# The mechanical properties of sperm tails revealed

Scientists at the University of York have shown that a sperm tail utilizes interconnected elastic springs to transmit mechanical information to distant parts of the tail, helping it to bend and ultimately swim toward an egg.

Previous studies, from approximately 50 years ago, showed that the tail, or flagellum, was made up of a complex system of filaments, connected by elastic springs resembling a cylinder-like structure. For many years scientists believed that this system provided the sperm tail with a scaffold, allowing it to swim in a hostile environment toward an egg.

New research at the University of York, however, has shown, through a mathematical model, that this system is not only needed to maintain the structure of the tail, but it is also vital to how it transmits information to very distant parts of the tail, allowing it to bend and move in its own unique way.

Distinct motion

Dr Hermes Gadêlha, mathematical biologist at the University's Department of Mathematics, said: "Sperm flagella with this sort of internal structure can be seen in almost all forms of life. Interestingly, although the sperm tail has an that is conserved across most species – animal and human - they all create slightly different movements in order to reach an egg.

"This suggests that the tail's structure is not the whole story to how they make their distinct tail-bending ."

Dr Gadêlha and collaborators had previously developed a mathematical formula for the way in which sperm move rhythmically through fluid, creating distinct fluid patterns, but scientists now needed to understand what was going on inside the sperm tail that allowed them to move in this way.

To understand the structure of the tail, scientists examined how different parts of the tail bent by moving the tail of a dead sperm. Surprisingly a movement that started near the head of the sperm, resulted in an opposite-direction bend at the tip of the tail, called the 'counterbend phenomenon', suggesting that mechanical information is transmitted along the interconnected elastic bands in order to create movement along the full length of the tail.

Dr Gadêlha calculated these bending movements to form a that would help hypothesize the triggers needed within the tail to make these distinct movements.

Complex 'boat'

Dr Gadêlha said: "If we imagine that the communication to distant parts of the tail is a bit like the communication between blindfolded rowers in a canoe boat. Blindfolded rowers can't see each other's motion to communicate what movement to make, and in the absence of shouting to each other, they must instead feel the mechanics of the boat and the movement that each rower is making in order to synchronize their motion.

"It seems that the molecular motors - the 'rowers' inside the sperm tail - are doing a similar thing, but in a much more complex 'boat'.

"The mechanism of a sperm tail first creates a sliding motion between filaments, inside this cylindrically arranged , finally resulting in a tail bending, a bit like the piston that converts back and forth motion in to rotation of the wheel on a train. Any one in this complex sequence appears to be able to trigger motion right through to the distant parts of the tail.

"The big question now is, are particular springs in the coupled-up to transmit specific biomechanical information, and just are these 'rowers' self-organize?

The research is published in Journal of the Royal Society Interface.

Explore further

Mystery of how sperm swim revealed in mathematical formula

More information: The counterbend dynamics of cross-linked filament bundles and flagella, Journal of the Royal Society Interface, rsif.royalsocietypublishing.or … .1098/rsif.2017.0065
Provided by University of York

Feedback to editors

May 31, 2017
And yet it is still firmly believed that life spontaneously erupted in some pond scum and that sex differentiation sprang up all by itself via random mutations and natural selection - no intelligence and design required.

Not only that, but that the whole blueprint of the yet-to-be born organism is carried in two separate parts that will somehow unite and form a unified whole - and this just happened all by itself with no intelligence and design required.

Same as saying that the dumb, disconnected IBM PC of the 1980s somehow managed to evolve it's own graphical user interface, ethernet or token ring cards, spawned its own communications protocol, created cables and laid them everywhere and then started accepting user input via a mouse - all by itself with no intelligence and design required.

If that last bit sound idiotically ridiculous to you, then consider the hyper complexity involved in the former. Yet people still believe that it somehow happened.

Jun 01, 2017
If that last bit sound idiotically ridiculous to you, then consider the hyper complexity involved in the former. Yet people still believe that it somehow happened.

I don't usually comment on people, but I wonder why on earth you continue to comment on matters that obviously are well above your understanding?

Nature has had mindboggling time to test all kinds of solutions and has evolved ever refined systems that we can observe today. But knowing that there are all these intermediate solutions present living and in fossils, it does not need that big a leap in reasoning to determine that systems have evolved gradually.
Considering all the gained knowledge supporting theory of evolution, it should be one of the last theories for anyone to try to downplay.

Jun 01, 2017
but I wonder why on earth you continue to comment on matters that obviously are well above your understanding?

Given his persitent reiteration of ludcrous statements - at this point the only thing I can think of is: He's on a mission to make religious people look as stupid as possible.

And he's doubtlessly succeeding.

Jun 04, 2017
This comment has been removed by a moderator.

Jun 04, 2017
This comment has been removed by a moderator.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more