Triops
Encyclopedia
Triops is a genus
of small crustacean
s in the order Notostraca
(tadpole shrimp). They are considered living fossil
s, with a fossil record that reaches back to the Carboniferous
, .
, by the form of the telson
, which bears a pair of long, thin caudal extensions in Triops, while Lepidurus bears a central platelike process.
Triops are sometimes called "living fossil
s". Fossil
s attributable to this genus have been found in rocks of Carboniferous
age, , and one extant species, Triops cancriformis
, has hardly changed since the Jurassic
period (approximately ).
, but some populations are dominated by hermaphrodite
s which produce internally fertilised eggs. Reproduction in T. cancriformis varies with latitude
, with sexual reproduction dominating in the south of its range, and parthenogenesis
dominating in the north.
Triops eggs enter a state of extended diapause
when dry, and will tolerate temperatures of up to 98 °C (208.4 °F) for 16 hours, whereas the adult cannot survive temperatures above 34 °C (93.2 °F) for 24 hours or 40 °C (104 °F) for 2 hours. The diapause also prevents the eggs from hatching too soon after rain; the pool must fill with enough water for the dormancy to be broken.
() meaning "three" and () meaning "eye". Franz Paula von Schrank
was the first author to use the genus
name Triops, coining it in his 1803 work on the fauna of Bavaria
. Their German
name was , which means 'three-eye' in English
. He collected and described specimens from the same locality in Regensburg
from which Schäffer
, another naturalist who had studied the Notostraca, obtained his specimens in the 1750s. However, other authors, starting with Louis Augustin Guillaume Bosc
, had adopted the genus name Apus for the organisms Schrank had named Triops.
Ludwig Keilhack used the genus name Triops in his 1909 field identification key of the freshwater fauna of Germany
. He suggested that the genus name Apus be replaced by Triops Schrank since an avian genus had already been described by Giovanni Antonio Scopoli
under the name Apus
. However, Robert Gurney
preferred the name Apus Schäffer. He suggested that the name '...Triops Schrank, may be returned to the obscurity from which it was unearthed'. This controversy continued and was not resolved until the 1950s.
In his 1955 taxonomic review of the Notostraca, Alan R. Longhurst supported Keilhack's genus name Triops over Apus. Longhurst provided historical evidence to support this position. The International Commission on Zoological Nomenclature
(ICZN) followed Longhurst in their 1958 ruling on the usage and origin of the genus names Triops and Apus. They rejected the genus name Apus and instead recognized the genus name Triops Schrank, 1803 (ICZN name no. 1246).
Although the taxonomy of the genus has not been reviewed since 1955, five species are widely recognised:
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 small crustacean
Crustacean
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 in the order Notostraca
Notostraca
The order Notostraca comprises the single family Triopsidae, containing the tadpole shrimp or shield shrimp. The two genera, Triops and Lepidurus, are considered living fossils, having not changed significantly in outward form since the Triassic. They have a broad, flat carapace, which conceals the...
(tadpole shrimp). They are considered living fossil
Living fossil
Living fossil is an informal term for any living species which appears similar to a species otherwise only known from fossils and which has no close living relatives, or a group of organisms which have long fossil records...
s, with a fossil record that reaches back to the Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
, .
Relatives and fossil record
The genus Triops can be distinguished from the only other genus of Notostraca, LepidurusLepidurus
Lepidurus is the larger of the two genera of tadpole shrimp. It contains the following species:*Lepidurus apus *Lepidurus arcticus *Lepidurus batesoni Longhurst, 1955*Lepidurus bilobatus Packard, 1883...
, by the form of the telson
Telson
The telson is the last division of the body of a crustacean. It is not considered a true segment because it does not arise in the embryo from teloblast areas as do real segments. It never carries any appendages, but a forked "tail" called the caudal furca is often present. Together with the...
, which bears a pair of long, thin caudal extensions in Triops, while Lepidurus bears a central platelike process.
Triops are sometimes called "living fossil
Living fossil
Living fossil is an informal term for any living species which appears similar to a species otherwise only known from fossils and which has no close living relatives, or a group of organisms which have long fossil records...
s". Fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s attributable to this genus have been found in rocks of Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
age, , and one extant species, Triops cancriformis
Triops cancriformis
Triops cancriformis, or tadpole shrimp , is a species of tadpole shrimp found in Europe, the Middle East and Japan....
, has hardly changed since the Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
period (approximately ).
Life cycle
Most species reproduce sexuallySexual reproduction
Sexual reproduction is the creation of a new organism by combining the genetic material of two organisms. There are two main processes during sexual reproduction; they are: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the...
, but some populations are dominated by hermaphrodite
Hermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...
s which produce internally fertilised eggs. Reproduction in T. cancriformis varies with latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...
, with sexual reproduction dominating in the south of its range, and parthenogenesis
Parthenogenesis
Parthenogenesis is a form of asexual reproduction found in females, where growth and development of embryos occur without fertilization by a male...
dominating in the north.
Triops eggs enter a state of extended diapause
Diapause
Diapause is the delay in development in response to regularly and recurring periods of adverse environmental conditions. It is considered to be a physiological state of dormancy with very specific initiating and inhibiting conditions...
when dry, and will tolerate temperatures of up to 98 °C (208.4 °F) for 16 hours, whereas the adult cannot survive temperatures above 34 °C (93.2 °F) for 24 hours or 40 °C (104 °F) for 2 hours. The diapause also prevents the eggs from hatching too soon after rain; the pool must fill with enough water for the dormancy to be broken.
Taxonomy
The name Triops refers to the appearance of three eyes, from the GreekGreek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
() meaning "three" and () meaning "eye". Franz Paula von Schrank
Franz Paula von Schrank
Franz von Paula Schrank was a German botanist and entomologist.Schrank was the first director of the botanical gardens in Munich from 1809 to 1832.Shrank was the first author to use the genus name Triops...
was the first author to use the genus
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...
name Triops, coining it in his 1803 work on the fauna of Bavaria
Bavaria
Bavaria, formally the Free State of Bavaria is a state of Germany, located in the southeast of Germany. With an area of , it is the largest state by area, forming almost 20% of the total land area of Germany...
. Their German
German language
German is a West Germanic language, related to and classified alongside English and Dutch. With an estimated 90 – 98 million native speakers, German is one of the world's major languages and is the most widely-spoken first language in the European Union....
name was , which means 'three-eye' in English
English language
English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...
. He collected and described specimens from the same locality in Regensburg
Regensburg
Regensburg is a city in Bavaria, Germany, located at the confluence of the Danube and Regen rivers, at the northernmost bend in the Danube. To the east lies the Bavarian Forest. Regensburg is the capital of the Bavarian administrative region Upper Palatinate...
from which Schäffer
Jacob Christian Schäffer
Jakob or Jacob Christian Gottlieb Schäffer or Schäffern was a German dean, professor, botanist, mycologist, entomologist, ornithologist and inventor.-Biography:...
, another naturalist who had studied the Notostraca, obtained his specimens in the 1750s. However, other authors, starting with Louis Augustin Guillaume Bosc
Louis Augustin Guillaume Bosc
Louis Augustin Guillaume Bosc was a French botanist, invertebrate zoologist, and entomologist.-Biography:...
, had adopted the genus name Apus for the organisms Schrank had named Triops.
Ludwig Keilhack used the genus name Triops in his 1909 field identification key of the freshwater fauna of Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
. He suggested that the genus name Apus be replaced by Triops Schrank since an avian genus had already been described by Giovanni Antonio Scopoli
Giovanni Antonio Scopoli
Giovanni Antonio Scopoli was an Italian physician and naturalist.-Biography:...
under the name Apus
Apus (genus)
The bird genus Apus comprise some of the Old World members of the family Apodidae, commonly known as swifts.They are among the fastest birds in the world. They resemble swallows, to which they are not related, but have shorter tails and sickle-shaped wings...
. However, Robert Gurney
Robert Gurney
Robert Gurney was a British zoologist most famous for his monographs on British Freshwater Copepoda and the Larvae of Decapod Crustacea . He was not affiliated with any institution, but worked at home, initially in Norfolk, and later near Oxford...
preferred the name Apus Schäffer. He suggested that the name '...Triops Schrank, may be returned to the obscurity from which it was unearthed'. This controversy continued and was not resolved until the 1950s.
In his 1955 taxonomic review of the Notostraca, Alan R. Longhurst supported Keilhack's genus name Triops over Apus. Longhurst provided historical evidence to support this position. The International Commission on Zoological Nomenclature
International Commission on Zoological Nomenclature
The International Commission on Zoological Nomenclature is an organization dedicated to "achieving stability and sense in the scientific naming of animals". Founded in 1895, it currently comprises 28 members from 20 countries, mainly practicing zoological taxonomists...
(ICZN) followed Longhurst in their 1958 ruling on the usage and origin of the genus names Triops and Apus. They rejected the genus name Apus and instead recognized the genus name Triops Schrank, 1803 (ICZN name no. 1246).
Although the taxonomy of the genus has not been reviewed since 1955, five species are widely recognised:
- Triops australiensisTriops australiensisTriops australiensis is an Australian species of Triops.-Distribution:Triops australiensis has a wide distribution across Australia, excluding the northernmost parts of Western Australia, Northern Territories and Queensland. It is also absent from Tasmania in the south, where it is replaced by...
(Spencer & Hall, 1895) - Triops cancriformisTriops cancriformisTriops cancriformis, or tadpole shrimp , is a species of tadpole shrimp found in Europe, the Middle East and Japan....
(Bosc, 1801) - Triops granariusTriops granariusTriops granarius is a species of tadpole shrimp with a broad distribution from Africa and the Middle East to China and Japan. They have elongated bodies and large flaps. Unlike most Triops species, males make up 40% of the population of this species. Males can be distinguished by their dark shade....
(Lucas, 1864) - Triops longicaudatusTriops longicaudatusTriops longicaudatus is a freshwater crustacean of the order Notostraca, resembling a miniature horseshoe crab. It is characterized by an elongated, segmented body, flattened shield-like brownish carapace covering two thirds of the thorax and two long filaments on the abdomen...
(LeConte, 1846) - Triops newberryiTriops newberryiTriops newberryi is a species of Triops found on the Western coast of North America, commonly in valleys throughout the states of Washington, Oregon, California, and small areas of Nevada and Mexico. They are found in vast numbers though in the Coachella Valley in California. T...
Thomas, 1921
External links
- Primeval-Shrimps.com > Triops - Collection of information with pictures and videos of Triops and other Branchiopoda.