Cataglyphis

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Cataglyphis
Cataglyphis nodus

Cataglyphis nodus

Systematics
Order : Hymenoptera (Hymenoptera)
Superfamily : Vespoidea
Family : Ants (Formicidae)
Subfamily : Scale ants (Formicinae)
Genre : Cataglyphis
Scientific name
Cataglyphis
Foerster , 1850
One of the best studied species is Cataglyphis bicolor
Cataglyphis nodus with a typically upright guest
Soldiers of Cataglyphis nodus fend off a black beetle of the species Tentyria rotundata , which has come too close to the nest entrance .

Cataglyphis , sometimes referred to as desert ants in German, is a genus of ants in arid areas of the Mediterranean, North Africa, Middle East and Central Asia. The species stand out in their habitat due to their diurnal lifestyle and extremely fast running. The genus , especially the species Cataglyphis bicolor and Cataglyphis fortis , have been intensively researched in terms of their way of life, especially their ability to orient themselves and eyesight, and are important model organisms for modeling behavior. In Cataglyphis nodus (= C. noda ) also was magnetic sense researched and proven.

features

Cataglyphis species belong to the scale ants (Formicinae), i.e. H. their free abdomen ( gaster ) adjoins the trunk section with a scale-shaped stalk member ( petiolus ). The animals are colored yellow, light brown or black. They sometimes appear silvery shiny due to the hair (setae, long, unicellular, thread-like, strongly chitinized outgrowths), which is used for thermoregulation through reflection ; the silver ant Cataglyphis bombycina gets its name from this.

From other genres of Formicinae they are following characteristics due to the combination differ : The mandibles are large and triangular, they carry on his gum line a row of teeth of five teeth (in a few species exceptionally seven), the outward increase from the inside to size. The second link of the maxilla ( stipes ) has large bristles. The first limb of the maxillary palps is flattened. The complex eyes sit noticeably far back on the head, always in the back half of the head. The spiracles on the first abdominal segment ( propodeum ) fused with the thorax are slit-shaped. In most species, long rows of bristles form a special structure called psammophores on the maxillae and on the outer edge of the mandibles, often also on the maxillary palps, which serve to hold back sand and dust when they eat.

In the sex animals the following characteristics are also developed: The wings of the females have very short hair (microtricha), the length of which is less than their distance from one another. Your leading edge is straight. In many species, however, the females are wingless. The males are the same size as the females, and their eyes are of the same size. The stipes of the maxilla have an appendage in the middle. The upper part of the fuselage is colored black, or it is two-colored with two longitudinal bands and an oval spot near the front edge.

The genus is morphologically very uniform, it is divided into nine species groups. Many species are extremely similar to one another and difficult to distinguish morphologically. However, such pairs or groups of species often show marked differences in preferred habitat and way of life. The most important characteristic carriers for the differentiation of the species are the genitals of the males. Modern analysis techniques such as For example, the signature of the hydrocarbons in the cuticle or analysis of the DNA sequence, numerous cryptospecies , which can hardly be distinguished morphologically , were also detected. The actual number of species of the genus can therefore hardly be reliably stated. For example, a study in Tunisia showed that what had previously been classified as " Cataglyphis bicolor " was in fact a complex of three closely related species ( bicolor , viatica , savignyi ). It could be proven that these species colonize different preferred habitats ( bicolor humid, savignyi drier), but only if they occur together (sympatric) in the habitat.

Habitat and way of life

All species are heat-loving (thermophilic). They inhabit dry habitats, from dry forests to steppes and rocky heaths to real deserts . They occur in corresponding areas from sea level to mountains (up to over 3000 meters above sea level). In deserts, they are among the species that penetrate the furthest into arid, hostile regions. Cataglyphis fortis lives in salt pans ( chotts ), which were left behind in the Sahara after temporary rainwater pools had dried out. It is almost the only colonizer of this extremely hostile habitat. With one exception, the species Cataglyphis floricola , which mainly harvests flower petals from plants, the species in the genus are specialized scavengers . Above all, they are adapted to the detection and utilization of dead flying insects that have been blown into the hot and dry habitats of Cataglyphis and perish here. To use this resource, the species of the genus have developed their own behavioral repertoire. They always hunt individually. In contrast to almost all other ants, there are neither paths marked by pheromones nor recruitment of conspecifics to food sources. The only remaining use of pheromones is to mark the entrance to their underground nest. The search activity is day-centered in almost all species with strongest running activity in the hot midday hours. In the central Sahara, Cataglyphis bombycina is the only insect that is still active in the midday heat of summer, with ground temperatures above 60 ° C, whereby the rapid movement keeps the period of ground contact short.

Cataglyphis species usually have a reproductive period in summer, with oviposition and larvae from around April to October and a peak in midsummer (July / August). During the reproductive period, the need for food and thus the activity of the workers is highest. By preferring the hottest time of day in the warmest period of the year, the animals live most of the time at the thermal limit, despite their very high resistance to high temperatures: their preferred activity temperature is only a few degrees below the deadly maximum temperature. So is z. B. with Cataglyphis cursor the activity maximum at 48 ° C. Even at 50 ° C (after 10 minutes of exposure) 50 percent of the workers die. For other species the values ​​are in similar ranges. Due to this lifestyle and their high temperature resistance, the Cataglyphis species occupy an ecological niche that allows them to avoid both the competition of other ant species, which are superior in direct interaction, as well as most potential predators (predators). But the way of life is bought with a high risk. In the investigation of colonies of Cataglyphis bicolor in Tunisia, individual losses of 16 percent of active workers daily (!), Mainly due to heat stress at high temperatures and predators at lower temperatures, were found. The life expectancy of a foraging worker of this kind was estimated here at 6.1 days.

The high temperature resistance with body temperatures of up to 53.6 ° C for Cataglyphis bombycina and 55.1 ° C for Cataglyphis bicolor is achieved by the animals primarily through the particularly intensive synthesis of heat shock proteins . It is also important to adapt the morphology and behavior in order to keep the body as far away as possible from the particularly hot floor surface itself. Many species have particularly long legs, while others lift the guest vertically up while running.

Unlike most other ants, colonies of Cataglyphis do not defend nesting or feeding territory. A specialized caste of soldiers defending the nest itself was only found in one species of Cataglyphis bombycina . Many other species (e.g. Cataglyphis cursor ) do not even defend the nest entrance itself. However, intruders into the nest itself, whether alien species or individuals of the same species from other colonies, are usually attacked. Cataglyphis species plunder brood and food supplies from foreign colonies when the opportunity arises. As usual with ants, nest mates are recognized by the special signature of the hydrocarbons in their cuticula .

Within the genus there are both species with only one queen per colony (monogynous) ( C. cursor , C. sabulosa , C. livida , C. bicolor , C. savignyi , C. hispanica ) and those with several queens (polygynous) ( C. niger , C. mauritanica ). In some species (e.g. C. velox ) the structure is variable. In the case of the polygynous species and populations, new colonies are usually created by dividing the mother colony, in which each young queen is followed by a part of the workers of the mother colony. In the case of the monogynous species, independent colony establishment by escaping queens predominates.

If the queen is lost, some Cataglyphis species are able to reproduce not only male offspring from unfertilized eggs, as usual (arrhenotoke parthenogenesis ), but also females (thelytoke parthenogenesis). This propagation path ( Amphitokie ) is very unusual and otherwise only a few Legimmen (. Eg chalcids been found TYPES). With Cataglyphis cursor , surplus females are then aggressively eliminated until a new queen remains.

Orientation skills

The working group of the zoologists Rüdiger Wehner and Harald Wolf has intensively researched the sense of direction of Cataglyphis for a long time. The ants orient themselves almost exclusively optically. Optical landmarks (landmarks) are important. However, an exact navigation via path integrals is essential for the strategy of this type. Regardless of which indirect and winding path you took to find a food object: The way back is in a straight line towards the nest. The respective angle to the position of the sun (sun compass), on the one hand, and the distance covered, on the other, serve for this orientation. A neural architecture was proposed according to which both variables could be mapped relatively easily by cyclic circuits. The animals are able to take into account the distance covered by the sun in the sky (position of the sun) as time progresses. In addition to the position of the sun itself, the angle of the polarized light in the cloudy sky is also used to determine the position. As with many insects, there are a few specialized ommatidia on the dorsal edge of the eye. Orientation is not affected by artificial difficulties (such as amputated limbs), but neither is it improved by exercise. The animals take into account the actual length of the path, not its projection into the plane, as can be demonstrated (on Cataglyphis fortis ) through experimental routes with ascending and descending sections. In experiments with legs artificially lengthened or shortened (by glued on "stilts"), the ants either ran past their nest or did not even get there. From this it can be concluded that the animals through an internal odometer ( odometer have) for counting their steps and to calculate accurate distances.

Investigations also showed that the ants walk here and there (“meandering”) while searching for food, but return in a straight line to the nest after finding prey. Field studies in Greece, published in 2018, indicated that this ability was primarily due to their magnetic sense.

swell

  • Alain Lenoir, Serge Aron, Xim Cerdá, Abraham Hefetz: Cataglyphis desert ants: a good model for evolutionary biology in Darwin's anniversary year - A review . Israel Journal of Entomology Vol. 39: 1-32, 2009
  • Rüdiger Wehner: Taxonomy, functional morphology and zoogeography of the Saharan desert ant Cataglyphis fortis (Forel 1902) stat. nov. Senckenbergiana biologica 64 (1/3), 1983, pp. 89-132.

Individual evidence

  1. ^ Pauline Nikola Fleischmann, Robin Grob, Valentin Leander Müller, Rüdiger Wehner and Wolfgang Rössler: The Geomagnetic Field Is a Compass Cue in Cataglyphis Ant Navigation. In: Current Biology. Volume 28, No. 9, pp. 1440–1444 (e2), 2018, doi: 10.1016 / j.cub.2018.03.043
  2. ↑ Norman Nan Shi, Cheng-Chia Tsai, Fernando Camino, Gary D. Bernard, Nanfang Yu: Keeping cool: Enhanced optical reflection and radiative heat dissipation in Saharan silver ants. In: Science 349, No. 6245, 2015, pp. 298–301, doi : 10.1126 / science.aab3564 .
  3. ↑ D. Agosti: Review and reclassification of Cataglyphis (Hymenoptera, Formicidae) . In: Journal of Natural History 24, 1990, pp. 1457-1505.
  4. ^ R. Wehner, S. Wehner, D. Agosti: Patterns of biogeographic distribution within the bicolor species group of the North African desert ant, Cataglyphis Foerster 1850 (Insecta: Hymenoptera: Formicidae) . In: Senckenbergiana Biologica 74, 1994, pp 163-191.
  5. ↑ B. Dietrich & R. Wehner: Sympatry and allopatry in two desert ant sister species: how do Cataglyphis bicolor and C. savignyi coexist? In: Oecologia 136, 2003, pp. 63-72, doi : 10.1007 / s00442-003-1245-0 .
  6. ↑ FX Dillier & R. Wehner (2004): Spatio-temporal patterns of colony distribution in monodomous and polydomous species of North African desert ants, genus Cataglyphis. Insectes Sociaux 51: 186-196.
  7. ↑ R. Wehner: Strategies against heat death. Thermophilicity and thermoregulation in desert ants (Cataglyphis bombycina). In: Acad. Knowledge Lit. , Mainz 1989, pp. 101-112.
  8. ↑ P. & R. Schmid-Hempel: Life duration and turnover of foragers in the ant Cataglyphis bicolor (Hymenoptera, Formicidae) . In: Insectes Sociaux 31, 1984, pp. 345-360.
  9. ^ R. Wehner: The architecture of the desert ant's navigational toolkit (Hymenoptera: Formicidae) . In: Myrmecological News 12, 2008, pp. 85-96.
  10. ↑ Rüdiger Wehner: Desert ant navigation: how miniature brains solve complex tasks. In: Journal of Comparative Physiology A 189 (8), 2003, pp. 579-588, doi : 10.1007 / s00359-003-0431-1 .
  11. ^ Georg Hartmann & Rüdiger Wehner: The ant's path integration system: a neural architecture . In: Biological Cybernetics Volume 73, No. 6, 1995, pp. 483-497, doi: 10.1007 / BF00199541 .
  12. ↑ Thomas Labhart: Polarization-sensitive interneurons in the optic lobe of the desert ant Cataglyphis bicolor. In: Naturwissenschaften 87, 2000, pp. 133-136.
  13. ^ Matthias Wittlinger, Rüdiger Wehner, Harald Wolf: The ant odometer: stepping on stilts and stumps. In: Science 312, No. 5782, 2006, pp. 1965-1967, doi : 10.1126 / science.1126912 .
  14. ^ Matthias Wittlinger, Rüdiger Wehner, Harald Wolf: The desert ant odometer: a stride integrator that accounts for stride length and walking speed . In: Journal of Experimental Biology 210, 2007, pp. 198-207, doi : 10.1242 / jeb.02657 open access.
  15. ^ Pauline Nikola Fleischmann, Robin Grob, Valentin Leander Müller, Rüdiger Wehner and Wolfgang Rössler: The Geomagnetic Field Is a Compass Cue in Cataglyphis Ant Navigation. In: Current Biology. Volume 28, No. 9, pp. 1440–1444 (e2), 2018, doi: 10.1016 / j.cub.2018.03.043

Web links

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