Tongue-eating louse

Description

Cymothoa exigua, or the tongue-eating louse, is a parasitic isopod of the family Cymothoidae. It enters fish through the gills. The female attaches to the tongue, while the male attaches to the gill arches beneath and behind the female. Females are 8-29 mm (0.3-1.1 in) long and 4-14 mm (0.16-0.55 in) wide. Males are about 7.5-15 mm (0.3-0.6 in) long and 3-7 mm (0.12-0.28 in) wide. The parasite severs the blood vessels in the fish's tongue, causing the tongue to fall off. It then attaches itself to the remaining stub of the tongue and becomes the fish's new tongue. C. exigua is quite widespread. It can be found from the Gulf of California southward to north of the Gulf of Guayaquil, Ecuador, as well as in parts of the Atlantic. It has been found in waters from 2 m (6 ft 7 in) to almost 60 m (200 ft) deep. This isopod is known to parasitize eight species in two orders and four families of fishes seven species of order Perciformes: three snappers (Lutjanidae), one species of grunt (Haemulidae), three drums (Sciaenidae), and one species of order Atheriniformes: one grunion (Atherinidae). New hosts from Costa Rica include the Colorado snapper, Lutjanus colorado and Jordan's snapper, L. jordani. In 2005, a red snapper parasitized by what could be C. exigua was discovered in the United Kingdom. As the parasite is normally found south of the Gulf of California, Mexico, this led to speculation that the parasite's range may be expanding; however, the isopod possibly traveled from the Gulf of California in the snapper's mouth, and its appearance in the UK was an isolated incident. Not much is known about the lifecycle of C. exigua. It exhibits sexual reproduction. The species starts as a juvenile in a short, free-living stage in the water column. Juveniles likely first attach to the gills of a fish and become males. As they mature, they become females, with mating likely occurring on the gills. The fertilized eggs are held in a marsupium, similar to a kangaroo. If no female is present within two males, one male can turn into a female after it grows to 10 mm (0.4 in) in length. The female then makes her way to the fish's mouth, where she uses her front claws to attach to the fish's tongue. C. exigua is not believed to be harmful to humans, except it may bite if separated from its host and handled.