LIFE SCIENCE

Two “lines of defense” help it ward off the enemy


Zhang Wei, a researcher at Peking University’s School of Life Sciences, and collaborators found that a tiny, colorful jumping spider uses two lines of defense to avoid being eaten by predators: camouflaging with plants and walking like ants. This combination of camouflage and behavioral mimicry helps small colored spiders hide from small predators such as other jumping spiders, but does not stop hungry praying mantises. The study was published May 17 in Interdisciplinary Science.

Imitating ants is an effective strategy to ward off enemies because they are not “delicious”. Ants usually have spikes and a jaw that cannot be underestimated, and many ants also use chemicals or venom as a means of attack.

“The Coolis spider was discovered in the last century, and it has ant-like morphological features and bright body color, but it has not been quantified.” Zhang Wei, the corresponding author of the paper, told China Science News that they therefore assumed that the spider’s ant-mimicking behavior and camouflage protective color were to ward off enemies, and carried out this study.

Koch kingfisher. Photo courtesy of Zeng Hua

Coriolis has been observed to move in an ant-like manner in the wild, and the researchers wanted to know how accurately they mimicked, whether they mimicked more than one type of ant, and how effective that imitation was at warding off predators.

To understand how mimicking ants help these spiders avoid being eaten, the researchers collected Coriolis from four geographic locations in southern Hainan and brought them back to the lab. For comparison, they also collected another jumping spider that does not mimic ants, as well as 5 symbiotic ants that they believe may serve as mimetic models.

In the lab, the researchers compared the behavior patterns of ants and spiders as they walked, including the details of how they used their limbs, and how fast they moved, acceleration, and whether they walked straight or curved in the process.

They found that the kingfisher spider walked less jumping than most jumping spiders, but more like an ant: lifting its forelimbs to mimic an ant’s tentacles, wiggling its abdomen, and walking in an ant-like manner. Of the 5 ant species, this spider walks more similarly to the 3 smaller ants, and their body size is also closer to the spider.

“The Coriolis spider may not be a perfect imitator because its gait characteristics and movement trajectory are very similar to those of many species of ants. If different ant models occupy different habitats, spiders can benefit from being a multi-model imitator rather than perfectly mimicking one type of ant. Zeng Hua, the first author of the paper and a postdoctoral fellow in Zhang Wei’s research group, said. Zhao Ming, a doctoral student in the team, is the co-first author of the paper.

Next, the researchers tested the spider’s defenses against two potential predators: a jumping spider with similar size, color vision, and specialized in preying on other spiders; The other is the praying mantis, which is a medium-sized predator with a monochromatic visual system and a wide range of diets.

The team also explored the role played by the spider’s bright body color. “Unlike most ant-mimicking ants, which mimic the brown or black body of ants, the body color of the Cocholis spider is very bright.” Zeng said, “From a human perspective, it seems to blend well with plants in the environment, and we wanted to test whether their body color could be used as camouflage to hide from predators.” ”

They first compared the body color of the kingfisher with its main host plants in the wild, the dragon boat flower and the base tree, to explain whether the body color of the kingfisher used to camouflage from the perspective of these two predators. They found that the ant-mimicking spider could camouflage itself better on the dragon boat flower to avoid the two predators, the jumping spider and the praying mantis, than the base and the tree.

Koch kingfisher on the dragon boat flower. Photo courtesy of Zeng Hua

When a predator is faced with a comic spider that mimics an ant and another non-mimic jumping spider of similar size, the spider as a predator has a higher probability of attacking the non-mimic jumping spider. In 17 trials, the spider launched 5 attacks, all against non-mimic jumping spiders. However, the probability of a praying mantis attacking both prey is the same.

“We initially thought that the two predators would behave similarly in the anti-predation experiment, but in fact, the behavior of the Cochellian antom was only effective against jumping spider predators, while the praying mantis showed an indiscriminate attack pattern against imitators and non-imitators.” Zhang Wei said the difference may be caused by the degree of harm that preying ants may cause. Mantis are much larger than ants, so they can easily eat prickly ants without serious harm, but this is not the case for jumping spider predators.

“For jumping spider predators, attacks on ants can cause serious damage, so they will be very careful and will only attack if they can tell Coriolis with a high degree of certainty that they can distinguish it from ants.” Zhang Wei added.

Further manipulation experiments found that losing a forefoot increased the risk of predation in the kingfisher, possibly because changes in morphology and behavior patterns made them much less accurate at mimicking ants.

The authors said that this study verified the behavioral mimicry of ants and the color camouflage of host plants by quantitative research methods, clarified the ecological significance of its special behavior and bright body color, explored its driving force through behavioral experiments, comprehensively analyzed the imperfect mimicry phenomenon formed under the action of natural selection, and provided new perspectives and examples for in-depth understanding of the evolution of biological phenotypic adaptability driven by selection pressure. (Source: China Science News Feng Lifei)

Corresponding author: Zhang Wei. Image from interviewee

The first author is Zeng Hua. Image from interviewee

Co-first author Zhao Ming. Photo courtesy of interviewee

Related paper information:http://doi.org/10.1016/j.isci.2023.106747



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