Salt sensitivity of the morphometry of Artemia franciscana during development: a demonstration of 3D critical windows

A 3D conceptual framework of 'critical windows' was used to examine whether the morphometry of Artemia franciscana is altered by salinity exposure during certain key periods of development. Artemia franciscana were hatched at 20 ppt (designated control salinity) and were then exposed to 10, 30, 40 or 50 ppt either chronically (days 1-15) or only on days 1-6, 7-9, 10-12 or 13-15. On day 15, maturity was assessed and morphometric characteristics, including mass, total body length, tail length and width, length of the third swimming appendage and eye diameter, were measured. Maturation and morphometry on day 15 were influenced by the exposure window and salinity dose. Artemia franciscana were generally larger following exposure to 10 and 40 ppt during days 1-6 and 7-9 when compared with days 10-12 and 13-15, in part due to a higher percentage of mature individuals. Exposure to different salinities on days 1-6 produced the greatest differences in morphometry, and thus this appears to be a period in development when A. franciscana is particularly sensitive to salinity. Viewing the developmental window as three-dimensional allowed more effective visualization of the complex interactions between exposure window, stressor dose and the magnitude of morphometric changes in A. franciscana.