19 July 2018 - 1pm - Zoology Museum
Exploring the fish microbiome: links with stress and disease in aquaculture
There is growing recognition that microbial communities associated with the gut and other mucosal surfaces have a critical influence on host health. The microbiome enhances immunity, pathogen defence, digestion, nutrient acquisition and metabolism, but is also sensitive to disruption by environmental stressors which may adversely affect host health and disease susceptibility. I will talk about our recent research examining how conditions experienced in aquaculture influence the fish microbiome. This includes a fundamental difference in the microbiome of wild and hatchery-reared Atlantic salmon fry, reflecting environmental and genetic diversity. We found that while the gut microbiome is strongly influenced by diet, prior environmental conditions have a lasting influence on microbiome structure. I will also talk about the effects of aquaculture-related stress on the fish microbiome. This includes how faecal cortisol levels are associated with abundance of beneficial Lactobacillus in the gut and how early life stress causes persistent effects on the microbiome including abundance of opportunistic pathogens.
Small world network and the Prisoner’s dilemma: how does cooperation survive?
Cooperation is observed across multiple species and a range of life histories, from slime molds to apes, hence the interest in a general explanation for the emergence and persistence of this behaviour within social groups. Evolutionary game theory, using models like the Prisoner’s dilemma, has been employed to investigate these questions. The distribution of links among interacting players in games like the Prisoner’s dilemma provides an interesting avenue to study how social populations evolve under different interaction networks. Small world network (SWN) connectivity allows regular (e.g., nearest neighbour) networks to gradually be altered to completely random interaction networks.
We studied how SWNs affected the invasion of cheaters into a spatially structured population of cooperators, varying the relative pay-offs for cheaters and the proportion of randomised links among players in an otherwise regular interaction network. We recorded the time a defector takes to invade the population, the final stable proportion of each strategy (cooperator or cheater) and the variability in this proportion across different network structures.
SWNs facilitate the invasion of defectors at lower pay-off levels than regular networks, by preventing the formation of blocks of cheaters and the reduced payoffs associated with those interaction blocks. In this scenario, the lower scoring cooperators are at an evolutionary disadvantage, as cooperation clusters can’t easily be formed to resist invasion. For a specific range of payoffs, the speed of invasion is significantly facilitated by the proportion of randomised links present. SWN links therefore influence the speed and stable state of evolutionary dynamics.