Effect of cryoprotectants, extenders and freezing rates on the fertilization rate of frozen striped catfish, Pangasius hypophthalmus (Sauvage), sperm

S. Kwantong, A.N. Bart-2003

Aquaculture Research, 34(10): 887 

Abstract:

The effects of four cryoprotectants (methanol, MeOH; dimethyl sulphoxide, DMSO; dimethyl acetamide, DMA; and ethylene glycol, EG), three extenders (calcium-free Hanks' balanced salt solution, C-F HBSS, Hanks' balanced salt solution, HBSS and sodium chloride, NaCl) and two different freezing procedures (one- and two-step) on the cryopreservation of striped catfish (Pangasius hypophthalmus (Sauvage)) sperm were investigated. Sperm were frozen using a controlled-rate freezer in 250 µL straws and stored for 2 weeks in a liquid nitrogen (LN₂) container. They were then airthawed at room temperature, and fertilization, motility and viability were assessed. The highest fertilization rate of 41% (81% of control) was achieved with the combination of 12% DMSO and 0.9% NaCl using a one-step freezing procedure (10°C min^-1). Also, DMA resulted in a higher fertilization rate (30% or 51% of the control) than MeOH (18% or 38% of the control) or EG (8% or 12% of the control). In addition, the three extenders used did not affect fertilization rates after cryopreservation with each cryoprotectant. There were no significant differences among the three cryoprotectant concentrations and between the one- and two-step freezing procedures. However, fertilization rates of cryopreserved sperm were significantly lower than the controls (P<0.05). The results of this study indicate that high fertilization rates of striped catfish eggs can be achieved using cryopreserved sperm when frozen at 10°C min^-1 in DMSO or DMA with either 0.9% NaCl or C-F HBSS.

(Aquaculture and Aquatic Resources Management, Asian Institute of Technology, Klong Luang, Box 4, Pathumthani 12120, Thailand. E-mail of A.N. Bart: bart@ait.ac.th)

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