Razorfish

Razorfish

The razorfish (Aeoliscus strigatus), also known as the jointed razorfish or coral shrimpfish, is a small marine fish in the family Centriscidae of the order Syngnathiformes. Closely related to seahorses, this species reaches a maximum body length of 15 centimetres. It possesses an extraordinarily compressed, razor-thin body almost completely encased in protective, transparent sutured bony plates. Its snout is long, tubular, and beak-like, housing a small, toothless mouth with pincer-like jaws. At the rear end of the body, where a caudal fin is typically situated, lies a sharp dorsal spine hinged at its base. Coloration in Aeoliscus strigatus is directly influenced by its environment. Individuals inhabiting aquatic vegetation such as seagrass beds exhibit a greenish-yellow to pale green back accompanied by a blurred, light brown longitudinal stripe. In contrast, specimens found over open sand, gravel, rubble, or coral reefs display a light silvery body marked by a prominent, dark black or brown median band running from the snout, through the eyes, down the entire side of the body. Their fins are greatly reduced and transparent, with the soft dorsal and caudal fins shifted to the ventral side. The defining ecological feature of the razorfish is its habit of swimming in a rigid, vertical posture with its head pointing downwards. Moving gracefully in synchronized schools, groups of razorfish orient themselves belly-forward and swim in the direction of their dorsal surface. This collective movement often gives a school the appearance of soldiers on parade. This peculiar vertical orientation allows them to blend in seamlessly with vertical structures in their habitat, such as sea whips, soft corals, and seagrass blades. Razorfish (Aeoliscus strigatus) are typically observed in large, synchronised schools, often numbering in the hundreds, where they exhibit a distinctive head-down, vertically oriented swimming posture. This behaviour, along with their silvery, laterally compressed bodies, provides camouflage among seagrass blades or the spines of sea urchins. They are primarily diurnal, actively feeding during daylight hours on small benthic invertebrates. Regarding their reproduction, these fish are oviparous, releasing eggs externally. While precise details on their spawning season are not extensively documented across all parts of their range, reproduction generally occurs after a courtship display involving pairs separating from the school. The fertilised eggs are pelagic, drifting in the water column before hatching. Larval development is planktonic, and the juveniles gradually adopt the characteristic head-down orientation and schooling behaviour as they mature. The exact clutch size and incubation period are not widely quantified, but their broadcast spawning strategy is typical of many marine teleosts. Distributed throughout coastal waters of the Indo-West Pacific, the razorfish occurs from East Africa, Madagascar, the Comoros, and Seychelles to Australia and New Caledonia, extending northwards to Sagami Bay in Japan. It is notably absent from the Red Sea. When threatened by larger predatory fish, a school will rapidly dart into the protective spines of Diadema sea urchins or the dense branches of staghorn corals. Divers value encounters with these unusual fish for their intriguing synchronized swimming, delicate armor, and fascinating defense strategies.