Retention of sperm motility in turbot, Scophthalmus maximus L.: the effects of time from activation, thermal shock and adenosine triphosphate levels

Four parameters were examined in order to define sperm quality in turbot Scophthalmus maximus L., sperm: (1) sperm motility, measured by direct counts of the number of active spermatozoa, expressed as % of total spermatozoa; (2) retention of motility after activation, measured by direct counts, 0–60min after activation, expressed as a % of the initial level of activity; (3) resistance to thermal stress, measured as change in retention of motility, and (4) adenosine phosphate (ATP) concentration, determined for samples of non-activated sperm. The proportion of motile spermatozoa at activation ranged from 34·8% to 97·6% (mean 76·3%) for the individual males tested. Turbot sperm retained on average 52% (range 27–90%) of its initial activity one hour after activation. Sperm samples which were stressed by cooling to –27°C retained only 8·6% (range 0–25%) of initial activity, compared to control samples which retained 49% (range 38–63%) of initial activity. The retention of motility after activation was not significantly related to the initial motility or the levels of ATP. Concentrations of ATP in turbot sperm (mean 0·46mg ATP/106 spermatozoa, equivalent to 9·2nmol ATP/108 spermatozoa) were comparable to those measured in mammals.