Gonapophysis

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The gonapophyses or valvulae (Valven) are paired appendages on the 8th and 9th abdominal segment of insects. They are part of the egg laying apparatus ( ovipositor ) and are therefore originally used to lay eggs. In many insects, the gonapophyses are also used as a copulatory device or as a lancing device .

Layout and function

Green hay horse with a clearly recognizable ovipositor

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 anterior 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

Wasp sting in the scanning electron microscope

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.

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.

supporting documents

  1. ↑ Gonapophysis. In: Herder-Lexikon der Biologie. Spektrum Akademischer Verlag, Heidelberg 2003, ISBN 3-8274-0354-5 .
  2. ↑ gonapophysis. on: thefreedictionary.com (Engl.)
  3. ↑ a b c Gerhard Seifert: Entomological internship. Georg Thieme Verlag, Stuttgart 1975, ISBN 3-13-455002-4 , pp. 310-312.