Lyre-shaped organ

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The lyre-shaped organ (also lyriform organ) is one of the sensory organs of arachnids (arachnida). Several split sensory organs are arranged parallel to a group and serve to perceive vibrations in the environment.

Arachnids can vibrate across a substrate, e.g. B. spread the ground, leaves or a spider web, perceive through their lyre-shaped organs. These are found in large numbers all over the body, but especially on the legs. This allows them to determine whether there are potential prey or enemies nearby. The spiders of the genus Dolomedes , which can walk on the surface of the water, use these sensory organs to locate insects that have fallen into the water. An important task of the lyre-shaped organs in the vicinity of joints is also to provide information about the position of the limbs in relation to one another. So they can also serve as proprioceptors .

The perception of air vibrations, on the other hand, is mostly carried out by other mechanoreceptors in arachnids, the trichobothria . The scorpions have no lyre-shaped organs. In this group of arachnids, the fissile organs are distributed irregularly over different areas of the body.

Gaubert first used the term lyre-shaped organ in his work Note sur les organes lyriformes des Arachnides in 1890 . He used it to describe sensory organs arranged in parallel, which are reminiscent of the strings of a lyre due to their different lengths. The cleft sense organs are narrow pit-like depressions in the cuticle , which are covered by a thin membrane. This transfers deformations, which arise from pressure on the relatively rigid cuticle, to two nerve endings , which transmit the stimulus. More than 20 sensory cleft organs can be arranged next to one another. Their lengths can be between 15 and 120 micrometers. Model tests have shown that this arrangement improves the perception of different stimuli and the intensity of the stimuli can be differentiated over a wide range.

Substrate vibrations can also be used by the spiders for communication and perceived with the lyre-shaped organs. As soon as a male spider encounters a female's pheromone trail , it drums high-frequency signals with the pedipalps onto the substrate, which the female can still decipher at a distance of one to two meters. The female responds with a specific signal. The temporal pattern of drumming and the proportion of low-frequency vibrations that are additionally generated by the males with the opisthosoma differ in different species of spiders.

literature

Individual evidence

  1. ^ Paul Gaubert: Note sur les organes lyriformes des Arachnides. In: Bulletin de la Société Philomatique de Paris, Series 8 , Vol. 3 (1890), Issue 1, pp. 14-16.
  2. ^ Friedrich G. Barth and Peter Pickelmann: Lyriform slit sense organs. Modeling on an arthropod mechanoreceptor. In: Journal of Comparative Physiology / A: Neuroethology, Sensory, Neural, and Behavioral Physiology , Vol. 103 (1975), Issue 1, pp. 39-54, ISSN  0340-7594
  3. ↑ Gerhard Heldmaier and Gerhard Neuweiler: Comparative Animal Physiology, Vol. 1: Neuro- and Sensory Physiology , p. 166.