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Related Concept Videos

Sperm Transport01:15

Sperm Transport

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The journey of sperm from its origin to the point of ejaculation begins within the seminiferous tubules of the testis. Here, Sertoli cells produce fluid that propels non-motile sperm through a series of conduits, starting with the straight tubules leading to the rete testis. This interconnected network of tubules acts as the initial pathway for sperm, guiding them into the efferent ductules and then into the epididymis for maturation.
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Fertilization01:38

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During fertilization, an egg and sperm cell fuse to create a new diploid structure. In humans, the process occurs once the egg has been released from the ovary, and travels into the fallopian tubes. The process requires several key steps: 1) sperm present in the genital tract must locate the egg; 2) once there, sperm need to release enzymes to help them burrow through the protective zona pellucida of the egg; and 3) the membranes of a single sperm cell and egg must fuse, with the sperm...
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Sperm Structure and Semen Composition01:22

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During ejaculation, males release around 2-5 milliliters of semen, which is a complex mixture of mature sperm and various fluids produced by accessory glands. The mature sperm cells measure approximately 60 micrometers in length and consist of a head, neck, midpiece, and tail. The head is flattened and tapered, measuring about 4 to 5 micrometers in length. It contains a nucleus with condensed chromosomes and an acrosome, a cap-like structure filled with enzymes essential for penetrating the...
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Spermatogenesis01:41

Spermatogenesis

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Spermatogenesis is the process by which haploid sperm cells are produced in the male testes. It starts with stem cells located close to the outer rim of seminiferous tubules. These spermatogonial stem cells divide asymmetrically to give rise to additional stem cells (meaning that these structures “self-renew”), as well as sperm progenitors, called spermatocytes. Importantly, this method of asymmetric mitotic division maintains a population of spermatogonial stem cells in the male...
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Spermatogenesis01:22

Spermatogenesis

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Spermatogenesis is a complex process that involves the development of sperm cells from undifferentiated stem cells in the seminiferous tubules of the testes. The process is essential for the production of mature and functional sperm cells that are capable of fertilizing an egg.
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Competition02:34

Competition

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When organisms require the same limited resources within an environment, they may have to compete for them. Competition is a net-negative interaction. Even if two competing individuals or populations do not interact directly, the overall fitness of both competitors is lowered as a result of not having full access to the limited resource.
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Updated: Dec 5, 2025

Assessing Differences in Sperm Competitive Ability in Drosophila
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Assessing Differences in Sperm Competitive Ability in Drosophila

Published on: August 22, 2013

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Within-ejaculate sperm competition.

Andreas Sutter1, Simone Immler1

  • 1School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.

Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
|October 19, 2020
PubMed
Summary
This summary is machine-generated.

Sperm competition, defined 50 years ago, explores fertilization battles between sperm from multiple males. This review highlights the intense, yet understudied, competition among sibling sperm within a single ejaculate.

Keywords:
genetic conflicthaploid selectionmeiotic drivemulti-level selection

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Area of Science:

  • Evolutionary Biology
  • Reproductive Biology
  • Behavioral Ecology

Background:

  • Sperm competition, first defined 50 years ago, is a significant area of research in evolutionary biology.
  • While inter-male sperm competition is well-studied, intra-ejaculate competition among sibling sperm remains poorly understood.
  • The high number of sperm in ejaculates suggests intense competition within a male's own sperm.

Purpose of the Study:

  • To review theoretical models predicting sperm trait evolution under haploid gamete control.
  • To synthesize current evidence for within-ejaculate sperm competition across diverse taxa.
  • To discuss challenges and technological advancements in studying intra-ejaculate sperm competition.

Main Methods:

  • Review of theoretical models on sperm trait evolution.
  • Synthesis of empirical evidence from various animal groups.
  • Discussion of conceptual and methodological challenges.
  • Exploration of novel technologies for studying sperm competition.

Main Results:

  • Parker's theoretical models provide predictions for sperm trait evolution.
  • Evidence for within-ejaculate sperm competition exists across numerous taxa.
  • Significant conceptual and practical hurdles impede the study of this phenomenon.

Conclusions:

  • Intra-ejaculate sperm competition is a crucial but under-explored aspect of reproductive strategies.
  • Further research, aided by new technologies, is needed to fully understand within-ejaculate sperm competition.
  • Understanding this competition offers insights into the evolution of sperm traits and reproductive success.