Effect of freezing rate for cryopreservation of Persian sturgeon (Acipenser persicus) spermatozoa.

This study examined the effect of freezing rate (-10 °C, -15 °C, -20 °C, -30 °C, and -40 °C/min) on motility parameters, rates of fertilization and hatching, ATP content, and indices of oxidative stress including thiobarbituric acid reactive substances and carbonyl derivatives of proteins in Persian sturgeon (Acipenser persicus) sperm. After sampling, sperm was diluted in an extender composed of 23.4-mM sucrose, 0.25-mM KCl, and 30-mM Tris-HCl, pH 8.0, containing 10% methanol and subsequently frozen in a programmable freezer. For postthaw sperm that were frozen at a rate of -40 °C/min, sperm motile duration (134 ± 27.01 seconds), sperm motile percent (60 ± 4.1%), fertilizability (72 ± 8.36% for fertilization rate and 65 ± 7.58% for hatching rate), and ATP content (4.8 ± 0.57 nmol/10(8) sperm) were significantly higher than for sperm frozen at any of the four slower rates (P < 0.05). Moreover, sperm cryopreserved using the fastest freezing rate had significantly lower levels of thiobarbituric acid reactive substances (0.5 ± 0.05 nmol/10(8) sperm) and carbonyl derivatives of proteins (41.3 ± 4.9 nmol/10(8) sperm) than sperm cryopreserved using all other freezing rates (P < 0.05). In addition, there is a significant difference (P < 0.05) between fresh sperm and the recovery of cryopreserved Persian sturgeon sperm using programmable freezing with -40 °C/min being the optimal freezing rate among those tested.

Effectiveness of glucose-methanol extender for cryopreservation of Huso huso spermatozoa.

The present approach was designed to evaluate the methanol-glucose extender effects on sperm cryopreservation in beluga sturgeon, Huso huso. Sperm quality was examined by measuring post-thaw sperm motility and fertilizing rate at hatching stage. We first tested the effect of glucose concentration (0, 0.10, 0.15, 0.20 and 0.30M) in a methanol extender on post-thaw sperm motility. The optimal cryopreservation conditions were found to be 0.2M glucose in the extender. Then, motility and fertilization rates of sperm cryopreserved with 0.2M glucose and 10% methanol (GM) were compared to Tris-sucrose-KCl in 10% methanol extender (TSKM). Additionally, sperm motility and fertilizing ability in relation to 15 and 30min equilibration in GM extender before and after cryopreservation were measured. Higher post-thaw sperm motility duration and percentage as well as fertilization rate were obtained with the GM extender when compared to TSKM extender. Equilibration of sperm in extender did not affect the motility quality of either fresh-diluted or frozen/thawed sperm, while fertilization rate showed a significant decline alone after 30min of post-thaw storage. Our results indicated that the use of a simple extender consisting of 0.2M glucose in 10% methanol can be an alternative cryopreservation method to those previously described for sturgeons.

Effects of dietary ß-glucan on the growth and innate immune response of juvenile Persian sturgeon, Acipenser persicus.

The present study evaluated the effects of different levels of dietary ß-glucan (MacroGard(®)) on growth performance and innate immune parameters in juvenile Persian sturgeon (Acipenser persicus). Fish (20.1 ± 0.8 g) were allocated into 12 tanks (15 fish per tank) and triplicate groups were fed a control diet or diets containing 0.1%, 0.2% and 0.3% ß-glucan. After six weeks of daily feeding (3.0% body weight day(-1)), humoral innate immune parameters (serum immunoglobulin (Ig) levels, lysozyme activity and alternative complement activity (ACH50)) and growth parameters (final weight, weight gain, specific growth rate (SGR), food conversion ratio (FCR)) were examined. Innate immune responses (lysozyme activity and ACH50) were significantly higher in 0.2% and 0.3% ß-glucan fed fish (P < 0.05). Similarly, elevated growth performance (final weight, SGR and FCR) was observed in fish fed 1%, 2% and 3% ß-glucan compared to the control group (P < 0.05). However, dietary ß-glucan had no significant effect on survival rate of fish (P > 0.05). These results indicate that ß-glucan can be considered as a beneficial dietary supplement for improving the immune response and growth performance of Persian sturgeon.

Effect of freezing rate on motility, adenosine triphosphate content and fertilizability in beluga sturgeon (Huso huso) spermatozoa.

Broodstock selection programs are currently underway for sturgeon species. To complement and further these selection programs we need to develop sperm cryopreservation procedures. In the present study, we describe the effects of freezing rate (-10°C, -15°C, -20°C, -30°C and -40°C/min) on gamete quality characteristics (i.e., duration of motility (s), motility percentage (%), ATP content (nmol/10(8) cells), fertilization rate (%), and hatching rate (%)) in beluga sturgeon, Huso huso. After sampling, beluga sturgeon sperm were diluted in an extender composed of 23.4mM sucrose, 0.25 mM KCl, and 30 mM Tris-HCl, pH 8.0 containing 10% methanol and subsequently frozen in a programmable freezer. Sperm frozen at -40°C/min resulted in means for duration of motility (134 s), motility percentage (69%), ATP concentration (4.8 nmol/10(8) cells), fertilization rate (72%) and hatching rate (65%) that were higher (P<0.05) than those for slower cooling rates. Based on our results, -40°C/min was the best freezing rate (among those tested) for cryopreservation of beluga sturgeon sperm.

Motility and fertility of cryopreserved semen in Persian sturgeon, Acipenser persicus, stored for 30-60 min after thawing.

We investigated the effect of storage times of frozen-thawed Persian sturgeon (Acipenser persicus) semen on the duration of sperm motility, percentage of motile sperm, and fertilization and hatching rates of fresh sperm and sperm stored for 0, 30, and 60 min at 4°C post-thawing. Frozen thawed semen analyzed immediately after thawing had similar quality characteristics as fresh semen. For cryopreserved semen stored for 30 min after thawing the characteristics did not differ to fresh semen and cryopreserved semen. For cryopreserved semen stored for 60 min a significant decline in the parameters was observed. Fertilization and hatching rates were not affected by storage times of maximally 30 min of storage.

Effects of short-term storage on the motility, oxidative stress, and ATP content of Persian sturgeon (Acipenser persicus) sperm.

The effective short-term storage of semen is essential when processing multiple sperm samples and when semen must be transported from collection sites to hatcheries for the fertilization of ova, or to laboratories for cryopreservation. In the present study, the spermatozoa of Persian sturgeon (Acipenser persicus) were used to evaluate the effects of short-term storage on quality parameters (the percentage of motile cells and the total period of sperm motility), oxidative stress indices, and the ATP content. Spermatozoa cells exhibited >50% motility during 6 days of storage where the average total duration of sperm motility varied from 376.42 ± 80.86 s initially to 19.28 ± 10.96 s after 6 days. No motile spermatozoa were recorded after 9 days of storage. The levels of oxidative stress indices (TBARS and CP) and antioxidant activity (SOD) increased significantly with the storage time. The ATP content also decreased significantly after 2 days of storage. The results of this study may facilitate successful reproduction management and cryopreservation protocols for this endangered fish.

Interrelationships among egg, larvae and maternal characteristics in Persian sturgeon Acipenser persicus

This study was aimed to observe the correlations among egg, larvae and maternal characteristics of Persian sturgeon. A total of 41 females were used and the variables including fertilization rate, incubation survival rate, larvae survival rate during yolk sac absorption (before feeding), and larvae survival rate after first feeding were determined. As a result, fertilization rate was positively correlated with three variables: incubation survival, larvae survival during yolk sac absorption, and GSI (gonadosomatic index). Also, maternal size (age, weight, total length) did not show a significant relation (P > 0.05) with incubation survival, larvae survival during yolk sac absorption and larvae survival at first feeding stage.