Facetotecta
| Facetotecta | ||||||||||
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Y Cypris larva |
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| Systematics | ||||||||||
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| Scientific name | ||||||||||
| Facetotecta | ||||||||||
| Grygier , 1985 |
The Facetotecta are a subclass of marine crustaceans that are known so far only from their larval stages (y-larvae). There are five Nauplius stages (y-Nauplius) and one Cypris stage (y-Cypris). The larvae were caught in polar to tropical waters, especially in the northern Atlantic and in the seas around Japan . It is assumed that it has a worldwide distribution and is of great importance in the marine ecosystem.
features
The y nauplii are between 250 and 620 µm long. More than half of their body is taken up by a large, flat head shield that has a pattern of folds and ridges on its outer surface. The first pair of antennas is two-part and has long bristles at the end, the second pair of antennas and the mandibles are almost identical and split into two branches. There are no other extremities behind the mandibles. There are three thorns at the end of the body. The eye consists of three ocelles . The intestine is without an anus. All five nauplius stages are completed within a week.
The y-cypris larvae are between 350 and 590 µm long. Your carapace is long and covers the head and part of the six-segment thorax . The abdomen consists of three segments, the telson ends in short branches. The only extremities on the head are the four-part first pair of antennas. Six two-branched front pairs of legs (thoracopods) with long bristles are used for swimming movement, the abdomen is limb. In addition to nauplius eyes, there are also compound eyes , usually consisting of nine ommatids . The cypris larvae live for several weeks.
The adult stage has not yet been found in the wild. One suspects a parasitic way of life. A group of scientists has succeeded in inducing the 20 HE hormone , which triggers molting in crustaceans, to bring about a metamorphosis of the y-cypris larvae. The new stage, known as Ypsigon, resembles a slug , has no limbs and does not show any other features that are characteristic of arthropods. It moves through peristalsis .
Systematics
The facetotecta be the thecostraca associated with a cancer animal class to the highly modified, sessile and parasitic live crustaceans include, among them the root cancers (Rhizocephala), the barnacles and barnacles .
literature
- Kurt Schminke: Crustacea, Krebse , page 598 in Wilfried Westheide & Reinhard Rieger (eds., 2007): Special Zoology - Part 1: Protozoa and Invertebrates (2nd edition). Elsevier, Spektrum Akademischer Verlag, Munich. ISBN 3-8274-1575-6
- Henrik Glenner, Jens Høeg, Mark Grygier & Yoshihisa Fujita: Induced metamorphosis in crustacean y-larvae: Towards a solution to a 100-year-old riddle. BMC Biol. 2008; 6: 21. doi : 10.1186 / 1741-7007-6-21
Web links
- WoRMS (2010). Facetotecta. World Register of Marine Species