Cryopreservation of sperm from brown trout ( Salmo trutta m. lacustris L.) and Arctic charr ( Salvelinus alpinus L.)

Abstract

Cryopreservation of brown trout ( Salmo trutta m. lacustris) and Arctic charr ( Salvelinus alpinus) sperm was studied by modifying sperm extenders and the amount of egg yolk (10 or 20%) as a protective component. Glycerol and dimethylsulphoxide (5–25%) in a 0.3 M glucose solution were compared as cryoprotectants for Arctic charr sperm. Milt pellets (ca. 0.05 ml) frozen on dry ice (−79°C) were stored in liquid nitrogen (−196°C). Fertilization rates with cryopreserved sperm ranged from 31 to 85% of the controls (fresh sperm) for brown trout and from 25 to 75% for Arctic charr. The storage time did not change these values, and only a minor part of the variation was caused by the type of extender. In brown trout, the fertilization procedure had a pronounced effect on post-thaw fertility. The highest fertilization rate was achieved when the eggs were inseminated using the fertilization diluent of Billard (1977) and water was added 5–6 min after the sperm. Addition of egg yolk to the extenders increased the fertilization rates in brown trout. For protection of Arctic charr sperm, glycerol proved to be better than DMSO. The crycprotective potential of both agents was dependent on the concentration. The highest fertilization rate was obtained by combining the optimal glycerol level (20%) with either 0.3 M glucose or Mounib's (1978) media.