Relationships between reproductive characteristics in male Vimba vimba L. and the effects of osmolality on sperm motility

In Vimba vimba, GSI, sperm volume, and spermatozoa concentration range from 3.4-7.4 %, 0.1-1.1 ml, and 13.3-34.8 × 109 spz ml−1, respectively. Gonad mass (r = 0.90) and sperm volume (r = 0.35) significantly correlated with weight of males. Significant correlation was also found between gonad mass and length of males (r = 0.85). Sperm motility (r = 0.99) and velocity (r = 098) significantly decreased after activation in Tris-HCl 20 mM, pH 8.5. Osmolality of the seminal plasma was 273.2 mOsmol kg−1. Sperm motility and velocity were significantly affected by the osmolality of the activation medium (P < 0.01). Hyper-osmolality compared to seminal plasma osmolality totally suppressed the sperm activation. At 15 s post-activation, the sperm motility significantly decreased at 240 mOsmol kg−1 in KCl or NaCl media. The highest sperm motility and velocity (at 60 s post-activation) were observed at 200 mOsmol kg−1 in NaCl, KCl, or sucrose media. In all treatments, the tip of the flagellum of spermatozoa became curled into a loop shape after activation of sperm in distilled water containing 20 mM Tris-HCl, pH 8.5 that shortened the flagellum.