The Réunion seahorse (Hippocampus borboniensis) is a species of marine fish belonging to the family Syngnathidae, which includes seahorses and pipefishes. It is primarily found around Réunion Island in the southwestern Indian Ocean, with some possible occurrences in nearby islands such as Mauritius and Rodrigues, although its exact distribution requires further study. The specific epithet "borboniensis" is derived from "Bourbon," the former name for Réunion Island.
Description The Réunion seahorse is a relatively small species, typically growing to a height of about 10 to 12 centimeters. Its body coloration is highly variable, ranging from shades of brown, grey, and yellow to reddish hues, allowing it to effectively camouflage itself within its habitat. Many individuals possess dermal appendages (skin flaps or filaments) that further enhance their camouflage, making them difficult to spot among corals and algae. Like other seahorses, it has an upright posture, a prehensile tail used for gripping, and a distinctive coronet (a crown-like structure) on its head, which can vary in shape and size between individuals.
Habitat and Distribution This seahorse species is endemic or near-endemic to the Mascarene Islands. It inhabits shallow coastal waters, typically found in coral reefs, rocky reefs, seagrass beds, and rubble zones. It is usually observed at depths ranging from 10 to 30 meters, but can occasionally be found deeper. Its preference for diverse underwater environments underscores its adaptability to different types of benthic substrates.
Diet and Behavior The Réunion seahorse is a carnivorous predator that feeds primarily on small crustaceans, such as copepods and amphipods, as well as other small invertebrates and zooplankton. It uses its long, pipe-like snout to rapidly suck in prey. Like all seahorses, it is a relatively sedentary animal, often spending long periods clinging to seaweed, corals, or other structures with its prehensile tail, waiting for prey to pass by.
Reproduction As with all seahorse species, the Réunion seahorse exhibits unique reproductive biology where the male is responsible for carrying the eggs. After an elaborate courtship ritual, the female deposits her eggs into a specialized brood pouch located on the male's ventral side. The male then fertilizes the eggs internally and carries them until they hatch, after which he releases fully formed, miniature seahorses into the water column.
Conservation Status The Réunion seahorse is listed as "Data Deficient" by the International Union for Conservation of Nature (IUCN) Red List. This classification indicates that there is insufficient information available to make a proper assessment of its risk of extinction. Potential threats to the species include habitat degradation due to coastal development, pollution, and climate change, as well as bycatch in fisheries and collection for the aquarium trade or traditional medicine, though specific data on these impacts are scarce. Further research into its population size, distribution, and ecological requirements is needed to accurately assess its conservation status and develop effective protection strategies.