The need for a framework addressing the temporal aspects of fish sperm motility leading to community-level standardization

Authors: Blackburn, Harvey; TORRES, LETICIA - Louisana State University; LIU, YUE - Louisana State University; TIERSCH, TERRENCE - Louisana State University

Submitted to: Zebrafish
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2022
Publication Date: 8/11/2022
Citation: Blackburn, H.D., Torres, L., Liu, Y., Tiersch, T.R. 2022. A framework addressing the temporal aspects of fish sperm motility leading to community-level standardization of assessment. Zebrafish. 19(4):119-130. https://doi.org/10.1089/zeb.2022.0006.
DOI: https://doi.org/10.1089/zeb.2022.0006

Interpretive Summary: Zebrafish sperm cell motility is problematic to assess due to the short life cycle, often less than one minute. This leads to varying points of comparison making it difficult for the research community to assess results across experiments and importantly as samples are prepared for cryopreservation and storage in gene banks. The reported research evaluated various fish sperm motion characteristics over the cell's life cycle. By capturing the dynamics and decay in performance over time three key times for evaluation were identified and these were at 10 sec, 30 sec, and 45 sec. It is suggested laboratories take measurements at all three times. Measuring processes were then placed in the context of a structure designed for the purpose of developing more consistent evaluation protocols across the zebrafish community.

Technical Abstract: Motility is a widely available parameter that can be used to assess sperm quality of aquatic species. Sperm from fishes with external fertilization usually undergo a dynamic and short-lived period of motility after activation. The common practice of assigning a single value at an arbitrary peak of motility is challenging for reproducibility, community-level standardization, and comparisons across studies. This study aimed to explore althernative statistical approaches to standardize motility reporting, and to develop an initial framework for community-level standards. Sperm samples from 14 zebrafish (Danio rerio) with a total of 21,000 cells were analyzed by use of computer assisted sperm analysis (CASA) with data collection starting at 10 sec after activation at 5-sec intervals for 50 sec. Four common motility variables were selected for analyses: VCL (curvilinear velocity), VSL (straight line velocity), BCF (beat cross frequency), and ALH (amplitude of lateral head displacement). Cluster analysis was used to evaluate sperm subpopulations within and among males over time, least square means (LSM) was used to explore temporal aspects, and the first derivative of the regression equations was used to calculate the rate of change for the motility parameters. Cluster analysis proved informative, but overlapping ephemeral clusters were not valuable for providing standardization options. Analysis of temporal aspects and rate of change indicated opportunities for standardization by reporting of overall motility-time functions and stable time windows for motility measurement. These approaches could minimize the inconsistencies caused by male-to-male variation and dynamic changes of subpopulations while providing comparable information. An overall temporal framework was identified for motility reporting along the collection-processing-cryopreservation-thawing process to provide a basis to further efforts of community-level standardization.