Sperm competition during the passage through the female reproductive tract in birds

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H03902
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Animal production science
• Research Institution: Shizuoka University
• Principal Investigator: Sasanami Tomohiro 静岡大学, 農学部, 教授 (80322139)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 受精 / 輸卵管 / 精子貯蔵管 / 精子 / 鞭毛 / ウズラ

Outline of Final Research Achievements

During passage through the female reproductive tract, the spermatozoa massively decrease in number, and only a small number of sperm are able to reach the site of fertilization. However, the exact mechanism of sperm selection is poorly understood. Here, we investigated sperm entry into the sperm storage tubules (SSTs) and subsequent fertilization success under a competitive situation created by artificial insemination of a sperm mixture obtained from two males. We found paternity of embryos was biased towards males with longer flagellum when a sperm from the two males strains was artificially inseminated into females. Our novel sperm staining method with two different fluorescent dyes showed that the biased fertilization was due to the better ability of the sperm to enter the SSTs. Our results indicated that sperm competition occurs to win a place in the SSTs, and that filling the SSTs with their own spermatozoa is a critical step to achieve better fertilization success.

Free Research Field

繁殖生物学

Academic Significance and Societal Importance of the Research Achievements

本研究では、受精能力の高い精子の特徴として，鞭毛の長さが重要であることを発見した。また，この精子の形質が精子貯蔵管(SSTs)への侵入に大きな影響を与え，これが父性に大きく影響することも明らかにした。加えて，SSTsに存在する抗酸化物質の発見は，これまで凍結保存が困難であったニワトリ・ウズラ等の家禽精子の液状保存に応用することが可能となり、その波及効果は非常に大きいと考えられる。これらの知見は、人工授精、体外受精等の人工的な授精技術の改良だけでなく、不妊治療および避妊薬の新しい視点からの開発に直接応用可能であることは言うまでもない。