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Article

Apical Sperm Hook Morphology Is Linked to Sperm Swimming Performance and Sperm Aggregation in Peromyscus Mice

Department of Biology, University of Maryland, College Park, MD 20815, USA
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Author to whom correspondence should be addressed.
Academic Editor: Ali Honaramooz
Received: 5 June 2021 / Revised: 16 August 2021 / Accepted: 27 August 2021 / Published: 1 September 2021
Mammals exhibit a tremendous amount of variation in sperm morphology and despite the acknowledgement of sperm structural diversity across taxa, its functional significance remains poorly understood. Of particular interest is the sperm of rodents. While most Eutherian mammal spermatozoa are relatively simple cells with round or paddle-shaped heads, rodent sperm are often more complex and, in many species, display a striking apical hook. The function of the sperm hook remains largely unknown, but it has been hypothesized to have evolved as an adaptation to inter-male sperm competition and thus has been implicated in increased swimming efficiency or in the formation of collective sperm movements. Here we empirically test these hypotheses within a single lineage of Peromyscus rodents, in which closely related species naturally vary in their mating systems, sperm head shapes, and propensity to form sperm aggregates of varying sizes. We performed sperm morphological analyses as well as in vitro analyses of sperm aggregation and motility to examine whether the sperm hook (i) morphologically varies across these species and (ii) associates with sperm competition, aggregation, or motility. We demonstrate inter-specific variation in the sperm hook and then show that hook width negatively associates with sperm aggregation and sperm swimming speed, signifying that larger hooks may be a hindrance to sperm movement within this group of mice. Finally, we confirmed that the sperm hook hinders motility within a subset of Peromyscus leucopus mice that spontaneously produced sperm with no or highly abnormal hooks. Taken together, our findings suggest that any adaptive value of the sperm hook is likely associated with a function other than inter-male sperm competition, such as interaction with ova or cumulous cells during fertilization, or migration through the complex female reproductive tract. View Full-Text
Keywords: sperm aggregation; sperm morphology; sperm motility sperm aggregation; sperm morphology; sperm motility
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MDPI and ACS Style

Hook, K.A.; Wilke, L.M.; Fisher, H.S. Apical Sperm Hook Morphology Is Linked to Sperm Swimming Performance and Sperm Aggregation in Peromyscus Mice. Cells 2021, 10, 2279. https://0-doi-org.brum.beds.ac.uk/10.3390/cells10092279

AMA Style

Hook KA, Wilke LM, Fisher HS. Apical Sperm Hook Morphology Is Linked to Sperm Swimming Performance and Sperm Aggregation in Peromyscus Mice. Cells. 2021; 10(9):2279. https://0-doi-org.brum.beds.ac.uk/10.3390/cells10092279

Chicago/Turabian Style

Hook, Kristin A., Lauren M. Wilke, and Heidi S. Fisher 2021. "Apical Sperm Hook Morphology Is Linked to Sperm Swimming Performance and Sperm Aggregation in Peromyscus Mice" Cells 10, no. 9: 2279. https://0-doi-org.brum.beds.ac.uk/10.3390/cells10092279

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