Cryopreservation of sperm of Labeobarbus brevicephalus (Pisces: Cyprinidae) from Lake Tana (Ethiopia)

The cryopreservation of the Lake Tana Labeobarbus semen had never been studied before. A combination of three extenders and two cryoprotectants (DMSO and glycerol) were used in Lake Tana Labeobarbus brevicephalus sperm cryopreservation. Among the above described cryo-diluent DMSO 10% had the best performance with all three extenders. Sperm of the L. brevicephalus maintained a higher fertilization rate in the three extenders at a dilution ratio of 1:3 (>= 85%), exceptionally in Extender 2 DMSO 15% sperm displayed lower value 55.9 +/- 0.3%. When pre-frozen cryoprotectants milt diluted at a ratio of 1:9, it provided higher fertilization rates in Extender 1 10% DMSO, Extender 3 glycerol 10% and DMSO 15% (92-97%). Highest equilibration (87.3 +/- 1.5%) and post-thaw (83.0 +/- 1%) motility were obtained from the diluent, Extender 3 plus DMSO 10%, which proved its suitability for preservation of sperm of the L. brevicephalus. The developed protocol suggests formulating an extending medium comprising of Extender 3 with 10% DMSO, 15% DMSO or Extender 1 with 10% DMSO and the dilution ratio of the cryoprotectant to milt should be 1:3. Two different single-step cooling rates (4 and 10 degrees C/min) were used. Additional studies should evaluate the viability, survival, and development of larvae produced from cryopreserved sperm. Besides, for sustainable use of sperm suitable oocyte sperm ratios and the feasibility of cryogenic gene banking should be investigated.

Automated summary

The cryopreservation of Lake Tana Labeobarbus semen was studied for the first time. DMSO 10% showed the best performance in the cryo-diluent, and a suitable preservation protocol was proposed for L. brevicephalus sperm. Further research is needed to evaluate the viability and development of larvae produced from cryopreserved sperm, as well as the sustainability and feasibility of cryogenic gene banking for sperm use.