Abstract
Globally there is a trend of declining fertility rates, particularly among urbanised nations. Today there is increasing evidence that reduced fertility in men is associated with increasing age with male factor infertility currently accounting for over a fifth of infertility cases. Parameters associated with spermatozoa quality include; motility types and speed, sperm cell concentration, ATP levels, DNA fragmentation, mtDNA content and Reactive Oxygen Species levels.
Using computer assisted sperm analysis, manual sperm counts, and luciferase ATP assays; motility types and speeds, sperm cell concentration, and ATP levels were investigated. Comparison was made between a total of 105 zebrafish, split between three genetically divergent young and old groups of zebrafish; ABz, SJD and WIK lines. Fluorescent cell staining was used to identify DNA fragmentation and comparison was made between young and old ABz fish. Here significant differences were found between young and old fish in levels of DNA fragmentation, and in all of the kinematic aspects of motility; average path velocity, curvilinear velocity, straight-line velocity as well as linearity and straightness of trajectory. These results suggest the sperm of younger zebrafish are more likely to be successful in fertilisation events as their sperm travel faster and in a more linear fashion than ‘old’ zebrafish sperm whilst also having better genomic integrity.
Complementary to the body of work, the time-course of motility post activation was successfully tracked in 36 samples from 13 zebrafish, illustrating the specific nature of Zebrafish motility.
The results presented have the potential to contribute to further research where zebrafish are used as a model for aging and male specific fertility studies.