Ligula intestinalis.

Abstract

Ligula intestinalis is a common pseudophyllidean cestode found in freshwater ecosystems worldwide. It has a complex life cycle involving a planktonic copepod as first intermediate host, a planktivorous fish as second intermediate host, and a fish-eating bird as the final host. The most conspicuous stage within the life cycle is the plerocercoid, which develops in the abdominal cavity of the fish host and has a substantial effect on its health, fecundity, and behaviour. It can cause epizootic cycles of mass mortality within fish populations. Molecular studies have demonstrated the existence of several lineages which represent separate species differing in the spectrum of fish hosts and geographical distribution. This parasite has recently been introduced to freshwater systems of Africa and Oceania, either by migratory birds or the trade in fish. L. intestinalis has been an ideal model to study ecological interactions, endocrine disruption, pollution monitoring, and genetic biodiversity.