Developmental speed affects ecological stoichiometry and adult fat reserves in Drosophila melanogaster

The elemental composition of organisms belongs to a suite of functional traits that change during development in response to environmental conditions. However, associations between adaptive variations in developmental speed and elemental body composition are not well understood. We compared body mass, elemental body composition, food uptake and fat metabolism of Drosophila melanogaster male fruit flies in relation to their larval development speed. Slowly developing flies had higher body carbon concentration than rapidly developing and intermediate flies. Rapidly developing flies had the highest body nitrogen concentration, while slowly developing flies had higher body nitrogen levels than flies with intermediate speed of development. The carbon-to-nitrogen ratio was therefore lower in rapidly developing flies than in slow and intermediate flies. We also had a group of flies grown individually and their body mass and elemental body composition were similar to those of rapidly developing individuals grown in groups. This suggests that rapid growth is not suppressed by stress. Feeding rates were lowest in the slowly developing flies. The amount of triacylglycerides was highest in the flies with intermediate developmental speed which optimizes development under many climatic conditions. Although low food intake slows down developmental speed and the accumulation of body fat reserves in slowly developing flies, their phenotype conceivably facilitates survival under higher stochasticity of their environments. Rapidly developing flies grew with less emphasis on storage build-up. Overall, this study shoes that a combination of bet-hedging, adaptive tracking and developmental plasticity enables fruit flies to respond adaptively to environmental uncertainty.</p

Impact of predator odor exposure and mechanical stress during the larval stage on body nitrogen and carbon concentrations in adult Drosophila melanogaster

Vispārīgā stresa paradigma paredz, ka plēsonības izraisīts stress ietekmē upuru vielmaiņu, to ķermenim liekot noārdīt enerģētiskās rezerves, kas noved pie pastiprinātas slāpekļa savienojumu izdalīšanas vidē. Darbā novērtēta plēsēja smaržas un mehāniskā kairinājuma ietekme kāpura stadijā uz augļu mušu imago fenotipu. Noskaidrots, ka plēsēja smaržas izraisīts stress samazina mušu ķermeņa masu, palielina slāpekļa koncentrāciju un samazina oglekļa un slāpekļa koncentrāciju attiecību. Līdzīgas fenotipa izmaiņas iepriekš novērotas audzējot kāpurus kopā ar dzīvu zirnekli un liecina, ka kāpuru ožai plēsēja atpazīšanā ir būtiskāka nozīme nekā citām maņām. Rezultāti ir pretrunā vispārīgajai stresa paradigmai un ir būtiski tās pilnveidošanai, kā arī ļauj labāk izprast plēsonības ietekmi uz ķīmisko elementu apriti dabā.The general stress paradigm predicts that predator-induced stress increases the metabolism of prey individuals and causes the breakdown of their energetic reserves. This leads to the increased excretion of nitrogen-containing compounds. This paper deals with the impact of predator scent and mechanical stress during the larval stage onto the imago phenotype of fruit flies. The results show that the predator odor-induced stress significantly decreased the dry body mass, increased body nitrogen concentration, and reduced carbon-to-nitrogen ratio in the adult flies. Similar phenotypic changes had previously been demonstrated in fruit flies reared with live spiders. This suggests that a sense of smell may have a more important role in the larvae to detect predators compared to the other senses. The results contradict the predictions of the general stress paradigm and might be essential to improve the theory. It also allows us to improve understanding of how predators affect element circulation in ecosystems

Body carbon and nitrogen concentrations of bumblebee Bombus terrestris castes and sexes inhabiting differing agricultural landscapes

Lauksaimniecības intensifikācija ir būtisks iemesls apputeksnētāju daudzveidības kritumam. Nozīmīgs mediators šajā procesā ir fizioloģisks stress, ko var novērot kukaiņu ķermeņa oglekļa un slāpekļa koncentrāciju izmaiņās. No maija līdz jūlijam divos biotopos ar atšķirīgu lauksaimniecības intensitāti, rapšu laukos un ābeļdārzos, tika izvietoti zemes kameņu stropi. Rapšu laukus apdzīvojušo kameņu ķermeņa oglekļa un slāpekļa koncentrāciju attiecība bija būtiski augstāka kā ābeļdārzos, bet ķermeņa masa mazāka, kas liecina par samazinātu muskuļu masu un fizioloģisku stresu. Tāpat rapšu laukos izvietotajos stropos novērots lielāks darba kameņu šūnu skaits. Tas liecina, ka novērotais stress saistīts ar investīcijām vairošanās procesā, ko nodrošina lielāks, bet mazāk daudzveidīgs, pieejamo resursu apjoms rapšu laukos, salīdzinot ar ābeļdārziem.Intensification of agriculture is a significant driver of insect pollinator biodiversity decrease. An important factor is stress, which can be observed as changes in insects’ body carbon to nitrogen concentrations. We placed colonies of buff-tailed bumblebees in oilseed rape fields and apple orchards, two landscapes differing in agricultural intensity. Bumblebees from oilseed rape fields had a higher body carbon-to-nitrogen ratio and lower body mass, indicating muscle mass loss and physiological stress. In addition, hives from oilseed rape fields had a higher number of worker and male cocoons. The finding suggests that the observed stress was associated with increased investment in reproduction, attained due to the higher amount but less diverse resources in oilseed rape fields, compared to apple orchards