Physiology, Diet & Symbiosis axis

 We use carbon and nitrogen stable isotope ratios to quantify diet on a subset of individual fish from each lake, each year. We also get isotope ratios from prey to standardize our measures against the environmental background. We supplement these coarse long-term measures with occasional short-term snapshots of stomach contents. Stickleback vary in benthic versus limnetic foraging behavior, and this variation will have both genetic (evolvable) and plastic components. We hope to trace both the evolution and plasticity of diet. This diet in turn will affect fish phenotypes including immune traits, and parasite infection risks. Diet analyses are being conducted by Dan Bolnick's, Blake Matthews' and Alison Derry’s labs. 

 We are tracking changes in immune phenotypes over time. This includes spleen histology and spatial transcriptomics, head kidney gene expression, and scoring peritoneal fibrosis. Fibrosis is induced by peritoneal cestode infections by a tapeworm called Schistocephalus solidus. We have observed substantial temporal change in fibrosis in the first half decade of the study, and confirmed that these changes are both heritable and infection-induced. Immune measurements are being done by Natalie Steinel’s lab, as well as the Bolnick and Weber labs. 

Sticklebacks host a variety of internal and external parasites. These parasite communities can vary significantly between different populations depending on many genetic and ecological factors.  In the field, we investigate individuals for different parasites (black spot, Dermocystidium, Glugea, Apatamon, etc) to obtain an infection score. We are especially interested in Schistocephalus solidus tapeworms (see photo to the left) which can reach up to 50% of the host's body mass and negatively affect an individual's survival. We have found that transplanted fish exhibit reduced infection rates compared to source lakes. The source lakes, on the other hand, have fairly stable infection rates over time: some lakes have high infection rates year after year, others have low infection rates. The experimental lakes exhibit much greater between-year fluctuations, in comparison.  Parasitology work is led by Dan Bolnick’s lab, with help from Jesse Weber and Natalie Steinel.

Using DNA sequencing, including targeted sequencing for bacteria, Archaea, fungi and protists and metagenomic sequencing, we are characterizing the changes and convergence in the gut microbiota of stickleback from each lake, year after year. We expect to see a convergence of gut microbiome in individual lakes as fish adapt to the new environment, including diet, genome, and environmental factors. This work is led by Kat Milligan-McClellan’s lab.