Intra- and interpopulation variability of cysts and adults of Artemia (Branchiopoda: Anostraca) in Siberian populations (morphometry)

Abstract

The size of Artemia cysts is an important indicator of their value as a food resource; to some extent, it allows to identify populations. The data on cysts of Artemia parthenogenetic populations (diameter, chorion thickness, and presence of spots on a shell), sampled in hyperhaline lakes of Western Siberia in different years, were analyzed, as well as the data on the morphometry of Artemia adults, reared from cysts at the same salinity. Significant intra- and interpopulation variability in the indicators was established. The absolute values of the cyst diameter were in the range of 210–330 µm, the mean values for the samples – 243.5–282.9 µm, the mean values for populations – 257.8–279.6 µm; the absolute values of the decapsulated cyst diameter were in the range of 196–294 µm, the mean values for the samples – 236.5–262.6 µm, the mean values for populations – 239.9–253.2 µm; the absolute values of the cyst chorion thickness were in the range of 3.3–16.9 µm, and the mean values for populations – 6.6–12.4 µm. In the main commercial fishing lakes, which account for about 70 % of the total catch of Artemia cysts in Russia, the cysts had similar mean population sizes: 262–268 µm. The absence of intrapopulation anchoring of the cyst diameter and chorion thickness values is concluded; so, they cannot serve as reliable indicators, identifying Siberian populations. Statistically significant correlation (r = −0.5) was established between salinity of a mother water body and Artemia embryo diameter. Cyst spotting, not exceeding 5 % in almost all the samples, reached 24 % in cysts of Kuchukskoye Lake. Analysis of morphometric indicators of Artemia adults, reared from cysts, showed as follows: the mean body length (9.27–11.63 mm), abdomen width (0.53–0.69 mm), and distance between eyes (1.36–1.52 mm) were closely correlated with salinity of a water body (r values were of −0.76; −0.62; and −0.67, respectively). Cluster analysis of a set of morphometric indicators of Artemia adults showed the unification of populations based on salinity.