Changes in external osmolality and ionic composition affect Megaleporinus obtusidens sperm motility

L-carnitine solution used on Rhamdia quelen thawed sperm activation boosts sperm movement, maintains larval quality, and permits to optimize the sperm use

The activation of cryopreserved sperm with solutions containing L-carnitine can improve sperm quality after thawing, owing to its involvement in several metabolic pathways. Sperm movement and viability for fertilization, hatching, and larval normality were assessed in Rhamdia quelen thawed sperm activated with L-carnitine solutions. Sperm from 24 males were cryopreserved in 0.25 mL straws. After thawing, the sperm movement was assessed by CASA (Computer-Assisted Sperm Analysis) in samples activated with distilled water containing 0.0 (control), 47.8, 96.2, 144.5, 192.3, and 240.7 mM L-carnitine, and another one with 79.9 mM D-fructose (control). Sperms from another 24 males were cryopreserved in an identical manner and used in the fertilization assays. Considering the sperm movement, fertilization assays were carried out using 0.0, 96.2, and 144.5 mM L-carnitine, and 79.9 mM D-fructose solutions. Greater motility and velocity were achieved with 144.5 mM L-carnitine at 28 and 18 s after activation, respectively. Linearity was not affected by time. The greater mean motility was provided by 144.5 mM as well as the greater mean velocity and linearity by 192.3 mM L-carnitine. Fertilization and hatching were not influenced; however, 144.5 mM L-carnitine and 79.9 mM D-fructose solutions produced more normal larvae. In summary, the L-carnitine solution increased sperm movement and maintained larval quality and production, similar to a conventional fructose activation solution.

Comparing accuracy of fish sperm motility measurements obtained from two computational extremes in tracking approaches: Nearest neighbor and multiple hypothesis tracking

We conducted a study to assess the accuracy of nearest neighbour (NN) and multiple hypothesis tracking (MHT) methods-which are opposite extremes in computational complexity-in determining the percentage of motile sperms and the number of sperms tracked in simulated data of fish sperm movements, and to evaluate the resulting number of tracking errors and analysis duration. Sperm tracking and swimming path assembly were assessed in 36 video clips (1 s length at 100 fps) of emulated Rhamdia quelen sperm kinetics at different densities (50, 100, 200 or 300 spermatozoa in the field of view) and motility rates (30, 60 or 90%). The MHT method accurately estimated the percentage of motile sperms, whereas NN underestimated it by up to 6.59%. Increase in sperm density reduced the number of sperms tracked from both trackers. With more than 50 sperms in the field of view, NN and MHT tracked 73% and 92% of the ground-truth sperm count, respectively. Both trackers showed a quadratic increase in tracking errors with increasing sperm density. The maximum percentage of errors at 90% motility was 12% for NN and 4.7% for MHT. The MHT tracker required up to 150 s to track 300 sperms, whereas NN completed the tracking procedure in less than 0.5 s. On maintaining a density of up to 100 sperms in the field of view, it was possible to obtain high accuracy, low number of tracking errors and an acceptable analysis duration with both tracking methods.

Impact of activation solutions on fresh and frozen-thawed sperm motility and fertilization success for two species of migratory freshwater fishes

Extracellular environment conditions, ionic concentration, pH, osmolality, and temperature influence sperm activation and sperm quality. The aim of this study was to evaluate the effects of different activating solutions on sperm quality and fertilization rate of fresh and post-thaw sperm in Brycon orbignyanus and Prochilodus vimboides. Activation solutions with ions: NaCl, KCl, CaCl₂ (150 mOsm kg^-1), without ions: glucose (150 mOsm kg^-1) and water: reverse osmosis (RO) (∼0 mOsm kg^-1) and tank water (TW) were tested. In experiment 1, fresh sperm motility was activated in each activating solution and motility rate (%), motility quality score (0-5), and motility duration (seconds) were subjectively evaluated using a microscope. In experiment 2, sperm was cryopreserved and post-thaw sperm quality was assessed in each activating solution. Methyl glycol was used as cryoprotectant and for B. orbignyanus a solution of BTS® 5% in water reverse osmosis - 325 mOsm kg^-1 was used as extender, while for P. vimboides it was used a solution of glucose 5% in water reverse osmosis - 325 mOsm kg^-1. In straw, cryoprotectant, extender, sperm were respectively 10%, 80% 10% (V/V). B. orbignyanus fresh sperm activated in NaCl, KCl, glucose solutions, TW and RO yielded higher averages for all the subjective parameters analysed. In fresh sperm of P. vimboides the highest values were observed when glucose solution was used for sperm motility activation, and the highest fertilization rates were observed in samples activated in glucose or RO solutions. B. orbignyanus post-thaw sperm activated in TW (45.1%) or RO (39.7%) presented the highest values for motility. The highest values of curvilinear velocity (VCL) were observed using glucose (69.5 μm s^-1), NaCl (67 μm s^-1) and KCl (68.4 μm s^-1), but the highest fertilization rates were observed when glucose (3.6%), RO (3.5%) and TW (2.5%) were used. P. vimboides post-thaw sperm activated in glucose solution presented the highest motility rate (41%), VCL (43.7 μm s^-1), fertilization rate (18.2%) and hatching rate (13.7%). In order to achieve the best seminal quality, fertilization and hatching rates in both fresh and post-thaw sperm, the glucose solution, TW and RO are indicated for use as sperm motility activators in B. orbignyanus, whereas for P. vimboides the glucose solution and RO are indicated.

Effects on fertility of motile sperm to egg ratio with use of cryopreserved Rhamdia quelen semen at different post-activation times

The aim in the present study was to evaluate the effects of motile sperm:oocyte ratio and the use of thawed spermatozoa at different post-activation times in artificial reproduction of gray catfish (Rhamdia quelen). Cryopreserved sperm samples were evaluated for sperm motility and velocity using Computer Assisted Sperm Analysis (CASA). The sperm activation curves were generated using a non-linear statistical model and were used to assess the spermatozoa velocity after thawing. Thus, the oocytes were mixed with thawed sperm at a motile sperm:oocyte ratio of 70,000, 90,000, 110,000, 130,000, 150,000 and 170,000. The thawed sperm were used at 11, 16 and 30 s after spermatozoa activation. At these times, the sperm velocities corresponded to 52, 37 and 21 μm/s. The effects of experimental factors (spermatozoa:oocyte ratio and time after sperm activation) on oocyte fertilization, egg hatching, and percentage of normal larvae were evaluated. The response surface analysis indicated there was no interaction (P >  0.05) between the motile spermatozoa:oocyte ratio and time after sperm activation on fertilization, hatching or percentage of normal larvae. The time after sperm activation, however, affected (P <  0.05) in a directly proportional waythe oocyte fertilization and egg hatching rates. The time after sperm activation affected the sperm velocity and oocyte fertilization and egg hatching rates. Thus, the use of thawed sperm immediately after sperm activation or with the greatest sperm velocities (11s; 52 μm/s; 62.59% motility) at a relatively lesser motile sperm:oocyte ratio (70,000:1) allows for acceptable fertilization (48.68% for fertilization; 29.61% for hatching) in Rhamdia quelen.