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Hippocampus ingensGiant Seahorse(Also: Pacific Seahorse)

By Bryan Kelley and Sharmaine Mojica

Geographic Range

Giant seahorses are found along the coast of the Eastern Pacific Ocean, from San Diego, California to Peru, including the Cocos, Malpelo, and Galapagos Islands. (Czembor, et al., 2012; Froese and Kesner-Reyes, 2012)

Habitat

Giant seahorses are found over reefs, and in protected bay and subtidal seagrass habitats, from 1-20 m in depth (most commonly from 3-18 m). They are often seen with their tails wrapped around black coral trees, strands of sea grasses and sea whips, and the branches of gorgonian corals, in order to camouflage themselves from predators. (Czembor, et al., 2012; Froese and Kesner-Reyes, 2012; Gomezjurado, 2005; M. Walker, 1999)

  • Range depth
    1 to 20 m
    3.28 to 65.62 ft

Physical Description

Adult giant seahorses may reach 30 cm in length. Populations display a wide array of body colors, as these animals can change their body color, depending on their environment. Body colors include maroon, yellow, and muddled brownish-green. The darkish body may have small dark and white spots and longitudinal streaks along the length of the body. The neck is curved at a right angle to the rest of the body. Atop the head is a bony structure called a coronet, which has five points, and an elongate snout extends from the front of the face. The backbone structure is unlike that of other vertebrates, with knobby, bony plated rings extending along the tail to the trunk. This makes the tail prehensile and flexible, able to coil around seagrass and other objects. This species displays sexual dimorphism: females typically have a dark patch located ventrally on the anal fin, while males have a slight keel on the chest and a brooding pouch, located under the tail. ("Species information: Hippocampus ingens", 2013; Koldewey, 2005)

  • Sexual Dimorphism
  • sexes colored or patterned differently
  • sexes shaped differently
  • Range length
    13 to 30 cm
    5.12 to 11.81 in
  • Average basal metabolic rate
    unknown cm3.O2/g/hr

Development

Smooth, pear-shaped, yellowish eggs are deposited by a female into a male's breeding pouch, where they are fertilized. The eggs embed in the lining of the brooding pouch and are supplied with oxygen by surrounding capillaries. They develop for 14-15 days, depending on water temperature. After release, typically during full moon high tides, pelagic young are independent. Juveniles are approximately 9 mm in length during the first two months of their lives. As growth proceeds, individuals become mature at approximately 5.4 cm in length. ("Pacific Seahorses, Hippocampus ingens", 2013; Beller, 2000; Froese and Kesner-Reyes, 2012; Gomezjurado, 2005)

Reproduction

Although these seahorses are not known to form lifelong pair bonds with mates as some species do, they still exhibit elaborate mating rituals. Males may be aggressive toward each other in competition for females, head butting and tail wrestling each other. Mating pairs will meet and rub their heads together, then intertwine their tails together and around a blade of sea grass or similar structure, performing a mating "dance" by bobbing up and down together. This behavior lasts for three days. Finally, a male will display his empty breeding pouch, which the female will fill with eggs using her ovipositor. After mating and transfer of her eggs to a male, a female typically will not mate again until he has given birth. ("Pacific Seahorses, Hippocampus ingens", 2013; Dames, 2000)

Reproductive activity has been observed in giant seahorses as early as 3 months of age in captivity; at this age, clutch sizes tend to be quite small and males are often unsuccessful at courtship displays. Successful reproductive attempts seem to begin around 6 months of age. Gestation lasts for 14-15 days and brood sizes of up to 2000 have been reported. A particular breeding season has not been identified for these seahorses, though it is thought that they may breed year round. Young are typically released during full moon high tides, providing optimum levels of resources to juveniles. ("Species information: Hippocampus ingens", 2013; Froese and Kesner-Reyes, 2012; Gomezjurado, 2005)

  • Breeding interval
    Individuals may mate again immediately after a clutch has been born (every 14-15 days).
  • Breeding season
    Spawning may occur year round.
  • Range number of offspring
    50 to 2000
  • Range time to hatching
    14 to 45 days
  • Range age at sexual or reproductive maturity (female)
    3 to 6 months
  • Range age at sexual or reproductive maturity (male)
    3 to 6 minutes

Males retain eggs in their brood pouches until they hatch. After young are released, they are independent and there is no further investment from either parent. (Froese and Kesner-Reyes, 2012)

Lifespan/Longevity

The lifespan of giant seahorses varies depending on environmental conditions; the estimated range is 3-5 years. (Beller, 2000)

  • Typical lifespan
    Status: wild
    3 to 5 years
  • Average lifespan
    Status: captivity
    unknown hours

Behavior

Little is known regarding specific behaviors of this species. In the wild, they are usually observed as solitary creatures, anchored around eelgrass by their prehensile tails. They are nocturnal and non-migratory. (Froese and Kesner-Reyes, 2012; Gomezjurado, 2005; Lourie, et al., 2004)

Home Range

There is no information available to suggest that these animals maintain a particular home range or territory.

Communication and Perception

Specific information regarding the way this species communicates and perceives the environment is scarce. As bony fish, their lateral line system determines pressure and water movements around them. They rely on vision to accurately locate prey when it comes within sight and during courtship, and they possess olfactory nares, which can detect dissolved chemicals. They are also capable of hearing; a clicking sound is produced when mating pairs touch heads as part of courtship behavior. ("Pacific Seahorses, Hippocampus ingens", 2013; Dames, 2000; Gomezjurado, 2005)

Food Habits

Diet consists mainly of small crustaceans and zooplankton. Giant seahorses eat brine shrimp (Artemia sp.) and mysids (Mysidae sp.), small, shrimp-like crustaceans that are high in protein and lipids. Juveniles may consume phytoplankton. Seahorses lack teeth, instead sucking prey in through their tube-like snouts. ("Pacific Seahorses, Hippocampus ingens", 2013; Froese and Kesner-Reyes, 2012; Gomezjurado, 2005)

Predation

However, Giant seahorses have been found in the stomachs of some large fishes. Juveniles face higher risks of predation than adults because of their small size. The camouflage abilities of this species are a great asset in avoiding predation. ("Pacific Seahorses, Hippocampus ingens", 2013; Foster and Vincent, 2004; Lourie, et al., 2004; "Pacific Seahorse- On Exhibit: The Secret Lives Of Seahorses", 2013)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Giant seahorses are predators of small crustaceans and zooplankton, while also being a food source to other animals. They may be hosts to parasites or fall victim to bacterial and fungal infections, particularly in captivity. (Foster and Vincent, 2004; Koldewey, 2005)

Commensal/Parasitic Species
  • Ichthyobodo sp. (Class Kinetoplastidea, Phylum Euglenozoa)

Economic Importance for Humans: Positive

Giant seahorses are important to the international aquarium trade. They are popular attractions in public aquaria, such as the Birch Aquarium in San Diego, CA and the Aquarium of the Pacific in Long Beach, CA. This species, like all other species of seahorse, is exploited for use in traditional Chinese medicine. These uses have led to population declines and heightened concerns regarding conservation. (Czembor, et al., 2012)

Economic Importance for Humans: Negative

There are no known adverse effects of giant seahorses on humans. (Czembor, et al., 2012)

Conservation Status

Habitat destruction and overfishing are the biggest threats to the giant seahorse; their populations have declined by 50% from 2007-2012. Each year, it has been reported that thousands of giant seahorses are accidentally caught by shrimp fisheries. While no species of seahorse has been listed as endangered in the U.S. Federal List, the IUCN Red List of Threatened Species cites them as vulnerable. In order to protect these animals, conservation actions have been implemented in some countries. Mexico, for example, has listed giant seahorses as a species subject to special protection, and fishermen are not allowed to intentionally catch these animals. In Panama, the species is listed as protected in a mandate managing coral reefs. ("Pacific Seahorses, Hippocampus ingens", 2013; Czembor, et al., 2012)

Contributors

Bryan Kelley (author), San Diego Mesa College, Sharmaine Mojica (author), San Diego Mesa College, Paul Detwiler (editor), San Diego Mesa College, Jeremy Wright (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

acoustic

uses sound to communicate

benthic

Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

ovoviviparous

reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.

phytoplankton

photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)

planktivore

an animal that mainly eats plankton

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

reef

structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

year-round breeding

breeding takes place throughout the year

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

References

Monterey Bay Aquarium Foundation. 2013. "Pacific Seahorse- On Exhibit: The Secret Lives Of Seahorses" (On-line). Monterey Bay Aquarium. Accessed February 05, 2013 at http://www.montereybayaquarium.org/animals/AnimalDetails.aspx?enc=n3f4wmcSJaPCN6qSlyAupQ==.

2013. "Pacific Seahorses, Hippocampus ingens" (On-line). Accessed February 05, 2013 at http://marinebio.org/species.asp?id=109.

2013. "Species information: Hippocampus ingens" (On-line). Smithsonian Tropical Research Institute: Shorefishes of the Tropical Eastern Pacific. Accessed June 21, 2013 at http://biogeodb.stri.si.edu/sftep/taxon_option_main.php?lvl=S&id=197.

Beller, P. 2000. "Hippocampus ingens" (On-line). Accessed February 05, 2013 at http://www.oceanoasis.org/fieldguide/hipp-ing.html.

Costeau, J. 1985. The Ocean World. New York: Harry N. Abrams, Inc..

Czembor, C., A. Rojas, A. Acero. 2012. "Hippocampus ingens" (On-line). The IUCN Red List of Threatened Species. Accessed February 19, 2013 at http://www.iucnredlist.org/details/10072/0.

Dames, N. 2000. "Biogeography of the Pacific Seahorse (Hippocampus ingens)" (On-line). San Francisco State University. Accessed June 21, 2013 at http://online.sfsu.edu/bholzman/courses/Fall00Projects/seahorse.html.

Foster, S., A. Vincent. 2004. "Life history and ecology of seahorses: Implications for conservation and management" (On-line). Accessed March 14, 2013 at http://www.equilibrioazul.org/documentos/life%20history%20of%20the%20sea%20horse%20management.pdf.

Froese, R., K. Kesner-Reyes. 2012. "Hippocampus ingens (Girard 1858): Pacific Seahorse" (On-line). Fishbase. Accessed June 21, 2013 at http://www.fishbase.org/summary/Hippocampus-ingens.html.

George, T. 2003. Seahorses. Brookfield, Connecticut: The Millbrook Press, Inc..

Gomezjurado, J. 2005. "International Aquarium Forum" (On-line). Syngnathid Husbandry in Public Aquariums. Accessed February 19, 2013 at http://www.intaquaforum.org/hg_FAI_Syngnathid05.pdf.

Koldewey, H. 2005. "Syngnathid Husbandry in Public Aquariums" (On-line). Accessed February 19, 2013 at http://www.intaquaforum.org/hg_FAI_Syngnathid05.pdf#page=72.

Lourie, S., S. Foster, E. Cooper, A. Vincent. 2004. A Guide to the Identification of Seahorses. Washington, DC: University of British Columbia and World Wildlife Fund.

M. Walker, S. 1999. Sea Horses. A division of Lerner Publishing Group: Carolrhoda Books.

Miller, S. 2002. Seahorses, Pipefishes, and Their Kin. Canada: Scholastic Inc..

Sammon, R. 1995. Secrets of the Coral Reefs: Exploring the Underwater Wonders. Stillwater, MN: Voyageur Press, Inc..

Swartz, S. 2001. Sea Horses and Pipefish. Carlsbad, California: Dominie Press, Inc..

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