Ovipositor
Ovipositor is the general term in the animal kingdom for an egg-laying apparatus developed in females . Although there are corresponding structures in different animal groups (for example in the bitterling ), this term is usually used for the laying apparatus of the insects. According to its very different training, it is also referred to as a laying apparatus , laying drill , laying stinger or laying tube . Functionally, it is used by the females to deposit eggs in various substrates.
Layout and function
The ovipositor is formed as a tube of the paired gonapophyses , which form in the area of the genital segments (8th and 9th abdominal segment) as formations on the front edge of the coxopodite of the two genital segments ( valvifer ). They are derived from corresponding formations of the rock jumpers , which form a simple laying pipe. At the base of the laying tube is the genital opening from which the eggs are pressed into the lumen of the tube.
Higher insects such as dragonflies , jumping fries , fringed-winged birds , beak- winged bugs and hymenoptera have an advanced ovipositor ( orthopteroid ovipositor). Here the second valvifer carries another pair of gonapophyses, which together with the two original valvulae form a double tube. Both the third and the second valvulae are folded over a rebate strip in a corresponding groove of the first, the second valvulae mostly forming the middle delimitation of the upper and lower half-tubes. The base of the gonapophyses is equipped with muscles (pro and retractor) that enable the valvulae on both sides to move against each other. The alternating movement allows an egg in the laying pipe to be transported to the top of the laying pipe.
Transformations
In some representatives of the hymenoptera, especially bees and wasps , a poison sting developed from this original ovipositor . The lumen of the original laying pipe (sting) transports the poison out of a poisonous bladder. This also explains the absence of the sting in male individuals.
In many other subgroups the laying apparatus can be changed. In some short-antennae terrors , the gonapophyses are severely regressed and not interwoven. They are short and hook-shaped, and the middle valvulae are greatly reduced. The middle valvulae are completely absent in the real crickets and the laying pipe is only formed from the first and third valvulae.
Atypical egg-laying apparatus
In addition to this basic type of ovipositor, insects also have numerous atypical oviposition apparatuses that probably developed independently of one another. So have diving beetles one described ovipositor functionally very similar ovipositor, which is not deduce from this. Tube-like formations also exist on the ventral side of the genital segments in various reticulated winged flies and camel neck flies . In numerous groups of insects, instead of a laying pipe, the rear abdomen segments are tapered and assume the function of laying eggs; these can usually be turned out and pulled back into the front segments.
supporting documents
- ^ Brohmer: Fauna of Germany. 2002
- ↑ a b c d Gerhard Seifert: Entomological internship. Georg Thieme Verlag, Stuttgart 1975, ISBN 3-13-4550-02-4 . Pp. 310-312
