Changes in Mesopotamian spiny eel, Mastacembelus mastacembelus (Bank & Solender in Russell, 1794) (Mastacembelidae) milt quality during a spawning period

Successive seminal collections from Leiarius marmoratus during the reproductive period

This study aim was to verify whether milt quality of male Leiarius marmoratus is maintained among successive samples collected during the same reproductive period. Ten reproductively mature males were used to evaluate four successive sperm samples collected at 10-day intervals. For these collections, seven males were injected with carp pituitary homogenate (CPH) at a dosage of 3.0 mg/kg body weight, in two applications (30% and 70%), at an interval of 10 h. The other three males were administered only saline (control). Injection with CPH or saline occurred prior to each of the four collections. Only one male from the control group released a small volume of milt (0.33 mL), and only during the first collection period. Of the seven males treated with CPH, five released milt during all four collections. Milt volume of the first sample collected (0.63 mL) did not differ from that of other samples (0.59-1.38 mL; P > 0.05). Sperm concentration was greater in the first samples collected (1.98 × 10⁹ spermatozoa/mL) compared to the other samples (0.35 × 10⁹ at 0.92 × 10⁹ spermatozoa/mL; P < 0.05). Sperm motility, curvilinear velocity, straightness, and morphological normality did not differ among the consecutive samples (P > 0.05). Average path velocity, straight-line velocity, oscillation, linearity, progression, and membrane integrity decreased slightly in the samples collected subsequent to the first sample (P > 0.05). In conclusion, milt quality decreased among successive collections; however, quality of all samples from all collections was sufficient for use for fertilization of oocytes.

Development of sperm cryopreservation protocol of endangered spiny eel, Mastacembelus armatus (Lacepede 1800) for ex-situ conservation

The study was conducted to develop sperm cryopreservation protocol for the endangered spiny eel, Mastacembelus armatus as well as to use the cryopreserved sperm in breeding. Activation of sperm was evaluated by observing motility in different osmolalities of NaCl solution (48-319 mOsmol/kg) and found that sperm motility decreased with increasing osmolality of the NaCl solution and it was totally inhibited at 319 mOsmol/kg. The highest motility and swimming duration of sperm were observed as 14.5 ± 0.5 min and 4.75 ± 0.25 min at 128 mOsmol/kg and 67 mOsmol/kg, respectively. The concentration of sperm was found to be 1.75 × 10¹⁰ to 2.25 × 10¹⁰ cells/ml. Evaluation of toxicity of cryoprotectants of dimethyl sulfoxide (Me₂SO) and methanol to sperm was performed at 5, 10 and 15% concentrations during 5-30 min incubation period and found that cryoprotectants with 5 and 10% concentrations produced better motility up to 10 min incubation. In the selection of suitable diluent for cryopreservation of sperm, Alsever's solution with 10% Me₂SO performed best producing 91.67 ± 1.67% and 65 ± 2.89% equilibration and post-thaw motility, respectively. In breeding trials, sperm preserved with Alsever's solution plus Me₂SO produced more or less similar fertilization (82.25 ± 4.46%) and hatching (12 ± 0.65%) to those preserved with 0.9% NaCl solution plus Me₂SO as 79.88 ± 4.67% and 11 ± 0.46% fertilization and hatching respectively. Fresh sperm used as control produced 87.63 ± 3.6% and 14 ± 0.5% fertilization and hatching respectively. Both cryopreserved and fresh sperm-derived fry performed well but the control fry showed a significantly better (P < 0.05) growth. Fry derived from four diluents did not show any significant (P > 0.05) growth difference but Alsever's solution plus Me₂SO produced better results.

Sperm quality of the Amazon catfish Leiarius marmoratus (Gill, 1870) after cold storage

This study aimed at assessing the sperm quality of the Amazon catfish, Leiarius marmoratus ¸ after refrigeration without extenders. After capturing the animals and stripping of semen, the following parameters were analyzed: progressive motility, motility quality score, duration of motility and sperm morphology. An aliquot of fresh semen from each male was kept at room temperature (28 ± 2°C) as a control, for further comparison with cooled semen. The semen from each animal was stored in extenders-free individual syringes. The syringes were kept in ice within polystyrene boxes at 13 ± 2°C. For both fresh and cooled semen, seminal parameters were evaluated every one-hour interval, reaching seven hours of analysis. Fresh semen showed a significant decrease in motility, motility quality score and duration of motility remaining viable only for three hours. Progressive motility of the cooled semen displayed a negative linear pattern (P<0.05). The duration of motility increased (P<0.05), reaching its peak after three hours of storage. The motility quality score showed a quadratic pattern. No statistical differences were observed when sperm morphology was assessed (P>0.05), even though the mean values of total abnormalities have increased over the storage time. Further studies focusing on the application of this technique should be performed, including the addition of extenders and cryoprotectants for preservation of the sperm over longer periods.