Eighteen spermiating males were randomly selected from a hatchery-reared
stock and electronically tagged to record changes in their sperm quality
parameters (spermatozoa morphology, ultrastructure and motility, ionic
composition and osmolality of the seminal plasma, and sperm volume and
density) during the spawning season. Stripping was performed at the
beginning of March, April and May. The Barbus barbus spermatozoon has a head without
acrosome, a midpiece with 4–6 mitochondria and proximal and distal
centrioles, and a flagellum with the typical 9+2 pairs of microtubules.
Apart from posterior width of the midpiece, morphological and
ultrastructural parameters changed significantly during the reproductive
season; generally by decreasing toward the end of reproductive season. Sperm
volume also decreased from 0.42 in March to 0.15 ml in May, and density from
18.81 in March to 12.45 × 109 spz ml−1 in May. Osmolality
(mOsmol kg−1) was 268 ± 4, 276 ± 2 and 268 ± 2 in March,
April and May respectively. Chloride, sodium, calcium and potassium ion
concentrations (mM) did not show significant differences between March and
April (Cl−: 125.3 vs. 120.5, Na+: 75.7 vs. 69.7, Ca2+: 0.4 vs. 0.3 and
K+: 84.7 vs. 84.0). The percentage of motile spermatozoa at 15 s post
activation did not show a significant difference between dates, but the
highest spermatozoa velocity at 15 s post activation was observed in April
(91.4 ± 3.2 µm s−1) and then decreased significantly towards
the end of the reproductive season (80.6 µm s−1 in
May). However, lowest spermatozoa velocity was measured in March (70.4 ± 1.9 µm s−1). This study supports the hypothesis that longer
spermatozoa swim faster. Within one stripping, velocity and percentage
motility decreased significantly with time post activation. In conclusion,
changes observed in B. barbus sperm parameters during the reproductive season, suggest
there is association between such changes and spermatozoa aging processes.