By Dr. Harold Hafs
At first glance, a sperm (Animal Science Image Gallery #5140, shown below) appears to be a relatively simple cell. Upon closer examination, however, Dick Saacke observed some subtle differences among sperm. For example, sperm from bull 1 (upper left in #5140) have longer heads than those from bull 2 (upper right in #5140). In other words, these two bulls had morphologically distinctive heads that could be identified even when sperm from the two bulls was mixed as in the lower two photos in #5140. These kinds of anatomical differences affect fertility, because they are associated with differences in the ability of sperm to penetrate an ovum.
Saacke later described the ultrastructural details of each of the main regions of a sperm. ASIG #5087 (shown below) is a summary of those studies, including detailed drawings of the head and each of the three major parts of the tail. Image 2a from #5087 (below) shows some of the complexity of the junction between the head and tail of a sperm, a weak point subject to breaking.
Taking advantage of this new information on sperm anatomy, Saacke and others developed improved sperm preservation methods that delayed morphological changes associated with sperm aging. ASIG #5074 (type 5074 in search box at ASIG to view) captures 7 images that summarize much of this information, with both light microscope and electron microscope photos of sperm during aging.
These studies over three decades are an outstanding example of the evolution of basic information and its practical application to preserving sperm at liquid nitrogen temperatures. Thereby, frozen bull sperm may be preserved for practical purposes almost indefinitely, thus enabling artificial insemination of cows world-wide with semen from any bull regardless of the bull’s location.
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Original creator of ASIG #5087: Vada Holter. Digital creator: Dick Saacke
Original and digital creator of ASIG #5140: Dick Saacke