Semen cryo-bank of the Malaysian Mahseer (Tor tambroides and T. douronensis)

Abstract

Ex situ conservation of Malaysian Mahseer (Tor tambroides and T. douronensis), the ecologically threatened freshwater fish species in Malaysia via semen cryo-banking was started in 2008 with the mature Tor species from four different locations in Peninsular Malaysia. At current stage, a total of 150 ml semen sample was collected from male fish of 73 T. tambroides and 15 T. douronensis and kept cryo-storage in liquid nitrogen (LN 2 ) in the semen cryo-bank at Freshwater Fisheries Research Centre (FFRC). Sperm motility after cryo-preservation was found to be reduced by an average of 15 and 30% for T. douronensis and T. tambroides respectively; i.e. with prefrozen motility 87.8 ± 7.9% (n = 73) and 88.8 ± 6.7% (n = 15), and post-thaw motility 54.9 ± 14.3% (n = 73) and 74.0 ± 11.2% (n = 15) for T. tambroides and T. douronensis respectively. The mean fertilization and hatching rates by using cryo-preserved semen in T. tambroides were 36.4 ± 10.5% (n = 360) and 34.5 ± 11% (n = 360) respectively; whereas were 89.8 ± 10.2% (n = 360) and 80.2 ± 16.6% (n = 360) respectively for fresh semen. Meanwhile, the survival rate of fry produced from cryo-preserved sperm (97.6 ± 3.1%, n = 360) was equally good (P > 0.05) when compared to the use of fresh sperm (99.7 ± 0.5%, n = 360). Sperm motility (%) during milt collection, before freezing and after thawing of each cryo-preserved semen samples was recorded. These tests were done with sperm from all semen samples and kept up to date into the Fishery Information Network System (INFOFins). The subsequent fertilization capacity and hatching rates of eggs fertilized with sperm from selected cryo-preserved semen sample were also quantified and recorded into INFOFins. Future prospects of the semen cryo-banking of Malaysian Mahseer is also reported and discussed in the present paper.

Sperm Cryopreservation of Some Freshwater Fish Species in Malaysia

“…Duration of sperm motility of Tor spp. was about 40-50 s and it slowed down drastically after 20 s of progressive movements (Chew et al, 2010b). For Isok barb, it was about 20 s and slowed down after 10 s of progressive movements.…”

“…So far only a few indigenous fish species, namely the P. jullieni, Tor spp, H. nemurus, P. nasutus and H. wetmorei were studied. Of which only studies on the P. jullieni, Tor spp., and H. nemurus were reported (Chew et al, 2010a;Chew et al, 2010b;Muchlisin et al, 2004), while studies on other species remain unpublished. The biology, ecology and reproduction biology of these indigenous fish species are described in the following:…”

“…The duration taken for equilibration is the time required for the cryoprotectant to permeate the cells. Equilibration duration between 15 min to 3 h has been practised for Malaysian fish species sperm cryopreservation and was found to be successful in maintaining a good post-thaw sperm motility (Chew et al, 2010b). In most circumstances, the equilibration duration is set at 15 to 30 min, but it can be varied depending on the type and concentration of cryoprotectant used (Tiersch, 2000).…”

“…The use of the vapour shipper method in freezing as reported in Tor spp. (Chew et al, 2010b) was convenient to be used in the field. Such method is simple to use, the cooling rate is more consistent and controllable and it consumes less liquid nitrogen and requires less space compared to the styrofoam cooler box or ice box method.…”

“…In this procedure which is performed after the addition of extender solution and cryoprotectant, the diluted semen sample is packed into polyethylene (PE) straws (Chew et al, 2010a;Chew et al, 2010b) or cryo-vials (Muchlisin et al ,2004). Extended semen sample is subjected to equilibration at temperature <10°C prior to freezing procedure.…”