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 Is it an ant? Is it a plant? No, it's a spider! 

  Date:
      May 17, 2023
  Source:
      Cell Press
  Summary:
      A species of tiny, colorful jumping spider employs two lines of
      defense to avoid being eaten: camouflaging with plants and walking
      like an ant.

      Researchers report that this combination of camouflage and movement
      mimicry helps the spiders evade spider-eating spiders but does
      not deter hungry praying mantises.


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FULL STORY
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A species of tiny, colorful jumping spider employs two lines of defense
to avoid being eaten: camouflaging with plants and walking like an ant.

Researchers report May 17th in the journal iScience that this combination
of camouflage and movement mimicry helps the spiders evade spider-eating
spiders but does not deter hungry praying mantises.

Mimicking ants is a good defense option because they do not make for good
eating; ants often have spiny defenses and biting mandibles (and they're
not afraid to fight back), and many also carry chemical repellants or
venom. Though the focal spider of this study -- Siler collingwoodi --was
already known to move in an ant-like fashion, the researchers wanted to
know how accurate its mimicry is, whether it mimics more than one ant
species, and how effective this mimicry is at discouraging predators.

The research team also explored the role of the spider's brilliant
coloration.

"Unlike typical ant-mimicking spiders that mimic the brown or black
body color of ants, S. collingwoodihas brilliant body coloration,"
says first author Hua Zeng, an ecologist at Peking University. "From a
human'sperspective, it seems to blend well with plants in its environment,
but we wanted to test whether their body coloration served as camouflage
to protect against predators."  To understand how ant-mimicry helps these
spiders avoid being eaten, the researchers collected wild ant-mimicking
spiders from four geographic locations in southern Hainan, China,
and brought them back to the lab. For comparison, they also collected
another type of jumping spider that doesn't mimic ants, as well as five
co-occurring ant species that they thought might serve as models.

Back in the lab, the researchers characterized and compared how the ants
and spiders moved in terms of how they used individual limbs, as well
as their speed, acceleration, and whether they followed a straight path
or took a more tortuous trajectory.

They found that, rather than jumping like most jumping spiders,
S. collingwoodi move like ants: by raising their front legs to mimic
an ant's antennae, bobbing their abdomens, and lifting their legs
to walk in an ant-like manner. Of the five ant species, the spiders'
walking style most closely resembled the three smaller ant species,
who are also closer to it in size.

"S. collingwoodiis not necessarily a perfect mimic, because its gait
and trajectory showed high similarity with multiple ant species," says
Zeng. "Being a general mimic rather than perfectly mimicking one ant
species could benefit the spiders by allowing them to expand their range
if the ant models occupy different habitats."  Next, the researchers
tested the spider's defenses against two likely predators: a similarly
sized jumping spider with color vision that specializes in preying upon
other spiders (Portia labiata) and a praying mantis (Gonypeta brunneri)
that is a generalist predator with a monochromatic visual system.

To explore the role of color camouflage, the researchers modeled how the
two predators would perceive S. collingwoodirelative to the other prey
species against the background of two plants that the spiders live on --
the red- flowering West Indian jasmine (Ixora chinensis) and the Fukien
tea tree (Carmona microphylla). They found that the ant-mimicking spiders
were better camouflaged from both spider and praying mantis predators
on the jasmine plant than the tea tree plant.

When the predators were given the choice of the ant-mimicking spider
and the other jumping spider, the predatory spider was more likely to
attack the non- mimic; out of 17 trials, the spider launched 5 attacks,
all of which were towards the non-mimic. Praying mantises, however,
attacked both prey species with equal alacrity.

"We initially thought that both predators would behave similarly in the
antipredation experiments, but in fact the simulated ant locomotion
of Siler collingwoodi only worked for the jumping spider predator,
while the praying mantis showed indiscriminate attacks on both ants
and mimics," says senior author Wei Zhang, an evolutionary ecologist at
Peking University.

This difference might be driven by each predator's likelihood of being
injured from eating an ant. The praying mantises are much larger than
their prey, so they can get away with eating spiny ants without risking
grave injury, but this is not the case for the predatory spiders.

"For the spider predator, a random attack on an ant could result in
injury, so they are very careful predators and will only attack if they
can distinguish S.

collingwoodifrom ants with a high degree of certainty," says Zhang.

However, losing a limb compromised the ant-mimicking spiders' ability
to avoid the predatory spider's attention, probably by preventing them
from accurately mimicking ants.

    * RELATED_TOPICS
          o Plants_&_Animals
                # Spiders_and_Ticks # Animals #
                Insects_(including_Butterflies) # Invasive_Species
          o Earth_&_Climate
                # Exotic_Species # Ecology # Environmental_Policy #
                Weather
    * RELATED_TERMS
          o Hobo_spider o Widow_spider o Spider_silk o Black_widow_spider
          o Yellow_sac_spider o Spider o Brown_recluse_spider o Tarantula

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Story Source: Materials provided by Cell_Press. Note: Content may be
edited for style and length.


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Journal Reference:
   1. Hua Zeng, Dong Zhao, Zixuan Zhang, Huize Gao, Wei Zhang. Imperfect
   ant
      mimicry contributes to local adaptation in a jumping
      spider. iScience, 2023; 106747 DOI: 10.1016/j.isci.2023.106747
==========================================================================

Link to news story:
https://www.sciencedaily.com/releases/2023/05/230517122115.htm

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