Seahorses are a genus (Hippocampus) of fish belonging to the family Syngnathidae, which also includes pipefish and leafy sea dragons. There are over 32 species of seahorse, mainly found in tropical and subtropical coastal and reef waters all over Pacific, Atlantic and Indian oceans. Colonies have also been found in European waters such as the Thames Estuary.BBC News - Rare seahorses breeding in Thames From North America down to South America there are approximately four species, ranging from very small in size (dwarf seahorses are only about an inch long) to those much larger, found off the Pacific Coast of Central America (the foot-long Hippocampus ingens). Hippocampus erectus are bigger and fatter seahorses found anywhere from Nova Scotia down to around Uruguay.NOVA Online | Kingdom of the Seahorse These fish form territories, with males staying in about one square meter of their habitat while females range about one hundred times that area. They bob around in sea grass meadows, mangrove stands, and coral reefs where they are camouflaged by murky brown and grey patterns that blend into the sea grass backgrounds. During social moments or in unusual surroundings, seahorses turn bright colors. According to co-founder of Project Seahorse, Amanda J. Vincent, mates can blush a shade of creamy yellow when meeting each other in the morning. She even encountered one male who took the shade of the orange tape she used to mark the grid in the study area.

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Pipefish (Syngnathidae) are small fish, which with the Seahorses form a distinct family. Pipefish look like straight-bodied seahorses with tiny mouths.

The name is derived from the peculiar form of their snout, which is like a long tube, ending in narrow and small mouth which opens upwards and is toothless. The body and tail are long, thin, and snake-like. They have a highly modified skeleton formed into armored plating. This dermal skeleton has several longitudinal ridges, so that a vertical section through the body looks angular, not round or oval as in the majority of other fishes. A dorsal fin is always present, and is the principal (in some species, the only) organ of locomotion. The ventral fins are constantly absent, and the other fins may or may not be developed. The gill-openings are extremely small and placed near the upper posterior angle of the gill-cover. Most of the pipe-fishes are marine, only a few being freshwater. Pipe-fishes are abundant on coasts of the tropical and temperate zones. Most species of pipefish are less than 20cm in length and generally inhabit sheltered areas in coral reefs, seagrass beds and sandy lagoons.

Many are very weak swimmers in open water, moving slowly by means of rapid movements of the dorsal fin. Some species of pipefish have tails that are prehensile as in seahorses. The majority of pipefishes have some form of a caudal fin (unlike seahorses), which can be used for locomotion. There are species of pipefish with more developed caudal fins, such as the group collectively known as flag-tail pipefish, are quite strong swimmers.

There are approximately 200 species of pipefish.

The leafy sea dragon, Phycodurus eques, is a marine fish related to the seahorse. It is the only member of the genus Phycodurus. These creatures are found around southern and western Australia and generally remain in shallow, temperate waters. Their name comes from their appearance, with long leaf-like protrusions coming from all over the body. These protrusions are not used for propulsion; they serve only as camouflage. The leafy sea dragon propels itself by means of a pectoral fin on the ridge of its neck and a dorsal fin on its back closer to the tail end. These small fins are almost completely transparent and difficult to see as they undulate minutely to move the creature sedately through the water, completing the illusion of floating seaweed.

Much like the seahorse, the leafy sea dragon's name is derived from its resemblance to another creature (in this case, a mythical creature). While not large by sea monster standards, they are very large for sea horses, growing at least 18 inches (45 cm). They feed on plankton and small crustaceans. Females deposit eggs on the tail of the male where they grow to maturity. They have become endangered through pollution and industrial runoff as well as collection by fascinated divers who are entranced by their unique appearance. In response to these dangers they have been officially protected by the Australian government.

A related species is the weedy sea dragon, which is multi-coloured and grows weed-like fins and can be much smaller than the leafy sea dragon. In the November 2006 issue of National Geographic magazine, marine biologist Greg Rouse is reported as investigating the DNA variation of the two sea dragon species across their ranges.

The leafy sea dragon is the official marine emblem of the state of South Australia. A biennial Leafy Sea Dragon Festival is held by the District Council of Yankalilla, South Australia. It is a festival of the environment, arts and culture of the southern Fleurieu Peninsula, with a theme of celebrating the leafy sea dragon. The inaugural festival in 2005 attracted over 7000 participants and visitors. [http://www.yankalilla.sa.gov.au/site/page.cfm?u=199]

The weedy sea dragon or common sea dragon (Phyllopteryx taeniolatus) is a marine fish related to the seahorse. It is the only member of the genus Phyllopteryx. It is found in water 3 to 50 m deep around the southern coastline of Australia, approximately between Port Stephens, New South Wales and Geraldton, Western Australia, as well as around Tasmania. Weedy sea dragons are named for the weed-like projections on their bodies that camouflage them as they move among the seaweed beds where they are usually found.

Weedy sea dragons can reach 45 cm in length. They feed on tiny crustaceans and other zooplankton, which are sucked into the end of their tube-like snout.

A more cryptic relative of the weedy sea dragon is the leafy sea dragon. In the November 2006 issue of National Geographic magazine, marine biologist Greg Rouse is reported as investigating the DNA variation of the two sea dragon species across their ranges.

The Aquarium of the Pacific in Long Beach, California and Melbourne Aquarium in Australia are the only facilities in the world to have successfully bred weedy sea dragons in captivity.

The weedy sea dragon is the marine emblem of the State of Victoria. DSE Victoria

The cape seahorse or knysna seahorse (Hippocampus capensis) is a species of fish in the Syngnathidae family. It is endemic to South Africa. Category: Category:Fauna of South Africa - It lives in the Knysna estuary and feeds on zooplankton and brine shrimp.