Facetotecta

Y cyprid larva

The Facetotecta are a subclass of marine crustaceans, which so far only through its instars (y - larvae ) are known. It has five nauplius stages ( nauplius y ) and a cypris stage (y - cypris ). The larvae were trapped in polar to tropical waters, especially in the northern Atlantic Ocean and in the seas around Japan. One starts with a worldwide distribution and a large significance in the marine ecosystem.

Features

The y- nauplii are 250-620 microns long. More than half of her body is occupied by a large, flat head plate having on its outer surface a pattern of folds and ridges. The first pair of antennae is bipartite and at the end with long bristles, the second pair of antennae and the mandibles are almost the same and divided into two branches. Behind the mandibles there are no other extremities. At the end of the body there are three spines. The eye consists of three ocelli. The intestine is no anus. All five nauplius stages are carried out within a week.

The y- Cyprislarven are 350-590 microns long. Your carapace is long and covers the head and part of the existing of six segments thorax. The abdomen consists of three segments, the telson ends in short branches. Only one limb at the top are the four -tiered first antenna pair. Six zweiästige, provided with long bristles anterior pairs of legs ( thoracopods ) are used for floating movement, the abdomen is without limbs. Besides Naupliusaugen also compound eyes from normally nine Ommatiden are available. The Cyprislarven live 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 by inducing the 20 -HE - hormone that triggers molting in a Crustazeen to bring about a metamorphosis of y- Cyprislarven. The new designated as Ypsigon stage resembles a slug, is without limbs and also shows no other features that are characteristic of arthropods. It moves away by peristalsis.

System

The Facetotecta be assigned to the Thecostraca, a crustacean class to the heavily modified, sessile and parasitic live crustaceans belong, including the root crabs ( Rhizocephala ), the barnacles and goose barnacles.