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Why small males have big sperm: dimorphic squid sperm linked to alternative mating behaviours
BACKGROUND: Sperm cells are the target of strong sexual selection that may drive changes in sperm structure and function to maximize fertilisation success. Sperm evolution is regarded to be one of the major consequences of sperm competition in polyandrous species, however it can also be driven by ad...
Autores principales: | , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
BioMed Central
2011
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3176235/ https://www.ncbi.nlm.nih.gov/pubmed/21831296 http://dx.doi.org/10.1186/1471-2148-11-236 |
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author | Iwata, Yoko Shaw, Paul Fujiwara, Eiji Shiba, Kogiku Kakiuchi, Yasutaka Hirohashi, Noritaka |
author_facet | Iwata, Yoko Shaw, Paul Fujiwara, Eiji Shiba, Kogiku Kakiuchi, Yasutaka Hirohashi, Noritaka |
author_sort | Iwata, Yoko |
collection | PubMed |
description | BACKGROUND: Sperm cells are the target of strong sexual selection that may drive changes in sperm structure and function to maximize fertilisation success. Sperm evolution is regarded to be one of the major consequences of sperm competition in polyandrous species, however it can also be driven by adaptation to the environmental conditions at the site of fertilization. Strong stabilizing selection limits intra-specific variation, and therefore polymorphism, among fertile sperm (eusperm). Here we analyzed reproductive morphology differences among males employing characteristic alternative mating behaviours, and so potentially different conditions of sperm competition and fertilization environment, in the squid Loligo bleekeri. RESULTS: Large consort males transfer smaller (average total length = 73 μm) sperm to a female's internal sperm storage location, inside the oviduct; whereas small sneaker males transfer larger (99 μm) sperm to an external location around the seminal receptacle near the mouth. No significant difference in swimming speed was observed between consort and sneaker sperm. Furthermore, sperm precedence in the seminal receptacle was not biased toward longer sperm, suggesting no evidence for large sperm being favoured in competition for space in the sperm storage organ among sneaker males. CONCLUSIONS: Here we report the first case, in the squid Loligo bleekeri, where distinctly dimorphic eusperm are produced by different sized males that employ alternative mating behaviours. Our results found no evidence that the distinct sperm dimorphism was driven by between- and within-tactic sperm competition. We propose that presence of alternative fertilization environments with distinct characteristics (i.e. internal or external), whether or not in combination with the effects of sperm competition, can drive the disruptive evolution of sperm size. |
format | Online Article Text |
id | pubmed-3176235 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2011 |
publisher | BioMed Central |
record_format | MEDLINE/PubMed |
spelling | pubmed-31762352011-09-20 Why small males have big sperm: dimorphic squid sperm linked to alternative mating behaviours Iwata, Yoko Shaw, Paul Fujiwara, Eiji Shiba, Kogiku Kakiuchi, Yasutaka Hirohashi, Noritaka BMC Evol Biol Research Article BACKGROUND: Sperm cells are the target of strong sexual selection that may drive changes in sperm structure and function to maximize fertilisation success. Sperm evolution is regarded to be one of the major consequences of sperm competition in polyandrous species, however it can also be driven by adaptation to the environmental conditions at the site of fertilization. Strong stabilizing selection limits intra-specific variation, and therefore polymorphism, among fertile sperm (eusperm). Here we analyzed reproductive morphology differences among males employing characteristic alternative mating behaviours, and so potentially different conditions of sperm competition and fertilization environment, in the squid Loligo bleekeri. RESULTS: Large consort males transfer smaller (average total length = 73 μm) sperm to a female's internal sperm storage location, inside the oviduct; whereas small sneaker males transfer larger (99 μm) sperm to an external location around the seminal receptacle near the mouth. No significant difference in swimming speed was observed between consort and sneaker sperm. Furthermore, sperm precedence in the seminal receptacle was not biased toward longer sperm, suggesting no evidence for large sperm being favoured in competition for space in the sperm storage organ among sneaker males. CONCLUSIONS: Here we report the first case, in the squid Loligo bleekeri, where distinctly dimorphic eusperm are produced by different sized males that employ alternative mating behaviours. Our results found no evidence that the distinct sperm dimorphism was driven by between- and within-tactic sperm competition. We propose that presence of alternative fertilization environments with distinct characteristics (i.e. internal or external), whether or not in combination with the effects of sperm competition, can drive the disruptive evolution of sperm size. BioMed Central 2011-08-10 /pmc/articles/PMC3176235/ /pubmed/21831296 http://dx.doi.org/10.1186/1471-2148-11-236 Text en Copyright ©2011 Iwata et al; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Research Article Iwata, Yoko Shaw, Paul Fujiwara, Eiji Shiba, Kogiku Kakiuchi, Yasutaka Hirohashi, Noritaka Why small males have big sperm: dimorphic squid sperm linked to alternative mating behaviours |
title | Why small males have big sperm: dimorphic squid sperm linked to alternative mating behaviours |
title_full | Why small males have big sperm: dimorphic squid sperm linked to alternative mating behaviours |
title_fullStr | Why small males have big sperm: dimorphic squid sperm linked to alternative mating behaviours |
title_full_unstemmed | Why small males have big sperm: dimorphic squid sperm linked to alternative mating behaviours |
title_short | Why small males have big sperm: dimorphic squid sperm linked to alternative mating behaviours |
title_sort | why small males have big sperm: dimorphic squid sperm linked to alternative mating behaviours |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3176235/ https://www.ncbi.nlm.nih.gov/pubmed/21831296 http://dx.doi.org/10.1186/1471-2148-11-236 |
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