Abstract
The study dealt with the improved brood production technique using cryopreserved
spermatozoa of catla (Cath calla) and mrigal (Cirrhinus cirrhosis) at the field level. The
sperm cryopreservation protocols of both species were standardized. The biology of
fresh spermatozoa, suitable activation solution, toxicity of cryoprotectant to
spermatozoa, suitable ratio of extenders and cryoprotectants and their combination in
the diluents were evaluated. For evaluating the quality, spermatozoa parameters such
as volume, concentration, pl-I, osmolality, and motility of fresh spermatozoa were
observed and the mean values Of their parameters were found 1.1±0.05 ul/g,
7.87x109±O.8 cells/ml, 8.2±0.7, 279.7±5YJ mOsmol/kg, and for catla and
5.6±1.8 gl/g, 7.1x109±1.8 cells/ml, 7.7±0.2, 288.1±10.1mOsmol/kg, and 96.1±1.1 % for
mrigal, respectively. Activation of spermatozoa motility was increased with increasing
concentration of the extending media, and motility found highest at 0.4% NaCl and
severely inhibited at 1 % NaCl. The toxicity of cryoprotectant (DM*) and methanol) to
spermatozoa was tested at the concentrations of 5%, 10%, and 15% at a incubation time
for 5-40 min. Cryoprotectants with 5% and 10% concentrations of DMSO produced
significantly (p<O.05) better motility during 5 and 10 min incubation. Two extenders
Alsevefs solution and egg-yolk citrate, and Lwo cryoprotectants DMSO and methanol
were used for cryopreservation of spermatozoa. Alsever's solution with DMSO at a
ratio of 1:9 showed the best performance producing 90.33±1.52% and
equilibration and post-thaw spermatozoa motility for catla and and 90±1.8%
equilibration and post-thaw spermatozoa motility for mrigal, respectively. The motility
Of cryopreserved sperm was checked weekly up to 8 weeks, and it was observed that
the motility decreased over the storage time. Four-week and 8-week stored
spermatozoa for both species were used in breeding tTia1s in two private hatcheries of
Mymensingh, and the fertilization and hatching rates of eggs were evaluated at field
level. For catla, 4-week stored spermatozoa produced fertilization and
53.33±0.57 % hatching; whereas 8-week stored spermatozoa produced
fertilization and 51.33±0.57 % hatching, respectively. Similarly the fertilization and
hatching rates using I-week and 8-week cryostnred sperm were 69.66±3.21 % and
and 64.66L1.15% and respectively for mrigal. The. growth
and survival of cryopreserved sperm originated seed were compared to those of
control fry up to II weeks and no significant differences (p>O.05) were found either in
growth (length weight) or in survival. The genotypes of produced broods were also
analyzed using DNA microsatellite markers to compare with their parents, and it was
found that the observed genotypes of offspring maintain the Mendelian rules. The
research suggested that this technique might be used in field level to produce
improved broods as well as quality seeds in commercial aqua farming