Most syngnathoids feed on a wide variety of small crustaceans (e.g., copepods and mysids), sometimes almost exclusively, as well as on other small invertebrates and the larvae of other fishes. The larger species, such as cornetfishes and trumpetfishes, also feed on larger fishes. Most gasterosteiform species ingest prey whole by quickly opening their mouths to produce a strong inward current, a suction mechanism called pipette feeding. In this manner, large prey items cannot be ingested, owing to the small terminal mouths, lack of teeth, and tubular snouts of many syngnathoid species. Most prey items are ingested from the substrate or when just hovering above it. Many gasterosteiforms rely on their highly developed camouflage to surprise prey items. This is the case in numerous species of pipefishes that slowly cruise over sandy bottoms with sea grasses, feeding on small crustaceans that fail to perceive them as a result of their cryptic appearance. Many species feed on small mysids and other crustaceans that are more free-swimming as well as fish larvae; they remain in strategic positions along the fringes of reefs, where they are exposed to currents that may contain these prey items. Some species, however, eat primarily in the water column (e.g., macroramphosids and aulorhynchids). Gasterosteiforms are preyed upon by larger carnivorous fishes, such as flatheads (Platycephalidae) and snappers (Lutjanidae). Because they move slowly, gasterosteiforms are ingested easily once they are discovered.
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