Haplotaxida

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Haplotaxida
Systematics
Trunk : Annelids (Annelida)
Class : Belt worms (Clitellata)
Subclass : Little bristle (Oligochaeta)
Subclass : Diplotesticulata
Superordinate : Haplotaxidea
Order : Haplotaxida
Scientific name of the  superordinate
Haplotaxidea
Jamieson , 1988
Scientific name of the  order
Haplotaxida
Brinkhurst , 1971

Haplotaxida is the name of an order in the subclass of belt worms (Clitellata), which, according to the current systematics on a cladistic basis, includes the families Haplotaxidae ( well worms ) and Tiguassuidae . All species belonging to this are freshwater inhabitants or - to a lesser extent - saltwater inhabitants . When it was set up in 1971, this group included all the little bristles (Oligochaeta) with the exception of the Lumbriculidae (also the order Lumbriculida) and thus also terrestrial species, which, according to current knowledge, is a paraphyletic group as it does not include the leeches, among other things .

features

The Haplotaxida show the typical original features of the paraphyletic few bristles. Like earthworms, they have a regular segmentation, a fully developed, segmented coelom that acts as a hydroskeleton and a simply constructed primary closed blood vessel system . Compared to the body length, they are very narrow and therefore have a thread-like appearance.

According to Barrie GM Jamieson 1988 (families Haplotaxidae and Tiguassuidae), the Haplotaxida have two pairs of testes in the 10th and 11th and two pairs of ovaries in the 12th and 13th segment, whereby they are called octogonadal because of their eight gonads , or just a pair of testicles in the 10th segment and a pair of ovaries in the 12th segment. In the latter, the anterior pair of gonads is preserved and the posterior pair receded.

Distribution, habitat and way of life

The Haplotaxida are distributed worldwide and live in various inland waters . They are predators that prey on other small annelids and swallow them whole.

Systematics

The order Haplotaxida was established in 1971 by Ralph O. Brinkhurst , who compared all the other little bristles to the Lumbriculidae (order Lumbriculida) in this taxon . On the basis of the anatomy of the genital organs, Barrie GM Jamieson restricted the scope of the Haplotaxida to the two families Haplotaxidae and Tiguassuidae in 1988 as part of a revision of the systematics of oligochaeta. The work of Erséus and Källersjö 2004 speak but who taxa Haplotaxida as well as the Tubificida dissolve in their previous scope, for the white worms with the confirmed as monophyletic group Crassiclitellata are more closely related than with the other Tubificida, in turn, together with the Well worms (Haplotaxidae) are to be regarded as a monophyletic group (the Naididae including former Tubificidae as well as Phreodrilidae , Haplotaxidae and Propappidae were examined in the group ). In doing so, however, the Haplotaxidae family is regarded as a paraphyletic group of relict taxa in its previous extent.

According to Barrie GM Jamieson 1988, the order Haplotaxida includes the following families :

The monophyletic group named by Erséus and Källersjö 2004, including the Haplotaxidae, includes at least the following families in extension of the aforementioned order (whereby the Tiguassuidae were not examined):

literature