How do the mouths of many gasterosteiform fishes differ from those of typical fishes?

Many fishes in the order Gasterosteiformes are characterized by having tubular mouths, which differ significantly from the more typical mouth structures found in many other fish groups.1

These specialized, elongated snouts often terminate in small mouths, which are frequently adapted for specific feeding strategies, such as sucking food rapidly into the mouth. For example, species like pipefishes, trumpetfishes, and snipefishes possess these prolonged, tubelike structures. In contrast, many other fish species exhibit more conventional jaw structures that are not elongated into such tubes.234