In the eyes of entomologists, the thousand-footed worms are not only famous for their large number of pairs, but also because of their elusive mating process. Previous attempts by entomologists to study the mating process of the chipods have been unsuccessful using their shedding shells. Now, entomologists have picked up the highest-purified imaging techniques to directly record their reproductive organs…
This UV-enhanced image shows two thousand-footed insects that maintain their mating posture. Photo credit: STEPHANIE WARE.
Last summer, evolutionary biologist Xavier Zahnle invited colleagues who studied the chima to conduct a visual study. At the time, Zahnle, a doctoral student at the University of California, Davis, had just produced a digital image of the rare internal structure of the male Pseudopolydesmus serrats genitalia, or reproductive limbs. Zahnle’s collaborators studied the hard-won images and tried to crack a question that has been asked for decades: How do male stoics release sperm?
The reason this is so difficult to answer is that the mating process of the thousand-footworm is difficult to observe – the specifics of the sexual behavior are hidden by the wiggling foot. The genitals of the female python are located at the Three-Body Problem section, which is from the head to the back. When preparing for mating, the female chinos push it out of their feet. At this time, the male thousand-footworm will use many of its own pairs of feet to catch the female thousand-foot worm, with two lengths of only 1 mm of reproductive limbs stuck female thousand-foot worm, and then a reproductive limb surface of the polysacchameter into the female thousand-footworm body.
As early as 1931, researchers studying the chinos put forward the hypothesis that a catheter called a fine tube in the reproductive limbs of the microposome simply transports sperm directly through the tube to the female micropoe. Zahnle’s team also supported this view in a 2019 review of polypseudodesmus. But for a long time, no one has been able to prove it.
This 3D model was made from microCT and shows the female’s external genitalia (green-turquoise) and the male’s outer genitalia (orange). PHOTO: XAVIER ZAHNLE.
To prove the hypothesis, Zahnle and Petra Sierwald, associate curator of spiders and polypods at the Field Museum of Nature in Chicago, and colleagues decided to use more sophisticated imaging techniques, such as scanning electron microscopy and ultraviolet fluorescence imaging. They applied these techniques directly to samples from the Field Museum’s collection, including a pair of P-pairs that were holding a mating pose. Serratus thousand-footed insect samples. As a result, the team gained a new understanding of the mating process of the thousand-footworm.
Micro-CT plays an important role in the observation of the internal structure of the micro-compute worm, which can produce a series of different grayscale images by X-raying the sample, while the denser parts are brighter in the picture. It is accompanied by a computer program that compiles the images into pixel blocks, so that researchers can instruct programs to color blocks of different structures and build 3D copies of samples. The researchers were able to study the modelofling of the samples from “every angle,” Zahnle said: “You can really feel how the genital seating is made up and where versus each other.” “
Zahnle’s micro-CT images show that the male micropodreleases of sperm in a much more tortuous way than previously thought, and that the fine tube does not lead straight to the exit of the hairy tube. According to the image, when the sperm passes through the capillary tube, it is released into a cavity, and then the sperm is released into the capillary tube. Zahnle said the fine tube “forms a complete ring, which is entirely intentional” and “contrary to what we mentioned in the 2019 article.” We were wrong. Earlier this year, he and his team published new results in the journal Arthropod Structure and Development.
Javier Alba-Tercedor, an aquatic biologist at the University of Granada in Spain, who was not involved in the study, said Zahnle’s study was “an excellent case for using Micro-CT.” Alba-Tercedor, who has won awards for research using Micro-CT, says the most time-consuming part of the process is coloring different structures. But once this step is done, other researchers can use the database to study the new structure of the sample.
In fact, Sierwald argues that Micro-CT has changed the way the study of the microposome shave. She began studying the chimas as early as 1997, but Micro-CT was still very rare, not to mention used in entomology research. She had initially planned to study the reproductive parts of female stoe by removing the shell, but the study failed because “the thousand-footworm snares will eat the shells they shed.” Without Micro-CT, “it means killing a lot of thousand-footworms for anatomy,” she said. With Micro-CT, however, there is no need to dissect these insects. In other words, the number of thousand-footed insects that died as a result of the experiment will be greatly reduced, and we can also study complete animals. “It’s a cool thing.” Micro-CT, she added, has greatly helped her understand how insect sex organs work.
Sierwald said the team has long hoped that imaging techniques will help researchers distinguish between the populations of the thousand-footed worms, show their geographical distribution, and understand how different species of chinopods are linked to other species of chinopods.
Thomas Simosen is an entomology researcher and curator at the Aarhus Museum of Natural History in Denmark. He said the new study was “fantastic” and also thought the method could help with the study. Morphological studies are as important as DNA studies for “understanding the diversity and evolution of arthropods,” he argues.
Zahnle is now focusing on the male thousand-footworm. For him, the thousand-foot bug showed people countless forms of appearance and their own functions. They don’t just have a lot of “legs,” he says, and these pairs range from “flat to large cylindrical to small fluffy”. After using Micro-CT for breakthrough research, Zahnle found himself with a large number of talented scientists in the field, and the number of entomology researchers using Micro-CT is growing. He wondered whether other species also had male P. “I wanted to show these structures with images, ” he says of a sperm-closed-loop tube like a thousand-footworm. “