Sweet smelling odorant transforms solitary locusts into aggressive swarms

2020 not only brought a worldwide pandemic with Covid-19 and severe forest fires in Australia, it also brought unusually large locust swarms in Africa and the middle East in regions where food is already scarce at the best of times. In particular East Africa saw its worst locust plague in decades. These swarms consisting of billions of locusts (Locusta migratoria) descend onto hundreds of square kilometres at a time, devouring crops, and other vegetation completely. 

The only defence is currently aerial spraying of pesticides which can be hit and miss as the swarms move fast and unpredictably. In addition, the chemicals can harm beneficial insects as well livestock and the environment. 

Researchers from China find the way forward

But new research shows that there is a light at the end of a very long tunnel. It has long been assumed that the swarms congregate due aggregation pheromone excretion that attracts more and more locusts. A Chinese research team headed by Xianhui Wang and Le Kang of the Chinese Academy of Sciences has discovered the key compound 4VA (4-vinylanisole), a molecule emitted by gregarious locusts. This compound is a volatile odorant and smells sweet to humans.

Locusts are solitary by nature and averse to socialising. But something happens when four to five locusts congregate. They will start to produce 4VA which will in turn attract more locusts and transform them into their gregarious state. 4VA attracts locusts of all sexes and ages whether they are in their solitary or gregarious state. As the group grows, more and more 4VA is emitted attracting locusts from ever larger distances contributing to the exponential growth of the swarm into millions and billions of individuals. The compound also contributes to the cohesion of the swarm over a longer period of time.

The researchers suggest using the molecule to lure the locusts away from crops and trap them. So far traps laced with 4VA have only had limited success. It is assumed that a larger concentration of the compound may be needed. But another factor could play an important role. It is also thought that 4VA is not the only chemical causing this mass congregation but that there are other background odours causing the behaviour by amplifying the swarming signal. More research is still needed on this.

The Chinese researchers also discovered that the locusts use the OR35 olfactory receptor of their antennae to detect 4-vinylanisole. They used the gene editing technique CRISPR-Cas9 to deactivate this particular receptor which in turn led to the locusts to ignore the presence of 4VA. The locusts showed no behavioural changes.

This discovery could lead to further research of chemicals that block the activity of this particular receptor. These chemicals could cause the locusts to stop congregating and turn back to their solitary and more peaceful way of life.

Sources

• https://www.sciencenews.org/article/locust-swarms-pheromones-pest-control

• https://www.nature.com/articles/s41586-020-2610-4.epdf

• https://cen.acs.org/biological-chemistry/chemical-communication/molecule-makes-locusts-swarm/98/i31

• https://www.sciencenews.org/wp-content/uploads/2020/09/091220_FullGuide.pdf

• https://www.nature.com/articles/d41586-020-02264-x

Gynandromorph animals – a rare phenomenon indeed

Gynandromorphs are animals with male characteristics in one half of their body and female characteristics in the other unlike hermaphrodites which also develop genitals of both sexes but show generally no other changes. Birds, insects and crustaceans are currently the only types of animals where gynandromorphism has been discovered and it is an extremely rare phenomenon.

In insects and birds, this is likely to be the result of an egg fertilised by two sperm, one with male, one with female chromosomes and on cell division forms an animal that is literally half male, half female. This is not just displayed in their genitalia but their plumage, markings, wing and body shape, and even their brains. 

For birds another explanation exists with the case of a chimera where two embryos start to develop but fuse into one. 

In crustaceans, however, the cause for gynandromorphism is unknown. The sex in crustaceans is hormonally determined and can vary due to environmental chemicals such as pesticides but is also subject to temperature. This means that a change in the environment of the crustacean could lead to the formation of a gynandromorph. 

In May 2005, a gynandromorph blue crab was found which showed the male characteristics of a blue claw tip and pointed underside “apron” on one side and the female red claw tip and rounded underside. 

The crab’s special genetic makeup helped researchers better understand the sexual development and breeding behaviours of blue crabs. 

In September 2020, a group of researchers came across an unusual looking bird while they were out capturing and banding birds. It was a rose-breasted grosbeak, but it showed the tell-tale signs of a male bird on the right side and female plumage on the left side. The bird was in its non-breeding plumage so the differences will be even more visible come spring when the colours become more vibrant. Annie Lindsay, the scientist who made the discovery had only come across another gynandromorph once before which was 15 years ago. 

It is unknown whether these very special birds behave more like males or females as they are extremely rare, so animal behaviour studies are extremely difficult. For this reason, we also don’t know yet whether gynandromorph birds are able to reproduce. After being able to observe a gynandromorph cardinal for 40 days between 2008 and 2010, it was documented that the bird didn’t have a mate and was also unable to sing but it wasn’t subjected to any antagonistic behaviour from other birds.

In Pennsylvania, another gynandromorph cardinal was spotted in 2019 which, again, showed male red feathers on his right side and tan coloured ones on his left. Depending on the reason for the gynandromorphism in this bird, it might also have a half male, half female brain. In this case it is unlikely that the bird would be able to sing (a solely male trait). Another interesting theory arises, as a pure male cardinal tried to court the gynandromorph bird. Gynandromorphs are usually infertile but there could be exceptions. As this particular individual’s left side is female and only the left ovary in birds is functional, offspring might be possible. We will have to wait and see.

A rare gynandromorph zebra finch was also able to shed light on whether sex differences are purely the result of hormone secretions during neonatal life or whether sex chromosome genes acting within cells could also contribute to these differences in cell function. After testing it became apparent that sexual differentiation is controlled by both.

Sources:

• https://www.sciencenews.org/article/bird-male-female-grosbeak-gynandromorph

• https://www.pnas.org/content/100/8/4873

• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1752225/

• https://www.vims.edu/newsandevents/topstories/archives/2005/dual_sex_crab.php

• https://www.sciencemag.org/news/2014/12/half-male-half-female-bird-has-rough-life

• https://www.livescience.com/64831-cardinal-gynandromorph.html

• https://www.iflscience.com/plants-and-animals/bilateral-gynandromorphs-animals-are-quite-literally-half-male-and-half-female/

Microbe protects mosquitos from malaria parasite

Research is a step closer to eradicating malaria

Malaria is a disease most commonly contracted in the tropical and sub-tropical regions of our planet by the protozoan Plasmodium. There are several different species of Plasmodium that cause malaria in various forms and severity. The malaria parasite is transmitted by the female Anopheles mosquito which bites mostly between dusk and dawn.

Sub-Saharan Africa accounts for 93% of worldwide cases and 94% of the 400,000 worldwide deaths caused by malaria. It is in this region where in 2017 a team of Kenyan and UK scientists found a novel method with significant potential to completely stop mosquitoes from transmitting the malaria causing parasite.

The discovery of a possible break in the transmission chain

Healthy mosquitoes often have microbial symbionts that can alter the biology of their hosts. One of these symbionts, Microsporidia MB which was found in around 5% of studied mosquitos had the effect that the mosquito could not be infected with Plasmodium falciparum, one of the most common and deadly malaria parasites in Africa. This was found in laboratory conditions but also works in nature as the microbe-carrying mosquitoes are prevented from also carrying the malaria parasite. 

This discovery could be a major factor in breaking the transmission chain. Thus far, most interventions have focussed on preventing humans from being infected through mosquito nets and chemoprophylaxis. Progress with insecticide treated mosquito nets has plateaued at an estimated 40% reduction so a different approach is necessary. Malaria presents a major burden on the economic development of sub-Saharan Africa therefore research into this debilitating disease is ongoing. The Kenyan-UK team says that these new findings have “enormous potential” to finally control the disease. One of the scientists, Jeremy Herren from the International Centre of Insect Physiology and Ecology in Kenya even spoke of data showing a “100% blockage” of malaria. 

Microsporidia MB settles in the insect’s midgut and ovaries and is not known to affect the insect’s fertility or survival. In addition, the microbe can be passed on from female mosquitoes to eggs and offspring, making it even more ecologically sound. 

More research is still needed

The beneficial microbe is closely related to fungi and lives as a symbiont with the Anopheles mosquito. One of the ideas is to release spores to suppress the disease, another to release spore infected insects into the wild. Further studies are still needed to find the best possible mechanism to control malaria transmission with these findings. 

Similar research already exists in combating dengue fever. For this disease, the MRC University of Glasgow Centre for Virus Research reports “using a transmission-blocking symbiont called Wolbachia to control dengue, a virus transmitted by mosquitoes. The Microsporidia MB symbiont has some similar characteristics, making it an attractive prospect for developing comparable approaches for malaria control”. 

Sources:

• https://healthpolicy-watch.news/breakthrough-malaria-parasite-transmission-blocking-microbe-found/

• https://www.nature.com/articles/s41467-020-16121-y

• https://thebiomedicalscientist.net/news/microbe-stops-malaria

• https://www.who.int/ith/diseases/malaria/en/

• https://qz.com/africa/1853116/kenyan-british-mosquito-scientists-use-microbe-to-stop-malaria/

Octopuses using tools for protection against predators

Octopuses are among the more unusual beings in the animal world. They not only possess three hearts, nine brains and blue blood, part of their behaviour also includes the use of tools. 

The use of tools was originally one of the defining features that set us humans apart from animals. Since then, an ever-growing wide variety of animals have been also observed to use tools. This ranges from chimpanzees using twigs to extricate well-hidden termites, capuchin monkey cracking nuts with rocks and bottlenose dolphins using sponges to retrieve prey from the bottom of the ocean. The list also includes crows and other birds using twigs to spear larvae, some even go as far as adapting them to their specific purpose. Invertebrates, however, had not been observed to acquire items to be used at a later stage before this study in 2009. 

The intelligence of octopuses

Octopuses have proven their intelligence in a number of ways. In experiments, they solved mazes and completed tricky tasks for food rewards. They are able to recognise humans and also read their behaviour to some degree. The latter has been shown through attempts of escape whenever the researcher wasn’t looking. 

Compared to all other invertebrates, octopuses have a much higher brain-to-body ratio which accounts in part for their high intelligence. It is even larger than numerous vertebrates, although not mammals. In addition, octopuses (as well as squids and cuttlefish) have evolved with a much larger nervous system and better cognitive capabilities. Each of their arms is equipped with its own brain enabling them to taste, touch and control basic actions independent from the central brain.

How octopuses use tools

Octopuses pick up coconuts to use them at a later point in time as protection from predators. They often carry them over distances of up to 20 meters along the ocean floor. They turn the coconuts so that the concave surface is on top, then wrap themselves over the coconut half, using their arms as legs in a form of “stilt walk” and tiptoe along the bottom of the ocean. During this transport the shell provides no protection from predator as the head and body are fully exposed. The benefit comes later when the octopus deploys one or more shells as a shelter to hide underneath as and when the need arises.

Julian Finn from La Trobe University in Bundoora, Australia, one of the researchers of the study recalls the first time he saw the tool wielding behaviour of the veined octopus (Amphioctopus marginatus) in Indonesia:

”While I have observed and videoed octopuses hiding in shells many times, I never expected to find an octopus that stacks multiple coconut shells and jogs across the seafloor carrying them. I could tell that the octopus, busy manipulating coconut shells, was up to something, but I never expected it would pick up the stacked shells and run away. It was an extremely comical sight -- I have never laughed so hard underwater."

Sources:

• https://www.sciencedirect.com/science/article/pii/S0960982209019149

• https://www.nhm.ac.uk/discover/octopuses-keep-surprising-us-here-are-eight-examples-how.htm

• https://www.scientificamerican.com/article/the-mind-of-an-octopus/

• https://www.tandfonline.com/doi/abs/10.1080/10888705.2010.483892

• https://www.sciencedaily.com/releases/2009/12/091214121953.htm

• https://www.nationalgeographic.com/news/2015/06/150605-octopus-tools-animals-ocean-science/

How ostrich eggshell beads helped our ancestors to survive

Ornaments have been worn by humans since the dawn of civilisation. They have been used to express our individuality and to signify relationships. From around 75,000 years ago beads begin to appear and from about 50,000 years ago they started to be made from ostrich eggshells. Ostrich eggshell beads are among the most commonly found archaeological artefacts in Africa.

Ostrich eggshell beads as currency

But these eggshell beads were not only used to adorn our bodies. A study published in March 2020 suggests that they were used as gifts to create a sense of indebtedness across groups of hunter-gatherers. Around 33,000 years ago they created a social safety net across a large part of southern Africa with ostrich eggshell beads as its currency.

Ostriches lived in dry, flat savannahs but not at the rock shelters where many of the beads were found. The assumption is that inland residents would have made the beads. The beads were then passed on from group to group over long distances. The discoveries show that this went on for tens of thousands of years.

Hunter-gatherer exchange networks exist today. Their purpose is to reduce survival risks by creating mutual support through gift-giving. The Ju/’hoãn people in southern Africa’s Kalahari Desert use this system to this day and are the basis for modelling how prehistoric hunter-gatherer groups might have operated. The practice of gift-giving for mutual benefit is called hxaro. Hxara partners live quite often live as far apart as 100km in areas with complementary resources.

Brian Stewart of the University of Michigan in Ann Arbor and his colleagues have concluded that the beads were given as gifts to create goodwill and unity across groups of hunter-gatherers. They suspect that groups in resource-rich areas such as the coastal Lesotho highland could have provided food to their inland counterparts where food and other resources were scarce, especially during times of drought. Whatever was given in exchange for the beads probably did not preserve through the millennia.

Determining the origin of the beads

The age of the beads was determined through carbon dating. This technique, however, cannot determine origin. For this purpose, an analysis of strontium isotopes in the ostrich shell beads that is compared to strontium isotopes in plant, soil, water and mammal teeth samples from different regions is used. Different geographical regions show different signature strontium concentrations which makes it possible to determine location.

Examining the size of beads also plays a role in determining age. Beads found at hunter-gatherer sites are usually smaller than those found at herder sites. As herding in Africa only started about 2000 years ago, sites with larger beads tend to be younger than those will smaller beads.

“I suspect these practices began long before 33,000 years ago, and not just in southern Africa.”

Stewart’s research matches the idea that different hunter-gatherer groups often contain in-laws and unrelated individuals who maintain contact for the benefit of all. Stewart speculates that this ancient exchange network is much more widespread, both historically and geographically by saying “I suspect these practices began long before 33,000 years ago, and not just in southern Africa.”

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Sources:

• https://www.sciencenews.org/article/hunter-gatherers-stone-age-social-networks-ostrich-eggshell-beads

• https://www.pnas.org/content/117/12/6453

• https://theconversation.com/the-tiny-ostrich-eggshell-beads-that-tell-the-story-of-africas-past-128577

• https://phys.org/news/2019-11-ostrich-eggshell-beads-reveal-years.html

• https://www.academia.edu/25714637/Beauty_and_the_Bead_Ostrich_Eggshell_Beads_through_Prehistory.