One tongue-eating louse, Cymothoa exigua, was described in our Halloween comic:
Free-swimming, juvenile Cymothoa exigua males attach to the gills of a fish host (1). Upon reaching a critical size, a single male turns into a female and moves to the mouth of the fish (1). It cuts off the blood supply to the tongue, which eventually falls off. The female then takes the place of the tongue. Males are sometimes found with the female (2), suggesting mating occurs in the mouth of the host. Females keep the fertilized eggs in their body for early development before they are released. Females release a single brood (480 - 720 eggs per female) and die (2). Only one female is ever found per fish host, suggesting that the presence of a female prevents other males from turning female (2). C. exigua is known to infect snapper fish including Lutjanus peru and L. guttatus (2) and is found in both the Atlantic and Pacific coasts of North America (1).
Other species of the genus Cymothoa also replace the tongues of their host (ex. C. spinipalpa and C. borbonica) (3,4). Males converting to females as needed is speculated to be a general feature of this group of isopods (1).
1) 10.2307/1444352
2) 10.7773/cm.v18i1.885
3) 10.1590/S0101-81752007000100032
4) 10.1007/s00227-013-2284-7
Parasite Comics Team:
Dr. Chenhua Li (Lead, Ideas), Dr. Þórey Jónsdóttir (Illustrator, Ideas), Dr. Stephen Pollo (Writer, Researcher), Yuanzhe Wang (Digital Consultant).