Xenoturbella

X. Bocki ( Westblad, 1949)
X. westbladi Israelsson, 1999

The Xenoturbella ( Gr. Lat. Strangers flatworms ) are a genus of animals within the Bilateria. It is the only genus in the family Xenoturbellidae, in turn, is the only family in the sub-tribe Xenoturbellida. The only a few centimeters long animals live marin on mud floors, the first animals were found in 1915 in the Skagerrak, but not described until 1949.

Features

The Xenoturbella be up to 4 cm long. They are characterized by a flattened body with a ventral center trough that is stood by cilia ( eyelashes gutter ). The mouth is also located in this groove.

They have a rather simple internal structure. Despite the lack of gonads, the animals form from germ cells, the embryos are stored in follicles. The animals have, with the exception of a vestibular organ ( statocyst ) few other defined organs. The cavity of the statocyst is flagellated and several statoliths, which are unlike any other known animal groups also ciliated and move within the statocyst, equipped. Furthermore, the animals have a diffuse nervous system below the epidermis (outer skin), which is also very rich glands. The only body cavity forming an after -free and saccular intestine, a secondary body cavity ( coelom ) is not available.

System

The genus now contains only two types of worm-like animals. Xenoturbella Bocki Westblad, 1949 and Xenoturbella westbladi Israelsson, 1999 Since the first description of a 1915 copy found that in 1949 was named Xenoturbella Bocki, the taxonomic classification of the genus is controversial. First, the animals found were identified as free-living flatworms. Then, they were kept for molluscs, then asked to Neumündern. Within the new mouths they, together with the Acoelomorpha the trunk Xenacoelomorpha. The Xenambulacraria are the sister group to the Ambulacraria ( gill hole Animals ( Hemichrodata ) and echinoderms ( Echinodermata ) ) represent.

Dissemination

Specimens of the species have so far been found on the coasts of Sweden, Scotland and Iceland.

Cilium Human gonad Organ (anatomy)

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