Morphometric characteristics of the population of Artemia crustaceans in Lake Kulundinskoe of Altai Krai

In southern Western Siberia, there are numerous hypersaline lakes. In the zooplankton communities of these lakes, brine shrimp of the genus Artemia Leach, 1819, are typically dominant. Scientific interest in these organisms stems from their exceptional osmoregulatory capabilities, the diversity of physiological, biochemical, and morphological traits among individual populations, and the presence of polyploidy. The practical significance of Artemia lies in the widespread use of its dia-pausing eggs as starter feed in aquaculture. This study aims to evaluate the impact of varying water availability phases on the morphological characteristics of the Artemia population in Lake Kulundinskoye, Altai Krai. Lake Kulundinskoye is located in the southern part of Western Siberia within the closed drainage basin of the Ob-Irtysh interfluve. Its surface area varies between 720 and 728 km2 depending on the year and season, with an average depth ranging from 2.6 to 3.0 m and a maximum depth of 3.5 to 4.0 m. Crustaceans were collected as part of zooplankton monitoring surveys conducted from April to October during 20062013 (regressive phase of water availability) and 2017-2022 (transgressive phase of water availability) at various sites across the lake (See Fig. 1). Plankton sampling followed standard methodologies at permanent observation stations. Samples were preserved in a 4% formalin solution. Twelve morphometric parameters of female individuals from the parthenogenetic population of the brine shrimp Artemia sp. in Lake Kulundinskoye were studied. These parameters included body length (tl), cephalothorax length (cl), abdominal length (al), abdominal width (aw), ovisac width (ow), ovisac length (ol), head width (hw), distance between the eyes (de), eye diameter (ed), length of the first antenna (la), and lengths of the right and left furcal branches (fl-r, fl-l). Only female individuals were used in this study, as males were rarely encountered and only during the transgressive period; therefore, data for males are not included. A total of 602 brine shrimp individuals were analyzed: 383 during the transgressive phase and 219 during the regressive phase of water availability. Mathematical processing of the collected data was conducted using descriptive statistics, correlation analysis, and principal component analysis. This processing was performed with Microsoft Excel 2013 and the PAST 4 software package. Since several variables did not follow a normal distribution, correlations were calculated using Spearman's rank correlation coefficient. Multivariate statistical analysis was carried out through Principal Component Analysis (PCA) based on the covariance matrix, as all variables shared the same scale. Statistically significant components (at a 95% confidence level) were identified from the scree plot using the Broken Stick method. The study demonstrated that changes in lake water content significantly affect the morphometric characteristics of the brine shrimp population. This influence is most likely due to alterations in the complex physicochemical factors of the lake's aquatic environment, primarily salinity. It was observed that different morphometric traits respond variably to these changes; however, all studied indicators exhibited increased variability during the transgressive phase of water content (See Figs. 2 and 3). A comparison of the size characteristics of the Artemia population using the Kruskal-Wallis test across different phases of water availability revealed significant differences in morphometric traits during these periods (See Tables 1 and 2). Principal Component Analysis (PCA) identified body length (tl) as having the greatest factor load in both phases of water availability, indicating that it drives changes in other dimensional traits of brine shrimp. Cephalothorax length (cl) exerted a significantly lower influence on these characteristics. The contribution of ovisac width (ow) was more pronounced during the transgressive phase, whereas cephalothorax length (cl) was more influential during the regression phase (See Table 3). Correlation analysis of the studied traits showed stronger associations during the transgressive phase. Body length was positively and statistically significantly correlated with other indices (See Tables 4 and 5). The article contains 3 Figures, 5 Tables, 29 References. the authors express their sincere gratitude to the staff of the IWEP SB RAS for their assistance in conducting the research. The Authors declare no conflict of interest.

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