Double tails
| Double tails | ||||||||||
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Double tails ( diplura ) |
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| Diplura | ||||||||||
| Borner , 1904 |
The double tails (Diplura) are an order of the six-footed . Of the 500 known species of the group, 15 are also common in Central Europe. Most species are 2 to 5 mm long, the Australian species Heterojapyx gallardi reaches a total length of almost 58 mm.
The main distribution have the double tails in the tropics and subtropics.
Double tails live in the ground as well as under stones, leaves or pieces of bark. Some species can also be found in the moss, others are cave animals . Generally they love moisture and are shy of light . The members of the Japygidae hunt springtails and live accordingly predatory, other species within the double tails feed on organic material in the soil or on fungal threads .
Anatomy of the double tails
The body of the double tails consists of more or less similar segments, with the first three segments after the head (thorax), as with all six-legged animals. The antennae of the animals are multi-limbed and consist of limbs, which are all provided with muscles (limb antenna). Eyes are completely absent from the double tails. The mouth parts are in a bag-like (entognathen) structure of the head and are pointed or scraping organs converted.
The abdomen (abdomen) of the animals consists of 10 segments, the first 7 individual segments still bearing remnants of the extremities originally present on all segments. The leftovers are called styli. On the last segment there are two very well-developed and mostly thread-shaped tail appendages cerci , which in the Japygidae are transformed into strong, single-link pincers. In the Projapygidae and some other groups, the cerci are very short and palpate.
Reproduction and development
The sperm are transferred indirectly in the double tails. The male releases a stalked sperm packet ( spermatophore ), which is ingested by a female. The eggs are laid as egg balls in small burrows, whereby these are hung on a thread in some representatives of the Campodeidae. Some species of the Japygidae guard the eggs and the young ( brood care ).
Position of the double tails in the phylogenetic system
The position of the double tails within the six-footed is not fully understood.
The most common classification of the double tails is that within a common group with the springtails and leg tinkers as sack-paws (Entognatha). The reason for this taxon formation is the mouth pocket in which the mouthparts are located and which is present in all three groups. These Sackkiefler are compared to the free jaws (Ectognatha) or insects as a sister group .
According to an alternative hypothesis (Kukalová-Peck (1987)), the Diplura alone could also be viewed as a sister group of insects, while a common taxon called Ellipura could in turn be viewed as a sister group of these two groups. The evolutionary different number of leg parts that are fused with the abdominal plates of the abdomen is regarded as the basic characteristic here. This feature and thus the hypothesis are very controversial.
literature
- Bernhard Klausnitzer: Diplura, double tails. In Westheide, Rieger (Hrsg.): Special zoology part 1: single-cell and invertebrate animals. Gustav Fischer Verlag, Stuttgart, Jena 1997; Pages 620-621.
