Meet the Strange Syngnathiformes
Syngnathiformes is the order of highly-specialized predatory fish known for their unusual appearance and adaptations. The most well known is the seahorse, but all of the syngnathids have similar features: long, narrow bodies that lack rings but are instead have a bony exterior that makes up armor, and small, tubular mouths used for sucking in prey. They are mostly ambush predators, either lying in wait for food to drift by or slowly stalking prey. Most have some form of sex reversal with the males caring for the eggs.
Seahorses are the poster child for extreme adaptations found in Syngnathiformes. They resemble horses with their long snout and upright bodies. They lack a tail fin and instead have a highly modified prehensile tail used for grasping corals and sea grass, which they anchor to waiting for shrimp or plankton to drift by. When they swim, it is using their small dorsal fin on their backs to propel them through the water (slowly) and pectoral fins located just behind their head to steer.
There are about 45 described species of seahorse. They are found throughout most of the words oceans, though they are absent from the arctic and antartic regions. They can be found in tropical, subtropical and temperate seas. They live in habitats ranging from sea grass beds, mangrove forests and and coral reefs.
The male seahorses has a brood pouch at the base of the tail where the female seahorse deposits eggs. He keeps the eggs in his brood pouch until they hatch, at which time he releases them into the ocean and their parental role is done. Some seahorse fry drif on the ocean currents for a while among plankton before settling, while others settle and being hitching on to things with their tails immediately.
Hippocampus denise next to finger for size comparison. Photo courtesy of Daniel, Daniel Kwok.
Pygmy Seahorses are still part of the genus Hippocampus which all seahorses belong but are distinctively different than their larger cousins. Pygmy Seahorses rarely grow over 1 inch in size. They have a single gill slit located behind their heads (probably a modification due to their small size). Pygmy seahorses eat different types of plankton, probably mostly copepods due to their small size, though more thorough research will be needed to determine this for sure. H. bargibanti has been observed picking plankton from the polyps of gorgonians it is found in.
Pygmy seahorses have so far only been described from different regions in the western pacific. This area of the pacific has some of the most diverse sea life on the planet, so it is unclear whether or not pygmy seahorses will be found in other parts of the world. Pygmy seahorses form close relationships with a host plant or animal, including gorgonians, colonial hydrazoans, and algae.
Most species of pygmy seahorses have only been discovered in the past 10 years, and it is believed there are many more not yet described. Unlike larger seahorse species, males do not have a brood pouch at the base of their tail. Eggs and embroyos are incubated in the trunk region and have a downward facing opening which the fry are released from.
Possible Trachyrhampus sp. Photo courtesy of Daniel, Daniel Kwok.
Pipefish are snake-like relatives of seahorses. They look like a stretched out seahorse, mostly swimming horizontally rather than vertically. Unlikely seahorses, most pipefish have a caudal (tail) fine that can be used for propulsion. Some pipefish are quite agile swimmers while others creep along the bottom barely using their caudal fins. Pipefish have an even wider distribution than seahorses, with some living in rivers and streams as well as inhabiting the worlds oceans. There are around two hundred different pipefish species described, ranging in size from a just couple inches to over 2 feet in length.
As with most other sygnathiformes, parenting duties of the pipefish falls on to the male. Courtship tends to be elaborately choreographed displays between the males and females. Pair bonding varies wildly between different species of pipefish. Male pipefishes have a specially developed area to carry eggs, which are deposited by the female. In some species this is just a patch of spongy skin that the eggs adhere to until hatching. Other species have a partial or even fully developed pouch to carry the eggs.
Pipehorses are a type of pipefish that morphologically appear between the seahorses and more traditional pipefish. They tend to have deeper bodies than most pipefish and often have a prehensile tail with no caudal fin. They are often thought to be pipefish, though they resemble sea dragons without (or with smaller) leafy appendages and appear to be closely related. Pipehorses of the genus Solegnathus are heavily consumed by traditional Chinese medicine.
Pipehorses are large, up to 20″ in length. They have a prehensile tale like a seahorse which they use to hitch to seagrass, seafans and corals. They are mostly found adjacent to reefs amoung soft corals and gorgonians. The notable exeption to this is the Alligator Pipefish, Syngthoides biaculeatus, which spends its life among seagrasses and sargassium rafts. All the described pipehorses only occur in the west pacific and indo pacific oceans.
Short-pouch pygmy pipehorse Acentronura breviperula from East Timor. Photo courtesy of Nick Hobgood.
Pygmy pipehorses are a small fish no larger than a couple inches that look like a cross between a seahorse and a pipefish. Most species have deep heads and bodies, and a prehensile tale to grasp corals and algae. Males sport a pouch to protect eggs laid by the female. Males tend to position themselves more upright like seahorses, while females tend to remain horizontal. It is likely that they are the evolutionary link between seahorses and pipefish. They have an unusual habit where at night they perch high on their algae hosts to avoid predation by nocturnal marine animals.
Pygmy pipehorses are found in many of the same habitats seahorses are, from seagrass beds to reefs. There are only 8 known species, but this is likely because they are not very well known and therefore have not been described.
Sea dragons are large relatives of the seahorse. There are only two of Sea Dragon, the Leafy Sea Dragon, and the Weedy Sea Dragon. Both are found off the coasts of Australia and live in temperate waters. They have lobes of skin that grow on they’re body to give them the appearance of seaweed, allowing it to camouflage with its surroundings. It primarily eats crustaceans including plankton and mysids, but its diet also includes shrimp and small fish. However, these two species are not actually closely related to one another, and instead are more closely related to the pipehorses than each other.
The male leafy sea dragon cares for the eggs. The female deposits up to 250 bright pink eggs on to the male’s tail. The eggs are attached brood patch on the underside of the male’s tail. The eggs take 9 weeks to begin to hatch. The male aids in the babies hatching by shaking his tail, and rubbing it against seaweed and rocks. Once born, the infant sea dragon is completely independent, eating small zooplankton until large enough to hunt mysids. It takes sea dragons over 2 years to reach sexual maturity.
There are 5 species of Ghost Pipefishes (also called False Pipefishes). They are similar to pipefish in many ways but have large, fan-like fins that help them stay camouflaged and a shorter, stocky build. They are found in tropical waters of the Indian Ocean, from Asia to Africa. Ghost pipefish species are no larger than 6 inches. They spend the majority of their time floating motionlessly, with the mouth facing downwards waiting for prey to float by. They feed on tiny crustaceans, mostly shrimp. Their camouflage is highly specialized to match either gorgonians, or crinoids, or algae and sea grasses.
Ghost pipefish tend to occur in pairs, though can sometimes be found in small groups. Unlike true pipefish, female ghostpipefishes use their enlarged pelvic fins to brood their eggs until they hatch. Young are born pelagic and spend their early life as part of the plankton.
East Atlantic Trumpetfish Aulostomus strigosus. Photo courtesy of Philippe Guillaume.
Trumpetfishes are found in tropical waters worldwide, with two species in the Atlantic and one in the Indo-Pacific. They are mostly reef-dwellers, where one species seems to prefer rocky habitats. They are relatively large for reef fish, the largest getting to almost 3 feet long. Similar to most members of the order Syngnathiformes, the bodies of trumpetfish are inflexible, supported by armored plating.
Trumpetfishes hunt by hovering almost motionlessly a few inches above the sea floor, inching their way towards unsuspecting prey. Once close enough, they rapidly dart in, and expand their jaws rapidly. Opening their tube-like mouths in quick succession creates a strong suction force, which draws prey straight into the mouth. Trumpetfish are known to feed almost exclusively on small, schooling reef fishes. Some Trumpetfish will partner up with other large fish that are normally harmless and match their color in order to sneak up on prey.
Cornetfish in Hawaii. Photo courtesy of cwilso.
Flute Mouths, also known as Cornetfishes, are possibly the largest of the Synghathiformes. They can grow up to 6 feet in length. They are similar to the trumpet fish, but are much longer and thinner. There are only 4 species, two are found across the globe, and one in the east pacific and one in the Atlantic. They generally live in coastal waters or on coral reefs, where they feed on small fishes, crustaceans and other invertebrates.
Shrimpfish next to the pier at Dauin. Negros, Philippines. Photo courtesy of dachalan
Shrimpfish, also called Razorfish, are a unusual fish also part of the sygnathiformes. Shrimpfish are flattened from side to side with long snouts and a sharp-edged belly. They live in schools and swim in a synchronized manner with their heads pointing downwards. Shrimp fish synchronize their swimming to look like leaves or other vegetative debris in the water, twisting and turning like a leaf caught in the current. The largest grows up to 8 inches.
Shrimpfish are found in the Indian and Pacific Oceans. Most live over sea grass beds, with one species preferring branching corals. They are broadcast spawners, not showing any parental care of the eggs or young, which are pelagic and live among the plankton.
Video still of snipefish at the Shedd aquarium. Courtesy of treegrow.
Snipefish, also known as Bellowfish, have a rigid and highly compressed body, enlarged dorsal spine that forms a spike, and a long snout. They are found in temperate waters on continental shelves. Unlike many sygnathids, these fish live in large schools. They are closely related to the Shrimpfish though swim in a normal orientation.
Seamoths are another unsual fish that shows just how diverse the Syngnathiformes are. What makes Sea Moths notable are their flattened bodies, the presence of large, wing-like, pectoral fins, and a body encased in thick, bony plates. Most species also have an elongated snout in front of their jaws. Their pelvic fins are also modified, allowing them to “walk” across the sea bottom where they live. Their jaws are highly specialized tube-like structure used to suck worms and other small animals from their burrow. Sea mothes do not care for their eggs, instead producing pelagic eggs
Sea moths are tropical, found in western pacific waters. They are found in sandy estuaries, usually bordering sea grass beds.
A Flying Gurnard, Dactylopterus volitans, in the Mediterranean east of Crete, Greece. Photo courtesy of Beckmannjan.
Flying Gurnards notable for their greatly enlarged pectoral fins. They have been observed to “walk” along sandy sea floors while looking for crustaceans and other small invertebrates by using their pelvic fins. They can be found throughout the worlds oceans, though most are from the Indo-Pacific. At least one is native to the Atlantic. The adults live on the sea bottom, but many species have an extended larval stage, which floats freely in the oceans. Flying gurnards were previously thought to be part of the Scorpaeniformes order, however DNA sequencing shows they are part of the Syngnathiformes order.
Kawahara, Ryouka; Miya, Masaki; Mabuchi, Kohji; Lavoue, Sébastien; Inoue, Jun G.; Satoh, Takashi P.; Kawaguchi, Akira & Nishida, Mutsumi (2008): Interrelationships of the 11 gasterosteiform families (sticklebacks, pipefishes, and their relatives): A new perspective based on mitogenome sequences from 75 higher teleosts. Mol. Phylogenet. Evol. 46(1): 224-236.
Kuiter, R.H. 2000. Seahorses, pipefish and their relatives: A comprehensive guide to Syngnathiformes. TMC Publishing, UK. 240 pp.