Substrate specificity of proteolytic activity in the testes fluid and seminal plasma of the common carp Cyprinus carpio

Effect of seawater temperature and pH on the sperm motility of the European eel

The current climate change situation could bring critical effects for marine species, especially those already considered endangered. Although some species can adapt fast to the environmental changes, it is necessary to get into the worst scenario and develop tools to anticipatedly assess the physiological effects of such environmental change. With this purpose, our study aims to determine the effect of a range of seawater temperatures and pHs on sperm motility in the European eel (Anguilla anguilla). Low seawater pH (6.5-7.4) decreased the eel sperm motility in comparison to the control (pH = 8.2). We also studied the combined effect of the pH of the artificial seminal plasma (the plasma where the sperm cells are suspended) with the pH of Artificial Sea Water (ASW, pH 7.8 or and 8.2). We did not find statistical differences in sperm motility and kinetic parameters caused by the artificial seminal plasma pH. However, seawater pH induced significantly higher values of total sperm motility, and the percentage of fast spermatozoa with a pH of 8.2 in comparison with a pH of 7.8. In contrast, the seawater temperature did not affect sperm motility parameters or sperm longevity. To study the effect of the interaction between seawater temperature and pH on sperm motility, two temperatures: 4 and 24 °C, and two pHs 7.8 and 8.2, were tested. There were significant differences between temperature and pH in several kinetic parameters and, in general, the lowest values were observed in the samples activated at low temperature and low pH (4 °C, pH 7.8). This work suggest that eel sperm motility and kinetics will not be affected by the expected changes in pH or temperature due to the climate change.

Optimization of artificial insemination outcomes of African catfish (Clarias gariepinus) with differing hatchery conditions

The African catfish is one of the most promising warm-freshwater species for aquaculture development in the upcoming years, although there are two primary limitations in its production: less-than-desirable survival rates and low larvae quality. In this study, a novel method of egg fertilization for this species was evaluated which has already been successfully utilized in the production of other finfish. The results indicate that dividing the semen designated for fertilization of eggs into smaller aliquots and adding it to the eggs at 30 s intervals (i.e., 0, 30 and 60 s), after activation of the eggs with water, increased the hatching rate percentage (97.1%) compared to control groups (87.9%) in which the entire portion of semen was added to eggs at the time of water addition for egg activation. Results with repeated evaluations in the field confirmed that eggs with greater biological quality were fertilized at a similar rate using the modified and control methods for fertilization, although when the eggs were of a lesser biological quality, the fertilization rate was greater using the modified methods than the control methods.

Sperm quality in fish: Determinants and affecting factors

Fish sperm quality assessment is helpful for optimizing production and for monitoring the environmental state. Sperm can be monitored relatively easy and, to date, various analyses have been applied and proven to be helpful in this task. Among them, sperm motility parameters such as sperm speed are one of the main performance traits during assisted fish reproduction. Apart from motility the sperm concentration, volume, and seminal plasma pH and osmolality are also frequently evaluated and are the main sperm quality indicators measured in fish sperm. However, other parameters also determine sperm fertilization potential. Recent knowledge reveals several additional parameters of high importance for sperm function. Among them are DNA integration, membrane stability, mitochondria status and enzymatic activity. Measuring all these parameters in fish sperm provides complex knowledge regarding male fertility and helps to improve broodstock maintenance protocols as well as gamete handling and fertilization processes. This review focuses on the presentation of the sperm quality measures for freshwater and marine species of the fish and provides information regarding recent methods of sperm quality evaluation.