Apical Sperm Hook Morphology Is Linked to Sperm Swimming Performance and Sperm Aggregation in <i>Peromyscus</i> Mice
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 relativel...
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-09-01
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| Series: | Cells |
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| Online Access: | https://www.mdpi.com/2073-4409/10/9/2279 |
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| author | Kristin A. Hook Lauren M. Wilke Heidi S. Fisher |
| author_facet | Kristin A. Hook Lauren M. Wilke Heidi S. Fisher |
| author_sort | Kristin A. Hook |
| collection | DOAJ |
| description | 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 <i>Peromyscus</i> 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 <i>Peromyscus leucopus</i> 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. |
| first_indexed | 2024-03-10T07:48:57Z |
| format | Article |
| id | doaj.art-041e613dd7544f7f8fb901d4cad1e274 |
| institution | Directory Open Access Journal |
| issn | 2073-4409 |
| language | English |
| last_indexed | 2024-03-10T07:48:57Z |
| publishDate | 2021-09-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Cells |
| spelling | doaj.art-041e613dd7544f7f8fb901d4cad1e2742023-11-22T12:23:37ZengMDPI AGCells2073-44092021-09-01109227910.3390/cells10092279Apical Sperm Hook Morphology Is Linked to Sperm Swimming Performance and Sperm Aggregation in <i>Peromyscus</i> MiceKristin A. Hook0Lauren M. Wilke1Heidi S. Fisher2Department of Biology, University of Maryland, College Park, MD 20815, USADepartment of Biology, University of Maryland, College Park, MD 20815, USADepartment of Biology, University of Maryland, College Park, MD 20815, USAMammals 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 <i>Peromyscus</i> 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 <i>Peromyscus leucopus</i> 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.https://www.mdpi.com/2073-4409/10/9/2279sperm aggregationsperm morphologysperm motility |
| spellingShingle | Kristin A. Hook Lauren M. Wilke Heidi S. Fisher Apical Sperm Hook Morphology Is Linked to Sperm Swimming Performance and Sperm Aggregation in <i>Peromyscus</i> Mice Cells sperm aggregation sperm morphology sperm motility |
| title | Apical Sperm Hook Morphology Is Linked to Sperm Swimming Performance and Sperm Aggregation in <i>Peromyscus</i> Mice |
| title_full | Apical Sperm Hook Morphology Is Linked to Sperm Swimming Performance and Sperm Aggregation in <i>Peromyscus</i> Mice |
| title_fullStr | Apical Sperm Hook Morphology Is Linked to Sperm Swimming Performance and Sperm Aggregation in <i>Peromyscus</i> Mice |
| title_full_unstemmed | Apical Sperm Hook Morphology Is Linked to Sperm Swimming Performance and Sperm Aggregation in <i>Peromyscus</i> Mice |
| title_short | Apical Sperm Hook Morphology Is Linked to Sperm Swimming Performance and Sperm Aggregation in <i>Peromyscus</i> Mice |
| title_sort | apical sperm hook morphology is linked to sperm swimming performance and sperm aggregation in i peromyscus i mice |
| topic | sperm aggregation sperm morphology sperm motility |
| url | https://www.mdpi.com/2073-4409/10/9/2279 |
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