''Triops cancriformis'', European tadpole shrimp or tadpole shrimp, is a species of tadpole shrimp found in

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...

to the

Middle East The Middle East ( ar, الشرق الأوسط, ISO 233: ) is a geopolitical region commonly encompassing Arabia (including the Arabian Peninsula and Bahrain), Asia Minor (Asian part of Turkey except Hatay Province), East Thrace (Europ ...

and

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

. Due to

habitat destruction Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

, many populations have recently been lost across its European range, so, the species is considered

endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and in ...

in the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...

and in several European countries. In captivity they commonly grow up to ; in the wild they can achieve sizes of . In the UK, there are just two known populations: in a pool and adjacent area in the Caerlaverock Wetlands in

Scotland Scotland (, ) is a Countries of the United Kingdom, country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a Anglo-Scottish border, border with England to the southeast ...

, and a temporary pond in the

New Forest The New Forest is one of the largest remaining tracts of unenclosed pasture land, heathland and forest in Southern England, covering southwest Hampshire and southeast Wiltshire. It was proclaimed a royal forest by William the Conqueror, fea ...

. The species is legally protected under Schedule 5 of the

Wildlife and Countryside Act 1981 The Wildlife and Countryside Act 1981 is an Act of Parliament in the United Kingdom implemented to comply with European Council Directive 79/409/EEC on the conservation of wild birds. In short, the act gives protection to native species (especia ...

(as amended). Fossils from the

Upper Triassic The Late Triassic is the third and final epoch of the Triassic Period in the geologic time scale, spanning the time between Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch and followed by the Early Jurassic Epoch. ...

( Norian) of Germany, around 237 million years old have been attributed to this species as the subspecies ''T. cancriformis minor'', due to their great similarity to modern day members of the species.Klaus-Peter Kelber - Triops
/ref> However, later research showed that their

ontogenetic Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult. The term can also be used to refer to the st ...

growth was quite different from the living species, and they were better considered a distinct species, "''Notostraca" minor'', with an uncertain position within

Notostraca The order Notostraca, containing the single family Triopsidae, is a group of crustaceans known as tadpole shrimp or shield shrimp. The two genera, ''Triops'' and '' Lepidurus'', are considered living fossils, with similar forms having existed sinc ...

. Genetic evidence also indicates that ''T. cancriformis'' only diverged from other ''Triops'' species around 23.7–49.6 million years ago.

Life cycle

''Triops cancriformis'' has a very fast life cycle, and individuals become mature in about two weeks after hatching. Their populations can be

gonochoric In biology, gonochorism is a sexual system where there are only two sexes and each individual organism is either male or female. The term gonochorism is usually applied in animal species, the vast majority of which are gonochoric. Gonochorism c ...

hermaphroditic In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have s ...

androdioecious Androdioecy is a reproductive system characterized by the coexistence of males and hermaphrodites. Androdioecy is rare in comparison with the other major reproductive systems: dioecy, gynodioecy and hermaphroditism. In animals, androdioecy has bee ...

. The latter is a very rare reproductive mode in animals, in which populations are made of hermaphrodites, with a small proportion of males. Due to this lack of males, early researchers thought Triops were

parthenogenetic Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and developmen ...

. The presence of testicular lobes scattered amongst their ovaries confirmed they were in fact hermaphroditic. Fertilized females or hermaphrodites produce diapausing eggs or cysts, able to survive decades in the sediment of the ponds and lakes they inhabit. These eggs are resistant to drought and temperature extremes.

Taxonomic history

In 1801,

Louis Augustin Guillaume Bosc Louis Augustin Guillaume Bosc (or Louis-Augustin Bosc d'Antic) (29 January 1759 – 10 July 1828) was a French botanist, invertebrate zoologist, and entomologist. Biography Bosc was born in Paris, the son of Paul Bosc d’Antic, a medical doctor ...

made the first officially recognised species description of ''Triops cancriformis''. He named this species ''Apus cancriformis''. Other authors used the name ''Apus cancriformis'' over the years but often with the wrong original author of this name. The genus name ''

Apus Apus is a small constellation in the southern sky. It represents a bird-of-paradise, and its name means "without feet" in Greek because the bird-of-paradise was once wrongly believed to lack feet. First depicted on a celestial globe by Petru ...

'' was pre-occupied by a genus of birds (described in 1777), rendering the name invalid for the tadpole shrimp. In 1909,

Ludwig Keilhack Ludwig may refer to: People and fictional characters * Ludwig (given name), including a list of people and fictional characters * Ludwig (surname), including a list of people * Ludwig Ahgren, or simply Ludwig, American YouTube live streamer and co ...

used the correct name "''Triops cancriformis'' (Bosc)" in a field identification key of the freshwater fauna of

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

. He took up the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

name proposed by Schrank and suggested that the genus name ''Apus'' be replaced with ''

Triops ''Triops'' is a genus of small crustaceans in the order Notostraca (tadpole shrimp). The long-lasting resting eggs of several species of ''Triops'' are commonly sold in kits as a pet. The animals hatch upon contact with fresh water. Most adult-st ...

'' Schrank since ''

'' had been used since 1777 as the genus name of some birds (commonly known as swifts). However, other authors disagreed with him and the controversy continued until the 1950s. In 1955, Alan Longhurst provided the original author of ''T. cancriformis'' as "''Triops cancriformis'' (Bosc, 1801)" with a full history of synonymy to support it. This was in a taxonomic review of the

that also supported using the genus name ''Triops'' instead of ''Apus''. In 1958, the International Commission on Zoological Nomenclature (ICZN) recognised the name ''Triops cancriformis'' (Bosc, 1801–1802) (ICZN name no. 1476) as officially the oldest. They also recognised the genus name ''Triops'' Schrank instead of ''Apus''. They followed Longhurst in these decisions.

Human uses

Although members of the genus ''Triops'' usually have no economic importance, the Beni-kabuto ebi albino variant of ''Triops cancriformis'' has been used to control mosquitoes and weeds in Asian rice fields. ''Triops cancriformis'' is the second most common species raised by hobbyists next to '' Triops longicaudatus''. They are particularly valued for their lower hatching temperature and somewhat longer lifespan as well as potentially larger size.

References

{{Taxonbar, from=Q132808 Taxa named by Louis Augustin Guillaume Bosc Crustaceans described in 1801 Notostraca Crustaceans of Asia Crustaceans of Europe Extant Late Triassic first appearances Norian species first appearances Rhaetian species Hettangian species Sinemurian species Pliensbachian species Toarcian species Aalenian species Bajocian species Bathonian species Callovian species Oxfordian species Kimmeridgian species Tithonian species Berriasian species Valanginian species Hauterivian species Barremian species Aptian species Albian species Cenomanian species Turonian species Coniacian species Santonian species Campanian species Maastrichtian species Danian species Selandian species Thanetian species Ypresian species Lutetian species Bartonian species Priabonian species Rupelian species Chattian species Aquitanian species Burdigalian species Langhian species Serravallian species Tortonian species Messinian species Zanclean species Piacenzian species Gelasian species Calabrian species Ionian species Tarantian species Holocene species