Why an unusual global export industry keeps growing in a developing country

Peer-Reviewed Publication

UNIVERSITY OF JOHANNESBURG

 

VIDEO: THE GLOBAL CITRUS EXPORT INDUSTRY BASED IN SOUTH AFRICA IS AN OUTLIER IN MANY WAYS, NOT LEAST FOR ITS CONTINUED VIGOROUS GROWTH. SOMEHOW, THE INDUSTRY IS NOW THE SECOND BIGGEST IN THE WORLD AFTER SPAIN, WHILE OPERATING FROM A DEVELOPING COUNTRY FACING MANY CHALLENGES. UJ RESEARCHERS SHINGIE CHISORO AND SIMON ROBERTS UNPACK CRITICAL FACTORS DRIVING THIS EXCEPTIONAL SUCCESS. view more 

CREDIT: THERESE VAN WYK, UNIVERSITY OF JOHANNESBURG.

The global citrus export industry based in South Africa is a surprising outlier in many ways, not least for its vigorous growth. Somehow, the diverse industry has emerged as the second biggest in the world after Spain.

Researchers Ms Shingie Chisoro and Prof Simon Roberts unpack the key factors driving this exceptional success in a study published in The European Journal of Development Research.

Chisoro is a PhD candidate and Roberts the Lead Researcher at the Centre for Competition, Regulation and Economic Development (CCRED), within the College of Business & Economics at the University of Johannesburg.

Resilient coalition of growers

Most unusual among the agriculture industries in South Africa, the Citrus Growers` Association of Southern Africa (CGA) has managed to stay intact and align a coalition of 1200 diverse growers.

It was founded in 1997, after shock liberalisation by the first democratic government in South Africa. In the almost 30 years since, it has served all the export citrus growers – since exporting citrus growers are mandated to register with the CGA.

The ability of the growers to come together and align their interests, to form the CGA, with the common goal to be competitive in export markets, is a key success factor for the industry. That coordination and collective organisation through the industry body is fundamental to the industry’s success.

Growers driving their industry

Farming in African economies means struggle. All the risk and associated costs in the value chain ultimately goes back to the growers.

Fruit can obviously only be marketed if it has been grown. Growing requires upfront investment in land preparation, planting material, farm and irrigation infrastructure and systems, chemicals, and continuous improvements in farming methods and technologies to produce quality fruit.

The CGA is doing well in making sure the growers get to drive the industry and succeed.

Organisation through the industry body has ensured that the interests of the most diversified and dispersed value chain participants are represented. Also, that they have collective “grower-power” to shape industry developments and investments for longer-term value creation.

Business and risk model

In value chains, stakeholders downstream from growers (logistics, sales and marketing) tend to appropriate more value, while the grower gets the least value despite often investing the most.

The CGA’s pursuit of value for growers has however created a different business risk and opportunity model for citrus growers in South Africa, compared to other agriculture industries.

Citrus growers own their fruit right through the value chain up until the final sale to overseas export markets, which is different from the case of a dairy farmer or maize (corn) miller. It then follows that if there is a hailstorm, drought, or war, the risk goes back to the citrus grower. But if market prices increase, the grower benefits also.

The CGA is trying to develop the systems and structures to ensure that value goes back to the grower. They do this to improve transparency in the value chain, in the distribution of economic rents – those costs charged in the value chain without any accompanying productivity or value-add.

Independent resources mandated by the government

To fund industry activities, the citrus growers have collectively agreed to a statutory export levy mandated by the National Agricultural Marketing Council. This is similar to other industries such as wine exports from South Africa.

Each citrus exporter in South Africa contributes to the industry levy, charged per carton of exported fruit. In this way, the CGA has access to ongoing and independent resources.

At the time of writing the levy is ZAR 1,64 per 15kg carton, which equates to USD 0,09 per 33 pound carton.

Leveraging industry export levies, the CGA has been able to invest in research and development, market access, and key inputs for export success.

In-house R&D for entrepreneurial response

A very strong in-house technical and research capacity gives the CGA the ability to respond quickly and independently to the requirements and changes in export markets.

The CGA has placed research and development (R&D) at the centre of the industry. They are also smart in how they leverage their R&D to be entrepreneurial in developing key inputs in new or improved cultivars, and crop protection products for established and new pests.

Given the high levels of concentration at the inputs level, the CGA keeps up its efforts to ensure competitive rivalry to bring somewhat cheaper inputs to the grower. It also means the CGA has to develop its own capabilities to play in this field.

Their in-house R&D means that they can more quickly respond to the demands of importing countries and concerns about possible pests and diseases that could block exports, compared to other industries in South Africa that outsource theirs to a government research institution.

Industry drives growth strategy

As an export industry, the CGA is dependent on the national South African government to open doors globally. Market access to export countries, ports, and logistics infrastructure all need to be facilitated by the government.

The collective organization through the industry body has served to strengthen the growers’ position in relation to the government. This has ensured constructive engagement between the industry and the government.

The citrus export industry in South Africa drives its own growth strategy, in collaboration with the government. The industry has been proactive in driving industry developments and ensuring long-term value creation.

Responsive to government priorities

In South Africa, the form of segregation known as apartheid was dismantled with the first democratic election in 1994. However, the exclusion of Black people from financial, business and agricultural activities created by apartheid is still an unfortunate reality for many.

In this context, building a sustainable industry in South Africa required the inclusion of previously excluded Black farmers and the balancing of different interests, to sustain a broad and stable coalition of players and stakeholders.

In response, the CGA developed supporting structures and institutions to include Black growers. Not only for local production, but also to encourage them to supply to export markets.

A fifth of the government-mandated export levy goes to develop Black farmers. In this way, government priorities do influence the CGA’s resources and activities. However, more needs to be done to include Black growers, but the industry is making progress.

Expanding from national to regional

The CGA has not only managed to stay intact since 1997, it has also grown beyond a national industry body, expanding into neighbouring countries.

The CGA of Southern Africa serves Namibia, Botswana, Eswatini and Zimbabwe as well. The regional coalition allows for the transfer of knowledge and technology to the southern African citrus growers and their service agents, leveraging the technical capacity of the CGA.

The CGA as a regional coalition of growers serves to facilitate exports on a regional basis into global markets.

Furthermore, the regional coalition is important for ensuring the biosecurity of the Southern African citrus industry and to control for pests and diseases. For example, if there is a disease in Zimbabwe, it will not destroy South Africa and the other countries, because their biosecurity measures can curb it quickly enough, conclude Chisoro and Roberts.

Funding

Funding was provided by the UK Economic and Social Research Council’s (ESRC) Global Challenges Research Fund (GCRF) (Grant no. ES/S0001352/1).                    

Deciphering outlier success in growing global exports

UNIVERSITY OF JOHANNESBURG

The citrus export industry in South Africa continues its global growth, while other export industries have not managed nearly the same success. To understand the critical factors driving this outlier industry in a challenged developing country, researchers Ms Shingie Chisoro (left) and Prof Simon Roberts (right) took a deep dive into the entire value chain. Chisoro is a PhD candidate and Roberts the Director at the Centre for Centre for Competition, Regulation and Economic Development (CCRED), within the Johannesburg School of Business (JBS) at the University of Johannesburg.

CREDIT

University of Johannesburg

Media Pack

Available at Google Drive without any login, registration or footprint from a computer at:

https://drive.google.com/drive/folders/1S91Hd2h4CwUIcpE24zc0FdK8jCQnDdjp?usp=sharing

 

The media pack includes:

PHOTOS of researchers

VIDEO and the ‘slides’ from the video in JPG format

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JOURNAL

European Journal of Development Research

DOI

10.1057/s41287-023-00591-z 

METHOD OF RESEARCH

Case study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Grower Power for Value Creation in High-Value Horticulture? The Case of Citrus in South Africa

 

Adaptation or avoidance? Microplastics ingestion under the microscope in invertebrates

Peer-Reviewed Publication

GRIFFITH UNIVERSITY

 

IMAGE: IMAGE ACQUIRED BY SCANNING ELECTRON MICROSCOPY SHOWING THE MORPHOLOGY AND SIZE DISTRIBUTION OF MICROPLASTICS. view more 

CREDIT: ELSEVIER

A study led by Griffith University researchers has exposed two generations of a sediment-dwelling invertebrate to microplastic and found that while the ‘parent’ generation experienced negative impacts, the ‘child’ generation did not, possibly suggesting a potential adaptation response. 

The study, led by PhD candidate Hsuan-Cheng Lu and the team from the ARI Toxicology Research Program in Griffith’s Australian Rivers Institute in collaboration with CSIRO, is the first metabolomics assessment in freshwater macroinvertebrate Chironomus tepperi to microplastic exposure. 

The results showed significant negative impacts on survival, growth, and emergence of C. tepperi in the parental generation, but no such adverse effects were observed in the subsequent generation. 

Metabolite profiles in parental generation indicated that ingestion of microplastics could have influence on bioenergetics through inhibition of food acquisition or nutrient assimilation, which subsequently affect the survival, growth and emergence of parental larvae. 

Larvae in unexposed conditions showed no differences in survival or metabolite profiles, suggesting that effects in the parental generation did not carry over to the next generation. 

“The results of the study suggest that Chironomus larvae have the potential to adapt within a generation to environmental stressors, such as low levels of microplastics in sediment,” Lu said. 

As contaminants of emerging concern, microplastics have been widely reported in global freshwater environments and freshwater sediment is considered as a major sink.  

Despite ingestion of microplastics being well documented in aquatic organisms, there is limited information on effects of microplastics on the freshwater sediment-dwelling – or benthic – invertebrates, especially at realistic environmental concentrations and across generations.  

This study provides insight into the lethal effects of microplastics on C. tepperi over two generations. Additionally, this study provides the first evaluation of metabolomics profiling to unravel the potential organismal and physiological responses of microplastics ingestion in C. tepperi. 

“While the findings of the present study suggest that Chironomus larvae can adapt to low levels of microplastics, the mechanism is unclear,” Lu said.  

“Do they learn not to ingest it? Is there a physiological adaptive mechanism? What happens in longer exposures? Do we see this adaptation continue in the 3rd and further generation, or is it lost?  

“Also, our experiment was done with low levels of microplastics, but microplastics contamination is expected to increase as our use of plastics continues to increase, so what would higher levels of microplastics do? 

“Future research should also be conducted to assess the energy uptake and allocation in response to MP exposure.” 

The research ‘Metabolomic responses in freshwater benthic invertebrate, Chironomus tepperi, exposed to polyethylene microplastics: A two-generational investigation’ has been published in the Journal of Hazardous Materials. 

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JOURNAL

Journal of Hazardous Materials

DOI

10.1016/j.jhazmat.2023.132097 

ARTICLE TITLE

Metabolomic responses in freshwater benthic invertebrate, Chironomus tepperi, exposed to polyethylene microplastics: A two-generational investigation

 

Cutting the odds of drug-resistant pathogens emerging in wastewater

Peer-Reviewed Publication

KING ABDULLAH UNIVERSITY OF SCIENCE & TECHNOLOGY (KAUST)

 

IMAGE: TREATING WASTEWATER FOR SAFE REUSE COULD PROVIDE AN INVALUABLE FRESHWATER RESOURCE. view more 

CREDIT: © 2023 KAUST; HENO HWANG.

The combination of chemical and physical stressors that bacteria face during wastewater treatment can impact the transfer of genes between them. But while certain combinations of stressors significantly increase the gene-transfer rate, other combinations reduce it, KAUST researchers have discovered. The finding could inform best practice design and management of wastewater treatment for reuse.

Globally, many regions are considering treated wastewater as a potentially invaluable freshwater source. “As part of the Saudi Vision 2030, water reuse and treatment rates need to be increased,” says Bothayna Al-Gashgari, a Ph.D. student in Peiying Hong’s group, who led the research. “Facilitating safe treatment and reuse is crucial,” she says.

Bacteria can naturally take up extracellular DNA (eDNA) from their surroundings and integrate the functional genes it contains into their genome. Treated wastewater can contain bacteria and eDNA at relatively high concentration. It can also expose bacteria to stressors known to enhance eDNA uptake and integration, including UV light, disinfection chemical byproducts and pharmaceuticals.

“Several studies have highlighted the potential impact of individual stressors in chlorinated wastewater on bacterial horizontal gene transfer,” Al-Gashgari says. But in a real wastewater environment, multiple stressors co-exist. “Our aim was to understand the effects of these factors in combination,” she says.

The researchers hypothesized that multiple stressors would have an additive effect on the gene-transfer rate. Surprisingly, a far more complex picture emerged[1], Hong says.

Depending on their modes of action, some combinations produced a synergistic large increase in gene-transfer rate, some had a neutral effect, while others decreased it.

“For example, when a stressor that can increase bacterial cell wall permeability, such as the pharmaceutical carbamazepine, was combined sequentially with a stressor that causes DNA damage, like solar irradiation, the two stressors had a synergistic effect,” Al-Gashgari says. “We also established that if one stressor interacts detrimentally and directly with the eDNA — such as chloroform — it can impede integration of DNA into the bacterial genome and result in an antagonistic effect.”

This complexity makes the combinatorial effect of multiple stressors difficult to predict, complicating the ability to assess whether unintentional consequences can arise in the downstream reuse environment, says Hong. However, the findings show clear conclusions on wastewater treatment, she says.

The key goal should be to keep the bacteria and eDNA in wastewater at such low concentrations that gene transfer is minimized.

“We argue that, rather than sand filtration, wastewater treatment facilities should retrofit microfiltration membranes because they can remove both bacteria and extracellular DNA to levels that would not facilitate natural transformation,” Hong says. “Installing and operating membrane microfiltration would be more expensive than sand filtration, but we urge utilities to take this precautionary approach.”

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JOURNAL

Nature Water

DOI

10.1038/s44221-023-00110-8 

ARTICLE TITLE

Impact of chemicals and physical stressors on horizontal gene transfer via natural transformation

 

From passerine birds to cranes - Neolithic bird hunting in Upper Mesopotamia

Peer-Reviewed Publication

STAATLICHE NATURWISSENSCHAFTLICHE SAMMLUNGEN BAYERNS

 

IMAGE: PILLAR 43 FROM GÖBEKLI TEPE DEPICTING A VULTURE WITH ITS WINGS SPREAD. VULTURES WERE NOT ONLY THE MOST IMPORTANT BIRDS IN THE ICONOGRAPHY OF EARLY NEOLITHIC HUNTER-GATHERER GROUPS, THEY WERE ALSO HUNTED. view more 

CREDIT: N. PÖLLATH, SNSB-SPM

Besides mammals, ranging from aurochs to hares, or fish, foragers also pursued an impressively large spectrum of bird species in Southeast Anatolia 11,000 years ago. They were hunted mainly, but not exclusively, in autumn and winter – at the time of year, when many bird species form larger flocks and migratory birds cross the area. The species lists are therefore very extensive: At the Early Neolithic settlement of Göbekli Tepe, for example, c.18 km northeast of present-day Şanlıurfa (SE Anatolia, Turkey), the researchers identified the remains of at least 84 bird species. Dr. Nadja Pöllath, curator at the Bavarian State Collection for Palaeoanatomy (Staatssammlung für Paläoanatomie München SNSB-SPM) and Prof. Dr. Joris Peters, chair of the Institute for Palaeoanatomy, Domestication Research and History of Veterinary Medicine at LMU München and director of the state collection, identified the Neolithic bird bones with the aid of the reference skeletons of the state collection.

The researchers were surprised by the large number of small passerine birds identified at Göbekli Tepe, comprising mainly starlings and buntings. In principle, the Early Neolithic inhabitants of Göbekli Tepe hunted birds in all habitats – mainly in the open grassland and wooded steppe in their direct surroundings, but also in the wetlands and gallery forest somewhat further away.

‘We do not know exactly, why they hunted so many small passerine birds at Göbekli Tepe. Due to their low live weight, the effort exceeds the meat yield by far. Perhaps they were simply a delicacy that enriched the menu in autumn, or they had a significance that we cannot deduce yet from the bone remains,’ Nadja Pöllath comments on her findings.

The inhabitants of Gusir Höyük, another Early Neolithic settlement on the shores of Lake Gusir, about 40 km south of the present-day provincial capital of Siirt, even further southeast in present-day Turkey, had a different approach: When fowling they pursued almost exclusively two species populating open hilly grasslands: the Chukar partridge (Alectoris chukar) and the grey partridge (Perdix perdix). They apparently ignored the avifauna of the nearby floodplains and the lake. Among several hundred fragments from Gusir Höyük, the archaeozoologists from Munich could not identify a single bone pertaining to waterfowl. ‘Gusir Höyük is the only Neolithic community in Upper Mesopotamia known to us that deliberately avoided wetlands and riverine landscapes when fowling, although they were present. Our results suggest that this was a cultural peculiarity of the Neolithic people inhabiting Gusir Höyük,’ said Prof. Dr. Joris Peters. ‘Our comparison of a number of Early Neolithic sites in the region revealed that the sites in the Euphrates Basin share many similarities regarding their meat procurement, while each community in the Tigris Basin seemingly developed its own subsistence strategy,’ adds Nadja Pöllath.

Neolithic settlers of Upper Mesopotamia hunted birds not only for their meat. Some species, such as cranes or raptors, certainly had a more symbolic meaning and served ritual purposes, the researchers suspect. In a future study, they will focus on these socio-cultural aspects of the human-avian relationship.

Tarsometatarsi (bone of the lower leg) of birds from the Göbekli Tepe site (from top to bottom): Eurasian jackdaw (Coloeus monedula), hooded crow (Corvus cornix), small duck (Anas crecca/Spatula querquedula), Chukar partridge (Alectoris chukar), medium-sized owl (Asio sp.).

Excavation at Gusir Höyük on the shores of Lake Gusir

CREDIT

J. Peters, LMU/SNSB-SPM

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JOURNAL

Archaeological and Anthropological Sciences

DOI

10.1007/s12520-023-01841-1 

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Distinct modes and intensity of bird exploitation at the dawn of agriculture in the Upper Euphrates and Tigris River basins

ARTICLE PUBLICATION DATE

25-Sep-2023

First experimental study to propose a therapy to correct memory deficit caused by disorders in the fetal alcohol spectrum

Research conducted in a mouse model identifies the neurobiological mechanism responsible for alterations in the memory of young individuals exposed to alcohol during pregnancy and lactation. This study proposes a therapy that can reverse the deficit

Peer-Reviewed Publication

UNIVERSITAT POMPEU FABRA - BARCELONA

 

IMAGE: FROM LEFT TO RIGHT: INÉS GALLEGO, ANTONI PASTOR, ALBA GARCIA-BAOS, OLGA VALVERDE AND RAFAEL DE LA TORRE. CREDIT: UPF. view more 

CREDIT: UPF

A research team of the Department of Medicine and Life Sciences (MELIS) at Pompeu Fabra University (UPF) involving the Hospital del Mar Research Institute has for the first time, in mice, identified and validated the neurobiological mechanism and therapy to correct memory deficit in individuals with fetal alcohol spectrum disorders (FASD). These results pave the way for studying whether the mechanism is the same in humans, which would enable improving the diagnosis and treatment of affected individuals. 

Fetal Alcohol Spectrum Disorder (FASD) includes a number of conditions suffered by infants who have been exposed to alcohol during pregnancy. The effects of FASD range from craniofacial morphological malformations or growth problems, in the most severe cases, to hyperactivity, emotional and motivational difficulties or defects in learning and memory, in the mildest cases. 

“In children of normal appearance, FASD is underdiagnosed and is often mistaken for hyperactivity or ADD”, explains Rafael de la Torre, coordinator of the Integrated Pharmacology and Systems Neuroscience Research Group at the Hospital del Mar Research Institute. “Since there is no diagnosis, there is no treatment, and symptomatic therapy is given to alleviate hyperactivity or other disorders such as anxiety”. 

The results of the study published in the journal Molecular Psychiatry, have allowed the researchers to observe that “exposure to alcohol need not be chronic for FASD to occur. Sporadic consumption ending in intoxication - getting drunk- is enough to observe alterations in memory, in mice”, explains Olga Valverde, study coordinator and director of the Research Group in Behavioural Neurobiology at the MELIS-UPF. 

The study shows that mice born to mothers that have consumed alcohol sporadically during pregnancy and lactation have a memory deficit that persists into adulthood. One of the reasons for this deficit is that alcohol affects the function of the endocannabinoid system, reducing the expression of the PPAR-𝛄 receptor. 

“The endocannabinoid system is greatly involved in learning and memory processes”, de la Torre explains. “That is why it is especially relevant that this decrease occurs during infancy, when the mice, male and female, are of learning age”. However, the reduction in PPAR-𝛄 does not occur throughout the brain. It is limited to the hippocampal astrocytes -cells that support neurons controlling functions such as their metabolism or the inflammation to which they are subjected- of the hippocampus.

After confirming the neurobiological mechanism by three different routes, the study also proposes an effective treatment with the drug pioglitazone, commonly used to control sugar and which stimulates PPAR receptors. According to the first author of the study, Alba Garcia-Baos, “manages to alleviate the cognitive memory deficits of individuals with FASD in infancy”. 

 

Optimism regarding studies in humans

The results of this study pave the way for studying the effects of other cognitive impairments caused by alcohol exposure during pregnancy. “In this work we have only studied alterations in memory, but there may be emotional, motivational or behavioural alterations related to FASD”, points out Valverde, who is also a full professor of Psychobiology at UPF. 

Although this study has been conducted in mice, the researcher is optimistic about confirming that this mechanism is replicated in humans “because we are two species of mammals that share many similarities”. In addition, if confirmed, “it would be relatively simple to carry out a study to validate whether the therapy we propose works in humans, since there are drugs that have similar effects to the ones we have used that are approved for use in children”.

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JOURNAL

Molecular Psychiatry

DOI

10.1038/s41380-023-02191-z 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

The role of PPAR-γ in memory deficits induced by prenatal and lactation alcohol exposure in mice

 

Origin of cultural learning: Babies imitate because they are imitated

Peer-Reviewed Publication

LUDWIG-MAXIMILIANS-UNIVERSITÄT MÜNCHEN

LMU study shows that babies learn to imitate others because they themselves are imitated by caregivers

People are constantly learning from others without even being aware of it. Social learning avoids laborious trial and error; the wheel does not have to be reinvented each time. But where does this ability come from, which forms the basis of cultural learning and consequently for the evolutionary success of the human species? A study led by Professor Markus Paulus.

Chair of Developmental Psychology and Educational Psychology at LMU, demonstrates that the ability has its roots in earliest childhood. “Children acquire their ability to imitate because they themselves are imitated by their caregivers,” says Markus Paulus.

Children are incredible imitators – thanks to their parents

For the study, the researchers looked at the interaction between mother and child over several months. The babies came into the lab for the first time at the age of 6 months, while their final visit was when they were 18 months old. As they engaged in various play situations, the interactions and imitations of mother and child were analyzed.

The longitudinal study shows that the more sensitive a mother was in her interactions with her six-month-old child and the more often she imitated the infant, the greater the child’s ability was at the age of 18 months to imitate others.

In the interaction between parents and child, mutual imitation is a sign of communication. Parents respond to the signals given by the child and reflect and amplify them. A mutual imitation of actions and gestures develops. “These experiences create connections between what the child feels and does on the one hand and what it sees on the other. Associations are formed. The child’s visual experience is connected to its own motor activity,” says Markus Paulus, explaining the neuro-cognitive process.

Children learn a variety of skills through imitation, such as how to use objects, cultural gestures like waving, and the acquisition of language. “Children are incredible imitators. Mimicry paves the way to their further development. Imitation is the start of the cultural process toward becoming human,” says Markus Paulus. In psychology, the theory that the ability to imitate is inborn held sway for a long time. The LMU study is further evidence that the ability is actually acquired.

 

The cultural transfer of knowledge is based on imitation

How well children learn to imitate others is crucially dependent on the sensitivity with which their parents respond to them. In this context, sensitivity is defined as the capability of a caregiver to pick up on the child’s signals and react promptly and appropriately to them. “The sensitivity of the mother is a predictor of how strongly she imitates her child,” says Dr. Samuel Essler, lead author of the study.

In addition, the study sheds light on what makes humans social beings, namely that our individual abilities only develop through interaction with others. Indeed, they owe their existence to the particular way in which humans raise their young.

“By being part of a social interaction culture, in which they are imitated, children learn to learn from others. Over the course of generations and millennia, this interplay has led to the cultural evolution of humans,” says Markus Paulus. “Through social learning, certain actions or techniques do not have to be constantly invented anew, but there is a cultural transfer of knowledge. Our results show that the ability to imitate, and thus cultural learning, is itself a product of cultural learning, in particular the parent-child interaction.”

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JOURNAL

Current Biology

DOI

10.1016/j.cub.2023.08.084 

ARTICLE TITLE

The cultural basis of cultural evolution: Longitudinal evidence that infant imitation develops by being imitated

ARTICLE PUBLICATION DATE

27-Sep-2023

 

Sperm swimming is caused by the same patterns that are believed to dictate zebra stripes

Peer-Reviewed Publication

UNIVERSITY OF BRISTOL

 

IMAGE: GRAPH view more 

CREDIT: HERMES GADÊLHA

Patterns of chemical interactions are thought to create patterns in nature such as stripes and spots. This new study shows that the mathematical basis of these patterns also governs how sperm tail moves.

The findings, published today in Nature Communications, reveal that flagella movement of, for example, sperm tails and cilia, follow the same template for pattern formation that was discovered by the famous mathematician Alan Turing. 

Flagellar undulations make stripe patterns in space-time, generating waves that travel along the tail to drive the sperm and microbes forward.

Alan Turing is most well-known for helping to break the enigma code during WWII. However he also developed a theory of pattern formation that predicted that chemical patterns may appear spontaneously with only two ingredients: chemicals spreading out (diffusing) and reacting together. Turing first proposed the so-called reaction-diffusion theory for pattern formation.

Turing helped to pave the way for a whole new type of enquiry using reaction-diffusion mathematics to understand natural patterns. Today, these chemical patterns first envisioned by Turing are called Turing patterns. Although not yet proven by experimental evidence, these patterns are thought to govern many patterns across nature, such as leopard spots, the whorl of seeds in the head of a sunflower, and patterns of sand on the beach. Turing’s theory can be applied to various fields, from biology and robotics to astrophysics. 

Mathematician Dr Hermes Gadêlha, head of the Polymaths Lab, and his PhD student James Cass conducted this research in the School of Engineering Mathematics and Technology at the University of Bristol. Gadêlha explained: “Live spontaneous motion of flagella and cilia is observed everywhere in nature, but little is known about how they are orchestrated.

“They are critical in health and disease, reproduction, evolution, and survivorship of almost every aquatic microorganism in earth."

The team was inspired by recent observations in low viscosity fluids that the surrounding environment plays a minor role on the flagellum. They used mathematical modelling, simulations, and data fitting to show that flagellar undulations can arise spontaneously without the influence of their fluid environment.

Mathematically this is equivalent to Turing’s reaction-diffusion system that was first proposed for chemical patterns.

In the case of sperm swimming, chemical reactions of molecular motors power the flagellum, and bending movement diffuses along the tail in waves. The level of generality between visual patterns and patterns of movement is striking and unexpected, and shows that only two simple ingredients are needed to achieve highly complex motion.

Dr Gadêlha added: “We show that this mathematical 'recipe’ is followed by two very distant species – bull sperm and Chlamydomonas (a green algae that is used as a model organism across science), suggesting that nature replicates similar solutions.

“Travelling waves emerge spontaneously even when the flagellum is uninfluenced by the surrounding fluid. This means that the flagellum has a fool-proof mechanism to enable swimming in low viscosity environments, which would otherwise be impossible for aquatic species.

“It is the first time that model simulations compare well with experimental data.

“We are grateful to the researchers that made their data freely available, without which we would not have been able to proceed with this mathematical study.”

These findings may be used in future to better understand fertility issues associated with abnormal flagellar motion and other ciliopathies; diseases caused by ineffective cilia in human bodies.

This could also be further explored for robotic applications, artificial muscles, and animated materials, as the team discovered a simple 'mathematical recipe' for making patterns of movement.

Dr Gadêlha is also a member of the SoftLab at Bristol Robotics Laboratory (BRL), where he uses pattern formation mathematics to innovate the next generation of soft-robots.

“In 1952, Turing unlocked the reaction-diffusion basis of chemical patterns,” said Dr Gadêlha. “We show that the ‘atom’ of motion in the cellular world, the flagellum, uses Turing's template to shape, instead, patterns of movement driving tail motion that pushes sperm forwards.

“Although this is a step closer to mathematically decode spontaneous animation in nature, our reaction-diffusion model is far too simple to fully capture all complexity. Other models may exist, in the space of models, with equal, or even better, fits with experiments, that we simply have no knowledge of their existence yet, and thus substantial more research is still needed!”

The study was completed using funding from the Engineering and Physical Sciences Research Council (EPSRC) and DTP studentship for James Cass PhD

The numerical work was carried out using the computational and data storage facilities of the Advanced Computing Research Centre, at the University of Bristol.

  

Stripe patterns

Stripe patterns in space time

CREDIT

Hermes Gadêlha

video [VIDEO] | EurekAlert! 

Paper:

‘The reaction-diffusion basis of animated patterns in eukaryotic flagella’ by James Cass and Dr Hermes Bloomfield-Gadêlha in Nature Communications.

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JOURNAL

Nature Communications

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Cells

ARTICLE TITLE

The reaction-diffusion basis of animated patterns in eukaryotic flagella

ARTICLE PUBLICATION DATE

27-Sep-2023