A diluent for prolonged motility of ocean pout (Macrozoarces americanus L.) sperm

The present study describes a new semen diluent (diluent C) which prolongs the sustained motility of ocean pout sperm, a distinguishing feature of the sperm of internally fertilizing teleosts. Sperm motilities were compared i n the new diluent (C), based on the ionic composition of ocean pout seminal plasma, vs. four other semen diluents (A, B, D and E) ordinarily used for extending the semen of external fertilizers. While sperm retained motility after extension of ocean pout semen in all of these diluents, motility was significantly reduced following sperm resuspension in diluents B and D. Sin ce sperm motility remained high in diluent C, formulated to closely mimic t he composition of ocean pout seminal plasma, it was selected for additional experimentation. Negative effects were observed on sperm motility after di lution (> 1:10) of ocean pout semen with diluent C, but sperm motility coul d be restored by replacement of the seminal plasma. Of practical importance for storage of ocean pout sperm at 4 degrees C, it was shown that semen di lution 1:3 in diluent C preserved sperm motility beyond 5 days. Although oc ean pout sperm tolerate a fairly wide range of K+ levels (0-30 mmol/l), the best motility was observed from 10-20 mmol/l [K+], similar to the ionic le vels found in seminal plasma. Finally, since no change in fertility of ocea n pout sperm occurred following 1:3 dilution of semen in diluent C, we conc lude that diluent C is an effective medium for in vitro artificial egg inse mination and prolonged motility of ocean pout sperm. (C) 1999 Elsevier Scie nce B.V. All rights reserved.