In some tropical flowers, tiny mites live that can perceive electrical stimuli. As a result, the arachnids recognize the electrical field generated by flower -visiting colibris. They also use electrostatic attraction to “jump up” on the bird beak, while the Kolibris are on the nectar. Quasi hitchhiking the mites then travel to the next flower, as biologists found out. This is made possible by special hair on the front legs of the mites, with which you can recognize loading differences and electric fields.
Man has five senses: seeing, smelling, tasteing, hearing and feeling. Some animals also have other senses. This also includes the electrical sense, with which the animals can perceive electrical fields and charges that attract each other or repel each other. For example, caterpillars, spiders as well as pollinating insects and birds have this ability to recognize predators or feed sources. Kolibris also recognize negatively invited flowers, while they are charged positively themselves. When the birds float over the flower and hit their wings, this creates an exchange of loads and an electric field. This facilitates the pollen.
Some tropical mites have apparently adapted their electrical sense to exactly these birds. According to assumptions, the mites use electrical signals to get to the beak of Kolibris, while they drink from the nectar of flowering and hitchhiking from flower to flower. If the beak touches a new flower, the mites crawl out of the nostrils of the colibris at lightning speed and leave their means of transport by running onto the plant. In this way, the nectar and pollen-eating mites expand their habitat and reach new food sources, although the arachnids themselves cannot fly or jump.
Electrostatic attraction between mite and the Kolibri
A team led by Carlos García-Rofledo from the University of Connecticut has now examined exactly how the mites’ electrical start. For this, the biologists observed the behavior of the mites on the flowers and in the laboratory, while they presented them with different electrical forces. In addition, they removed parts of the legs of the arachnids and looked at them under the scanning electron microscope to make out the origin of the electrical sense. The mites belonged to 19 types of the genera Procolaelaps Berlese and Lasioseius. They came from two plant species from Costa Rica (Costus Malortianus and Musa Velutina), which are regularly visited by 14 different colibri species.
The tests showed that the mites do not recognize all electrical fields, but only so -called modulated fields. Their amplitude (approximately 250 to 550 volts) and frequency (120 Hertz) are similar to the electrical fields that arise when the wings of the colibris. The mites also prefer positively invited fields. “These results confirm that mites can recognize small load fields typical of Kolibris in moist environments,” said the team. Further attempts showed that the mites not only recognize the electrical field on the beak of Kolibris due to their electrical sense, but also “jump up” by the electrostatic attraction and then fly to the next flower with the birds.
“This study represents a rare example in which both the recognition of a host and transport to it are conveyed electrically,” write García reedo and his colleagues. Due to this ability, the mites are even one of the fastest land animals if they bridge the gap between flower and beak within a few milliseconds due to the electrostatic attraction. With this passive flight through the air, you can reach a speed of 150 body length per second.
When leaving the Kolibri snab, the mites have to make a little more effort, but their electrical sense will probably also help them. In their attempts, the researchers observed that the mites start to run immediately as soon as the electrical field subsides. This also happens when a colibri flies and ground a new flower – “during the discharge, which is connected to closing the circuit as soon as a colibri touches a flower,” as the team explains. The mites then run away from the beak.
Electrosensors on the front legs
But how do the mites recognize the electrical fields of the colibris? The tests showed that the mites stretch their front legs actively and searching towards the electrostatic force – similar to ticks looking for a host. Without their front legs, however, the mites do not recognize the electrical fields. This suggests that the cells that act as electrical sensors in the mites sit on these legs – similar to ticks, in the forefront of which chemical, mechanical and thermal sensors lie. This was confirmed by the microscopy images: “We found a group of sensory bristles in both front targets (the mites) structures that are similar to the Haller organs, which are related to chemical, mechanical and infrared sensitivity to ticks and other parasitic acarina Stand, ”report García reedo and his colleagues. “At the top of the Tarsus, we also watched three bristles that resemble trichobothria, a hair type that serves as mechanical and electrical sensors in spiders.”
Accordingly, the mites have typical hair on their front legs for some arachnids as sensors. However, it is still unclear whether only one or more of these sensors are involved in the electrical sense of the mites and is to be further researched. In follow-up studies, the researchers also want to investigate whether the individual mites have adapted themselves to the loads and electrical fields of individual coli bodies or flower types.
Source: Carlos García-Robledo (University of Connecticut) et al.; Proceedings of the National Academy of Sciences, DOI: 10.1073/PNAS.2419214122