Translated material
Synchronous digging club
You will not surprise anyone with the collective behavior of insects now, but we did not expect this from Drosophila. And the Drosophila melanogaster larvae, it turns out, coordinates their actions during food and get significant advantages from this.
Food is almost the main occupation of the larva that it starts, barely hatched from the egg. In four days, she needs to increase the weight by 200 times. In order to optimize the process, saving the energy necessary for absorption and grinding, the larva emits digestive enzymes, softening tissues of the fetus on which it lives, or the nutrient medium in the tube. Half-liquid food has another important advantage: you can bury it in it, hiding from sunlight, predators or an OS-parasitoids, which strive to lay their eggs into the delicate body of the larva.
Moving, the larva does not stop eating, since with each muscle contraction it swallows a piece of food. The depth of immersion is determined by the ability to breathe. At the back end of the larva, the breathing tubes are located, and air should enter them. Burring into food, she digs a well, the walls of which collapse after a while. Then the larva has to reverse and start all over again.
The wider the well, the less often it crumbles; Digging will be safer and more effective if you act not alone, but together to dig a large hole. That is exactly what Drosophila larvae do, when there are a lot of them: they are united in groups that scientists called clusters, and dig into food. Clusters are preserved until air access will stop (Fig. 1).
In the laboratory, larvae live in test tubes, at the bottom of which a layer of a dense nutrient medium will be poured. Having hatched, they crawl along the layer of food, looking for each other. In these searches, pheromone helps them - two long -chain fatty acids [2]. Having gathered together, they form a cluster - a group in which more than four individuals, buried in food by more than half the body. Usually a cluster in a test tube consists of 10-100 larvae.
The pheromone serves as a guide to the guns, but does not encourage them to dig into the food together. Some senses should participate in synchronization of actions. Scientists did not test smell and taste, but checked how they form clusters of the larvae of mutant lines that are devoid of light or mechanism. It turned out that mutants also form clusters, but not as effective as wild -type larvae. The effectiveness of clustering was determined by the number of united individuals and by the average depth to which they buried.
Normal larvae that grew in complete darkness also experienced problems with clustering, which made it possible to conclude about the importance of vision for teamwork. Moreover, the darkness did not interfere with the grumbling activity of larvae as such, it interfered only with clustering.
The usual laboratory test tubes in which flies and larvae live were uncomfortable for observation, since only a number of larvae closest to the wall were visible in them, and all clusters could not be taken into account. Therefore, scientists arranged a reality show “behind the glass”, filling the food between two glasses. 30 larvae were placed in this “sandwich” and watched their behavior.
What allowed them to do this? Perhaps the mechanoreception is a “elbow feeling”, which helped not to form clusters. But the main role, of course, played vision. The photoreceptors of the larvae are able to fix the movement of the border of the feed or the change in the illumination that moved neighbors created. However, the ability to synchronize in larvae is not completely congenital, they acquire an appropriate skill in the development process.
Recently, Barry Kondron and his colleagues found that there is a critical period of development in which larvae learn to recognize their own kinds [3]. If at this time, from the second to the middle of the third age, they will grow them in isolation, and then put them together, they will not be able to unite. Development in complete darkness will also lead to a similar effect. And if you take a larva, grown alone, in the dark or blind, and plant it to the group of “full -fledged” individuals, it will not flush into the team.
Researchers note that a cluster is a kind of closed club. No loan will be able to take advantage of the efforts of its members. The club lives on the principle: "He who does not work does not eat."
It was shown that due to the vision and training of the larvae, Drusophilas are cooperated for joint digging, which allows them to feed effectively and defend themselves from enemies and external conditions. The authors of the work note that the contribution of mechanical systems to the formation of clusters has yet to be found out.
It is interesting that other experts also presented their opinion on this: Matthew Louis, the head of the group in the center of genomic regulation of the Barcelona Institute of Science and Technology and the associate professor of the University of California at Santa Barbara (USA), and its Portuguese colleague Gonzalo de Polavii from the center from the center Studies of the unknown - the Shampolimo Foundation [4]. They remembered the work of Professor Kyoto University (Japan) Yoshiki Kuramoto, who in 1984 proposed a model explaining collective behavior as the interaction of poorly connected oscillations.
According to this model, each individual seeks to adjust the frequency of its actions to the average frequency of the group, and if the difference between individual frequencies is not too high, and the relationship between the group members is quite strong, the oscillations become synchronous. The model proposed by Kuramoto explained friendly applause in the auditorium. And Barry Kondron and his colleagues watched the behavior of larvae in the triples and found that the central individual in these triples synchronizes the frequency of their muscle contractions with the frequency of the left or right neighbor. Therefore, the connection of neighbors on the cluster is quite strong.
Lewis and de Polavia suggest that each larva, contracting, produces weak vibrations that are tangible in a nutrient medium. Other larvae perceive these vibrations using mechanoreceptors and synchronize the frequency of contraction according to the Kuramoto model.
According to researchers, it would be interesting to check whether all types of Drosophila are practicing a joint digging. For example, D. Simulans , a view close to D. Melanogaster, does not show a tendency to aggregation. Probably the differences are genetically predetermined, which means that genes should be sought. So the work is still not the edge.
Natalia Reznik
1. Dombrovski M., Poussard L., Moalem K., Kmecova L., Hogan N., Schott E., Vaccari A., Action S., Condron B. Cooperative Behavior Emerges Amongst Drosophila Larvae // Curr. Biol. 2017.27. P. 2821–2826. DOI: 10.1016/J.Cub 2017.07.054
2. Mast JD, De Moraes CM, Alborn HT, LAVIS LD, SERN DL EVOLVED DIFFERENCES IN LARVAL SOCIAL Behavior Medated byle Pheromones // Elife. 2014. 3. E04205. DOI: 10.7554/Elife.04205
3. Slepian Z., Sundby K., Glier S., McDaniels J., Nystrom T., Mukherje S., Acton, ST, Condron B. Visual Attraction in Drosophilaryva Develops Duringa Period and IS Modulated by Crowding Conditions // J. Comp. Physiol. A. 2015. 201. P. 1019–1027. DOI: 10.1007/S00359-015-1034-3
4. Louis M., de Polavieja G. Collectivebehavior: Social Diging in Drosophila Larvae // Curr. Biol. 2017. 27. R1002 - R1023. DOI: 10.1016/J.Cub 2017.08.023