Dridi, S. | Search bioRxiv

bioRxiv2019

Diffuse Reflectance Spectroscopy reveals heat stress-induced changes in hemoglobin profile in chicken breast

Global rise in incidence of woody breast (WB) syndrome imposes a significant economic burden on the poultry industry. The increase in WB is due to the large increase in the weight of chickens these days within a very short period. An early determination of WB can significantly reduce losses to the poultry industry. Diffuse reflectance spectroscopy provides a noninvasive and rapid method to interrogate tissue function. The sensitivity of DRS to the distinct absorption spectra of oxygenated and deoxygenated hemoglobin allows accurate quantification of average hemoglobin concentration and vascular oxygenation within the sampled tissue. In this study, we used diffuse reflectance spectroscopy to monitor breast hemoglobin concentration (THb) and vascular oxygen saturation (sO2) of 16 chickens that were exposed to heat stress (HS). HS is an important cause of WB myopathy in chickens. Animals were exposed to heat-stress (HS) and optical data were acquired at three time points: at baseline prior to heat stress, 2 days, and 21 days after initiation of HS. Our results show that animals from control and HS groups had a steady decay in optically derived breast hemoglobin concentration consistent with independent i-STAT measurements made on blood sampled from the femoral artery and could provide a noninvasive technology for monitoring tissue function in the poultry industry.

bioengineering↗

bioRxiv2019

Plasticity in evolutionary games

The ability to respond appropriately to environmental cues is fundamental to the success of all forms of life, but previous theoretical studies of the evolution of plasticity make so diverse assumptions that the conditions under which plasticity can emerge in evolving populations are unclear when fitness is frequency-dependent. We study the effect of adding plastic types to symmetric evolutionary games. Since frequency-dependence induces an evolutionary change in the environment of players, one might expect that plastic individuals who can adapt their phenotypes to the environment could have a fitness advantage over simpler purely genetically determined phenotypes. In our model, plastic individuals can detect the type of their opponent before an interaction and condition their action on it. Even though it might appear as an outstanding advantage, such an ability cannot guarantee global stability in all games for even the smallest positive plasticity costs. We identify classes of games where plasticity can or cannot be globally or locally stable. In games where the standard replicator dynamics converge to a pure state, costly plasticity cannot invade an equilibrium population. Costly plasticity can however be locally stable, but the way to achieve this is not to play the best-response to any possible encountered type. Rather, part of the stability success of plastic types is based on establishing Pareto-efficiency as residents; in certain social dilemma games such as the Prisoners Dilemma and the Snowdrift game, this implies that plastic types need to cooperate with a strictly positive probability in order to ensure their stability against invasion by pure types. Zero-sum games always allow for the global stability of plastic types. This study offers a more principled way of thinking about the evolutionary emergence of plasticity in social scenarios, and helps demonstrate that such an emergence is strongly dependent on the type of game individuals are faced with.

evolutionary biology↗