Seahorse

**Seahorses** are a type of teleost fish. They are in the genus ***Hippocampus.*** They are called 'seahorses' because their head looks like a horse's head. There are about 32–48 species of seahorse. Seahorses live in tropical oceans.

Seahorses use camouflage to hide.

## Fossil record

The earliest known seahorse fossils are _H. sarmaticus_ and _H. slovenicus_.

## Reproduction

Seahorses are unique because the male hatches the eggs in a pouch on his belly. The female inserts her ovipositor into the male’s brood pouch. She places dozens to thousands of eggs in the pouch. As the female releases her eggs, her body slims while his swells. The male releases his sperm directly into the water. The sperm then fertilize the eggs in the pouch. The fertilised eggs are then embedded in the pouch wall. They get nutrition and oxygen from the fluid in the pouch. In the pouch, the salinity of the water is controlled. This prepares the newborns for life in the sea.

Both animals then sink back into the seagrass and she swims away. The eggs then hatch

Throughout gestation, which in most species requires two to four weeks, his mate visits him daily for 'morning greetings'. They interact for about 6 minutes. The female then swims away until the next morning, and the male vacuums up food through his snout.

Research published in 2007 shows that the males release sperm into the surrounding sea water during fertilization, and not directly into the pouch as previously thought.

### Birth

The number of young released by the male seahorse averages 100-200 for most species, but may be as low as 5 for the smaller species, or as high as 1,500.

When the fry are ready to be born, the male expels them with muscular contractions. He gives birth at night and is ready for the next batch of eggs by morning when his mate returns.

Like almost all other fish species, seahorses do not take care of their young after birth. Infants are susceptible to predators or ocean currents which wash them away from feeding grounds or into temperatures too extreme for their  bodies. Fewer than 0.5% of infants survive to adulthood. This is why litters are so large. These survival rates are actually fairly high compared to other fish, because of their protected gestation. This makes the process worth the cost to the father. The eggs of most other fish are abandoned immediately after fertilization.

Seahorses are the only fish that experience true male pregnancy.

## Species

There are 46 species in this genus:

- _Hippocampus abdominalis_ <small>Lesson, 1827</small> (big-belly seahorse)
- _Hippocampus algiricus_ <small>Kaup, 1856</small> (West African seahorse)
- _Hippocampus angustus_ <small>Günther, 1870</small> (narrow-bellied seahorse)
- _Hippocampus barbouri_ <small>Jordan & Richardson, 1908</small> (Barbour's seahorse)
- _Hippocampus bargibanti_ <small>Whitley, 1970</small> (pygmy seahorse)
- _Hippocampus breviceps_ <small>Peters, 1869</small> (short-headed seahorse)
- _Hippocampus camelopardalis_ <small>Bianconi, 1854</small> (giraffe seahorse)
- _Hippocampus capensis_ <small>Boulenger, 1900</small> (Knysna seahorse)
- _Hippocampus casscsio_ <small>Zhang, Qin, Wang & Lin, 2016</small> (Beibu Bay seahorse)
- _Hippocampus colemani_ <small>Kuiter, 2003</small> (Coleman's pygmy seahorse)
- _Hippocampus comes_ <small>Cantor, 1850</small> (tiger-tail seahorse)
- _Hippocampus coronatus_ <small>Temminck & Schlegel, 1850</small> (crowned seahorse)
- _Hippocampus curvicuspis_ <small>Fricke, 2004</small> (New Caledonian seahorse)
- _Hippocampus dahli_ <small>J. D. Ogilby, 1908</small> (lowcrown seahorse)
- _Hippocampus debelius_ <small>Gomon & Kuiter, 2009</small> (softcoral seahorse)
- _Hippocampus denise_ <small>Lourie & Randall, 2003</small> (Denise's pygmy seahorse)
- _Hippocampus erectus_ <small>Perry, 1810</small> (lined seahorse)
- _Hippocampus fisheri_ <small>Jordan & Evermann, 1903</small> (Fisher's seahorse)
- _Hippocampus guttulatus_ <small>Cuvier, 1829</small> (long-snouted seahorse)
- _Hippocampus haema_ <small>Han, Kim, Kai & Senou, 2017</small> (Korean seahorse)
- _Hippocampus hippocampus_ <small>(Linnaeus, 1758)</small> (short-snouted seahorse)
- _Hippocampus histrix_ <small>Kaup, 1856</small> (spiny seahorse)
- _Hippocampus ingens_ <small>Girard, 1858</small> (Pacific seahorse)
- _Hippocampus japapigu_ <small>Short, R. Smith, Motomura, Harasti & H. Hamilton, 2018</small> (Japanese pygmy seahorse)
- _Hippocampus jayakari_ <small>Boulenger, 1900</small> (Jayakar's seahorse)
- _Hippocampus jugumus_ <small>Kuiter, 2001</small> (collared seahorse)
- _Hippocampus kelloggi_ <small>Jordan & Snyder, 1901</small> (great seahorse)
- _Hippocampus kuda_ <small>Bleeker, 1852</small> (spotted seahorse)
- _Hippocampus minotaur_ <small>Gomon, 1997</small> (bullneck seahorse)
- _Hippocampus mohnikei_ <small>Bleeker, 1854</small> (Japanese seahorse)
- _Hippocampus nalu_ <small>Short, Claassens, R. Smith, De Brauwer, H. Hamilton, Stat & Harasti, 2020</small> (South African pygmy seahorse or Sodwana pygmy seahorse)
- _Hippocampus paradoxus_ <small>Foster & Gomon, 2010</small> (paradoxical seahorse)
- _Hippocampus patagonicus_ <small>Piacentino & Luzzatto, 2004</small> (Patagonian seahorse)
- _Hippocampus planifrons_ <small>Peters, 1877</small> (flatface seahorse, false-eye seahorse)
- _Hippocampus pontohi_ <small>Lourie & Kuiter, 2008</small> (Pontoh's pygmy seahorse)
- _Hippocampus pusillus_ <small>Fricke, 2004</small> (pygmy thorny seahorse)
- _Hippocampus reidi_ <small>Ginsburg, 1933</small> (longsnout seahorse)
- _Hippocampus satomiae_ <small>Lourie & Kuiter, 2008</small> (Satomi's pygmy seahorse)
- _Hippocampus sindonis_ <small>Jordan & Snyder, 1901</small> (Sindo's seahorse)
- _Hippocampus spinosissimus_ <small>Weber, 1913</small> (hedgehog seahorse)
- _Hippocampus subelongatus_ <small>Castelnau, 1873</small> (West Australian seahorse)
- _Hippocampus trimaculatus_ <small>Leach, 1814</small> (longnose seahorse)
- _Hippocampus tyro_ <small>Randall & Lourie, 2009</small> (Tyro seahorse)
- _Hippocampus waleananus_ <small>Gomon & Kuiter, 2009</small> (Walea soft coral pygmy seahorse)
- _Hippocampus whitei_ <small>Bleeker, 1855</small> (White's seahorse)
- _Hippocampus zebra_ <small>Whitley, 1964</small> (zebra seahorse)
- _Hippocampus zosterae_ <small>Jordan & Gilbert, 1882</small> (dwarf seahorse)

## Phases of courtship

Seahorses exhibit four phases of courtship.

### Phase one

This initial courtship takes place about 30 minutes after dawn on each courtship day. In this phase, the males and females will remain apart during the night, but after dawn they will come together in a side-by-side position, brighten, and engage in courtship.

### Phase two

This phase begins with the female beginning her pointing posture, by leaning her body towards the male, who will lean away and quiver. It can last up to 54 minutes.

### Phase three

The third phase begins with the females brightening and assuming the pointing position. It lasts for 9 minutes.

### Phase four

The final phase includes 5–8 bouts of courtship. Each bout begins with both the male and female anchored to the same plant about 3 cm apart; usually they are facing each other and are still bright from the previous phase.

## Related pages

- Syngnathiformes
- Cornetfish