Hippocampus erectusHorsefish(Also: Northern seahorse)

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Geographic Range

Hippocampus erectus is found from Cape Cod (and rarely Nova Scotia), Canada to Argentina and into the Gulf of Mexico. (Aquatic Bookshop)

Habitat

Hippocampus erectus is strictly marine in habitat, and is found in seaweed and on coral reefs at depths of .5 - 30 m. (Aquatic Bookshop)

Physical Description

The seahorse, including several species in the genus Hippocampus, is one of the most unusual in appearance of all fishes. Its upright position, horse-like head set at right angles to the body, and jointed armor make it resemble a knight in a chess set. The seahorse has a prehensile tail, which it uses to hold onto seaweed and coral. The scales have been replaced by rings of about 50 rectangular bony plates, encasing the body in a semi-rigid skeleton. The eyes can swivel independently or converge to achieve binocular vision. The most distinguishing feature between the male and the female seahorse is the kangaroo-like pouch that the male has on its ventral side, used for reproduction. (Grolier, 1996)

Hippocampus erectus is a large species of seahorse, growing up to 5 inches long. H. erectus is easily separated from other species of seahorse by a pattern of dark lines on a lighter background in its coloring. H. erectus also has 18 to 21 dorsal-fin rays. (Bohlke and Chaplin, 1968, pg. 183)

Reproduction

Seahorses reproduce sexually through internal fertilization and spawn during every season. With Hippocampus erectus, as with all seahorses, it is the male that cares for the young. Male seahorses have an incubation pocket, similar to the pouch of a marsupial mammal, on the lower side of the tail, with an opening that can be closed off. During courtship, female H. erectus spray between 250 and 650 eggs into the male brood pocket, depending on the size of the individual. Development in the brood pocket lasts between 20 and 21 days. After hatching, the free embryos are carried in the pouch until they are capable of fairly active swimming. When it is time for the incubated young to be born, the prospective father holds fast to a plant stem or some other object by his prehensile tail. He bends rapidly, sharply, backward and forward; the pouch opens and a baby seahorse pops out. With brief intervals between births, the jerking motions are repeated until the pouch is emptied. Each infant seahorse emerges head first and is a swimming, independent miniature of the adult. Newborn H. erectus are about 5/8 of an inch in length, and within 8-10 months reach their maximum size of 5 inches in length. (Moyle and Cech, 1982, pg. 120; Schultz, 1948, pg. 114; National University of Singapore)

One of the complications of seahorse birth is that some of the unhatched seahorses may die within the pouch before birth, and this soon results in the formation of gas. The male then virtually becomes a balloon and is quickly buoyed to the surface, where he is immediately be picked off by some hungry fish. (Herald, 1961, pg. 148)

  • Average age at sexual or reproductive maturity (female)
    Sex: female
    273 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    273 days
    AnAge

Lifespan/Longevity

  • Average lifespan
    Status: captivity
    4.7 years
    AnAge

Behavior

Hippocampus erectus swims weakly, propelled largely by the rapid motion of its dorsal fin and pectoral fins. H. erectus, when moving from one perch to another, moves so slowly that it would take one about 5 minutes to cross a bathtub. (Grolier, 1996, Schultz, 1948, pg. 12)

The seahorse is unusual in that it actually practices monogamy, meaning that a seahorse will mate exclusively with the same partner during their lifetime. Members of a pair perform greeting dances every morning to confirm their bond and are slow to find a new mate if their partner disappears or dies. (Coral Forest)

Sound-making has a sexual significance in Hippocampus erectus, as it does in all seahorses, which produce snapping or clicking noises by tossing their heads. At the back of the head is a star-shaped bony crest known as the coronet. This has a loose articulation with the rear edge of the skull. When a seahorse suddenly lifts its head, this edge slips under the coronet, and then, as the head is lowered, snaps out, an action which presumably produce the sound. "A mating pair of seahorses consisted of slow swimming, either together or apart, accompanied by occasional noisy snapping of the head. Clicks were often produced alternately by the fishes, and during their actual embrace, these sounds were loud and almost continuous." (Marshall, 1966, 171)

Communication and Perception

Food Habits

The seahorse, like all of the species of the family Syngnathidae, require living food. They are unable to move rapidly enough to chase their prey. Instead, the seahorse uses its elongated snout to suck in small crustaceans. Seahorses have an almost pinpoint accuracy within the 1 inch range. Young Hippocampus erectus may feed for as long as ten hours of each day and consume up to 3600 baby brine shrimp during that time. (Herald, 1961, pg. 147; Moyle and Cech,1982, pg. 294)

Economic Importance for Humans: Positive

Worldwide there is a huge demand for seahorses for traditional Chinese medicine and the aquarium trade. Seahorses are considered a powerful aphrodisiac and are used to treat an array of ailments including asthma, impotence, infertility, throat infections and lethargy. Seahorses are also extremely popular in the aquarium trade and as tourist curios. (Coral Forest)

Conservation Status

Seahorse populations in the wild could vanish if they continue to be exploited for traditional Chinese medicines, the aquarium trade, and as tourist curios. Countless seahorses are also lost every year with the destruction of their coral reef, sea grass, and mangrove habitats. More than 20 million seahorses are collected each year, causing some seahorse populations to crash by 50% over the last five years. These and other results from the first major study of the international trade in seahorses released by TRAFFIC, a global wildlife trade monitoring group, suggest that Hippocampus erectus should be considered threatened. (Coral Forest)

Other Comments

Seahorses are also known for their prehensile tails. In the first two weeks or month of life, a young seahorse is extremely agile and may bend the tail backward in a reverse crescent, but the tail is prehensile only in a forward direction. Adult seahorses seldom carry the tail in a straight position, usually having it coiled forward. (Marshall, 1966, pg. 37)

Contributors

Nick Gardiner (author), University of Michigan-Ann Arbor.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

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.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

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.

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.

tactile

uses touch to communicate

References

Aquatic Bookshop. http://www.seahorses.com/SEA_PIPE/seahorse/hippocam/kuda.htm

Bohlke, J. E., and C. C. G. Chaplin. 1968. Fishes of the Bahamas and Adjacent Tropical Waters, Second Edition. University of Texas Press, Austin, Texas.

Coral Forest. http://www.blacktop.com/coralforest/SeaHorse.html

Grolier's Electronic Encyclopedia. 1996.

Herald, E. S. 1961. Living Fishes of the World. Doubleday & Company, Inc., Garden City NY.

Marshall, N. B. 1966. The Life of Fishes. The World Publishing Company, Cleveland.

Moyle, P. B. and J. J. Cech, Jr. 1982. Fishes: An Introduction to Ichthyology. Prentice-Hall, Inc. Englewood Cliffs New Jersey.

National University of Singapore. http://www.nus.sg/Courses/khoo/ab3214/new0001.htm

Schultz, L. P. 1948. The Ways of Fishes. D. Van Nostrand Co., Inc. New York.