Spermatozoa concentration, seminal plasma composition and their physiological relationship in the endangered stellate sturgeon (Acipenser stellatus) and Russian sturgeon (Acipenser gueldenstaedtii ).

Comparative studies of ionic composition, osmolality, protein concentration and pH of seminal plasma along with spermatozoa concentrations were carried out in stellate sturgeon, Acipenser stellatus, and Russian sturgeon, Acipenser gueldenstaedtii. Analysis of A. gueldenstaedtii sperm showed significantly higher concentrations of Na(+) (34.58 ± 4.61 mm), Ca²(+) (0.35 ± 0.12 mm), Mg²(+) (0.70 ± 0.25 mm), Cl(-) (13.50 ± 4.04 mm) and proteins (0.60 ± 0.29 mg/ml) in the seminal plasma than did seminal plasma of A. stellatus: Na(+) (20.08 ± 10.75 mm), Ca²(+) (0.28 ± 0.06 mm), Mg²(+) (0.29 ± 0.05 mm), Cl(-) (7.50 ± 3.00 mm) and 0.30 ± 0.11 mg/ml proteins. Significantly higher concentration of K(+) (5.42 ± 1.06 mm) was observed in A. stellatus compared to A. gueldenstaedtii K(+) (2.29 ± 0.50 mm). Concentration of Na(+) was positively correlated with osmolality (r = 0.819), levels of Cl(-) (r = 0.922) and Mg²(+) (r = 0.727) and pH (r = 0.848). The concentration of Mg²(+) was positively correlated with protein concentration (r = 0.774), Na(+) (r = 0.727), Cl(-) (r = 0.872) and Ca²(+) (r = 0.801). A positive relationship was also found between concentration of K(+) and spermatozoa concentration (r = 0.709). Results revealed strong inter-species differences in several parameters. The data should be useful for artificial fertilization and for cryopreservation of sturgeon sperm.