Triops cancriformis
| Triops cancriformis | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Triops cancriformis |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Triops cancriformis | ||||||||||||
| ( Bosc , 1801) |
Triops cancriformis is a gill pod of the genus Triops from Europe. From a purely morphological point of view, he is considered the phylogenetically oldest extant (living today) species .
Tribal history
Triops cancriformis is, like all large gill pods (large branchiopods), a so-called "primeval shrimp", a " living fossil ". Triopsid fossils were first described under the name Triops cancriformis in the 1930s from more than 220 million year old sedimentary rocks of the lower Upper Triassic ( Hassberge Formation , Middle Keuper ) of the Steigerwald and assigned to their own subspecies ( Triops cancriformis minor ). Remains of a form identified as Triops cf. cancriformis come from the Upper Upper Triassic ( palynostratigraphically dated to the Middle to Late Rhaetian , i.e. almost 20 million years younger than the Steigerwald finds) of the Culpeper Basin ( Newark supergroup ) in the US state of Virginia. Older records of the species were reported from the Voltzien sandstone (Upper Buntsandstein, border area Lower / Middle Triassic ) of the Vosges in the early 1970s . The subspecies Triops cancriformis permiensis from the lower layers of the Salagou Formation (higher lower or middle Perm ) of the Lodève Basin in southern France is even older . The earliest records are therefore at least 40 million years older than the first dinosaurs , and Triops cancriformis has hardly changed morphologically since the Permian .
Triops cancriformis has long been considered the most long-lived recent species in terms of geological and phylactic history , due to Ferdinand Trusheim's assignment of the fossils in the Steigerwald in 1937. More recent studies, which are based not on morphology but on genetics ( molecular clock ), come to the conclusion that Triops cancriformis was formed during adaptive radiation near the Cretaceous-Paleogene boundary about 66 million years ago.
description
The Greek generic name "Triops" means "the three-eyed". Slightly above the complex eyes , the animals have another light-sensing organ, the nauplius eye, a single eye ( ocellus ) to perceive differences in brightness. The species of the genus Triops have about 35 to 71 pairs of leaf-shaped legs that are used for swimming and for feeding. The first pair of legs has long Y-shaped appendages.
The approximately six to eight centimeters long Triops cancriformis (the largest known specimen reached a length of eleven centimeters) is on average slightly larger than the American Triops longicaudatus and is content with slightly lower temperatures (approx. 20 to 24 ° C) than this species . Triops cancriformis but requires higher temperatures than in the same habitat encountered shed tail ( Lepidurus apus ), which is therefore also referred to as "spring sign cancer" while the heat more loving Triops is considered the "summer sign cancer". Both species are typical inhabitants of the floodpumps of the floodplains that form in spring .
Reproduction and development
After hatching from the "permanent eggs" ( embryos encapsulated in cysts in a diapause with decades of hatchability), the nauplius larva goes through several further larval stages. The animals reach their final size and sexual maturity after just a few weeks . The reproduction usually takes place in an asexual way through self-fertilization (autogamy) with the help of a hermaphrodite .
The cysts of T. cancriformis and the American T. longicaudatus, often referred to as “eggs”, are offered in the pet trade from offspring, but those of the European species are less common. A larger aquarium of 20 liters or more is recommended for species-appropriate keeping and a water temperature of 20–24 ° C. The bottom must be covered with fine sand so that the animals can bury their eggs in it. Since Triops do not like strong currents, a diaphragm pump with an air lift filter is recommended. Spirulina and chlorella algae are often accepted as food . If the crabs are larger, they also include carrots, cucumber, duckweed and occasionally animal foods such as red mosquito larvae . Life expectancy is on average 2-3 months. However, T. cancriformis can live up to 6 months.
Subspecies
There are three recent subspecies. The Latin epithet "cancriformis" has the meaning "cancerous", "cancerous shaped"
- Triops cancriformis cancriformis
- Triops cancriformis simplex
- Triops cancriformis mauretanicus
Individual evidence
- ^ Ferdinand Trusheim: Triopsiden (Crust. Phyll.) From the Keuper Franconia. Paleontological Journal. Vol. 19, No. 3-4, 1938, pp. 198-216, doi : 10.1007 / BF03042241
- ↑ a b c d Klaus-Peter Kelber: Triops cancriformis (Crustacea: Notostraca): A remarkable fossil from the Triassic Central Europe. In: Norbert Hauschke, Volker Wilde: Trias - A completely different world. Publishing house Dr. Friedrich Pfeil, Munich 1999, ISBN 978-3-931516-55-0 , pp. 383-394 (digital copy: PDF 13.9 MB)
- ↑ Pamela JW Gore: Triassic Notostracans in the Newark Supergroup, Culpeper Basin, Northern Virginia. Journal of Paleontology. Vol. 60, No. 5, 1986, pp. 1086-1096 ( JSTOR 1305186 )
- ^ Georges Gand, Jacques Garric, Jean Lapeyrie: Biocénoses à triopsidés (Crustacea, Branchiopoda) du Permien du bassin de Lodève (France). Geobios. Vol. 30, No. 5, 1997, pp. 673-700, doi : 10.1016 / S0016-6995 (97) 80157-X
- ↑ Africa Gómez, Bernd Hänfling, Ronald A. Jenner, Robert L. Hammond, Thomas C. Mathers: Multiple global radiations in tadpole shrimps challenge the concept of 'living fossils' . In: PeerJ . tape 1 , April 2, 2013, ISSN 2167-8359 , p. e62 , doi : 10.7717 / peerj.62 , PMID 23638400 ( peerj.com [accessed February 2, 2019]).
- ↑ a b Dietrich Heidecke, Volker Neumann: On the spread and ecology of Triops cancriformis Bosc. and Lepidurus apus L. in the GDR. Hercynia, new episode. Vol. 24, No. 2, 1987, pp. 166-173 (digital version: PDF 3.2 MB)
- ^ Erwin J. Hentschel, Günther H. Wagner: Zoological dictionary. ( UTB , vol. 367). 6th edition, Gustav Fischer Verlag, Jena 1996, ISBN 3-334-60960-X , p. 150.
Web links
- Tadpole Shrimp - Living Fossils! Website of the biologist Erich Eder on the website of the University of Vienna
- Gillfoot video clips on Refugium Gartenteich (limno-kosmos.de), private website of the environmental and species conservationist Günter H. Stanjek