How did you compose this image?
The December 3 Biophysical Journal cover image is a fold of tissue from the utero-vaginal junction of a female zebra finch's reproductive tract, visualized using selective plane illumination microscopy. It shows multiple sperm storage tubules where the female can store sperm after mating. We wanted to convey the complexity of the tissue with its folded structure and the twisting, convoluted tubules packed densely within it. The punctate autofluorescence highlights the entrances to the tubules. You can imagine the difficult journey that sperm make when navigating this space, to be accepted into the storage tubules before ultimately making their way to the ovum.
How does this image reflect your scientific research?
We are a cross disciplinary team of researchers working on reproductive physiology of birds using optical biophysics techniques. We combined our expertise to overcome the challenges of imaging the thick, muscular structure of the female reproductive tract of birds. The image was taken using a label-free method while keeping the tissue alive. In the image, we can see the openings to multiple sperm storage tubules where the female stores sperm in her reproductive tract. Our study is the first description of these structures in 3D and we found a previously unknown structural feature — a constriction at the opening of these tubules, which suggests that female birds can actively select sperm for storage and therefore influence the paternity of their offspring.
Can you please provide a few real-world examples that relate to your research?
We have found a constriction at the opening of the sperm storage tubules which may act as a gate-like structure for the selective storage of sperm. By understanding the selective processes by which the female can perform “quality-control” on sperm after mating has occurred, we can develop strategies to incorporate these selection criteria into artificial insemination and in vitro fertilisation techniques, thereby improving their success. This may be particularly important in captive breeding programs where the availability of fertile individuals is often low and artificial insemination and/or in vitro fertilization are the most feasible options for sustaining the population.
How does your research apply to those who are not working in your specific field?
Although this study was conducted on birds, females of a number of species across the animal kingdom — from birds to reptiles (e.g., snakes) to mammals (e.g., bats) can store sperm in specialized organs like the sperm storage tubules seen in this image. Studies like ours help us understand why the ability to store sperm evolved and how sperm interact with the female reproductive tract during storage. There has been a gap in the tools required for imaging sperm storage organs in 3D. Our work bridges this gap. Ultimately, understanding these post-mating processes will have important implications for fertility research across animals, including in humans.
Do you have a website where our readers can view your recent research?
Readers can read about our work and more on the reproductive physiology of birds at https://nicolahemmings.wordpress.com/. More on developments in light sheet microscopy and its use for studying cellular interactions can be found at https://www.nottingham.ac.uk/engineering/people/tania.mendonca.