In situ study of adult Artemia salina morphometry and its relationship to the physicochemical water parameters in the saltwork of Sahline (Tunisia)

The morphometric characteristics of the adult natural population of the brine shrimp Artemia salina from the saltwork of Sahline were surveyed in order to establish the relationship between morphometry and environmental water parameters. The field work was performed monthly from October 2005 to June 2006. During this period, the variation in water temperature, salinity, pH, and concentrations of dissolved oxygen and nutrients (orthophosphate, nitrite, nitrate and ammonium) were monitored. Adult Artemia samples (male and female) were randomly collected and stored in plastic containers and transferred to the laboratory for morphometric characterisation. Results show that adult specimens appear in the saltwork of Sahline from December through June. The population sampled in June had significantly lower values in all morphometric characters when compared to the other samples. Concerning male specimens, correlation analysis of the morphometric parameters and environmental conditions indicate that the strongest correlations were between temperature and total length (r xy = −0.656), salinity and total length (r xy = −0.558), and between pH and width of head (r xy = 0.559). For female specimens, the strongest correlations were between total length and salinity (r xy = −0.610), total length and temperature (r xy = −0.537) and between total length and pH (r xy = 0.583). No correlations were observed between dissolved oxygen concentrations or ammonium levels and any morphometric parameters. The principal component analysis (PCA) revealed that diameter of compound eyes, width of second abdominal segment and width of third abdominal segment, for male specimens, and total length, abdominal length and width of the ovisac, for female specimens, are the morphometric parameters that show the greatest variation between samples.