Instead of jumping, it crawls ingeniously: researchers report on a small jumping spider that mimics the movements of ants to protect itself from predators. Interestingly, she didn't perfect her performance, but apparently simplified it in a targeted manner. The scientists explain that the spider can probably imitate several species of defensive insects thanks to its “imperfect” acting quality.
They only pretend to be dangerous: Some harmless animals take advantage of the appearance of resilient species in their habitat to deter predators. This so-called mimicry is often based on the imitation of the appearance - as in the case of harmless fly species, which benefit from the deterrent "image" of the wasps with their yellow-black markings. In addition, however, the strategy of behavioral mimicry is also known: some insect species imitate the characteristic movements of defensive creatures in their homeland with amazing perfection.
An example of this are certain representatives from the group of jumping spiders. Instead of hopping like their relatives, they crawl in a characteristic way. It seems obvious that by doing this they imitate ants to deter predators. Because these insects are armed with sharp biters and lively acid glands and are therefore unpopular as prey animals. The researchers led by Hua Zeng have now investigated the concept of ant imitation in the jumping spider species Siler collingwoodi, which hunts tiny insects on flowering plants in Asia. She herself, in turn, is also the target of predators - such as other spider species. The researchers now wanted to know more precisely which ant species the little crawler mimics and to what extent the concept actually protects them from predators.
Targeting an ant actress
The researchers collected specimens of S. collingwoodi in different regions of China and brought them to the laboratory. The team also obtained specimens of five species of ants co-occurring with these spiders, which they thought might serve as models for them. For comparison, the team also studied jumping spiders of a "normal" species that don't mimic ants. In the laboratory, the researchers then characterized and compared the movements of the ants and spiders using video recordings and models.
It became clear in detail how S. collingwoodi mimics ants: it lifts its front legs to imitate the antennae of an ant and moves its abdomen and legs in a characteristic way. However, as the team points out, what emerged was that this mimicry is not specific to any particular ant species. According to them, in contrast to other known cases of the concept, it is a decidedly “imperfect mimicry”. "S collingwoodi is not a specialized mimic, but its running style is similar to that of several ant species at the same time," says Zeng. According to the researcher, there is a plausible explanation for this apparently imperfect adaptation: The rather basic imitation could provide the spiders with flexible protection in regions where different ant species dominate. This could open up wider distribution possibilities for the species.
Movement mimicry combined with camouflage
The researchers were able to show that the concept works effectively through experiments with potential predators of S. collingwoodi: These predators are jumping spider species that target other members of their group. As the team reports, tests with such predatory spiders showed that when given the choice between the ant-mimicking spiders and "normal" jumping spiders, they always avoided the actresses. The quality of their presentation is therefore sufficient for protection and it can also be assumed that if these spiders imitated the walking style of a certain ant species too perfectly, the deterrent effect could be less effective.
However, the ant spectacle does not protect the small spiders against a larger enemy, as further experiments have shown: Praying mantises like to grab the ant actresses just as much as other jumping spiders. However, the researchers explain that these predators also need have less fear of an accidental attack on an ant. In contrast to predatory spiders, praying mantises are much larger than their prey. However, S. collingwoodi apparently protects itself against the mantis by an additional concept, as the scientists were able to prove through visual comparisons as part of their study. Thanks to its colorful coloring, the sophisticated ant actress is also well camouflaged in its typical living environment: it is difficult for the praying mantis to recognize it on the reddish blossoms of a shrub common in China.
Source: Cell Press, Article: iScience, doi: 10.1016/j.isci.2023.106747