Background: Sperm quality and the number of sperm introduced into the uterus during artificial insemination (AI) are pivotal factors influencing pregnancy outcomes. However, there have been no reports on the relationship between sperm concentration at AI and sperm quality in Hanwoo cattle. In this study, we examined sperm quality and pregnancy rates after AI using sperm inseminated at different concentrations. Methods: We evaluated the motility, viability, and acrosomal membrane integrity of sperm at different concentrations (10, 15, 18, and 20 million sperm/straw) in 0.5-mL straws. Subsequently, we compared the pregnancy rates after AI with different sperm concentrations. Results: After freeze-thawing, sperm at the assessed concentrations showed similar viability and acrosomal membrane integrity. After AI, cattle in the 10 million group had significantly lower pregnancy rates compared to those in the 18 and 20 million groups. Conversely, there were no statistically significant variances observed between cattle in the 10 and 15 million groups. Conclusions: Sperm at concentrations of 10, 15, 18 and 20 million per straw exhibited comparable motility, viability, and acrosomal membrane integrity. However, a concentration of at least 18 million sperm per straw is required to achieve a consistent rate of pregnancy rate in Hanwoo cattle after AI.

The ant species, Vollenhovia emeryi Wheeler (Hymenoptera: Myrmicinae) is endemic in East Asia and has invaded into North America. In this species, the queen caste shows polymorphism in its wing morphology; long-winged queen and short-winged queen, and two morphs are thought not to coexist in nature. This research is conducted to 1) deduce the phylogeographical structure of the two wing morphs in South Korea and to trace the distribution pattern from East Asia to North America, and 2) investigate the Wolbachia and WO phage infection frequency of the species. Either individuals or colonies of V. emeryi were collected from 80 locations, encompassing 68 locations in South Korea, 11 in Japan, and one in USA. Among the collected samples in South Korea, the long-winged morph is dominant and considered as the ancestral type, while the short-winged morph is very rare and derived character. The origin of the US population is neither Korea nor Japan at least in this study. However, we do not exclude the possibility that its origin is the other parts of Japan or the other countries. All of the long-winged morph are infected with Wolbachia, while the short-winged seems to be geographically partially infected. It suggests the possibility that the short wing trait is linked with the evolution of resistance to Wolbachia infection. Bacteriophage WO infection status has no correlation with host insect lineage.