Microphallus
Encyclopedia
Microphallus is a genus
of parasitic trematodes (flukes) in the family Microphallidae. The Greek name means "tiny penis
".
s, bird
s, and mammal
s, some species having complex life cycles involving more than one host.
For example, Microphallus piriformes
parasitizes the rough periwinkle (Littorina saxatilis); when these are eaten by herring gull
s it infects the bird and lays its eggs in the bird's feces to infect new periwinkles.
Other intemediate hosts include, for example New Zealand mud snail
Potamopyrgus antipodarum and others.
causes its host, the rough periwinkle, to move upwards, making it more vulnerable to predation by herring gull
s. Microphallus pseudopygmaeus chemically castrates
(parasitic castration
) its host, the snail Onoba aculeus
, and causes it to grow larger than normal (it is not clear if this gigantism benefits the host or parasite or if it is a non-adaptive side-effect). Microphallus papillorobustus causes its host, the lagoon sand shrimp
(Gammarus insensibilis) to swim upwards, making it more vulnerable to predation. Some species of this genus "hitch-hike" on the manipulations of other species; for example, Microphallus hoffmanni parasitizes the same sand shrimps as Microphallus papillorobustus but does not manipulate the shrimps itself, instead benefiting from the latter's manipulation of the host.
genotype data show that Microphallus is a single outbred species with high levels of gene flow among South Island populations. The parasite exclusively uses Potamopyrgus antipodarum as the intermediate host, and the final hosts are waterfowl
. Embryonated Microphallus eggs are ingested from sediment and hatch in the snail's gut
, penetrate the intestine, and migrate to the gonads
and digestive gland. 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 are common by 90 days post-exposure at 16°C in the lab. The life cycle is completed when snails containing metacercariae are consumed by waterfowl.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of parasitic trematodes (flukes) in the family Microphallidae. The Greek name means "tiny penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...
".
Hosts
They are parasitic on a variety of molluscs, crustaceanCrustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s, bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s, and mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s, some species having complex life cycles involving more than one host.
For example, Microphallus piriformes
Microphallus piriformes
Microphallus piriformes is a parasitic trematode . It belongs to the Plagiorchiata, a large suborder of the digenean fluke order Plagiorchiida. M...
parasitizes the rough periwinkle (Littorina saxatilis); when these are eaten by herring gull
Herring Gull
The European Herring Gull is a large gull , and is the most abundant and best known of all gulls along the shores of western Europe. It breeds across Northern Europe, Western Europe, Scandinavia and the Baltic states...
s it infects the bird and lays its eggs in the bird's feces to infect new periwinkles.
Other intemediate hosts include, for example New Zealand mud snail
New Zealand Mud Snail
The New Zealand mudsnail, Potamopyrgus antipodarum, sometimes previously known as Potamopyrgus jenkinsi, is a species of very small or minute freshwater snail with a gill and an operculum, an aquatic gastropod mollusk in the family Hydrobiidae....
Potamopyrgus antipodarum and others.
Parasite-host interactions
Several species are notable for manipulating or influencing their hosts. Microphallus piriformesMicrophallus piriformes
Microphallus piriformes is a parasitic trematode . It belongs to the Plagiorchiata, a large suborder of the digenean fluke order Plagiorchiida. M...
causes its host, the rough periwinkle, to move upwards, making it more vulnerable to predation by herring gull
Herring Gull
The European Herring Gull is a large gull , and is the most abundant and best known of all gulls along the shores of western Europe. It breeds across Northern Europe, Western Europe, Scandinavia and the Baltic states...
s. Microphallus pseudopygmaeus chemically castrates
Chemical castration
Chemical castration is the administration of medication designed to reduce libido and sexual activity, usually in the hope of preventing rapists, child molesters and other sex offenders from repeating their crimes...
(parasitic castration
Parasitic castration
Parasitic castration is the strategy, by a parasite, of blocking reproduction by its host, completely or in part. For example, Hemioniscus balani, a parasitic castrator of hermaphroditic barnacles, feeds on ovarian fluid, so that its host loses female reproductive ability but still can function as...
) its host, the snail Onoba aculeus
Onoba aculeus
Onoba aculeus, common name the pointed cingula, is a species of minute sea snail, a marine gastropod mollusk or micromollusk in the family Rissoidae....
, and causes it to grow larger than normal (it is not clear if this gigantism benefits the host or parasite or if it is a non-adaptive side-effect). Microphallus papillorobustus causes its host, the lagoon sand shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
(Gammarus insensibilis) to swim upwards, making it more vulnerable to predation. Some species of this genus "hitch-hike" on the manipulations of other species; for example, Microphallus hoffmanni parasitizes the same sand shrimps as Microphallus papillorobustus but does not manipulate the shrimps itself, instead benefiting from the latter's manipulation of the host.
Life cycle
Microphallus sp. is a widespread and locally common undescribed parasite in New Zealand lakes and streams. Multilocus allozymeAllozyme
Variant forms of an enzyme that are coded by different alleles at the same locus are called allozymes. These are opposed to isozymes, which are enzymes that perform the same function, but which are coded by genes located at different loci....
genotype data show that Microphallus is a single outbred species with high levels of gene flow among South Island populations. The parasite exclusively uses Potamopyrgus antipodarum as the intermediate host, and the final hosts are waterfowl
Waterfowl
Waterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans....
. Embryonated Microphallus eggs are ingested from sediment and hatch in the snail's gut
Reproductive system of gastropods
The reproductive system of gastropods varies greatly from one group to another within this very large and diverse taxonomic class of animals...
, penetrate the intestine, and migrate to the gonads
Reproductive system of gastropods
The reproductive system of gastropods varies greatly from one group to another within this very large and diverse taxonomic class of animals...
and digestive gland. Following successful establishment, the parasite then undergoes asexual reproduction
Asexual reproduction
Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. A more stringent definition is agamogenesis which is reproduction without...
, 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 are common by 90 days post-exposure at 16°C in the lab. The life cycle is completed when snails containing metacercariae are consumed by waterfowl.