Pea louse
| Pea louse | ||||||||||||
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An adult pea louse sucks sap from the stalk of a pea |
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| Acyrthosiphon pisum | ||||||||||||
| Harris , 1776 |
The pea louse ( Acyrthosiphon pisum ), also known as the pea aphid , is an aphid from the family of the tube aphids . It is considered to be a pest on various useful plants from the subfamily of the butterflies , such as peas , field beans , alfalfa and clover . An analysis of their genome was published in 2010 by a group of researchers. They were the first to completely decipher the nucleotide sequence of a hemimetabolic insect from the phylogenetically original group of the Schnabelkerfe . The pea louse could become a new biological model organism .
description
The genotype of the pea louse is of particular interest for molecular biology research because it can produce very different manifestations of characteristics ( phenotypes ) based on the same genome.
Life cycle
The different forms, adapted to the respective seasonal conditions, include winged and wingless females, which can reproduce asexually. The genetically identical larvae are born alive . If the days in the pea louse's distribution area get shorter in autumn, this induces the development of males and sexual females, which can also be winged or wingless. After mating, fertilized eggs are laid which hibernate and result in a wingless generation of parthenogenic females the next spring .
features
The adult animals are up to three millimeters long. They are pale yellowish to light green. A reddish color variant is created by increased temperatures. This phenotype can also be passed on or transformed epigenetically .
The eyes are colored red. The two antennae are as long as the body, their distal limbs, like those of the legs, are brown. The pea louse has stinging-sucking mouthparts with which it can penetrate the vascular bundles of the plants and feed on the plant juices. The siphunculi or siphons , tubular organs at the rear end of the tube aphids, sit on conical skeletal elements. The cauda, that is the tail at the rear end of the body of the adult animals, is long and has six hairs. With their help, the aphids can get rid of the honeydew , which is formed as excretion fluid from the excess assimilates of the plant sap. The honeydew contains sugar and is quickly colonized by sooty fungi , which can hinder photosynthesis in plants.
The nymphs are similar to the adult animals, but do not yet have a cauda. You need to strip off the honeydew with your hind legs.
Way of life
Originally a species widespread in the Palearctic , the pea louse is now found worldwide. The cultivation of a number of species from the range of host plants preferred by the pea lice has contributed to this worldwide distribution. In addition to the legume species that are also native to Central Europe, such as field beans , peas and lentils , these plants also include tropical and subtropical crops such as pigeon peas , fenugreek or Sesbania grandiflora .
The pea lice suckle on the phloem , that is the part of the vascular bundle of the vascular plants , in which nutrients and other assimilates are transported. The aphids damage the host plants not only by depriving them of important nutrients, they are also carriers of various viral infections that can quickly spread through the phloem in the plant. They include viruses that cause mosaic and leaf roll symptoms.
symbiosis
The pea lice live in symbiosis with bacteria of the species Buchnera aphidicola and Regiella insecticola . These live in special cells of the pea lice, the bacteriocytes , where they take on special tasks in the construction or remodeling of sugar molecules and amino acids. The bacteria are passed on to the offspring via the eggs. The genome of Buchnera aphidicola was sequenced around the turn of the millennium and could be compared with that of the pea louse. However, there appears to have been little gene transfer between the two species in the course of evolution .
behavior
The pea lice fall to the ground in case of danger. They almost always land (more than 95%) on their feet. This is achieved passively through a special posture: the feelers on the head and the two long hind legs are stretched upwards in an arch. The advantage is the higher chance of finding support on deeper leaves or of reaching a host plant more quickly on the ground. The fall reaction is not only triggered by mechanical stimuli such as vibrations of the plant parts, but also by pheromones , which are released from the siphons when there is a risk of secretion. These alarm pheromones, which are released by the aphids together with a defense secretion, serve as a signal for the other conspecifics. The presence of hoverfly larvae of the species Syrphus corollae , which feed on aphids, also leads to a fall reaction of the pea lice. The hoverfly larvae then also leave the plant because the prey density is considerably lower.
Individual evidence
- ↑ International Aphid Genomics Consortium: Genome Sequence of the Pea Aphid Acyrthosiphon pisum. PLoS Biology 8, 2, e1000313, February 2010 doi : 10.1371 / journal.pbio.1000313 full text online at PLoS ONE
- ↑ Karin Hollricher: Small genome really big FAZ .NET of April 13, 2010
- ↑ David L. Stern, Jennifer A. Brisson: The pea aphid, Acyrthosiphon pisum: An emerging genomic model system for ecological, developmental and evolutionary studies. BioEssays, 28, 7, pp. 747-755, July 2006
- ↑ Alexander W. Shingleton, Geoffroy C. Sisk and David L. Stern: Diapause in the pea aphid (Acyrthosiphon pisum) is a slowing but not a cessation of development. BMC Developmental Biology, 3, 7, 2003 doi : 10.1186 / 1471-213X-3-7 full text at Biomed Central (PDF, engl.)
- ↑ Lucian Haas: The art of falling of the pea louse. In: Deutschlandfunk . February 25, 2012, Retrieved February 26, 2012 .
- ↑ P. Wohlers: The escape reactions of the pea louse Acyrthosiphon pisum triggered by alarm pheromones and additional stimuli. Entomologia Experimentalis et Applicata, 27, 2, pp. 156-168, January 1980 doi : 10.1007 / BF00573890
- ^ B. Niku: Consequences of the fall reaction of pea lice [Acyrthosiphon pisum] for syrphid larvae [Syrphus corollae]. BioControl, 21, 3, pp. 257-263, September 1976 doi : 10.1007 / BF02371759
Web links
- Acyrthosiphon pisum at Fauna Europaea
- Acyrthosiphon pisum (Harris) factsheet at Aphidweb (engl.)