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Fertility signaling in queens of a North American ant (1999)

Ortius, Diethe ; Heinze, Jürgen

Springer

Behavioral ecology and sociobiology 45 (1999), S. 151-159

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ISSN: 1432-0762

Keywords: Key words Reproductive competition ; Ants ; Aggression ; Dominance rank ; Fertility recognition ; Leptothorax

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract In most species of advanced eusocial insects, the partitioning of reproduction between nestmates is thought to be regulated by means of primer pheromones or other chemical cues, which presumably influence the behavior of co-queens and workers such that they maximize their own inclusive fitness. Here we show that in multi-queen colonies of the Nearctic ant, Leptothorax sp. A, physical dominance in concert with chemical cues, which signal the ovarian development of a queen, are used to control reproduction of competing queens and to influence worker behavior. The analysis of ranks obtained during two fighting periods in the annual colony cycle revealed a strong link between individual aggressiveness of a queen and her fertility. During the adoption of newly mated queens in autumn, the resident, egg-laying α-queen was more likely to start aggression first and keep her high rank position compared to the fighting period after hibernation. We suggest that this is proximately caused by the α-queen having much stronger developed ovaries in autumn than the young queens, whereas after hibernation, the ovaries of all queens are similarly inactive. Interactions during the first weeks after the end of hibernation and intrinsic, individual differences in aggressiveness appear to be crucial for the dominance rank achieved later. Queens which were allowed to become fertile when their nestmate queens still were kept under prolonged hibernation, were immediately socially dominant over the latter when all queens were reunited, though no aggression occurred. In another experiment, queen antagonism was prevented by spatial separation in different parts of the same nest and all queens began to lay eggs. Workers stayed preferentially with queens with high actual fecundity rather than with those which had had high social status before separation. This and further evidence suggest that ovarian status is communicated, most likely by a chemical cue perceived by co-queens and workers, affects the direction of their aggressive behavior, and allows them to discriminate among queens.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002650050548

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Vinylogous β-Carotenes: Generation, Storage, and Delocalization of Charge in Carotenoids (1997)

Broszeit, Guido ; Diepenbrock, Felix ; Gräf, Oliver ; [et al.]

Weinheim : Wiley-Blackwell

Liebigs Annalen 1997 (1997), S. 2205-2213

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ISSN: 0947-3440

Keywords: Carotenoids ; C26—C70 β-carotenes ; Cyclic voltammetry ; Photoelectron spectroscopy ; Semiempirical calculations ; Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: In this paper, we report on the synthesis of β-carotenes of variable chain length with between 5 and 23 double bonds (1-7). These oligoenes were prepared by McMurry and Wittig reactions. The tetradecapreno-β-carotene 7 would seem to be the longest β-carotene yet reported. Furthermore, we investigated the electronic properties using cyclic voltammetry and photoelectron spectroscopy (UPS) to generate open-shell and closed-shell ions of carotenoids in solution and in the solid state, respectively. With increasing chain length (≥ 11 double bonds), even the generation of tetracations and tetraanions could be observed by cyclic voltammetry. Extending the number of conjugated bonds causes the potentials to converge to limiting values. All electron-transfer processes occur in one-electron steps, which are close to each other in pairs. The potential difference between the first oxidation potential and the first reduction potential is a linear function of the reciprocal chain length. Despite the different techniques used (CV and UPS) and the different condensed phases, there is an excellent correspondence between the energies of the radical cation states generated by the two methods. This shows that the radical cation formation is principally determined by the chain length. The structures of the ion states were investigated using semiempirical methods at the NDDO level. Charge delocalization and bond relaxation are not identical and do not utilize the same number or the same kind of atoms. It can be shown that from the length of 20 double bonds onwards, the effective conjugation length for doubly-charged cations converges slowly to a limiting value.

Additional Material: 10 Ill.