Messmate pipefish

The messmate pipefish (Corythoichthys haematopterus) is a marine fish belonging to the Syngnathidae family. It lives across the tropical Indo-Pacific, ranging from East Africa to the Vanuatu Islands. Sometimes sold in the aquarium trade, it goes by the name dragonfaced pipefish, as well as bloodspot pipefish, reef pipefish, reeftop pipefish, and yellow-streaked pipefish. This fish can glow—under blue or ultraviolet light, it re-emits the light as yellow, a trait called biofluorescence. This glow may help with communication between its own kind and with camouflage.

Adults have a long, narrow body and snout, a soft-rayed dorsal fin, and a caudal fin. They measure between 9 and 18 centimeters, averaging 13 centimeters. Their color varies, but most have a pale body, a striped or net-like head, faint brown horizontal stripes along the trunk and tail, and a dorsal fin without pale spots. Females show less visible bands and have dark blotches on the underside of their front trunk rings. Males may have bright blue bars across the belly of the front trunk. Males also have a brood pouch on the underside near the tail, where eggs are held under fleshy folds instead of protective plates. Juveniles lack color patterns but have spiny, serrated ridges on the trunk and tail, plus a membranous fin fold along the tail. As they grow to about 4 centimeters, their colors appear, and the ridges become mostly smooth in adults. Fish from the Seychelles have very few markings, and any present are light brown and irregular. In contrast, those from Sri Lanka and the Pacific are well-patterned, with a strongly net-like head pattern. This species can be told apart from other *Corythoichthys* pipefish by its 17 trunk rings. It has 48 to 54 rings total, 16 rays on the pectoral fins, and about 29 dorsal fin rays.

Messmate pipefish live in shallow seawater, from the surface down to about 19.8 meters deep. They stay near sandy bottoms in reefs, seagrass, coral, and rocky areas. They cannot handle changes in salinity and prefer warm water. Their population size and abundance are unknown.

The larval stage lasts about one month, during which the fish drift with ocean currents. This long larval phase lets them cross deep ocean straits that other marine animals with shorter larval periods cannot. Adults are secretive and rarely swim up into the water column except to find a mate.