A group of highly modified and specialised ray-finned fishes that include seahorses, pipefishes, seadragons, ghostpipefishes, flutemouths, trumpetfishes, snipefishes and other related groups. The order comprises six families and more than 370 species.
Syngnathiformes are found worldwide in tropical and temperate waters, with the greatest diversity in the Indo-Pacific. Although most species inhabit warm coastal marine waters, some live in freshwater and several tropical pipefishes are found in the lower reaches of rivers and streams. Many species have restricted distributions.
Characteristics: Most Syngnathiformes have slender elongate bodies with a small mouth at the end of a long tubular snout, and armoured bodies partially or completely encased in bony rings or dermal plates. They share various specialisations of the skeleton, including the absence of anterior processes directly connecting the pelvic fins to the cleithra, the absence of supramaxillary, orbitosphenoid and basisphenoid bones and the absence of a strong ligament (Baudelot’s ligament) connecting the shoulder girdle to either the posterior cranial base or an anterior vertebra.
Syngnathiformes vary considerably in size, ranging from one-centimetre long pygmy seahorses to 1.5 metre-long flutemouths. Although most species are cryptically-colored often with dermal appendages to camouflage themselves further, some pipefishes have striking colour patterns.
Biology and behaviour: Although most are slow moving ambush predators and feed on small crustaceans, the larger flutemouths and trumpetfishes actively prey on other fishes. Pipefishes of the genus Doryrhamphus are known to clean parasites from other reef fishes.Reproduction and early life history: Syngnathiformes exhibit a variety of reproductive strategies. Some form monogamous pair bonds and have complex and elaborate courtship rituals. Members of some families release eggs and sperm directly into the water, whereas seahorses, pipefishes and ghostpipefishes are all egg brooders. Female ghostpipefishes brood their eggs in a pouch formed by their greatly enlarged pelvic fins. The family Syngnathidae – seahorses, pipefishes and their relatives – has the most highly evolved reproductive strategy whereby males brood the eggs. Females lay their eggs either into an enclosed pouch on the male’s abdomen or onto a highly specialised area on the male's underside. Males then incubate and nourish the developing embryos until they are born or hatch as miniature fully-formed young.
Fisheries and aquaculture: Many pipefishes and seahorse species are popular aquarium fishes. Fortunately several species are now aquacultured for sale in the live aquarium trade and the Traditional Chinese Medicine industry.
Conservation Status: Many seahorse and some pipefish species are included on the IUCN Red List of Threatened species due to their exploitation for sale as curios or their use in the Tradition Chinese Medicine Industry. All members of the families Syngnathidae and Solenostomidae are listed as protected species under the Commonwealth Environment Biodiversity and Conservation Act, 1999 (EPBC Act).
Fossil record: Gasterosteiformes have an extensive fossil record dating back to the Eocene. Fossil snipefishes have been found in deposits dating back at least 75 million years near Nardò, southeastern Italy. In addition, the Monte Bolca beds of northeastern Italy, dating back about 52 millions years, contain many fossils of five gasterosteiform families.
Braga Goncalves, I., Ahnesjö, I. & Kvarnemo, C. (2015). Embryo oxygenation in pipefish brood pouches: novel insights. J. Exp. Biol. 218: 1639-1646. Abstract
Britz, R. & G.D. Johnson. 2002. “Paradox Lost” Skeletal ontogeny of Indostomus paradoxus and its significance for the phylogenetic relationships of Indostomidae (Teleostei, Gasterosteiformes). Am. Mus. Nov. 3382: 1–43.
Fritzsche, R.A. 1984. Gasterosteiformes: development and relationships (p. 398-405). In Moser, H.G., W.J. Richards, D.M. Cohen, M.P. Fahay, A.W. Kendall, Jr. & S.L. Richardson, eds. Ontogeny and systematics of fishes. Am. Soc. Ichthyol. Herpetol. Spec. Publ. No. 1.
Kawahara, R., M. Miya, K. Mabuchi, S. Lavoue, J.G. Inoue, P. Takashi, A . Kawaguchi & M. Nishida. 2008. Interrelationships of the 11 gasterosteiform families (sticklebacks, pipefishes, and their relatives): A new perspective based on mitogenome sequences from 75 higher teleosts. Mol. Phylog. Evol. 46(1): 224–236.
Keivany, Y. & J. Nelson. 2006. Interrelationships of Gasterosteiformes (Actinopterygii, Percomorpha). J. Ichthyol. 46, Suppl. 1: S84-S96.
Kuiter, R. H. 2009. Seahorses and their relatives. Aquatic Photographics, Seaford, Australia. 333 pp.
Johnson, D.G. & C. Patterson. 1993. Percomorph phylogeny: a survey of acanthomorphs and a new proposal. Bull. Mar. Sci. 52(1): 554-626.
Nelson, J.S. 1971. Comparison of the pectoral and pelvic skeleton and of some other bones and their phylogenetic implications in the Aulorhynchidae and Gasterosteidae (Pisces). J. Fish. Res. Board Can. 28: 427–442.
Nelson, J.S. 2006. Fishes of the World. Hoboken, New Jersey : John Wiley & Sons, Inc. 4th Ed. 601 p.
Parenti, L.R. & J. Song. 1996. Phylogenetic significance of the pectoral-pelvic fin association in acanthomorph fishes: a reassessment using comparative neuroanatomy, pp. 427–444. In Interrelationships of Fishes. Academic Press.
Paxton, J.R., J.E. Gates, D.J. Bray & D.F. Hoese. 2006. Gasterosteiformes, In Beesley, P.L. & A. Wells (Eds). Zoological catalogue of Australia. Volume 35 Fishes. ABRS & CSIRO Publishing, Australia. Part 2.
Pietsch, T.W. 1978. Evolutionary relationships of the sea moths (Teleostei: Pegasidae) with a classification of gasterosteiform families. Copeia 1978: 517–529.
Takata, Y. & K. Sasaki. 2005. Branchial structures in the Gasterosteiformes, with special reference to myology and phylogenetic implications. Ichthyol. Res. 52(1): 33-49.
Wilson AB, Vincent A, Ahnesjo I, Meyer A (2001) Male pregnancy in seahorses and pipefishes (family Syngnathidae): rapid diversification of parental brood pouch morphology inferred from a molecular phylogeny. J. Hered. 92: 159–166.