Hippocampinae

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Hippocampinae
Temporal range: Middle Miocene–present
Idiotropiscis australe.jpg
Idiotropiscis australe
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Syngnathiformes
Family: Syngnathidae
Subfamily: Hippocampinae
Bonaparte, 1835
Genera

Between 1 and 6 (see text)

Kyonemichthys rumengani, one of several small syngnathids discovered in the West Pacific in recent years Kyonemichthys rumengani.jpg
Kyonemichthys rumengani , one of several small syngnathids discovered in the West Pacific in recent years

The Hippocampinae are a subfamily of small marine fishes in the family Syngnathidae. Depending on the classification system used, it comprises either seahorses and pygmy pipehorses, [1] or only seahorses. [2]

Contents

Genera

Seahorses

Pygmy pipehorses

Description

All seahorse and pygmy pipehorse species have a prehensile tail (a character shared with some other syngnathids), [4] a fully enclosed brood pouch, a short head and snout angled ventrally from the abdominal axis, and no caudal fin. [5] The species in the genera Acentronura, Amphelikturus and Kyonemichtys resemble pipefishes, which explains why pygmy pipehorses are sometimes grouped in the pipefish subfamily Syngnathinae. [6] The species of Idiotropiscis are more seahorse-like in appearance in having a deeper body and discontinuous superior trunk and tail ridges. [7] The main differences between this pygmy pipehorse genus and the seahorses is that the latter have an upright posture, and the angle of their head relative to the abdominal axis is greater. [7]

Etymology

The subfamily Hippocampinae is named after the seahorse genus Hippocampus , which is derived from the Ancient Greek ἱππόκαμπος (hippokampos), a compound of ἵππος, "horse" and κάμπος, "sea monster". The morphologically intermediate nature of pygmy pipehorses is reflected in the name "pipehorse", a combination of the first syllable of "pipefish" and the second syllable of "seahorse". "Pygmy" is added to distinguish them from the larger pipehorses of the genus Solegnathus , which are distant relatives of the pygmy pipehorses. [8] Other common names that have been applied to pygmy pipehorses include "bastard seahorse", "little pipehorse" and "pygmy pipedragon".

Systematics

Due to the morphologically intermediate nature of the pygmy pipehorses between pipefishes and seahorses, the taxonomic placement of this group remains contentious, and three different classifications have been proposed for the subfamily Hippocampinae. No well-resolved phylogeny exists, making it impossible to settle this issue at the present time.

Phylogenetic analyses based on five nuclear genetic loci recovered the genera Hippocampus and Idiotropiscis as sister taxa, suggesting that seahorses and pygmy pipehorses are a monophyletic group [9] and hence share a common evolutionary origin. However, the same phylogeny indicates that if the subfamily Hippocampinae is accepted as valid, then the pipefish subfamily Syngnathinae is paraphyletic, because the former is not a sister group of the latter, but is nested within it. [9]
This classification system disregards both genetic data and the morphological characters shared by seahorses and pygmy pipehorses. As seahorses have a sister taxon relationship with Idiotropiscis , and other pygmy pipehorse genera are likely basal to this group (given their more pipefish-like appearance), this classification would also make the Syngnathinae paraphyletic.
This classification places all pygmy pipehorses into the subfamily Acentronurinae. Based on the nuclear DNA phylogeny, the exclusion of the seahorses from this group likely makes it paraphyletic. However, such a placement is partially supported by an alternative molecular phylogeny that is based on a combination of nuclear and mitochondrial markers and that recovered a group comprising pygmy pipehorses and several pipefishes as a sister lineage of Hippocampus . [10]

As the genus Hippocampus consists of two morphologically distinct forms, it has been suggested that it should be split into two distinct genera, Hippocampus and a new genus comprising the pygmy seahorses. Pygmy seahorses have a single gill opening on the back of the head (instead of two on the sides as in normal seahorses), and the males brood their young inside their trunk, instead of in a pouch on the tail. [11] A molecular phylogeny confirms that the pygmy seahorses are a monophyletic sister lineage of all other seahorses. [10]

Evolution and fossil record

A simplified reconstruction of the evolution of seahorses from a pipefish-like ancestor based on a combination of genetic data, fossils and the body structure of living species. Although some species have become extinct, the major stages of evolution are still represented in living species. The timing of only two evolutionary events is known with some certainty: the evolution of the first pipefishes and the evolution of seahorses. The placement of the pipefish-like pygmy pipehorses has yet to be confirmed by genetic data. Syngnathid phylogeny.jpg
A simplified reconstruction of the evolution of seahorses from a pipefish-like ancestor based on a combination of genetic data, fossils and the body structure of living species. Although some species have become extinct, the major stages of evolution are still represented in living species. The timing of only two evolutionary events is known with some certainty: the evolution of the first pipefishes and the evolution of seahorses. The placement of the pipefish-like pygmy pipehorses has yet to be confirmed by genetic data.

The morphology of pygmy pipehorses suggests that they are an evolutionary link between pipefishes and seahorses, and that seahorses are upright-swimming pygmy pipehorses. Molecular dating indicates that Hippocampus and Idiotropiscis diverged from a common ancestor during the Late Oligocene. [9] During this time, tectonic events in the Indo-West Pacific resulted in the formation of shallow-water areas, which considerably changed marine habitats in this region. [12] Particularly important was the establishment of vast seagrass meadows where there had previously been deeper water. [13] This has led to speculation that the earliest seahorses managed to establish themselves as a new species because, unlike pygmy pipehorses, they were selectively favoured in such habitats. Not only can seahorses manoeuver exceptionally well in dense seagrass meadows, [14] but the upright seagrass blades would have provided camouflage for their bodies and in that way improved their ability to ambush prey and avoid detection by predators. [9] An alternative explanation for the evolution from pygmy pipehorse to seahorse is based on the finding that a vertically bent head is more efficient in capturing prey because it increases the animal's strike distance, which is considered particularly useful in tail-attached sit-and-wait predators. [15] In that case, the evolution of an upright posture would merely be a means of maximising the angle between head and abdominal axis.

There is as yet no fossil evidence for the evolution of seahorses from a pygmy pipehorse ancestor, as the fossil record of both groups is very sparse. The only pygmy pipehorse species of which fossils have been found ( Hippotropiscis frenki) lived in the Central Paratethys Sea (the modern-day Tunjice Hills of Slovenia, north of the Mediterranean Sea) during the Middle Miocene, [3] i.e. during a time when seahorses had already evolved. [9] In fact, the oldest known seahorse species, Hippocampus sarmaticus and H. slovenicus , were found at the same site. [3] Independent geological confirmation of the genetic data would require finding a fossil site from the Oligocene in which seahorse-like pygmy pipehorses are present, but seahorses are not. Given the fact that Idiotropiscis is endemic to temperate Australia and the most basal seahorse lineages occur in Australia and the tropical West Pacific, [16] these regions are the most likely candidates for such a site.

Related Research Articles

<span class="mw-page-title-main">Seahorse</span> Genus of bony fishes

A seahorse is any of 46 species of small marine bony fish in the genus Hippocampus. "Hippocampus" comes from the Ancient Greek hippókampos (ἱππόκαμπος), itself from híppos (ἵππος) meaning "horse" and kámpos (κάμπος) meaning "sea monster" or "sea animal". Having a head and neck suggestive of a horse, seahorses also feature segmented bony armour, an upright posture and a curled prehensile tail. Along with the pipefishes and seadragons they form the family Syngnathidae.

<span class="mw-page-title-main">Syngnathidae</span> Family of fishes

The Syngnathidae is a family of fish which includes seahorses, pipefishes, and seadragons. The name is derived from Ancient Greek: σύν, meaning "together", and γνάθος, meaning "jaw". The fused jaw is one of the traits that the entire family have in common.

<span class="mw-page-title-main">Pipefish</span> Subfamily of fishes

Pipefishes or pipe-fishes (Syngnathinae) are a subfamily of small fishes, which, together with the seahorses and seadragons, form the family Syngnathidae.

<span class="mw-page-title-main">Syngnathiformes</span> Order of fishes

The Syngnathiformes are an order of ray-finned fishes that includes the leafy seadragons, sea moths, trumpetfishes and seahorses, among others.

The pygmy seahorses comprise several species of tiny seahorse in the syngnathid family or Syngnathidae. Family Syngnathidae is part of order Syngnathiformes, which contains fishes with fused jaws that suck food into tubular mouths. They are found in Southeast Asia in the Coral Triangle area. They are some of the smallest seahorse species in the world, typically measuring less than 2 centimetres (0.79 in) in height.

<i>Hippocampus sarmaticus</i> Extinct species of fish

Hippocampus sarmaticus is an extinct species of seahorse, found in 2005 in the coprolitic horizon of the Tunjice hills Lagerstätte in Slovenia, along with the related Hippocampus slovenicus.

The Yucatán pipefish is a demersal fish species native to the Gulf of Mexico.

<i>Acentronura</i> Genus of fishes

Acentronura is a genus of pygmy pipehorse native to the Indian and Pacific oceans. The name is derived from the Greek ακεντρονουρα, or a-kentron-oura, and refers to the lack of a sting on the tail.

Amphelikturus dendriticus, the pipehorse, is a species of pygmy pipehorse native to the western Atlantic Ocean. This small, highly camouflaged pipefish is rarely seen. This species grows to a length of 7.5 centimetres (3.0 in) TL. This species is the only known member of its genus.

<i>Leptoichthys fistularius</i> Species of fish

Leptoichthys fistularius, the brush-tailed pipefish, is a species of pipefish of the family Syngnathidae, found in shallow to intermediate depths off the coast of southern Australia, usually in seagrass beds. This species is the largest known species of pipefish, growing to a maximum of 63 cm (25 in) in length. Like other pipefishes, the male carries the fertilized eggs in a pouch under his tail until they hatch. The genus name comes from the Greek leptos meaning "thin" and ichthys meaning "fish", the specific name refers to the resemblance of the head of this species to that of the fluteheads or cornetfishes of the family Fistulariidae.

<i>Kyonemichthys rumengani</i> Species of fish

The thread pipefish, also known by its Japanese standard name Hari-youji, is a species of pipefish native to the Pacific Ocean around Indonesia, where it is found at depths from 15 to 20 m. This species grows to a length of 2.68 cm (1.06 in), and is the only known member of its genus.

<span class="mw-page-title-main">Syngnathoidea</span> Superfamily of fishes

Syngnathoidea is a superfamily of the pipefish order Syngnathiformes. It is divided into two families, the speciose pipefish Syngnathidae, which includes the sea horses and monotypic Solenostomidae, the ghost pipefishes, which has just five species. The superfamily occurs worldwide in tropical, subtropical and temperate seas, especially in coastal waters around rock and coral reefs and among sea weed and sea grass beds. However, there are also pelagic species of pipefish and even freshwater species. In total the superfamily comprises in excess of 50 genera and nearly 300 species.

<i>Acentronura breviperula</i> Species of fish

Acentronura breviperula, also known as the shortpouch pygmy pipehorse, dwarf pipehorse and northern little pipehorse, is a species of pygmy pipehorse, a member of the family Syngnathidae, the seahorses and pipefishes. It occurs in the Indo-Pacific region from the eastern Andaman Sea, through the Malay Archipelago to the Western Pacific as far east as New Guinea and the northern Great Barrier Reef.

Lissocampus bannwarthi is a species of marine pipefish belonging to the family Syngnathidae.

<i>Lissocampus caudalis</i> Species of fish

Lissocampus caudalis, also called the Australian smooth pipefish or the smooth pipefish, is a species of marine fish belonging to the family Sygnathidae.

Lissocampus fatiloquus, also known as prophet's pipefish is a species of marine fish belonging to the family Syngnathidae. The species has been noted in a variety of habitats including sargassum, seagrass beds and sandy substrates along the coast of Western Australia from Shark Bay to Rottnest Island. Their diet is thought to consist of small crustaceans such as copepods. Reproduction occurs through ovoviviparity in which the males brood eggs before giving live birth.

<i>Lissocampus runa</i> Species of fish

Lissocampus runa, also known as the javelin pipefish is a species of marine fish belonging to the family Syngnathidae. This species can be found in algae beds, rocky reefs, tidepools, and estuaries along the coast of southern Australia from Broken Head Nature Reserve in New South Wales to Rottnest Island, Western Australia. Their diet is thought to consist of small crustaceans such as copepods. Reproduction occurs through ovoviviparity in which the males brood eggs before giving live birth.

Nannocampus pictus, also known as the reef pipefish, is a species of marine fish belonging to the family Syngnathidae. They can be found inhabiting reefs and seagrass beds of the western Indian Ocean and the eastern coast of Australia including the Great Barrier Reef. Members of this species can grow to lengths of 10 cm and their diet likely consists of small crustaceans such as copepods. Reproduction occurs through ovoviviparity in which the males brood eggs before giving live birth.

<i>Hippocampus nalu</i> Species of seahorse endemic to South Africa

Hippocampus nalu, the Sodwana pygmy seahorse, African pygmy seahorse or Honeypot seahorse, is a South African species of pygmy seahorse in the family Syngnathidae.

Cylix tupareomanaia, the Manaia pygmy pipehorse, is a species of syngnathid, the family of seahorses and pipefish, and is endemic to New Zealand. It was first described in 2021, and is found in the northern parts of the North Island of New Zealand.

References

  1. 1 2 Kuiter, R.H. (2000) "Seahorses, Pipefishes and their Relatives – A Comprehensive Guide to Syngnathiformes." TMC Publishing, Chorleywood, UK.
  2. 1 2 Wilson N., Rouse G. (2010). "Convergent camouflage and the non-monophyly of 'seadragons' (Syngnathidae: Teleostei): suggestions for a revised taxonomy of syngnathids". Zoologica Scripta. 39 (6): 551–558. doi:10.1111/j.1463-6409.2010.00449.x. S2CID   56351380.
  3. 1 2 3 4 Žalohar, J.; Hitij, B. (2012). "The first known fossil record of pygmy pipehorses (Teleostei: Syngnathidae: Hippocampinae) from the Miocene Coprolitic Horizon, Tunjice Hills, Slovenia". Annales de Paléontologie . 98 (2): 131–151. doi:10.1016/j.annpal.2012.02.003.
  4. ↑ Dawson, C.E. (1982). "Review of the Indo-Pacific pipefish genus Stigmatopora (Syngnathidae)". Records of the Australian Museum . 34 (13): 575–605. doi: 10.3853/j.0067-1975.34.1982.243 .
  5. ↑ Gomon, M.F. (2007). "A new genus and miniature species of pipehorse (Syngnathidae) from Indonesia". Aqua, International Journal of Ichthyology . 13 (1).
  6. 1 2 Froese, Rainer; Pauly, Daniel (eds.) (2013). "Acentronura tentaculata" in FishBase . May 2013 version.
  7. 1 2 Kuiter, R.H. (2004). "A New Pygmy Pipehorse (Pisces: Syngnathidae: Idiotropiscis) from Eastern Australia" (PDF). Records of the Australian Museum . 56 (2): 163–165. doi:10.3853/j.0067-1975.56.2004.1420. Archived from the original (PDF) on 6 November 2013. Retrieved 9 May 2013.
  8. ↑ Wilson, A.B., Ahnesjö, I., Vincent, A.C. and Meyer, A. (2003). "The dynamics of male brooding, mating patterns, and sex roles in pipefishes and seahorses (family Syngnathidae)". Evolution . 57 (6): 1374–1386. doi: 10.1111/j.0014-3820.2003.tb00345.x . PMID   12894945.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  9. 1 2 3 4 5 Teske, P.R.; Beheregaray, L.B. (2009). "Evolution of seahorses' upright posture was linked to Oligocene expansion of seagrass habitats". Biology Letters . 5 (4): 521–523. doi:10.1098/rsbl.2009.0152. PMC   2781918 . PMID   19451164.
  10. 1 2 Healy Hamilton, Norah Saarman, Beth Moore, Graham Short, & W. Brian Simison: A Multigene Phylogeny of Syngnathid Fishes. PDF Archived 21 April 2013 at the Wayback Machine
  11. ↑ Smith, Richard E. Pygmy seahorse research
  12. ↑ Wilson, M. E. J. & Rosen, B. R. 1998 Implications of paucity of corals in the Paleogene of SE Asia: plate tectonics or centre of origin? In Biogeography and geological evolution of SE Asia (eds R. Hall & J. D. Holloway), pp. 165–195. Leiden, The Netherlands: Backhuys Publishers.
  13. ↑ Brasier, M.D. (1975). "An outline history of seagrass communities". Palaeontology . 18: 681–702.
  14. ↑ Flynn, A. J.; Ritz, D. A. (1999). "Effect of habitat complexity and predatory style on the capture success of fish feeding on aggregated prey". Journal of the Marine Biological Association of the United Kingdom . 79 (3): 487–494. doi:10.1017/S0025315498000617. S2CID   86160386.
  15. ↑ van Wassenbergh, S., Roos, G. and Ferry, L.; Roos; Ferry (2011). "An adaptive explanation for the horse-like shape of seahorses". Nature Communications . 2 (1): 164. Bibcode:2011NatCo...2E.164V. doi: 10.1038/ncomms1168 . PMID   21266964.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  16. ↑ Teske PR, Cherry MI, Matthee CA (2004). "The evolutionary history of seahorses (Syngnathidae: Hippocampus): molecular data suggest a West Pacific origin and two invasions of the Atlantic Ocean". Molecular Phylogenetics and Evolution . 30 (2): 273–86. doi:10.1016/S1055-7903(03)00214-8. PMID   14715220.
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