I urval från Stockholms universitets publikationsdatabas

• A key malaria metabolite modulates vector blood seeking, feeding, and susceptibility to infection

  2017. S. Noushin Emami (et al.). Science 355 (6329)

  Artikel

  Malaria infection renders humans more attractive to Anopheles gambiae sensu lato mosquitoes than uninfected people. The mechanisms remain unknown. We found that an isoprenoid precursor produced by Plasmodium falciparum, (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP), affects A. gambiae s. l. blood meal seeking and feeding behaviors as well as susceptibility to infection. HMBPP acts indirectly by triggering human red blood cells to increase the release of CO2, aldehydes, and monoterpenes, which together enhance vector attraction and stimulate vector feeding. When offered in a blood meal, HMBPP modulates neural, antimalarial, and oogenic gene transcription without affecting mosquito survival or fecundity; in a P. falciparum-infected blood meal, sporogony is increased.

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• Idiosyncratic development of sensory structures in brains of diapausing butterfly pupae

  2017. Philipp Lehmann (et al.). Proceedings of the Royal Society of London. Biological Sciences 284 (1858)

  Artikel

  Diapause is an important escape mechanism from seasonal stress in many insects. A certain minimum amount of time in diapause is generally needed in order for it to terminate. The mechanisms of time-keeping in diapause are poorly understood, but it can be hypothesized that a well-developed neural system is required. However, because neural tissue is metabolically costly to maintain, there might exist conflicting selective pressures on overall brain development during diapause, on the one hand to save energy and on the other hand to provide reliable information processing during diapause. We performed the first ever investigation of neural development during diapause and non-diapause (direct) development in pupae of the butterfly Pieris napi from a population whose diapause duration is known. The brain grew in size similarly in pupae of both pathways up to 3 days after pupation, when development in the diapause brain was arrested. While development in the brain of direct pupae continued steadily after this point, no further development occurred during diapause until temperatures increased far after diapause termination. Interestingly, sensory structures related to vision were remarkably well developed in pupae from both pathways, in contrast with neuropils related to olfaction, which only developed in direct pupae. The results suggest that a well-developed visual system might be important for normal diapause development.

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• Do respiratory limitations affect metabolism of insect larvae before moulting? An empirical test at the individual level

  2016. Sami M. Kivela, Philipp Lehmann, Karl Gotthard. Journal of Experimental Biology 219 (19), 3061-3071

  Artikel

  Recent data suggest that oxygen limitation may induce moulting in larval insects. This oxygen-dependent induction of moulting (ODIM) hypothesis stems from the fact that the tracheal respiratory system of insects grows primarily at moults, whereas tissue mass increases massively between moults. This may result in a mismatch between oxygen supply and demand at the end of each larval instar because oxygen demand of growing tissues exceeds the relatively fixed supply capacity of the respiratory system. The ODIM hypothesis predicts that, within larval instars, respiration and metabolic rates of an individual larva first increase with increasing body mass but eventually level off once the supply capacity of the tracheal system starts to constrain metabolism. Here, we provide the first individual-level test of this key prediction of the ODIM hypothesis. We use a novel methodology where we repeatedly measure respiration and metabolic rates throughout the penultimate- and final-instar larvae in the butterfly Pieris napi. In the penultimate instar, respiration and metabolic rates gradually decelerated along with growth, supporting the ODIM hypothesis. However, respiration and metabolic rates increased linearly during growth in the final instar, contradicting the prediction. Moreover, our data suggest considerable variation among individuals in the association between respiration rate and mass in the final instar. Overall, the results provide partial support for the ODIM hypothesis and suggest that oxygen limitation may emerge gradually within a larval instar. The results also suggest that there may be different moult induction mechanisms in larva-to-larva moults compared with the final metamorphic moult.

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