Flagellar phenotypic plasticity in volvocalean algae correlates with Péclet number

• Autores: Solari, C.A.; Drescher, K.; Ganguly, S.; Kessler, J.O.; Michod, R.E.; Goldstein, R.E.
• Año de publicación: 2011
• Idioma: inglés
• Tipo de recurso: artículo
• Fuente: J. R. Soc. Interface 2011;8(63):1409-1417
• Materia: Evolution; Flagella; Fluid dynamics; Nutrient uptake; Phenotypic plasticity; Volvox; Algae; Cells; Fluids; Nutrients; Evolution; Flagella; Nutrient uptake; Phenotypic plasticity; Volvox; Mutagenesis; alga; algal growth; article; cell size; Chlamydomonas reinhardtii; colony formation; extracellular matrix; flagellum; fluid flow; Gonium pectorale; mathematical computing; multiple linear regression analysis; nonhuman; nutrient concentration; nutrient limitation; nutrient uptake; Peclet number; phenotypic plasticity; plant life cycle stage; sedimentation; somatic cell; spheroid cell; swimming; velocity; volvocalean alga; Volvox; Volvox barberi; volvox carteri; algae; Chlamydomonadales; Chlamydomonas reinhardtii; Gonium pectorale; Volvox; Volvox barberi; Volvox carteri
• Institución: Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales

Flagella-generated fluid stirring has been suggested to enhance nutrient uptake for sufficiently large micro-organisms, and to have played a role in evolutionary transitions to multicellularity. A corollary to this predicted size-dependent benefit is a propensity for phenotypic plasticity in the flow-generating mechanism to appear in large species under nutrient deprivation. We examined four species of volvocalean algae whose radii and flow speeds differ greatly, with Péclet numbers (Pe) separated by several orders of magnitude. Populations of unicellular Chlamydomonas reinhardtii and one- to eight-celled Gonium pectorale (Pe ∼ 0.1-1) and multicellular Volvox carteri and Volvox barberi (Pe ∼ 100) were grown in diluted and undiluted media. For C. reinhardtii and G. pectorale, decreasing the nutrient concentration resulted in smaller cells, but had no effect on flagellar length and propulsion force. In contrast, these conditions induced Volvox colonies to grow larger and increase their flagellar length, separating the somatic cells further. Detailed studies on V. carteri found that the opposing effects of increasing beating force and flagellar spacing balance, so the fluid speed across the colony surface remains unchanged between nutrient conditions. These results lend further support to the hypothesized link between the Péclet number, nutrient uptake and the evolution of biological complexity in the Volvocales. © 2011 The Royal Society.