Spiral gall louse
| Spiral gall louse | ||||||||||||
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Gall of the spiral gall louse ( Pemphigus spirothecae ) |
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| Pemphigus spirothecae | ||||||||||||
| Passerini , 1860 |
The spiral gall louse ( Pemphigus spirothecae ), or late spiral gall louse , late leaf stem aphid or poplar aphid , is a gall-producing aphid from the family of bladder lice (Pemphigidae). The scientific name translates as "bladder louse [in] a twisted container" ( Greek σπεῖρα speira "twist", Latin theca "shell"). It occurs on the leaf stalks of black and pyramid poplars and forms a conspicuous, 2–4 cm large plant gall on the stem of a poplar leaf, which can be found from late April to November.
First described was pemphigus spirothecae of the Italian scientist Giovanni Passerini in 1860. Emanuel Witlaczil made in 1884 to the first comprehensive work on the pemphigus spyrothecae which, however, turned out a number of points to be incorrect.
distribution
The spiral gall louse is widespread wherever its host plants, the black and pyramidal poplars, can be found. So it occurs mainly in the climatically warm-temperate areas of the northern hemisphere , particularly frequently in Central Europe , where it occurs in large numbers on host plants. For some time it has also been found sporadically in North America , where it was probably introduced from Europe.
Generation succession
The spiral gall louse shows a holocyclic generation sequence , that is, there is an alternation between three virginly reproducing generations and one sexually reproducing generation. In total there are four generations in the course of a year that can be found in different parts of the poplar. Three of the generations live in the gall at least for a longer period of time.
Fundatrix
The first link in the generation sequence is the fundatrix . Fundatrix is the technical term for the wingless parent mothers of the following generations who hatch in spring from the eggs in which they have overwintered. The fundatrix of the spiral gall louse is initially almost half a millimeter in size, has a brownish-green color and strongly pronounced rear legs. Fundatrices hatch in April in the bark of the poplar tree, from where they move to the stalk of a poplar leaf, on which they stay for about a week, and then prick the stalk of one of the leaves that are not very well defined at this time of the year, thus initiating gall formation.
The fundatrix sheds its skin four times in the gall. The first time after three weeks, then another three times at intervals of one week. The female fundatrix is fully grown after 42–49 days. Adult fundatrices are about 1.6 mm long and 0.9 mm wide and have four-limbed antennae that are about 0.25 mm long. You then begin to deposit embryos in eight egg tubes or ovarioles . Ten offspring of the next generation can be found in each ovariole . A Fundatrix has a total of 80 offspring, many of which wither in the ovarioles before hatching. On average, one to two Virginopara hatch from the ovarioles per day . There is only ever one fundatrix in a bile , from which the entire bile population is derived.
Virginopara
The larvae that hatch from the ovarioles of the fundatrix are called Virginoparae , Virgo generation or L2 stage . They appear for the first time at the end of May, occasionally slip out of the ovarioles until the end of August and, with a lifespan of around 80–90 days, can still be found in the galls in late October and early November. After hatching, they are around 0.5 mm in size, light yellow and have longer antennae than young fundatrices . When fully grown , Virginoparae are about 1.3 mm long and 0.7 mm wide, which makes them somewhat smaller and slimmer than fundatrices . They also have five-part antennae, which are around 0.35 mm longer than the antennae of the fundatrices .
Some representatives of this generation have stronger extremities than the rest of the Virginoparae and apart from the function of reproduction they also have the function of defending the bile. Unlike the rest of their generation, these soldier lice are often unable to develop further through molting , which means that they cannot reproduce. The spiral gall louse is one of the few species from the aphid field that has some kind of social organization. These soldier lice position themselves in the bile according to a specific, innate pattern in order to offer the population the best possible protection against attacking enemies.
The pemphigus spyrothecae has another evolution historical advantage by soldiers lice in their population, as they leave, in rare cases, their bile and other Pemphigus - spirothecae immigrate -Gallen. This enables the spiral gall lice from different biliary populations to combine their DNA . This new combination of genetic material is made possible by the fact that some soldier lice can shed their skin and later lay eggs from which the next generation hatches. Common virgin macaws molt for the first time after three weeks, then every six days. 38–40 days after hatching, this generation begins to produce ovarioles . In each of these ovarioles , in contrast to the ovarioles that are laid by the fundatrix , only four embryos can be found. Since some offspring are already stunted in the ovarioles , mostly only about 30 offspring are born instead of the expected 32. In this generation a renewal takes place over the course of the year , that is, that from the eggs of the Virginopara generation, in addition to the Sexuapara , other Virginopara hatch.
Sexuapara
The Sexuaparae arise from the eggs of the Virginoparae, from which they hatch around July. Initially, they are white in color, which distinguishes them from the other generations in the bile. They are somewhat slimmer than Funda Trice and Virgin Oparae .
Sexuaparae molt four times in 40 days and during this time change their color from a light greenish-yellow hue over the entire body to a blackish head and thorax and a velvety green rear part. When fully grown, they are almost 2 mm long and 0.7 mm wide with six-segmented, 0.6 mm long antennae. After the last moult, they have the characteristic two pairs of wings and spend a few more days in the bile before they leave it via the entrance hole. After leaving, they look for a convenient place on the poplar bark to lay their ovarioles , from which up to eight offspring of the next generation can hatch.
Sexual
The fourth generation of the spiral gall louse , the wingless Sexuales , is the only one in the series of generations that consists of two sexes with a male to female ratio of around 3: 5. The males have a glassy green color and are about 0.7 mm long and 0.3 mm wide. The much larger females are about 1 mm long and 0.4 mm wide. Inside her body is a large egg that can be seen from the outside. The antennae are about 0.14 mm long in both sexes. Sexuals molt four times within three days after hatching from the egg tubes , until they are sexually mature. After mating, the female lays 6–8 eggs in niches in the poplar bark, which will survive the winter and from which the Fundatrix generation will hatch in spring . The eggs are elongated oval and around 0.6 mm long and 0.28 mm wide.
bile
The typical bile form of Pemphigus spirothecae is created by a three-fold rotation of the petiole, in which a population of aphids lives part of their generation cycle to protect against external dangers such as predators or the weather and feeds on the inside of the plant bile by sucking the sap. The bile of the pemphigus spirothecae is a histoid bile that belongs to the surrounding galls. In addition to the characteristics of a walling gall, it has some characteristics of closed marrow galls and pouch galls .
The bile usually forms on the petiole just below the leaf. This is called the distal position. On the other hand, it occurs less frequently at the opposite end of the stem, the basal position. However, several galls can also form which lie next to one another or externally merge into one another.
Basic structure
The bile is a three-fold spiral that has a clear bulge in the middle and becomes significantly thicker from the edges. The outer skin of the bile is usually smooth. However, there are also some specimens that have a rough surface, which is due to the increased occurrence of lenticels .
The inside of the bile is covered with a fine layer of thin white hairs. In cross-section, the bile forms an oval shape that narrows towards the entrance holes with the thickest point on the side opposite the entrance holes. The tissue of the bile is yellowish to white in summer and shows a reddish-brown color in late autumn. The inside of the bile is a spherical to oval cavity, delimited by the upper and lower ends of the bile, which are fused together over a width of 0.5–1 cm and close the tissue in a cup shape.
Microscopic structure
The bile of the spiral gall louse shows no differentiation in its tissue layers according to the basic structure of the stem axis of a young poplar leaf, which is why the gall tissue is assigned to the prosoplasmic galls.
While the youth branch axle distinguishes a poplar leaf through several thick vascular bundles in the middle, which are surrounded by a storage tissue with large memory cells and be completed by a fixed severed strengthening layer of cuticle, it differs significantly compared to tissue of a pemphigus - spirothecae -Galle on some points. The epidermis and strengthening tissue are more pronounced and extend over several rows of cells. The strengthening tissue can be completely absent in some areas. The largest part has a diffusely grown tissue that has a lot of starch and protein.
Growth process
At the end of April, the fundatrix on the leaf stalk of the poplar triggers the growth process with the help of proteins called cytokines , which are injected into the tissue layers of the stalk during the suction process on the leaf stalk. Cytokines are glycoproteins that change the growth and specialization of tissue cells and are used by most biliary pathogens to initiate and control bile formation.
In this case, the cytokines cause the stalk to bend 180 degrees over the spiral gall louse and to twist around it in a two-and-a-half to three-fold spiral until it is completely enclosed by the stalk. The spiral can be rotated in either direction. After another 2–5 days, the stem rotates another 180 degrees. If the fundatrix is removed during this time or if it leaves the place by itself in order to start the formation of gall again at a position on the stem that is more favorable for you, a spiral rotated by 360 degrees remains on the stem. Often times, the fundatrices pierce several places before they stay in one place. What remains are the characteristic turns on the petioles that have not spiraled up into galls.
The growth process is completed between the middle and the end of May, i.e. 6–8 weeks after the Fundatrix has pierced. At this point, the galls are greenish in color and 2–4 cm in diameter. In mid-July the flight holes are more pronounced. Some galls show a light to stronger red color on the side facing the sun, which intensifies even further in the course of summer. The galls turn darker and darker by autumn, and there is no longer any growth in size.
Formation of the flight holes
In the second half of August, the so-called flight holes are formed in the bile , which enable the winged sexuaparae to leave the bile. The entrance holes form an oval opening of the bile along a slit of two sections of the spiralized bile. They are caused by the fact that the tissue around the entrance hole is less pricked by the aphids inside.
The sucking activity of the aphid larvae leads to a growth process in the tissue due to the simultaneous application of cytokines during the process, which serves to regenerate and enlarge the damaged tissue. Due to the lack of suction, the tissue can no longer grow and thus opens the entrance hole a little. The winged sexuapara can leave the bile through the gap created in the bile. What exactly prevents the larvae from sucking in the area of the entrance holes is not known.
In addition to the function of creating an exit for the sexual parents , the flight holes are used to convey excretions of the bile population out of the bile.
Natural enemies
As soon as the bile flight holes open, the spiral gall louse population becomes susceptible to predators, which can invade the bile and severely decimate the population.
Such enemies are, for example, often in the fall in bile of spirothecae pemphigus searchable hoverfly family Syrphidae or type Heringia heringi . Further, Pemphigus spirothecae by flower bugs as Anthocoris minki threatened. These predators, individual Pemphigus - spirothecae often decimate strong and even completely wipe out some bile populations populations. This is made easier by the fact that there are some galls in which there are no soldier lice and which are therefore relatively defenseless against invading enemies.
In addition to these enemies, the spiral gall louse is endangered by the occurrence of fungal infections , bacteria and viruses , which can also be responsible for mass death within the galls. These diseases can be caused by and cause a by contamination of the bile by precipitates of residents Pemphigus - spirothecae dies -Population before the Galle opens.
Harmful effect
While the direct harmful effect of Pemphigus spirothecae on the host plant is low, it can be observed that many leaves infected by Pemphigus spirothecae fall off the trees even before the first sexual parents leave the bile. In general, infected leaves fall off the trees much earlier than unaffected leaves. The size of leaves whose stalk is affected is on average larger than that of unaffected leaves. In addition, the length of the petiole is lengthened by about 1/4 in the case of infected leaves, and leaves with an infected stalk turn yellow and brown on average two weeks earlier than unaffected leaves.
When the flight holes are opened in August, excrement of the bile population is secreted, which in larger parks is noticeable as the presence of honeydew , which can contaminate objects under the tree.
literature
German speaking
- Rolf Beiderbeck, Ingo Koevoet: Plant galls along the way. Origin and destination . Kosmos, 1979, ISBN 3-440-04751-2 .
- Ernst Küster: The galls of plants . Leipzig 1911.
- László Tóth: On the biology of the aphid Pemphigus spirothecae pass. Journal of Applied Entomology , 1939, Issue No. 26, pp. 297-311.
- Gerolf Lampel: Investigations on the morphing sequence of Pemphigus spirothecae PASS. 1860 . Reprint from Bulletin of the Natural Research Society Freiburg , Vol. 58, Fasc. 1 (1968-1969).
- Erik Schwarzenbach: The formation of flight holes in galls from Pemphigus spirothecea Pass. Die Naturwissenschaften , 1962, edition 49/4, p. 91.
English speaking
- Paul CD Johnson, John A. Wihtifield, William A. Forster and William Amos: Clonal mixing in the soldier-producing aphid Pemphigus spyrothecae (Hemiptera: Aphididae) . Molecular Ecology , 2002, Issue No. 11, pp. 1525-1531.
- Shigeyuki Aoki and Utako Ourosu: Soldiers of a European Gall Aphid, Pemphigus spirotecae (Homoptera: Aphidoidea): Why Do They Molt? . Journal of Ethology , 1986, Issue No. 4, pp. 97-104.
- Jabus G. Tyerman and Bernard D. Roitberg: Factors affecting soldier allocation on clonal aphids: a life-history model and test . Behavioral Ecology , 2004, Issue No. 15, pp. 94-101.
Individual evidence
- ^ Hans Jürgen Buhr: Directory of the plant galls. (No longer available online.) December 14, 2006, archived from the original on September 28, 2007 ; Retrieved May 29, 2008 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ a b c d e f g h i j k l m n o p q r László Tóth: On the biology of the aphid Pemphigus spirothecae Pass. Journal of Applied Entomology , 1939, Issue No. 26, pp. 297-311.
- ↑ a b c d e Occurrence, development and natural enemies of pemphigus spyrothecae (Homoptera, Pemphigidae) , JOURNAL OF FOREST SCIENCE , 48, 2002 (6), pp 248-270 ( ( Page no longer available , searching web archives: as pdf downloadable ))
- ↑ Robin Rosetta: aphid terminology. Oregon State University, April 23, 2003, accessed May 29, 2008 : "Fundatrix: mature wingless stem mother which hatches from over-wintering eggs."
- ↑ a b Pemphigus spirothecae Pass. Spiral gall louse. March 1, 2002, archived from the original on July 25, 2008 ; Retrieved May 29, 2008 .
- ↑ Shigeyuki Aoki, Utako Ourosu: Soldiers of a European Gall Aphid, Pemphigus spirotecae (Homoptera: Aphidoidea): Why Do They Molt? . Journal of Ethology , 1986, Issue No. 4, pp. 97-104.
- ↑ Jabus G. Tyerman and Bernard D. Roitberg: Factors Affecting soldier allocation on clonal aphids: a life-history model and test . Behavioral Ecology , 2004, Issue No. 15, pp. 94-101.
- ^ A b c Paul CD Johnson, John A. Wihtifield, William A. Forster and William Amos: Clonal mixing in the soldier-producing aphid Pemphigus spyrothecae (Hemiptera: Aphididae) . Molecular Ecology , 2002, Issue No. 11, pp. 1525-1531.
- ^ A b Gerolf Lampel: Investigations on the morphing sequence of Pemphigus spirothecae PASS. 1860 . Reprint from Bulletin of the Natural Research Society Freiburg , Vol. 58, Fasc. 1, 1968-1969.
- ↑ Dr. Fritz P. Müller: The new Brehm library - aphids - biology, economic importance and control . A. Ziemsen Verlag, Wittenberg, Lutherstadt 1955.
- ↑ Ernst Küster: The galls of the plants . Leipzig 1911.
- ^ Rolf Beiderbeck, Ingo Koevoet: Plant galls on the wayside. Origin and destination . Kosmos, 1979, ISBN 3-440-04751-2 .
- ↑ a b Erik Schwarzenbach: The formation of flight holes in galls from Pemphigus spirothecea Pass. Die Naturwissenschaften , 1962, edition 49/4, p. 91.
Web links
- Maria Pfeifer: spirals, bags, clubs, rolls - the spiral gall louse. January 3, 2005, accessed May 29, 2008 .
- Thomas Lohrer: Weihenstephan University of Applied Sciences: Plant Protection. (No longer available online.) Institute for Horticulture, March 29, 2007, formerly in the original ; Retrieved May 29, 2008 . ( Page no longer available , search in web archives )
- Insect box: spiral gall louse. May 29, 2008. Retrieved May 29, 2008 .
- Holger Daniels: Pemphigus spirothecae on Populus tremula. (No longer available online.) December 6, 2001, formerly in the original ; accessed on May 29, 2008 . ( Page no longer available , search in web archives )
