Male spiders are attracted by a female like planets orbiting a star


Date:
December 6, 2021
Source:
Max-Planck-Gesellschaft
Summary:
The tiny male golden orb-weaving spider faces a considerable
challenge when searching for a mate. He is a fraction of the size of
the massive female, but must carefully enter her web and approach
her without being noticed, because the cannibalistic female will
kill and eat him if he makes one wrong move on her web. Add to
this gamble the competition he faces from other males also on the
delicate arena of the web, and you have a complex optimization
problem that even human analysts would find daunting. Yet these
little spiders barely have what we would recognize as a brain. How
then do they manage?


FULL STORY ==========================================================================
The tiny male golden orb-weaving spider faces a considerable challenge
when searching for a mate. He is a fraction of the size of the massive
female, but must carefully enter her web and approach her without being noticed, because the cannibalistic female will kill and eat him if he
makes one wrong move on her web. Add to this gamble the competition he
faces from other males also on the delicate arena of the web, and you
have a complex optimization problem that even human analysts would find daunting. Yet these little spiders barely have what we would recognize as
a brain. How then do they manage? This is a question that has captivated
Alex Jordan and members of his lab at the Max Planck Institute of Animal Behavior for over a decade. Now, teaming up with researchers from the
Weizmann Institute of Science, they are closer to an answer.


==========================================================================
The solution appears to lie in animal magnetism, or more correctly, in
the effective physical forces that males and females experience on the
elastic surface of the spider web. "Our initial concept was to explore
the idea that these spiders moving on the web behave like electrons
orbiting a nucleus, or planets orbiting a star," says Jordan, who leads
the Integrative Behavioral Ecology Lab at the Max Planck Institute of
Animal Behavior, and is co-senior author on the study. From this initial
idea, a research program was born, leading the two teams to develop a
physical model and perform experiments in the Panamanian rainforest.

Competitive web arena While the details of the precise physics
ultimately diverged from both atomic and cosmic levels, the concept
proved useful. "Imagine electrons orbiting a nucleus, or a massive star
in space, so large that it generates its own gravitational field pulling
in objects around it -- the giant, cannibalistic female can be thought of
in the same way," says Jordan. "Now imagine smaller planets, satellites,
or comets coming near this attractive force -- these are our tiny, brave males." Approach the star (or female) too rapidly, or at the wrong angle,
and you risk getting caught up in her attractive pull. On a cosmic scale,
this will result in a cosmic collision that vaporizes the planet. For
the intrepid male, an incorrect approach means falling into a fatal
attraction and ending up as prey.

"Working in the rainforests of Panama, I've seen over-zealous males
fall victim to the cannibalistic females many times, especially when
they take the wrong path, or approach the female too fast," says Sylvia
Garza, co-author of the study, who spent months in Panama as a Master's
student recording the behavior of male and female spiders, then using machine-learning approaches to track their every movement.

Vibratory cues Just as the smaller planets have their own gravitational
pull, the males also attract one another -- initially approaching the
perceived rival. The males also start to repel each other as they get
closer and closer, in this way behaving much more like electrons around
a nucleus.

"The motion of these males resembles interactions between particles that attract or repel one another depending on the distance between them,"
says Amir Haluts, a physicist by training and lead author of the study
from the Weizmann Institute of Science. Co-senior author Nir Gov, also
from the Weizmann, says: "We use models to map the effective physical
forces that males experience, allowing us to explain their motion on the
web, as well as contest dynamics of males of different sizes." As the
males orbit one another, they will eventually come too close together,
crashing into each other in open fighting. All this is played out on
the surface of the web, which acts as the conduit for the vibrations
males use to communicate, but which can also alert the female to their
presence and lead to a fatal attack.

The team's research demonstrates that the seemingly complex
decisions that males make, balancing risk and reward, life and
death, do not require advanced intelligence or understanding of the
game they are playing. Instead, the same solutions can be achieved
by sensing vibrations on the web and responding to the physical
forces of attraction and repulsion, just as physical particles
might do. "Early on, I was perplexed by our first results, which
showed that these males could solve these complex tasks apparently
without the required cognitive machinery," says Jordan. "I joked
with Nir that it's almost like these males are electrons orbiting
around the female 'nucleus'. This led to us coining the term 'Atomic
Spiders' and it turns out that it may not be that far from the truth." ========================================================================== Story Source: Materials provided by Max-Planck-Gesellschaft. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Amir Haluts, Sylvia F. Garza Reyes, Dan Gorbonos, Robert Ian
Etheredge,
Alex Jordan, Nir S. Gov. Spatiotemporal dynamics of animal contests
arise from effective forces between contestants. Proceedings of
the National Academy of Sciences, 2021; 118 (49): e2106269118 DOI:
10.1073/ pnas.2106269118 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211206113047.htm

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