Biometrical variation of Artemia urmiana cysts harvested in north part of the Lake Urmia (I) (IRAN)
Alireza Asem1, Nasrullah Rastegar Pouyani1, Naser Agh2
1. Department of Biology, Faculty of Science, Razi University, Kermanshah, IRAN
2. Artemia and Aquatic Animals Research Center, Urmia University, Urmia, IRANSummary:
Artemia is a small Crustacea from Class Branchiopoda, Phylum Arthropoda. Artemia urmiana is a unique species of Artemia reported from Lake Urmia. The objectives of this study were to determine the diameter of untreated and decapsulated cysts and its chorion thickness in cysts harvested from 11 harvesting sites in north part of the Lake. Tukey Test was used, for comparison of data. Means of only 2 pair untreated cyst samples were significantly different, but analyzing decapsulated cyst showed presence of vast differences among the samples harvested from different sites (19 pair samples) and as well as among the cysts harvested from the same site. Consequently no variations were observed amongst the diameters of untreated cysts but high variation amongst diameters of decapsulated ones. In order to differentiate the cyst samples, Hierarchical Cluster Analysis was used. As diameters of decapsulated cysts showed high variations, mean of diameters of decapsulated and C.V in each station was used in Hierarchical Cluster Analysis. According to results obtained from this analysis, the cyst samples were grouped in 4 collections. Largest cysts were found in S3-1 station (259.34 ? 2.25 micrometer) and smallest size in S2 station (249.79 ? 5.14 micrometer). Largest decapsulated cysts were fund in S6-4 (251.6 ? 2.23 micrometer) and smallest in S4-1 (238.75 ? 2.23 micrometer). Thickest chorions were observed in S4-1 (9.38 micrometer) and thinnest chorions belong to the cysts harvested from S6-4 (2.04 micrometer). Results obtained indicate that diameter of decapsulated cyst is a natural character for the population and environmental factors do not influence it considerably, but it seems that environmental factors do considerably influence the diameter of untreated cysts that include chorion layer too. Therefore it could be finally concluded that biometrical studies of decapsulated cysts could probably be used as a tool for differentiating different Artemia population within the same biotope.
