Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mutation speeds up sperm of zebra finches

18.07.2017

In zebra finches, sperm velocity and morphology and hence reproductive success strongly depend on a specific mutation on one of the sex chromosomes. Scientists of the Max Planck Institute for Ornithology in Seewiesen found that those males that possess two different versions of the chromosome, one regular and one inverted, benefit from an optimal sperm design. However, the genetically inferior types cannot go to extinction as for the ideal morphology a combination of both forms is needed (heterozygotes), which is not possible without also producing the suboptimal types (homozygotes). According to the scientists, this effect can partly explain infertility in zebra finch males.

The “goal” of each sperm is fertilizing the ovum, which implies winning a fierce race through the long female reproductive tract. The competitors in this race are the “sibling” sperm from the same male, but often also sperm from other males. Given such competition and the resulting strong selection, it is inevitable that only the fittest reproduce. In the course of evolution, the best sperm design will thus have prevailed. In a small Australian songbird, the zebra finch, however, scientists have still found sperm of various morphology and velocity.


Gene inversion gives reproductive advantage to zebra finches

Wolfgang Forstmeier / MPI for Ornithology


Sperm cell consisting of a head which contains the genomic DNA and the acrosome, a midpiece which harbors the mitochondria for energy production and a tail which generates propulsion.

Pavlína Opatová / Czech Academy of Sciences

Together with colleagues from the Czech Republic, researchers from the Max Planck Institute for Ornithology in Seewiesen found that an inversion of a large fragment of the sex chromosome Z is responsible for sperm design, with immediate consequences for sperm swimming speed and hence for fertilization rate and for a male’s reproductive success.

Every male possesses two Z chromosomes, one of which they inherited from the mother and one from the father. Z chromosomes exist in two versions, the regular one (A) and the inverted type (B). “Only if a male possesses both types, meaning that it is heterozygous AB instead of homozygous AA or BB, the male’s sperm show a long midpiece which contains the motor for fast swimming” says Ulrich Knief, first author of the study.

Animals with two identical forms of the Z chromosome (i.e. the homozygous males) cannot produce the superior sperm and hence show lower fertilization rates. The study is based on paternity analyses of 435 males in the absence of sperm competition and another 482 males under competition with other males. The study clearly shows that heterozygous males had higher fertilizing success under both conditions.

The superior sperm of heterozygous males can reduce fertility problems, but heterozygous males will always produce 50% homozygous sons, such that the genetic variation in the population does not get depleted, because the optimal genotype cannot go to fixation. For many years, the evolutionary biologist Wolfgang Forstmeier has been puzzled by the high rates of infertility in this species, asking why evolution seems unable to fix this problem despite strong selection against infertile males.

“This study is a first step into the direction of answering this question” says Forstmeier. “With an inheritance system with two sets of chromosomes, evolution is stuck when only the combination of both creates the perfect genotype.”

While the researchers from Seewiesen were interested in the fitness consequences of the Z chromosome inversion, another group of scientists from the lab of Jon Slate from the University of Sheffield arrived at the same results through a wholly different approach. These scientists examined specific breeding lines of zebra finches, which had been selected for either short or long sperm.

In a genome-wide search for variants affecting sperm morphology they independently discovered the Z chromosome inversion. Their study can thus show that the relevant genetic information for sperm morphology is almost exclusively found on this sex chromosome.

“Rather than being redundant, the studies nicely complement each other by the fact that two research teams arrived at the same conclusion coming from very different approaches” explains Bart Kempenaers, senior author of the study.

Contact:
Prof. Dr. Bart Kempenaers
Max Planck Institute for Ornithology, Seewiesen
Department Behavioural Ecology & Evolutionary Genetics
Phone: +49 172 835 1578
E-Mail: b.kempenaers@orn.mpg.de

Dr. Ulrich Knief
Ludwig Maximilian University of Munich
Division of Evolutionary Biology
Phone: +49 89 2180 74101
E-Mail: knief@biologie.uni-muenchen.de

Publication:
DOI 10.1038/s41559-017-0236-1

Dr. Sabine Spehn | Max-Planck-Institut für Ornithologie
Further information:
http://www.orn.mpg.de

More articles from Life Sciences:

nachricht Seeing on the Quick: New Insights into Active Vision in the Brain
15.08.2018 | Eberhard Karls Universität Tübingen

nachricht New Approach to Treating Chronic Itch
15.08.2018 | Universität Zürich

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

Im Focus: Lining up surprising behaviors of superconductor with one of the world's strongest magnets

Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur

What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

2018 Work Research Conference

25.07.2018 | Event News

 
Latest News

Unraveling the nature of 'whistlers' from space in the lab

15.08.2018 | Physics and Astronomy

Diving robots find Antarctic winter seas exhale surprising amounts of carbon dioxide

15.08.2018 | Earth Sciences

Early opaque universe linked to galaxy scarcity

15.08.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>