Syngnathidae
by C. E. Dawson
Slender and elongate gasterosteiforms, with or without a prehensile tail, with body armoured by dermal plates arranged to form a series of rings and with or without a fleshy external integument. Mouth small, terminal, usually on a protruding tubiform snout; without true teeth; gill opening reduced to a pore located in the membrane above the opercle; gill membranes fused to body and isthmus; 4 complete gill arches, the gills lobate; spinous dorsal and pelvic fins absent, other fins variously present or absent. Sexually dimorphic, the males incubating the eggs under trunk or tail; eggs exposed or partly to completely enclosed within a well-defined brood pouch. Larvae and early post-larvae often replicate adults, but there are significant differences between young and adults in some genera (see Dawson and Allen, 1978).
Syngnathids range from boreal regions to southern cold-temperate waters. Species abundance is perhaps highest in temperate-subtropical areas and greatest diversity (about 70% of recognized species) is in the tropical-subtropical Indo Pacific. Predominantly marine but estuarine and freshwater forms are not uncommon, some are oceanic but most syngnathids are taken in inshore waters and within the 50 m depth range. These fishes have little economic value but they are sometimes sold as curios and some (especially seahorses) are popular aquarium exhibits .
Genera about 55; in Clofnam area 5.
Recent revisions (on a regional basis only): Fritzsche (1980), Dawson (1982a).
Note on taxonomic methods. Counts of trunk rings begin with the ring bearing the pectoral-fin base and end with the ring bearing the anus, except in species lacking pectoral fins wherein the first complete ring behind the gill opening is counted as the second trunk ring. Tail-ring counts begin with the first ring behind the anus (usually bearing anal fin) and end with the penultimate ring, excluding the terminal element bearing the caudal fin. Body ring counts are reported as number of trunk rings + number of tail rings. All finrays are counted separately.