Hippocampus

The hippocampus (named after its resemblance to the seahorse, from the Greek ἱππόκαμπος, "seahorse" from ἵππος hippos, "horse" and κάμπος kampos, "sea monster") is a major component of the brains of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. The hippocampus is located under the cerebral cortex; and in primates it is located in the medial temporal lobe, underneath the cortical surface. It contains two main interlocking parts: Ammon's horn and the dentate gyrus.

In Alzheimer's disease, the hippocampus is one of the first regions of the brain to suffer damage; memory loss and disorientation are included among the early symptoms. Damage to the hippocampus can also result from oxygen starvation (hypoxia), encephalitis, or medial temporal lobe epilepsy. People with extensive, bilateral hippocampal damage may experience anterograde amnesia—the inability to form and retain new memories.

Seahorse

Seahorse is the name given to 54 species of small marine fishes in the genus Hippocampus. "Hippocampus" comes from the Ancient Greek word hippos meaning "horse" and kampos meaning "sea monster". The word "seahorse" is often written as two separate words (sea horse), or hyphenated (sea-horse). Having a head and neck suggestive of a horse, seahorses also feature segmented bony armour, an upright posture and a curled prehensile tail.

Habitat

Seahorses are mainly found in shallow tropical and temperate waters throughout the world, from about 45°S to 45°N and live in sheltered areas such as seagrass beds, estuaries, coral reefs, or mangroves. Four species are found in Pacific waters from North America to South America. In the Atlantic, H. erectus ranges from Nova Scotia to Uruguay. H. zosterae, known as the dwarf seahorse, is found in the Bahamas.

Colonies have been found in European waters such as the Thames Estuary.

Three species live in the Mediterranean Sea: H. guttulatus (the long-snouted seahorse), H. hippocampus (the short-snouted seahorse), and H. fuscus (the sea pony). These species form territories; males stay within 1 m² (11 sq ft) of habitat, while females range about one hundred times that.

Hippocampus (mythology)

The hippocampus or hippocamp, also hippokampoi (plural: hippocampi or hippocamps; Greek: ἱιππόκαμπος, from ἵππος, "horse" and κάμπος, "monster"), often called a sea-horse in English, is a mythological creature shared by Phoenician and Greek mythology, though the name by which it is recognised is purely Greek. It was also adopted into Etruscan mythology. It has typically been depicted as having the upper body of a horse with the lower body of a fish.

Mythology

Phoenician and Lydian

Coins minted at Tyre around the 4th century BC show the patron god Melqart riding on a winged hippocampus and accompanied by dolphins. Coins of the same period from Byblos show a hippocampus diving under a galley.

A gold sea-horse was discovered in a horde from the kingdom of Lydia in Asia minor, dating to the 6th century BC.

Greek and Roman

In the Iliad, Homer describes Poseidon, who was god of horses (Poseidon Hippios), earthquakes, and the sea, drawn by "brazen-hoofed" horses over the sea's surface, and Apollonius of Rhodes, being consciously archaic in Argonautica, describes the horse of Poseidon emerging from the sea and galloping away across the Libyan sands. This compares to the specifically "two-hoofed" hippocampi of Gaius Valerius Flaccus in his Argonautica: "Orion when grasping his father’s reins heaves the sea with the snorting of his two-hooved horses." In Hellenistic and Roman imagery, however, Poseidon (or Roman Neptune) often drives a sea-chariot drawn by hippocampi. Thus hippocampi sport with this god in both ancient depictions and much more modern ones, such as in the waters of the 18th-century Trevi Fountain in Rome surveyed by Neptune from his niche above.