SEM study of diversity in the cyst surface topography of nine parthenogenetic Artemia (Crustacea: Anostraca) populations from China

Abstract

The cysts of nine Chinese populations of parthenogenetic Artemia were studied by scanning electron microscope. In the 270 cysts examined, 15 different morphological patterns were recognized with most of them not recorded in previous studies and the "tubercled shell surface" being the most common pattern. Results also displayed high intrapopulation variability, with the maximum of 11 patterns (in 30 cysts) recorded from the Barkol population. No positive correlation between the diversity of cyst shell patterns and ploidy compositions was found. Principal components analysis suggests higher similarity among coastal populations than among inland populations, which may be attributed to the identity of physicochemical conditions among coastal salterns and dissimilarity among inland saline lakes.

Ultrastructural diversity in the shell of Artemia resting eggs

“…TEM observation shows that the OM is either flat or undulant (Figure 2), which is obviously corresponding to the smooth and nonsmooth surfaces of resting eggs demonstrated by SEM (Asem & Sun, 2014;Wang & Sun, 2007b). SEM observations on large samples revealed a high diversity of shell surface topology, not only among populations but also within a population (Asem & Sun, 2014;Wang & Sun, 2007b). Therefore, the variations observed by TEM based on a small number of specimens do not reflect the real diversity of OM, and the "between-population" variation here reported may not represent the real differences between populations.…”

“…TEM observation shows that the OM is either flat or undulant (Figure 2), which is obviously corresponding to the smooth and nonsmooth surfaces of resting eggs demonstrated by SEM (Asem & Sun, 2014;Wang & Sun, 2007b). SEM observations on large samples revealed a high diversity of shell surface topology, not only among populations but also within a population (Asem & Sun, 2014;Wang & Sun, 2007b).…”

“…Wang and Sun (2007b) found six types of surface topography when observing the resting eggs from seven Artemia populations in China. More recently, the study of nine parthenogenetic Artemia populations from China further recognized 15 types of surface topography (Asem & Sun, 2014). Both studies also found that the polymorphism of the surface morphology of Artemia resting eggs exists not only among populations but also within populations.…”

The Morphological Differentiation and Evolutionary Origins of Artemia in China

“…Previous works on the morphometrics of Artemia have shown that morphological differences can effectively describe the differences among most bisexual populations [15][16][17][18][19], and even in asexual species, where the populations found in coastal China, inland China, Europe and Africa also exhibit significant morphological differences [20]. However, Asem [21] found no significant differentiation among the populations in China. Further, these studies did not perform a comparison between bisexual and asexual populations, which might make it challenging to determine if bisexual and parthenogenetic Artemia can be distinguished solely based on their morphological characteristics.…”