''Microphallus turgidus'' is a widespread and locally common flatworm

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

lakes and streams. Multilocus allozyme genotype data show that ''Microphallus turgidus'' is a single outbred species with high levels of gene flow among South Island populations. ''Microphallus turgidus'' is commonly found in the abdominal muscles of

grass shrimp ''Palaemonetes'', its common names include glass shrimp, ghost shrimp, feeder shrimp, is a genus of caridean shrimp comprising a geographically diverse group of fresh water, brackish and marine crustaceans. Conventionally, ''Palaemonetes'' incl ...

Life cycle

''Microphallus turgidus'' exclusively uses the snail ''

Potamopyrgus antipodarum The New Zealand mud snail (''Potamopyrgus antipodarum'') is a species of very small freshwater snail with a gill and an operculum. This aquatic gastropod mollusk is in the family Tateidae. It is native to New Zealand, where it is found throug ...

'' as the first intermediate host, a shrimp as the secondary intermediate host, and the final hosts are typically

waterfowl Anseriformes is an order of birds also known as waterfowl that comprises about 180 living species of birds in three families: Anhimidae (three species of screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which i ...

. Embryonated ''Microphallus turgidus'' eggs are ingested from sediment and hatch in the snail's gut, penetrate the intestine, and migrate to the gonads and

digestive gland The hepatopancreas, digestive gland or midgut gland is an organ of the digestive tract of arthropods and molluscs. It provides the functions which in mammals are provided separately by the liver and pancreas, including the production of digestive e ...

. Following successful establishment, the parasite then undergoes asexual reproduction, replacing much of the host's reproductive tissue and digestive gland, which results in complete sterilization of the snail. The first visible parasite developmental stages (blastocercariae) are detectable after approximately 75 days post-exposure and

metacercariae Trematodes are parasitic flatworms of the class ''Trematoda'', specifically parasitic flukes with two suckers: one ventral and the other oral. Trematodes are covered by a tegument, that protects the organism from the environment by providing secr ...

are common by 90 days post-exposure at 16 °C in the lab. The life cycle continues through a secondary intermediate host, such as the glass shrimp '' Palaemonetes pugio'', and is completed when the shrimp infected by the metacercariae are consumed by waterfowl or mammals.

Host

''Microphallus turgidus'' are more common in wild animals that live in salt marshes and are considered as definite host. The first intermediate host is the

hydrobiid Hydrobiidae, commonly known as mud snails, is a large cosmopolitan family of very small freshwater and brackish water snails with an operculum; they are in the order Littorinimorpha. Distribution Hydrobiidae are found in much of the world, ...

snail, on its immature form called a cercaria, it develops into snail. The most common is the second intermediate hosts, grass shrimp, ''Palaemonetes pugio''. Metacercariae of the parasite usually encyst in grass shrimp abdominal muscle, and though adult ''P. pugio'' average only 2.9 cm in length, a shrimp can be infected with more than 100 parasites.

Symptoms / effects

Numerous reports of changes in the host behavior after the parasitic infection influenced the host-parasite survival, host predation, and parasite transmission. Parasite induced behavior changes include hyperactivity, sluggishness, fatigue, disorientation, altered habitat selection, and reduced predator avoidance. In fact, it is rare are to find a locality where the grass shrimp ''Palaemonetes pugio'' is not infected. At certain shrimp collection sites, near all specimens of ''P. pugio'' are infected, some with more than 100 parasites. The intensity of infection varies from one locality to another and may be due, at least partially, to geographic differences in salinity. Heavily infected shrimp are more likely to be eaten by a predator than uninfected shrimp, have lower swimming stamina, and spend more time swimming and less time motionless in the presence of a predator. Thus, ''M. turgidus'' may increase the predation of ''P. pugio'' in the wild.

References

{{Taxonbar, from=Q6839865 Molluscs described in 1958 Plagiorchiida Parasites of molluscs Parasites of birds