They mainly infect aquatic birds, but often infest fish as larvae.

[3] Some species of Galactosomum cause infected fish to swim closer to the surface and colorfully flash their underbellies.

[4] In fish, symptoms can be similar to those of whirling disease caused by the unrelated parasite Myxobolus cerebralis.

[3] Gastropods hosting select species suffer from sensory impairment due to infestation.

This makes these prey animals more likely to be consumed by aquatic birds, providing a host for the parasite to reach the mature stage of its life cycle.