species have bony rings around the body or ganoid (thick, bony, enameled, and diamond-shaped) plates rather than scales. Families within the order are Gasterosteidae (sticklebacks), Aulorhynchidae (tubesnouts), Indostomidae (indostomid or paradox fish), Aulostomidae (trumpetfishes), Fistulariidae (cornetfishes), Centriscidae (shrimpfishes), Macrorhamphosidae (snipefishes), Solenostomidae (ghost pipefishes), Syngnathidae (pipefishes, seahorses, sea dragons, and pipehorses), Pegasidae (pegasids or dragonfish), and Hypoptychidae (sand lances).