Seasonal changes in the milt quality of spotted scat, Scatophagus argus: Implications for artificial propagation

Physiological evaluation of seasonal sperm quality in a biannual spawner, Pacific abalone: Effects on in-vitro fertilization and cryotolerance

Pacific abalone, Haliotis discus hannai, is a highly valuable gastropod mollusk commonly found in Southeast Asia. The present study aims to analyze the seminal plasma quality, sperm quality, and cryotolerance of the Pacific abalone sperm during its reproductive season. The seminal plasma quality was evaluated by analyzing biochemical and metabolite composition, enzymatic activity (superoxide dismutase, catalase, and glutathione), and lipid peroxidation (LPO) activity. The sperm quality was evaluated by analyzing motility, concentration, volume, ATP content, acrosome integrity (AI), plasma membrane integrity (PMI), mitochondrial membrane potential (MMP), DNA integrity, and fertilization potential. The cryotolerance capacity was evaluated by analyzing post-thaw motility, AI, PMI, MMP, and DNA integrity. Seminal plasma osmolarity was significantly higher (1123.3 ± 1.5 mOsmL-1) in May compared to other reproductive periods, with Cl- (516.8 ± 0.5 mM) and Na+ (460.2 ± 0.4 mM) as the dominant ions. The seminal plasma pH remained constant at 6.8 throughout the reproductive season. Improved enzymatic activity and lower LPO were detected in May or June. Sperm quality indicators were similar in May and June, except for sperm production. The fertilization potential (May: 93.0 ± 4.4%, June: 86.0 ± 7.2%) and hatching rate (May: 86.6 ± 5.78%, June: 82.3 ± 3.2%) of Pacific abalone were significantly higher in May or June than they were in other reproductive seasons. The motility (May: 50.19 ± 2.35%, June: 49.96 ± 1.60%), AI (May: 44.02 ± 3.46%, June: 42.16 ± 3.61%), PMI (May: 54.12 ± 3.29%, June: 52.82 ± 2.58%), and MMP (May: 44.02 ± 3.46%, June: 42.16 ± 3.61%) of the cryopreserved sperm were similar in May and June compared with those preserved in other reproductive seasons. The DNA integrity of the cryopreserved sperm was similar in May (80.3 ± 6.7%) or June (78.9 ± 7.4%) and had a higher cryotolerance than in other reproductive seasons. Hence, it can be suggested that May and/or June are suitable periods for sperm physiology experiments, artificial reproduction, and sperm cryopreservation of Pacific abalone.

Carotenoid composition in wild-caught spotted scat (Scatophagus argus) broodstocks: effects on gonad development

The carotenoid reserves of broodstocks have a considerable impact on reproductive performance, maturity, fecundity, spawning, and yolk-sac larvae quality. The purpose of this study was to elucidate the most effective strategy for enriching broodstock in artificial breeding programs by examining changes in the carotenoid profile of wild-caught spotted scat (Scatophagus argus) broodstocks during the reproductive season. The predominant carotenoids such as fucoxanthin, astaxanthin, lutein, and β-carotenoids were examined in muscle, liver, and gonad (testis and ovary) samples from both the genders. The results revealed that total carotenoid levels differed significantly (p < 0.05) among tissues during sexual maturation. The muscle fucoxanthin levels increased gradually (0.014 ± 0 .01 < 0.017 ± 0.00 < 0.019 ± 0.01 mg/100 g) during testicular maturation and were comparatively higher than that of the liver and testis. The astaxanthin content of the ovary was relatively low and increased with ovarian maturation (2.013 ± 0.18 < 6.106 ± 0.28 < 8.871 ± 0.73 mg/100 g). The scat's mature ovary (9.446 ± 0.53 mg/100 g) had a higher concentration of lutein in comparison with testis (0.821 ± 0.07 mg/100 g). In the testis, the highest concentration of β-carotene could be observed during the mature stage (1.765 ± 0.08 mg/100 g). In female scat, the β-carotene content of muscle showed an inverse relationship with maturation indicated by a gradual decrease from immature stage. Finally, it is proposed that carotenoids are preferentially mobilized and conserved in the gonads, which are indispensable to improve gonadal development and the productive potential of S. argus, a leading candidate species.