Hippocampus spp. are from the family of Syngnathidae (Seahorses, Pipefishes). There are over 70 species of seahorses. In Mauritius two species have been recorded; Hippocampus histrix, Thorny seahorse and Hippocampus kuda, Spotted seahorse, Cheval de mer.
Seahorses have a tubular snout with a small mouth at the end, and a flexible neck. The body is encased in bony plates, arranged in rings. They use their tails (caudal fins absent) to grab on to leaves, algae, corals, sponges and other structures. Its dorsal fin is proximal to the head rather than tail tip. Pectoral and anal fins are present.
Hippocampus histrix has a narrow slender body that is completely covered by long thorns. It has a long head and long tapered snout that is as long as its head. Its colouring and pattern is variable and matches that of its background. It can therefore appear cream to grey, greenish, yellow or brown to burgundy-red. It reaches a maximum height of 15 cm.
Hippocampus kuda has no spines. It is also commonly called the Estuary seahorse or Yellow seahorse. It has an elongated body with rounded bumps. It has a short, thick snout and large head. Its body colour is variable from shades of yellow to cream or red with blotches and many small dark spots, but it is usually dark in colour with a grainy appearance. It can reach a length of between 17 to 30 centimeters.
Both species are carnivorous and feeds on tiny crustaceans and planktonic organisms. The male fertilizes the eggs, and incubates, aerates protects and provides the embryos with adequate nutrients in its ventral brood pouch.
Hippocampus histrix is found throughout the Indio Pacific Region. It prefers moderately deep waters, usually below 15 meters in depth. It is usually found in soft corals or sponges but may also frequent algae-rubble or rocky reefs.
Hippocampus kuda is also found throughout the Indo Pacific Region. It inhabits both benthic habitats in coastal waters with soft or rocky bottoms, sheltered waters of estuaries or mangroves. It can also sometimes be seen clinging to drifting Sargassum seaweed in open waters.
All the Hippocampus spp. are listed in CITES. Both Hippocampus histrix and Hippocampus kuda are listed as ‘Vulnerable’ under the IUCN Red List of threatened species. Population trend is decreasing due to threats from habitat loss and degradation. Hippocampus kuda is also vulnerable to fishing and collecting for the aquarium and traditional medicine trade.
Seahorses swim upright. They make use of their dorsal and pectoral fins to do so.
Juveniles seahorses are called ‘pups’.