Functional sperm assessments of African Lion Panthera leo (Mammalia: Carnivora: Felidae) in field conditions

Wild African Lion Panthera leo populations are decreasing due to inbreeding and reduced genetic variability. Thus, the use of assisted reproduction in the species could one day become essential. Before this is possible, however, studies need to be conducted on the basic reproductive traits of the species, especially those regarding sperm cells. This study aimed to analyze the semen of African Lions in field conditions. We included seven captive African Lions in our study. The animals were chemically restrained and electro-ejaculated. Twenty sperm samples were selected and analyzed for sperm motility and progressive motility, sperm motility index, and sperm morphology. In addition, the samples were analyzed for membrane and acrosome integrity (hypoosmotic swelling test and fast green/rose Bengal dyes, respectively) and assessed for cytochemical activity of the mitochondria. We found that sperm motility rate was 75.25%±2.03, progressive motility rate was 3.25%±0.10, and sperm motility index was 70.12%±1.71. We found morphologic abnormalities roughly at the expected rate with 34.61%±7.22 of the sperm cells having an intact plasma membrane and acrosome integrity of 92.27%±2.73; high mitochondrial activity was 54.26±4.88% and absence of mitochondrial activity was 2.72±0.68% in the sperm cells. These findings show that conventional tests for sperm motility and sperm morphology bring about the expected results for lions according scientific literature. Though a hypoosmotic swelling test may be performed using different concentrations, it might lead to a higher number of sperm cells with membrane damage. Fast green/rose Bengal stain and 3’3 diaminobenzidine assay, however, can be used in sperm analysis of lions in field conditions.