Unusual motility characteristics of sperm of the spotted wolffish

Unlike the sperm of most teleosts, that of the spotted wolffish Anarhichas minor is motile on stripping, remains motile for at least 2 days and loses motility when exposed to sea water. Computer assisted sperm analysis (CASA) was used to quantitatively examine the motility characteristics of spotted wolffish sperm. Straight line velocity (VSL), beat cross frequency (BCF) and percentage motility were the most sensitive indicators of movement. Sperm trajectories were very different to those of other teleosts examined, showing large side-to-side movements of the sperm head and a more wiggly' behaviour which may be an adaptation to swimming in the viscous gelatinous egg mass. VSL was not altered by pH from 5.0 to 9.0, but was lower at pH4.5. It was highest at 200 to 500mOsm and decreased rapidly at 200mOsm and more slowly at >500mOsm. It is suggested that the unusual characteristics of spotted wolffish sperm in its trajectory and duration of motility, its release in a fully activated state and its greatly decreased motility in both fresh and sea water are related to a spawning strategy involving mixing of sperm with eggs contained in a gelatinous mass rather than release directly into water in proximity to the ova. Copyright 2002 Published by Elsevier Science Ltd on behalf of The Fisheries Society of the British Isles.