From the Indostomidae there is only one species that is known. The name of this species, Indostomus paradoxus, makes reference to a peculiar array of characteristics which are present in the species. While the individual row of spines in front of the dorsal fin is the main characteristic that shows this fish is related to the sticklebacks, the tube like head is elongated and the bony external skeleton is much more indicative of the pipe fish or seahorse group. Very little is known about the anatomy and habits of the Indostomus making a correct classification difficult until a more thorough study of this fish has been done.
Sticklebacks make up five genera, most of which have just one species.
They live exclusively in the cold and temperate zones of the northern hemisphere with at least two genera living in the ocean and two genera living in fresh water while at least one genera is known to live in brackish water. These fish do not have scales, but instead have numerous vertical narrow bony plates that develope in the dermis. Under a microscope a fine network of lamellae is revealed. In front of the dorsal fin there is a number of free standing moveable spines that vary in number with each species. The diet of the stickleback fish consist mostly of insect larvae, worms, fish eggs, small crustaceans and young fish.