Ligula intestinalis

Ligula and Schistocephalus anterior

Ligula intestinalis is a species of parasitic cestode (tapeworm) that primarily infects fish and birds. It belongs to the family Diphyllobothriidae. This parasite has a complex life cycle involving multiple hosts, including copepods, fish, and birds.

Life Cycle

The life cycle of Ligula intestinalis involves three main stages: the coracidium, the plerocercoid, and the adult tapeworm.

Coracidium

The life cycle begins when eggs are released into the water through the feces of an infected bird. These eggs hatch into free-swimming larvae called coracidia. The coracidia are ingested by small aquatic crustaceans known as copepods.

Plerocercoid

Inside the copepod, the coracidium develops into a procercoid larva. When an infected copepod is eaten by a fish, the procercoid migrates to the fish's body cavity and develops into a plerocercoid larva. The plerocercoid can grow significantly in size and cause physical and behavioral changes in the fish host.

Adult Tapeworm

The life cycle is completed when a bird eats an infected fish. Inside the bird's digestive system, the plerocercoid develops into an adult tapeworm, which attaches to the bird's intestine and begins producing eggs, thus continuing the cycle.

Hosts

Ligula intestinalis has a wide range of hosts at different stages of its life cycle:

• Copepods (first intermediate host)
• Various species of freshwater fish (second intermediate host)
• Fish-eating birds (definitive host)

Pathology

In fish, the plerocercoid stage of Ligula intestinalis can cause significant pathology. Infected fish often exhibit abdominal swelling, reduced growth rates, and altered behavior, making them more susceptible to predation by birds. This is advantageous for the parasite, as it increases the likelihood of transmission to the definitive host.

Control and Prevention

Controlling Ligula intestinalis infections involves managing the populations of intermediate and definitive hosts. This can include measures such as:

• Reducing bird populations in aquaculture areas
• Managing fish populations to reduce the incidence of infection
• Monitoring and treating water bodies to control copepod populations

Related Pages

• Cestode
• Diphyllobothriidae
• Parasitic life cycle
• Copepod
• Fish pathology