Monday, May 08, 2023

The evolution of honey bee brains

Specialized neurons in some insect brains, related to highly evolved behaviors, may have developed from a multifunctional ancestor

Peer-Reviewed Publication

UNIVERSITY OF TOKYO

European honey bee worker. — IMAGE: THE RESEARCHERS STUDIED HONEY BEES EXHIBITING DIFFERENT BEHAVIORS: FORAGERS, NURSE BEES, AND QUEENS. HONEY BEES IN GENERAL HAVE BEEN A KEY INSECT MODEL FOR BETTER UNDERSTANDING LEARNING AND MEMORY FOR MORE THAN 100 YEARS. view more
CREDIT: 2023 HIROKI KOHNO

Researchers have proposed a new model for the evolution of higher brain functions and behaviors in the Hymenoptera order of insects. The team compared the Kenyon cells, a type of neuronal cell, in the mushroom bodies (a part of the insect brain involved in learning, memory and sensory integration) of “primitive” sawflies and sophisticated honey bees. They found that three diverse, specialized Kenyon cell subtypes in honey bee brains appear to have evolved from a single, multifunctional Kenyon cell-subtype ancestor. In the future, this research could help us better understand the evolution of some of our own higher brain functions and behaviors.

Are you “busy as a bee,” a “social butterfly” or a “fly on the wall”? There are many ways we compare our behavior to that of insects, and as it turns out there may be more to it than just fun idioms. Studying insects could help us understand not only how their behavior has evolved, but also the behavior of highly evolved animals, including ourselves. Mammalian brains are big and complex, so it is difficult to identify which behaviors and neural and genetic changes have co-developed over time. By comparison, insect brains are much smaller and simpler, making them useful models for study.

“In 2017, we reported that the complexity of Kenyon cell (KC) subtypes in mushroom bodies in insect brains increases with the behavioral diversification in Hymenoptera (a large and varied order of insects)” explained Professor Takeo Kubo from the Graduate School of Science at the University of Tokyo and co-author of the current study. “In other words, the more KC subtypes an insect has, the more complex its brain and the behaviors it may exhibit. But we didn’t know how these different subtypes evolved. That was the stimulus for this new study.”

The team from the University of Tokyo and Japan’s National Agriculture and Food Research Organization (NARO) chose two Hymenoptera species as representatives for different behaviors: the solitary turnip sawfly (which has a single KC subtype) and the sophisticated, social honey bee (which has three KC subtypes). As the sawfly has a more “primitive” brain, it is thought to contain some ancestral properties of the honey bee brain. To uncover the potential evolutionary pathways between them, the researchers used transcriptome analysis to identify the gene expression profiles (the genetic activity) of the various KC subtypes and speculate their functions.

“I was surprised that each of the three KC subtypes in the honey bee showed comparable similarity to the single KC type in the sawfly,” said Assistant Professor Hiroki Kohno, co-author from the Graduate School of Science. “Based on our initial comparative analysis of several genes, we had previously supposed that additional KC subtypes had been added one by one. However, they appear to have been separated from a multifunctional ancestral type, through functional segregation and specialization.” As the number of KC subtypes increased, each subtype almost equally inherited some distinct properties from an ancestral KC. These then modified in different ways, resulting in their varied present-day functions.

The researchers wanted a specific behavioral example of how ancestral KC functions are present in both the sawfly and the honey bee. So, they trained sawflies to engage in a common honey bee behavior test, where they learn to associate an odor stimulus with a reward. Although challenging at first, the team was eventually able to engage the sawflies in the memory task. The researchers then manipulated a gene called CaMKII in sawfly larvae, which in honey bees is associated with forming long-term memory, a KC function. When the larvae became adults, their long-term memory was impaired, indicating that the gene plays a similar role in both sawflies and honey bees. Although CaMKII was expressed (i.e., was active) across the entire single KC subtype in sawflies, in honey bees, it was preferentially expressed in only one KC subtype. This suggests that the role of CaMKII in long-term memory was passed down to the specific KC subtype in the honey bee.

Despite differences in the size and complexity of insect and mammalian brains, there are commonalities in terms of function and the basic architecture of the nervous system. That is why the model proposed in this study for the evolution and diversification of KC subtypes may help towards better understanding the evolution of our own behavior. Next, the team is interested in studying KC types acquired in parallel with social behaviors, such as the honey bee’s “waggle dance.”

“We would like to clarify whether the model presented here is applicable to the evolution of other behaviors,” said Takayoshi Kuwabara, doctoral student and lead author from the Graduate School of Science. “There are many mysteries about the neural basis that controls social behavior, whether in insects, animals or humans. How it has evolved still remains largely unknown. I believe that this study is a pioneering work in this field.”

This image illustrates how the diverse and complex Kenyon cell (KC) subtypes of the honey bee evolved from the ancestorlike single KC subtype, represented by the turnip sawfly.

CREDIT

2023 Takayoshi Kuwabara

Behavior test with turnip sawf [VIDEO] |

Paper Title:

Takayoshi Kuwabara, Hiroki Kohno, Masatsugu Hatakeyama, Takeo Kubo. Evolutionary dynamics of mushroom body Kenyon cell types in hymenopteran brains from multi-functional type to functionally specialized types. Science Advances. DOI: 10.1126/sciadv.add4201

Funding:

This research was supported by Grant-in-Aid for Scientific Research (B) 20H03300 (TKubo) and Grant-in-Aid for JSPS Fellows 21J20847 (TKuwabara).

Useful Links
Graduate School of Science: https://www.s.u-tokyo.ac.jp/en/

About the University of Tokyo
The University of Tokyo is Japan's leading university and one of the world's top research universities. The vast research output of some 6,000 researchers is published in the world's top journals across the arts and sciences. Our vibrant student body of around 15,000 undergraduate and 15,000 graduate students includes over 4,000 international students. Find out more at www.u-tokyo.ac.jp/en/ or follow us on Twitter at @UTokyo_News_en.

JOURNAL

Science Advances

DOI

10.1126/sciadv.add4201

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Evolutionary dynamics of mushroom body Kenyon cell types in hymenopteran brains from multi-functional type to functionally specialized types.

ARTICLE PUBLICATION DATE

5-May-2023

Why are there so few insects in the ocean?

New hypothesis says it’s to do with how they harden their shells

Peer-Reviewed Publication

TOKYO METROPOLITAN UNIVERSITY

Different cuticle hardening mechanisms in crustaceans and insects. — IMAGE: CRUSTACEANS HARDEN THEIR SHELLS WITH CALCIUM, WHILE INSECTS HARDEN THEM WITH OXYGEN. THESE MATCH WHAT IS ABUNDANT IN THEIR RESPECTIVE HABITATS. view more
CREDIT: TOKYO METROPOLITAN UNIVERSITY

Tokyo, Japan – Scientists from Tokyo Metropolitan University have proposed a hypothesis for why insects are so rare in marine environments. They previously showed that insects evolved a unique chemical mechanism to harden their shells which uses molecular oxygen and an enzyme called multicopper oxidase-2 (MCO2). Now, they argue that this gives them a disadvantage in the sea, while it confers advantages that help them on land, placing MCO2 at the heart of insect eco-evolution.

Insects are some of the most successful organisms on the planet. They are said to make up the most biomass of all terrestrial animals and have a significant impact on the global ecosystem. However, their abundance is matched by their startling rarity in the sea. Very few insects call the sea home, even though their biological ancestors came from there. It is a pervading mystery of science, one which scientists have been trying to answer for many years.

Now, researchers from Tokyo Metropolitan University led by Assistant Professor Tsunaki Asano have proposed a solution based on evolutionary genetics. The latest in molecular phylogenetics has taught us that both crustaceans and insects are part of the same family, Pancrustacea, and that insects were a branch that left the sea and adapted to the land. They share an important feature, an exoskeleton consisting of a wax layer and hard cuticle. In previous work, the same team showed that when insects adapted to terrestrial environments, they evolved a unique gene that creates an enzyme called multicopper oxidase-2 (MCO2) that helps them harden their cuticles using oxygen. MCO2 mediates a reaction where molecular oxygen oxidizes compounds called catecholamines in the cuticle, turning them into agents that bind and harden the surface. This is in contrast to crustaceans who harden their cuticles using calcium from sea water instead. The team’s claim is that this makes the land far more suitable for insects due to the abundance of oxygen. The sea is now a harsh environment due to both the lack of oxygen and the abundance of better adapted organisms.

But it is not just that the sea is not as hospitable for insects anymore. The hardening and drying of the cuticle via the MCO2 pathway lead to a biomaterial which is not only protective, but also lightweight. They postulate that this may be why insects gained the ability to climb plants, glide, and eventually fly. This allowed them to migrate and occupy previously empty niches in the ecosystem, a strong driving force that led to their sheer numbers. Again, this is in contrast to crustaceans, whose shells are significantly denser, with a strong correlation between density and the degree of calcification.

Of course, insects are hardly the only arthropods to adapt to the land, so it’s clear that MCO2 is not strictly necessary for success in “terrestrial niches.” However, the nature of insect cuticles speaks volumes about their success in the terrestrial environment. In fact, the team believe that MCO2 might be a defining feature of insects: “no MCO2, no insects.” Their work promises an entirely new highlight on the role that cuticle hardening might play in insect evolution and terrestrialization.

JOURNAL

Physiological Entomology

DOI

10.1111/phen.12406

ARTICLE TITLE

Eco-evolutionary implications for a possible contribution of cuticle hardening system in insect evolution and terrestrialisation

New concept for lithium-air batteries

Research project in Germany aims to improve the stability of this novel battery type

Business Announcement

UNIVERSITY OF OLDENBURG

Battery test bench — IMAGE: A LITHIUM-AIR BATTERY CELL IN FRONT OF A TEST BENCH. view more
CREDIT: FRAUNHOFER IFAM

Lithium-air batteries, also known as lithium-oxygen batteries, are candidates for the next generation of high-energy electricity storage devices. Their theoretical energy storage capacity is ten times that of conventional lithium-ion batteries of the same weight, but they are not yet chemically stable enough to provide a reliable solution. Now a newly launched collaborative research project in which a team from the University of Oldenburg, Germany, led by chemist Professor Dr. Gunther Wittstock is participating is testing a new concept to extend the life of these battery cells.

The project, entitled "Alternative materials and components for aprotic lithium-oxygen batteries: chemistry and stability of inactive components – AMaLiS 2.0", is led by IOLITEC Ionic Liquids Technologies, a company based in Heilbronn, Germany. The MEET (Münster Electrochemical Energy Technology) Battery Research Center at the University of Münster and the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in Bremen are also taking part. The project will receive around 1.1 million euros in funding from the Federal Ministry of Education and Research over a three-year period.

Lithium-air batteries basically work in the same way as conventional battery types, but in this type of battery the reaction of lithium ions with oxygen from the air at the positive electrode is used to generate electricity. The big advantage is that lithium-air batteries can store almost as much energy per kilogram as fossil fuels. This means that they have a similar specific energy to today's batteries but weigh much less, which makes them attractive for use in electric cars as well as in stationary energy storage. "However, before we get that far there are still a number of technical problems to be solved," Wittstock underlines. One of these challenges is the lack of electrolyte that are chemically stable at both the positive and the negative electrode. These conductive fluids or solids are located in the area between the two electrodes.

Oxygen from the air is reduced in lithium-air batteries

In lithium-air batteries, one of the electrodes is made of metallic lithium while the other – called the gas diffusion electrode – consists of a porous porous network and conducting material where oxygen (O2) from the air is reduced in an oxidation-reduction reaction. When the battery is discharging, positively charged lithium ions move across the electrolyte from one electrode to the gas diffusion electrode, where they combine with oxygen and electrons from an external electrical circuit to form lithium oxide. This generates an electric current which can be used to provide energy for electrical devices. During charging, lithium and oxygen separate once more and the ions and electrons travel in the opposite direction.

To increase the stability of the lithium-air battery, the project team aims to design a membrane that separates the positive electrode from the negative electrode, thus allowing different electrolytes to be used on either side. "This would significantly expand the options for electrolytes," says IOLITEC's project coordinator Dr Thomas Schubert. The scientists plan to test a separator with a special coating on each side that protects both the lithium electrode and the gas diffusion electrode.

The Oldenburg team led by Wittstock is using various methods, including surface spectroscopy and scanning electrochemical microscopy (SECM), to investigate the processes on the surfaces of the separator and electrodes. IOLITEC is developing the separating layer together with a team from MEET Battery Research Center at the University of Münster which is headed by Verena Küpers. "We are testing different coatings that are specifically adapted to the challenges posed by each type of electrode," Küpers explains.

The MEET team also carries out test measurements. At the Fraunhofer IFAM, a team led by Dr Daniela Fenske is developing a new type of gas diffusion electrode made of nanostructured titanium carbide. "It will be combined with a special membrane that prevents parasitic air components such as carbon dioxide or water vapour from entering the cell," Fenske explains. The researchers' end goal is to develop a prototype that proves that a stable, rechargeable system is achievable. For this, the construction of a flat cell with a surface area of 25 square centimetres is planned.

An online adaptive model for streaming anomaly detection based on human-machine cooperation

Peer-Reviewed Publication

HIGHER EDUCATION PRESS

An Online Adaptive Model for Streaming Anomaly Detection based on Human-Machine Cooperation — IMAGE: FIG.1 THE PROCESSING FLOW OF ISPFOREST view more
CREDIT: HIGHER EDUCATION PRESS LIMITED COMPANY

Anomaly detectors are used to distinguish differences between normal and abnormal data, which are usually implemented by evaluating and ranking the anomaly scores of each instance. A static unsupervised streaming anomaly detector is difficult to dynamically adjust anomaly score calculation.

To solve the problem, a research team led by Prof. Zhiwen Yu published their new research on 15 April 2023 in Frontiers of Computer Science co-published by Higher Education Press and Springer Nature.

The team proposed a human-machine interactive streaming anomaly detection method, named ISPForest, which can be adaptively updated online under the guidance of human feedback. In particular, the feedback will be used to adjust the anomaly score calculation and structure of the detector, ideally attaining more accurate anomaly scores in the future.

The experimental results demonstrated that the utility of incorporating feedback can improve the performance of anomaly detectors with a few human efforts.

In the research, they analyze the anomaly detection principle of the space partitioning forest model. To improve the original anomaly detector, they add the human feedback mechanism for the detection result during the streaming anomaly detection process. Firstly, in the light of the relationship between forest structure and anomaly score calculation, they construct regional likelihood function and instance likelihood function, respectively, to depict the consistency of the detection results and the human feedback. Then, the parameters and structures of the original anomaly detector are adjusted timely according to the gradient decrease process following the principle of maximum likelihood estimation. Finally, an uncertainty function of the detection results is designed to control the frequency of human-machine interaction.

Experimental results on the effects of feedback reveal that combining anomaly detectors with human feedback is meaningful for adapting to a dynamic environment, and the performance of the detector is improved promptly with a small increase in labor costs. Future work can consider the extension of the method and explore the time-series anomaly detection under the feedback mechanism.

Fig.2 An example of updating process