Gyrodactylus leptorhynchi is a small monogenean (about 0.5 mm long) obligate ectoparasite which parasitizes freshwater bay pipefish.

[3] Gyrodactylus leptorhynchi has a bilobed cephalic region containing cephalic glands, pharynx, indistinct esophagus, intestinal crura, stout hamuli, male reproductive system (including brood pouch) with no evident seminal vesicle, prostatic glands and vas deferens in male systems, a marginal hook (used for attaching to the host) and spiked sensilla[1] (sensing organ).

[5] Gyrodactylus infections in fish tanks can be treated using a combination of formalin, trichlorfon and praziquantel for a minimum of 17 days with none/little risk for bay pipefish mortality.

[1] The common technique to detect Gyrodactylus infection is microscopic examinations of skin scrapes, however, (Cone et al., 2013) contests that this practice is both damaging to the pipefish but also unreliable.

The authors, Cone et al. (2013), recommend examining live pipefish in a cool seawater Petri dish under a microscope.