Gyrodactylus leptorhynchi
Gyrodactylus leptorhynchi is a tiny flatworm parasite, about 0.5 mm long, that lives on freshwater bay pipefish. It is an obligate ectoparasite, meaning it must live on a host. This species is the seventh Gyrodactylus found on bay pipefish and the first described from the Pacific coast of North America. It can enter fish farms and aquariums and may spread very quickly, sometimes within 10 days.
Most Gyrodactylus parasites tend to gather around a male’s brood pouch to infect newborns, but G. leptorhynchi is mainly found on the fish’s body, especially the dorsal fins. It has a direct life cycle with no intermediate host, taking about 1–5 days from birth to producing live young. The parasite attaches to the host with a marginal hook, which can irritate and damage tissue.
Anatomically, it has a bilobed head with glands, a simple gut, a strong attachment hook, and parts of the male reproductive system. Gyrodactylus species occur worldwide in both seas and fresh water. In wild fish, how common G. leptorhynchi is remains unknown, but infections are more common in captive settings.
Treating infections in tanks can involve a combination of formalin, trichlorfon, and praziquantel for at least 17 days; these drugs can also be used individually, and some people use mebendazole, though completely eradicating the parasite from a tank can be difficult. The usual way to detect infection is to examine skin scrapings under a microscope, but this method can injure the pipefish and may be unreliable. An alternative recommended approach is to inspect live pipefish in a cool seawater Petri dish under a microscope.
This page was last edited on 3 February 2026, at 20:35 (CET).