Spermatozoa motility traits of chub (Squalius cephalus L.) under the influence of various water factors

Spermatozoa of different species are characterised by specific traits of movement and sensitivity spectrum to individual environmental factors. The present study aimed to evaluate spermatozoa motility traits and the effect of some water factors such as osmolality, sodium, potassium concentration, and pH on chub spermatozoa movement characteristics. Motility parameters characterising spermatozoa motility were determined using computer-assisted sperm analysis (CASA) and standardised conditions. Other features were also determined, such as the composition of seminal plasma and purine and pyridine nucleotide concentration in spermatozoa. The milt volume of chub from a natural watercourse ranged from 0.5 to 3.5 mL, and the mean spermatozoa concentration was 21.5 × 109 mL−1. Percentage of motile spermatozoa varied from 70% to 99%. Spermatozoa achieved VCL velocity of 53.7 µms−1, LIN of 75.0%, ALH of 0.85 µm, BCF of 15.4 Hz at 10 s post-activation and motility duration of 40 s in distilled water at 15°C and pH 8. The increasing osmolality of the external environment increased motility duration and slightly improved velocity. Motility duration was prolonged in sodium and potassium chloride solutions compared to non-ionic sugar solutions. In order to trigger the best chub’s spermatozoa motility trait, an ionic solution of osmolality of 150–200 mOsm kg−1 and pH 7–8 should be used. Osmolality close to the osmolality of seminal plasma 280 mOsm kg−1 immobilises spermatozoa. In seminal plasma, higher dispersion between the Na+ and K+ concentration was detected in chub compared to other representatives of Cypriniformes. The mean ATP concentration in immotile spermatozoa was 37.9 pmol 10−6 cells. Although some peculiarities in milt were detected, the spermatozoa motility traits of chub and its sensitivity to the environment are typical for Cypriniformes. Research in fish from different taxa according to their sensitivity to environmental components should continue as they differ from each other.