Sensory Bristles Organize With Minimum Communication

Biological Strategy

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Coordinate Systems

Nature is full of systems that work in harmony by following simple rules that lead to complex behavior, such as fish swimming in a school or migrating grasshoppers flying in swarms. Coordinated behavior is also observed in how a slime mold grows, how our own neural network functions, and how some animals vote on where to live or move.

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Respond to Signals

To interact with its environment, a living system must not only sense a variety of signals, but also respond to them. To be energy- and material-efficient, those responses must be appropriate to the signal. This generally requires sensing thresholds to trigger an appropriate level of response (for example, hiding under a shrub versus running away to avoid a predator). Response strategies are tied to a specific signal and often have a response threshold, which determines how strong a signal must be to warrant expending energy to respond. One example is a plant that lives in arid regions in South Africa. Its seed capsules remain closed until rainfall triggers them to open to release the seeds. But the plant only responds to a second rainfall, thus protecting against releasing its seeds before there is enough sustained water for them to grow.

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Sense Shape and Pattern in a Living System

Living systems must identify other living systems and objects to navigate, feed, escape predators, find resources, and more. The ability of living systems to “see” varies widely, with “seeing” including not only sight, but other means of sensing shapes or patterns, such as smell or echolocation. For example, a hawk can see much more detail than humans while other organisms can see far less detail. Nevertheless, each living system is capable of detecting shapes and patterns to the extent it needs to for survival. In addition to perceiving physical shapes or patterns, living systems can also sense landscape patterns at various scales. The purple sea urchin, for example, does not have eyes, yet can pick out fine details in its environment by using its entire surface as a compound eye. The urchin’s spines shield light coming from wide angles, further refining its focus.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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The sensory organ precursors (starting point of sensory bristles) of fruit flies organize themselves with minimal knowledge and communication.

“Computational and mathematical methods are extensively used to analyze and model biological systems…We provide an example of the reverse of this strategy, in which a biological process is used to derive a solution to a long-standing computational problem…All large-scale computing efforts, from web search to airplane control systems, use distributed computing algorithms to reach agreement, overcome failures, and decrease response times. Biological processes are also distributed. Parallel pathways are used to transform environmental signals to gene expression programs, and several tasks are jointly performed by independent cells without clear control.”

[A long-standing distributed computing problem is that of electing a local set of leaders, called the maximal independent set or MIS, in a network of connected processors.]

“The selection of neural precursor during the development of the [fruit fly] nervous system resembles the MIS election problem. The precursors of the fly’s sensory bristles [sensory organ precursors (SOPs)] are selected during larvae and pupae development from clusters of equivalent cells…a cell that is selected as a SOP inhibits its neighbors by expressing high level of the membrane-bound Delta, which binds and activates the transmembrane receptor protein Notch on adjacent cells…This lateral-inhibition process is highly accurate…resulting in a regularly spaced pattern in which each cell is either selected as SOP or is inhibited by a neighboring SOP…Thus, as in the MIS problem every proneural cluster must elect a set of SOPs (A) so that every cell in the cluster is either in A or connected to a SOP in A, and no two SOPs in A are adjacent.”

“Although similar, the biological solution differs from computational algorithms in at least two aspects. First, SOP selection is probably performed without relying on knowledge of the number of neighbors that are not yet selected. Second, mathematical analysis demonstrated that SOP selection requires nonlinear inhibition that in effect reduces communication to the simplest set of possible messages (binary).” (Yehuda et al. 2011:182-183)

Last Updated August 18, 2016

References

Journal article

On Nonexistence of any λ 0 -invariand positive harmonic function, a counter example to stroock' conjecture

Communications in Partial Differential Equations | 25/06/2007 | Yehuda Pinchover

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Reference

Journal article

A biological solution to a fundamental distributed computing problem

Yehuda A; Alon N; Barad O; Hornstein E; Barkai N; Bar-Joseph Z

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