Computer-Assisted Sperm Motion Analysis in Measuring Reproductive Effects in Bass

Science Center Objects

The objective of this research is to assess the sensitivity of female and male LMB reproductive capabilities at the time of year when they are physiologically preparing for spawning season (also known as gonad recrudescence).

Figure 1. Largemouth bass, Micropterus salmoides.

Figure 1. Largemouth bass, Micropterus salmoides. Photo by USFWS digital library.

The Science Issue and Relevance: Intersex is a nonspecific term used for a range of gonadal abnormalities in which both male and female characteristics are present in a gonad. It most commonly describes the occurrence of female immature egg cells, or oocytes, within a male gonad. The detection of these abnormalities may be visible by eye but usually are detected by microscopy. Male gamete (sperm cell) quality has been negatively correlated with the degree of feminization in intersex roach (Rutilus rutilus), a fish found in fresh and brackish waters outside the United States; however, such rigorous investigations are generally lacking for popular sportfishes, such as smallmouth bass (Micropterus dolomieu) and largemouth bass (LMB; Micropterus salmoides), outside the Chesapeake Bay watershed. Sperm motility is one of the most important parameters to consider in evaluating the fertilizing ability of sperm, and thus reproductive capability. Sperm quality parameters, in combination with data collected at multiple levels of biological organization (i.e., molecular, organ, individual, and population level), can yield results that describe overall bass condition and identify potential impacts intersex may have on a population. 

Figure 2. An extracted piece of testis from a largemouth bass

Figure 2. An extracted piece of testis from a largemouth bass from which sperm were obtained for assessing sperm motility. The fish were exposed at CERC and mailed overnight to WARC for analysis.

Methodology for Addressing the Issue: The objective is to assess the sensitivity of female and male LMB reproductive capabilities at the time of year when they are physiologically preparing for spawning season (also known as gonad recrudescence). Subjective sperm motility measurements will be performed by computer-assisted sperm motion analysis using male LMB gonads overnighted to WARC from the CERC outdoor experimental systems that mimic the natural environment under controlled conditions, also known as mesocosm exposures.

Future Steps: The sperm motility data will be combined with other biological endpoints including those from histology, immune function assays, gene expression analysis, and spawning data. These data will inform natural resource managers of sportfish and municipal wastewater treatment plants.

 

 

Sperm motility analysis

Figure 3.  An image from computer-assisted sperm motion analysis of largemouth bass sperm motility. The cells’ movement is tracked, where the green lines indicate progressive movement, the blue color reflects less motile cells, and the red are immotile.