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Veru, L.

Publications and source records attributed to Veru, L..

2 recordsLinked to original sources
bioRxiv2020

Induction of long-lived potential aestivation states in laboratory An. gambiae mosquitoes

BackgroundHow Anopheline mosquitoes persist through the long dry season in Africa remains a gap in our understanding of these malaria vectors. To span this period in locations such as the Sahelian zone of Mali, mosquitoes must either migrate to areas of permanent water, recolonize areas as they again become favorable, or survive in harsh conditions including high temperatures, low humidity, and an absence of surface water (required for breeding). Adult mosquitoes surviving through this season must dramatically extend their typical lifespan (averaging 2-3 weeks) to 7 months. Previous work has found evidence that the malaria mosquito An. coluzzii, survives over 200 days in the wild between rainy seasons in a presumed state of aestivation (hibernation), but this state has so far not been replicated in laboratory conditions. The inability to recapitulate aestivation in the lab hinders addressing key questions such as how this state is induced, how it affects malaria vector competence, and its impact on disease transmission. MethodsWe compared survivorship of mosquitoes in climate-controlled incubators that adjusted humidity (40-85% RH), temperature (18-27 {degrees}C), and light conditions (8-12 hours of light). A range of conditions were chosen to mimic the late rainy and dry seasons as well as relevant extremes these mosquitoes may experience during aestivation. ResultsWe found that by priming mosquitoes in conditions simulating the late wet season in Mali, and maintaining mosquitoes in reduced light/temperature, mean mosquito survival increased from 18.34 +/- 0.65 to 48.02 +/- 2.87 days, median survival increased from 19 (95% CI: 17-21) to 50 days (95% CI: 40-58), and the maximum longevity increased from 38 to 109 days (p-adj < 0.001). While this increase falls short of the 200+ day survival seen in field mosquitoes, this extension is substantially higher than previously found through environmental or dietary modulation and is hard to reconcile with states other than aestivation. Future work will expand on these findings, looking to further extend the gains in life span while also investigating transcriptional changes in genes affecting aging, metabolism, and epigenetic regulation; hormone and nutrient levels; and vector competence for malaria causing parasites. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=94 SRC="FIGDIR/small/031799v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@7dc905org.highwire.dtl.DTLVardef@189bd4org.highwire.dtl.DTLVardef@19ea253org.highwire.dtl.DTLVardef@1b32a3d_HPS_FORMAT_FIGEXP M_FIG C_FIG

ecology↗
bioRxiv2020

Massive windborne migration of Sahelian insects: Diversity, seasonality, altitude, and direction

Knowledge on long-distance migration of insects is especially important for food security, public health, and conservation-issues that are especially significant in Africa. During the wet season, the Sahel nourishes diverse life forms which are soon purged by the long dry season. Windborne migration is a key strategy enabling exploitation of such ephemeral havens. However, our knowledge of these large-scale movements remains sparse due to the virtual invisibility of insects flying at altitude. In this first cross-season investigation (3 years) of the aerial insect fauna over Africa, we sampled crepuscular and nocturnal insects flying 40-290 m above ground in four Sahelian villages in Mali, using sticky nets mounted on tethered helium-filled balloons. Nearly half a million insects were caught, representing at least thirteen insect orders following preliminary sorting of the collections. At least 100 insect families were determined to have been captured at altitude in samples collected on 222 nets, obtained in 125 collections over 96 nights. Control nets (raised momentarily to >40 m during system launch and retrieval) confirmed that the insects were captured at altitude, not near the ground. Thirteen ecologically and phylogenetically diverse species were studied in detail. The flight activity of all species peaked during the wet season every year across localities up to ~100 km apart, and occurred over multiple nights, suggesting regular migrations. Species differed in flight altitude, seasonality, and correlations with aerial temperatures, humidity, and wind speed. All taxa exhibited frequent migrations on southerly winds, accounting for the recolonization of the Sahel from southern source populations. "Return" southward movement at the end of the wet season occurred in most taxa but no selectivity for such winds was detected. Extrapolation of aerial density to estimate the seasonal number of migrants crossing Mali at latitude 14{degrees}N suggested numbers in the trillions, even for the modestly abundant taxa. Assuming 2-10 hours of flight, the nightly distances traversed exceed tens and even hundreds of kilometers. Two migration strategies were proposed: "residential Sahelian migration" and "round trip migration". The unprecedented magnitude and diversity of long-range windborne insect migrations highlight the importance of this life strategy in their impact on Sahelian and neighboring ecosystems.

ecology↗