Sperm motility and seminal fluid composition in the burbot, Lota lota

Abstract

Sperm motility and composition of the seminal fluid in Lota lota were investigated. Fives after motility initiation, 88.2 ± 12.4% of the spermatozoa were motile, their mean average path swimming velocity was 61.6 ± 16.3 μm s−1 and their principal swimming type the linear motion (77.4 ± 20.9%). In distilled water the rate of motile spermatozoa decreased to 0% in 40s. In 25–50 mosmol kg−1 electrolyte (NaCl) or non-electrolyte (glucose, sucrose) solutions, motility was prolonged for 10s and these solutions can therefore increase the efficiency of artificial fertilization when used for sperm motility activation. When semen was diluted in electrolyte or non-electrolyte solutions with osmolalities higher than 50 mosmol kg−1, sperm motility rates and swimming velocities decreased, and at osmolalities of 400 mosmol kg−1 motility was completely suppressed. In the seminal fluid with an osmolality of 290.08 ± 45.22 mosmol kg−1, sodium levels of 139.86 ± 23.79 mmol × 1−1, potassium levels of 11.59 ± 2.45 mmol × 1−1 and calcium levels of 0.20 ± 0.08 mmol × 1−1, sperm motility was inhibited. Under in vitro conditions, artificial saline solutions resembling the seminal plasma composition and 400 mosmol kg−1 NaCl or glucose solutions were useful as motility inhibiting solutions for predilution of semen. Sperm motility was not affected by pH 7.5–9.0, but at pH 6 the motility rate and the swimming velocity were reduced; seminal fluid pH was 8.47 ± 0.02. Therefore buffering of the artificial saline solutions can provide more stabile conditions for semen during storage and activation. Temperature optimum of semen was between 2 and 5°C. At higher temperatures semen became spontaneously motile. Therefore, controlled temperature conditions are an important factor for handling of semen. The qualitative, organical composition of seminal fluid was similar as in other fresh water teleosts.