The roles of Green Fluorescent Proteins and photo-acclimation on the physiological and behavioural responses of Anemonia viridis

Abstract

Studying the fundamental relationships between marine organisms is vital in determining the biological implications of changing environments. In many cases, these environments are underpinned by photosynthetic primary production, and directly affected by variation in abiotic stressors such as light condition and temperature. Photosymbiotic relationships between unicellular plants and multicellular animals are well studied, yet their complexity and interspecies variation leaves many questions unanswered. Respirometry is a well-known method for quantifying physiological impacts of these stressors, however, commercially available respirometry equipment has significant limitations. Chapter 1 therefore describes a novel open source (OS) photo-respirometer to reduce these limitations, whilst maintaining comparable precision and accuracy to explore complex ecological relationships. A temperate example of the algae-cnidarian symbiosis was used to showcase the data collection ability of our photo-respirometer. Results suggest that the photosynthetic efficiency of A. viridis – Symbiodinium symbioses may be influenced by light intensity, acclimation condition and the presence or absence of green fluorescent proteins (GFPs). This first study concludes that the photo-respirometer is a viable alternative to commercial systems and would be advantageous as a single base apparatus for multiple metabolic studies within marine contexts. Chapter 2 explores the behavioural implications of GFP expression and acclimation condition on phototactic responses of A. viridis to light intensity gradients. Phototactic responses did not differ between morphs, suggesting that GFP expression may have alternative functions or be a vestigial trait in this species. Acclimation to low light intensity elicited the greatest phototactic responses but is potentially influenced by water flow direction. This suggests that either water movement or oxygen concentration are limiting factors for phototaxis in temperate cnidarian-algal symbioses and should be the focus of future studies.