From so simple a beginning

Evolution and Biodiversity

Light-sensitive types

18 February 2026 / / 0 Comments

Stolen chloroplasts influence the behaviour of the lettuce sea slug

Lettuce sea slug avoids strong light to protect its kleptoplasts

The chloroplasts carried by the lettuce sea slug Elysia crispata need light for photosynthesis. But light must not be too intense, and the green sea slug knows that light-sensitivity, Xochitl Vital and colleagues explain.

The lettuce sea slug, Elysia crispata, has chloroplasts in its body that have been ‘stolen’ from algae and give the animal a green appearance. Chloroplasts are small organelles of plant cells. The lettuce sea slug and some other Elysia species suck out the content of cells of filamentous algae and digest the contents. Except for the chloroplasts, which they keep intact and incorporate in special cells in the wall of their extensive intestinal tract.

In the green sea slugs, the chloroplasts continue what they did in the algae: with the help of sunlight, they capture carbon dioxide and convert it into carbohydrates and fats. This process, photosynthesis, produces oxygen. In a handful of Elysia species the chloroplasts, which are now called kleptoplasts, remain functional for months. These green sea slugs cannot survive without them. The lettuce sea slug is one of them. While it ensures that the stolen chloroplasts can capture sunlight, it avoids high light intensity, as Xochitl Vital and colleagues show, because excessive sunlight is harmful for the stolen chloroplasts.

Elysia species belong to the Sacoglossa or sap-sucking sea slugs. The lettuce sea slug lives in the western Atlantic Ocean and the Caribbean, on and near coral reefs, at depths of 5 to 10 meters. It is about 5 centimetres long and feeds on several algae species.

Solar energy

For a long time, the question was: why do green sea slugs like the lettuce sea slug retain the stolen chloroplasts for months? According to some researchers, once these animals have accumulated enough chloroplasts, they could henceforth live on solar energy just like plants. Others suspected that the chloroplasts are to be digested as food.

It turns out there is some truth to both. Green sea slugs cannot live solely on the carbohydrates and fats produced by kleptoplasts. They need to keep eating. But the products of photosynthesis help survive periods of food shortage. Also, they are used to boost fertility. So, the animals do use solar energy.

But in the event of a prolonged food shortage, the kleptoplasts can be digested, so they also form an emergency food supply.

Sun damage

Another question was: how do the lettuce sea slug and other green sea slugs keep their stolen chloroplasts active? Chloroplasts originate from photosynthesizing cyanobacteria. More than a billion years ago, a distant ancestor of plants absorbed such bacterium, which evolved into an integrated cell organelle within its ‘host’. Most of its genetic material (DNA), including genes for the synthesis and repair of its thousands of proteins, migrated to the host’s cell nucleus. Chloroplasts are therefore dependent on the plant’s genetic material for their maintenance. They kept only a few genes themselves.

Green sea slugs, however, only retain stolen algal chloroplasts, not the cell nuclei containing the maintenance genes. The lack of maintenance genes is critical because the kleptoplasts are exposed to a significant risk. Under intense light, aggressive oxygen compounds will form that damage the kleptoplasts’ proteins. Plants can scavenge these oxygen compounds or repair the damage thanks to the maintenance genes they acquired from resident cyanobacteria in the distant past. But how should green sea slugs maintain their kleptoplasts?

The researchers had previously shown that chloroplasts of some algae kept some of the original maintenance genes. This is effective in some cases, depending on Elysia and algae species. But maintenance abilities of the lettuce sea slug are poor. Nevertheless, its kleptoplasts remain active for up to three months.

Acclimatized

The lettuce sea slug, it turns out, protects its kleptoplasts by searching for low-light areas, even though this is not optimal for photosynthesis. Moreover, green sea slugs have flaps with a wavy edge on each side, parapodia, which they can fold over the kleptoplasts to block sunlight.

Now, the researchers show that the lettuce sea slug adapts its behaviour to the light tolerance of its kleptoplasts. Within plants, chloroplasts can acclimate to the environment: they can adapt to the amount of light available. In sea slugs, kleptoplasts cannot acclimate. They remain adapted to the light level they were exposed to in the algae they were stolen of. A lettuce sea slug with chloroplasts from algae grown in a habitat with high irradiance will choose a place with higher light intensity than a sea slug with chloroplasts from algae grown in a less bright location.

Surprising

In conclusion: the animals are actively looking for a place where the kleptoplasts can perform photosynthesis as much as possible without suffering significant sun damage.

It will help. Still, it is surprising that the lettuce sea slug and some other Elysia species recognize chloroplasts when they suck up the contents of algae, leave them intact and incorporate them into their cells. And that they manage to keep the stolen chloroplasts in good condition for months without having all necessary tools to do so. And that, apparently, it is worth the effort.

Willy van Strien

Photo: Elysia crispata. Pauline Walsh Jacobson (Wikimedia Commons, Creative Commons CC By 4.0)

Thanks to stolen chloroplasts, some Elysia species can regenerate a new body from a loose head

Sources:
Vital, X.G., S. Cruz, N. Simões, P. Cartaxana & M. Mascaró, 2026. The photoacclimation state of stolen chloroplasts affects the light preferences in the photosynthetic sea slug Elysia crispata. Journal of Experimental Biology 229: jeb251281. Doi:10.1242/jeb.251281
Burgués Palau, L., G. Senna & E.M.J. Laetz, 2024. Crawl away from the light! Assessing behavioral and physiological photoprotective mechanisms in tropical solar‑powered sea slugs exposed to natural light intensities. Marine Biology 171: 50. Doi: 10.1007/s00227-023-04350-w
Morelli, L., V. Havurinne, D. Madeira, P. Martins, P. Cartaxana & S. Cruz, 2024. Photoprotective mechanisms in Elysia species hosting Acetabularia chloroplasts shed light on host-donor compatibility in photosynthetic sea slugs. Physiologia Plantarum 176: e14273. Doi: 10.1111/ppl.14273
Cruz, S. & P. Cartaxana, 2022. Kleptoplasty: getting away with stolen chloroplasts. PLoS Biology 20: e3001857. Doi: 10.1371/journal.pbio.3001857
Cartaxana, P., E. Trampe, M. Kühl & S. Cruz, 2017. Kleptoplast photosynthesis is nutritionally relevant in the sea slug Elysia viridis. Scientific Reports 7: 7714. Doi: 10.1038/s41598-017-08002-0

Nest tail

9 February 2026 /

Sloppy tail camouflages the nest of a blue manakin

Blue manakin adds sloppy tail to its nest

A female blue manakin builds a nest with a tail made of debris attached to it. This is not without reason: the tail protects against predators, according to Cassiano Bueno Martins and colleagues.

A bird’s nest often looks neat. But not the nest of the blue manakin, Chiroxiphia caudata. Beneath the bowl-shaped structure, less than 5 centimetres high, hang one or more long, messy strands of plant material, such as old leaves, mosses, and twigs. You can hardly tell it is a nest anymore. And that is just the point, Cassiano Bueno Martins and colleagues write.

The blue manakin is a small bird that lives in the Atlantic forests of southeastern Brazil, the far northeast of Argentina, and eastern Paraguay. Males are a beautiful blue with a black head and red crown; they sing and dance to attract females, most males never succeeding. The olive-green females care for the offspring. They build their nests in a shrub or young tree, often above a stream.

Camouflage

A nest with eggs or young is vulnerable to predators. It must therefore be as unobtrusive as possible. And perhaps, Martins hypothesized, the sloppy tails on the blue manakin’s nests are a form of camouflage. A nest with such a tail is visible but not easily recognized as a nest. The shape is obscured.

He tested this by collecting abandoned nests and attaching them to branches in a new location. He clipped the tails of half of the nests. After placing two plasticine eggs in each nest, he set up a video camera that would trigger whenever an animal came in front of it. During twenty days, it recorded what happened; the incubation period is eighteen days.

Functional

Most nests remained untouched, but not all. And whether a tail was attached to the nest or not made a significant difference. One or both eggs were stolen from nests without tails ten times more often than from nests with tails: 20 percent compared to 2 percent. The culprits were other bird species, including a toucan and a motmot.

The tail on blue manakin nests appears to offer protection against predators that search for food by sight during the day. But the question remains to what extent this works when a nest is occupied, i.e., when there are real eggs in it or when the activity of the mother and her young could attract attention. In any case, the tail is not a sloppy feature, but a functional addition.

Willy van Strien

Photo: Blue manakin male. Dario Sanches (Wikimedia Commons, Creative Commons CC BY-SA 2.0)

Watch the courtship of blue manakin on YouTube

Source:
Martins, C.B., D.L. Bruno & M.R. Francisco, 2026. Why do birds construct nest tails? A test of disruptive camouflage in the blue manakin. Biology Letters 22: 20250453. Doi: 10.1098/rsbl.2025.0453

Matricide

26 November 2025 /

Ant workers obey parasitic queen

Queens of the yellow meadow ant may be displaced by Lasius orientalis

The presence of a queen in a colony of yellow meadow ants is essential for the workers, her daughters. Yet, the parasitic ant Lasius orientalis induces the workers to commit matricide, as Taku Shimada and colleagues witnessed.

A colony of the yellow meadow ant, Lasius flavus, is sometimes taken over by a queen of Lasius orientalis. And what is more: the workers assist her in this takeover, according to Taku Shimada and colleagues. To their own detriment, because the takeover heralds the end of the original colony. How do they get so crazy?

The yellow meadow ant occurs in Asia, North Africa and Europe; Lasius orientalis occurs in parts of Asia.

Population replacement

The yellow meadow ant, a light-coloured insect, lives in underground nests and engages in animal husbandry: the ants breed root aphids in their nests and consume the honeydew they excrete. The ants only appear above ground in July and August, during nuptial flights. Multiple young queens jointly establish a colony. Later, the queens fight for dominance until only one queen remains per nest.

Lasius orientalis has another life cycle. Like some other ant species, it is temporarily parasitic. Young queens of these species are unable to establish a colony on their own, but require a well-functioning colony of another species to settle. A young queen invades such a colony and eliminates the legitimate queen. She then makes the orphaned workers – daughters of the missing queen – serve her, parasitizing on their workforce. They care for the eggs laid by the intruder as if it were eggs of their own queen.

Once the parasite produced her own workers, they maintain the new colony that then is no longer parasitic, but independent. Gradually, the members of the original colony are replaced by strangers.

Hostile takeover

But don’t think that a parasitic lifestyle is easy. A parasitic queen must overcome significant obstacles before she can take over a colony. First, she must enter the nest without being discovered as a stranger and chased away or killed. To achieve this, she must somehow acquire the correct colony scent. And once inside, she struggles to attack and kill the resident queen, which is fiercely defended by her colony.

For that last hurdle, Lasius orientalis, upon entering a nest of the yellow meadow ant, has a gruesome solution: she doesn’t attack the queen herself, but leaves that job to the workers present, the daughters that normally defend their mother so ferociously. That is quite something!

Manipulation

Shimada shows how it happens. The intruder sprays the legitimate queen several times with a fluid from her abdomen, likely formic acid. Formic acid is a corrosive defence agent that also functions as an alarm signal. The sprayings make the workers increasingly nervous and aggressive to their mother, which is laden with formic acid. It escalates to such a point that the workers kill their mother after a few days. Then only the hostile queen remains. The workers accept her and allow themselves to be abused;  from now on, they work for the benefit of an alien colony.

There’s another shameless species: Lasius umbratus, a temporarily parasitic ant that conquers Lasius japonicus colonies. Also this ant manipulates the behaviour of the conquered workers so that they kill their own mothers.

Willy van Strien

Photo: Yellow meadow ant, winged queens. Dat doris (Wikimedia Commons, Creative Commons CC BY-SA 4.0)

The story on YouTube

Source:
Shimada, T., Y. Tanaka & K. Takasuka, 2025. Socially parasitic ant queens chemically induce queen-matricide in host workers. Current Biology 35: R1065–R1080. Doi: 10.1016/j.cub.2025.09.037

Safe under the covers

28 October 2025 /

A stinkbug (Megymenum gracilicorne) mother covers her eggs with fungal hyphae

Females of Megymenum gracilicorne culture fungi in an organ on their hind legs

Females of the stinkbug Megymenum gracilicorne protect their eggs in a surprising way, namely with fungal threads they grow on their hind legs, as Takanori Nishino and colleagues discovered.

A striking white, woolly patch can be seen on both hind legs of adult females of the stinkbug Megymenum gracilicorne. It resembles a hearing organ, like some insects have, and the initial assumption was that it was used to perceive sound. But that is not the case, as Takanori Nishino and colleagues demonstrate. Through a multifaceted study, they investigated what the structure is, and they discovered it to be a specific organ that had never been found before.

So, what do we see on the female hind legs and what is its function?

Fungal culture

The bug Megymenum gracilicorne lives in Japan on wild plants of the cucumber family. It sometimes becomes a pest in cucumber and pumpkin cultivation. The researchers show that the structure on the hind legs of females consists of a thick and rigid cuticle with about 2000 pores. On the inside, this cuticle is lined with a layer of glandular cells that connect to the pores and secrete sugar-rich substances. Fungi grow from the pores, creating the white, woolly patch.

This means that the hind legs of females carry a nutrient-rich habitat for fungi. Adult females cultivate fungi on their hind legs, so to speak. They don’t do this without reason, of course. What benefits do the fungi provide to the bugs?

Parasitic wasps repelled

The bugs transfer the fungi to their eggs, the surface of which is covered with sugars, the researchers saw. Each time a female lays an egg, she scrapes fungal threads from one hind leg with the tip of the opposite one and smears them onto the egg. She lays the eggs in a row. After a few days, such a row is fully overgrown with fungus.

The fungus appears to protect the eggs of Megymenum gracilicorne from parasitic wasps. Given the opportunity, these wasps lay their eggs inside the bug eggs; after hatching, the parasitic wasp larvae then consume the eggs’ contents. Although parasitic wasps are attracted to fungus-covered eggs, their ovipositors cannot penetrate a thick layer of fungus to deposit an egg. Thus, the fungus does not deter the predator by its odour but forms a physical defence.

In exchange for sugars and shelter they get from the bug, the fungi provide protective material for the bug eggs: a form of symbiosis. The white structure on females’ hind legs is a hitherto unknown external symbiotic organ, and this collaboration between stinkbug and fungi is new to biology.

Collect

When young stinkbug nymphs hatch, they are covered in fungi. But they lose it during their development, and an adult female must collect fungi to culture. She is not very choosy, so the researchers found multiple fungal species on each female’s hind legs. However, she is careful enough not to select pathogenic fungi. How she manages to avoid these is still unknown.

Willy van Strien

Photo: Megymenum gracilicorne female. The white line on the hindleg is the fungus-growing organ. ©Minoru Moriyama

Source:
Nishino, T., M. Moriyama, H. Mukai, M. Tanahashi, T. Hosokawa, H-Y. Chang, S. Tachikawa, N. Nikoh, R. Koga, C-H. Kuo & T. Fukatsu, 2025. Defensive fungal symbiosis on insect hindlegs. Science 390: 279-283. Doi: 10.1126/science.adp6699

Two species, nevertheless brothers

23 September 2025 /

Messor ibericus queen produces sons of a different species

Two species from one mother: Messor ibericus and Messor structor

Queens of the Iberian harvester ant Messor ibericus have four types of offspring: not only workers, queens, and males of their own species, but also males of another species. Biologically impossible? Yannick Juvé and colleagues explain how it became reality.

Colonies of the ant Messor ibericus in Southern Europe are home to a queen, workers, and males of Messor ibericus – but also males of another species: Messor structor. This is odd, as colonies of Messor structor are absent from most areas where Messor ibericus lives. For instance, on Sicily, where the nearest Messor structor colony is on the mainland, more than 1,000 kilometres away.

It was a mystery how this could happen, but the solution that Yannick Juvé and colleagues now propose is no less puzzling. They discovered that these structor males are sons of the ibericus queen, and therefore brothers of the ibericus males.

It could not get any crazier, although in biology, you are never sure.

Mama’s boys

It will not be a surprise that there is a complicated story behind this. Yet it is an understandable story. Just keep in mind that ants, like bees and wasps, have an unusual system for sex determination.

In most animal and plant species, each individual, male or female, has two sets of chromosomes, small bodies in the cell nuclei that contain the hereditary material DNA; one set comes from the mother, the other from the father. Eggs and sperm each have one set of chromosomes, and after fertilization, a new individual develops with a double set, inheriting characteristics from both parents. But this is not the case with ants, bees, and wasps: females (queen or worker) have two sets of chromosomes, while males have only one. This is because males develop from unfertilized eggs. They are therefore literally mama’s boys; they have no father.

A queen mates with one or more males, stores the sperm and later lays eggs which she may or may not fertilize.

In two steps, Messor ibericus deviated from this pattern.

Hybrid workers

The first step was that an ibericus queen mates not only with males of her own species, but also with those of another species, Messor structor. She stores both types of sperm, and she can apparently distinguish between them. Eggs fertilized with ibericus sperm produce young queens, while eggs fertilized with structor sperm produce workers, which are hybrids with DNA from an ibericus mother and a structor father. If a queen does not mate with a structor male, she cannot produce workers and is unable to establish a colony; interspecies matings are necessary.

It is weird – and it is amazing that fertilization with sperm from another species is possible – but it happens in some other ant species as well. Such species exploit males of another species. These males gain nothing from it, because their sperm only produces worker bees, which do not reproduce. It is sperm parasitism.

Seed eaters

A quick aside: why do ibericus workers have to be hybrids? One hypothesis is that this allows for a distinction between queens and workers. In species with regular, that is, non-hybrid, workers, there is no genetic difference between queens and workers. The difference in form and behaviour that both types of females exhibit as adults is a consequence of the food they receive as larvae. Future queens receive a higher-protein diet, with a greater proportion of animal matter. But Messor species are harvester ants; they collect and eat exclusively seeds. This makes it difficult to differentiate in the diet of female larvae. A genetic difference is then helpful.

And because workers, not queens, are produced with foreign sperm, hybridization does not compromise the inheritance of the ants’ own DNA. Queens, which reproduce, are 100 percent ibericus.

Trick

Back to the main story. The production of hybrid workers was the first step towards the unusual lifestyle of Messor ibericus. It worked, but it confined the species to the area where Messor structor lived. Further dispersion was impossible.

To become independent of the presence of Messor structor, ibericus queens took a second step, Juvé now discovered: they produce structor males themselves, alongside males of their own species. And that step is unique.

Ibericus queens produce structor males by laying eggs with a nucleus that contains only a paternal set of chromosomes. They retrieve this set from a structor sperm cell they have in storage. This requires a trick that has not yet been clarified. Queens may either strip eggs of maternal DNA before fertilization or destroy it afterwards. The result: a son; in this case not a mama’s boy, but a foreign child. It sounds simple, but it must have been difficult to match the foreign paternal chromosome set with the maternal cell machinery.

Domesticated

Once successful, ibericus queens always had structor males in their colony to produce workers and new structor sons. Messor ibericus was no longer restricted to the presence of Messor structor and now has a much larger distribution range.

In the areas where the two species coexist, part of France, Switzerland, and northern Italy, ibericus queens still mate with structor males from structor colonies.

But elsewhere they produce two types of sons: hairy ibericus sons and nearly hairless structor sons. The structor males are an integral part of the life cycle of Messor ibericus. They are isolated from their own species; they do not encounter them, and even if they did, they would not be able to mate with a structor queen. They form a completely domesticated lineage.

Mutual parasites

While structor males initially were abused as sperm suppliers that could not produce fertile offspring themselves (the first step), the situation took on a new dimension after the second step. Domesticated structor males do have offspring that can reproduce: their sons. The ibericus colony ensures this reproduction, so the domesticated structor males are also parasitic themselves. Dependency and parasitism have become mutual.

What seemed biologically impossible, does exist. Apparently, in evolution, everything even remotely conceivable – no matter how improbable or complex – will eventually come into existence.

Willy van Strien

Photos: Males of two species from the same mother: Messor ibericus on the left and Messor structor on the right. Photo from the researchers (Creative Commons CC BY 4.0)

Sources:
Juvé, Y., C. Lutrat, A. Ha, A. Weyna, E. Lauroua, A.C. Afonso Silva, C. Roux, E. Schifani, C. Galkowski, C. Lebas, R. Allio, I. Stoyanov, N. Galtier, B.C. Schlick-Steiner, F.M. Steiner, D. Baas, B. Kaufmann & J. Romiguier, 2025. One mother for two species via obligate cross-species cloning in ants. Nature, 3 September online. Doi: 10.1038/s41586-025-09425-w
Romiguier, J., A. Fournier, S.H. Yek & L. Keller, 2017. Convergent evolution of social hybridogenesis in Messor harvester ants. Molecular Ecology 26: 1108-1117. Doi: 10.1111/mec.13899

Lights in a spider web

15 September 2025 /

Ensnared fireflies lure others into the trap

Spider Psechrus clavis with fireflies in her web

The Taiwanese spider Psechrus clavis will not immediately consume a firefly that has flown into her web. That is because the insect’s lanterns still glow for an hour, attracting even more tasty fireflies, Ho Yin Yip and colleagues write.

Fireflies exchange sexual messages with light produced by chemical reactions in special organs in their abdomen. The winter firefly Diaphanes lampyroides from Taiwan is an example. Males and females use light signals to locate each other. It is an effective communication system.

The Taiwanese spider Psechrus clavis exploits this sexual signal. If a glowing firefly lands in her web, she uses it to intercept more fireflies.

Glow

Fireflies are also called glowworms. Both names are misleading, as they are neither flies nor worms, but beetles (family Lampyridae). Adult females have no wings, and lying on the ground at night, they emit light to attract males; depending on the species, they do this continuously or intermittently. Males locate females by flying around. In some species, males do not emit light; in others, they produce a constant glow, and in still others, they emit series of flashes to reveal their presence.

Male firfly Diaphanes lampyroides

In Diaphanes lampyroides, both males and females emit a constant glow in the dark. Males have two ‘lanterns’, females have four.

For the spider Psechrus clavis their light comes in handy.

Decoy

Psechrus clavis is active in the dark. Females weave an irregular sheet-web horizontally above the ground. It was already known that the white silk of the web and the yellow stripe on the abdomen of the spider, which hangs below the web, attract insects, particularly moths. Now, it appears that the catch is greater when male fireflies are ensnared in the web (female fireflies never end up in a web, since they do not fly).

The researchers observed that the spider simply leaves such a firefly hanging, while she immediately consumes any other prey. The two lanterns of a captured male firefly continue to glow for an hour. And this light attracts other male fireflies, many of which will also fly into the web. Field experiments with LED lights in spider webs confirm the attractivity of the light.

By sparing a male firefly and using it as a decoy, Psechrus clavis catches more of these beetles. A clever strategy.

The question is why male fireflies are attracted to a glowing male in a Psechrus clavis web. Aren’t they looking for females? Probably, males have difficulty distinguishing the two immobile lights of a captive male from the four lights of a stationary female; the lights are the same colour. It is better then to approach all immobile lights than to miss a chance to encounter a female.

Manipulation

Another question is why a man caught in a web keeps glowing. Its light is of no use anymore. Perhaps, the researchers write, it is a response to danger: fireflies also use their lights to deter predators. Or perhaps the spider forces him to keep glowing.

The latter seems unlikely. But Xinhua Fu and colleagues described exactly such a case of coercion last year. Their research concerned another Asian spider, namely Araneus ventricosus, which is also active at night and weaves an orb web. One of this spider’s prey species is the firefly Abscondita terminalis, a species in which immobile females regularly broadcast single-pulse light signals with one lantern, while flying males produce flash trains with two lanterns.

A male’s behaviour changes radically once he has flown into the web of Araneus ventricosus. He starts emitting light signals that mimic those of a female: single-pulse flashes emitted from a single lantern. Other males are attracted to this signal and also become ensnared – to the spider’s advantage.

Apparently, the spider Araneus ventricosus manipulates the captive male, but it is unknown how. She uses venom to paralyze prey, and researchers hypothesize that her bite or venom affects the nervous system of a captive male firefly in such a way that it switches to an abnormal, feminine light signal.

Willy van Strien

Photos:
Large: the Taiwanese spider Psechrus clavis with fireflies in her web. ©Tunghai University Spider Lab
Small: winter firefly Diaphanes lampyroides, male. LiCheng Shih (via Flickr, Creative Commons CC BY 2.0)

Sources:
Yip, H.Y., S.J. Blamires, C-P. Liao & I-M. Tso, 2025. Prey bioluminescence-mediated visual luring in a sit and wait predator. Journal of Animal Ecology, 27 August online. Doi: 10.1111/1365-2656.70102
Fu, X., L. Yu, W. Zhou, C. Lei, R.R. Jackson, M. Kuntner, Q. Huang, S. Zhang & D. Li, 2024. Spiders manipulate and exploit bioluminescent signals of fireflies. Current Biology 34: PR768-R769. Doi: 10.1016/j.cub.2024.07.011
Lai, C-W.,  S. Zhang, D. Piorkowski , C-P. Liao & I-M. Tso, 2017. A trap and a lure: dual function of a nocturnal animal construction. Animal Behaviour 130: 159-164. Doi: 10.1016/j.anbehav.2017.06.016

Race against overheating

4 September 2025 /

Namib Desert beetle cools down by running fast

Namib Desert beetle runs to cool down

The Namib Desert beetle withstands the heat of the sun-drenched desert by running. Carole Roberts and colleagues explain this unexpected fact.

The Namib Desert beetle, Onymacris plana, regularly sprints across the scorching sand of the Namibian desert dunes when the sun is shining and there’s no wind. You might think this wouldn’t turn out well: the creature would overheat. But Carole Roberts and her colleagues show that the beetle actually loses heat by running. How strange!

The beetle is about 2 centimeters long and black, has a horizontally flattened body, long legs, and fused elytra, so it cannot fly. These animals forage during the day for food, blown-in organic matter, and males also search for females. The dunes in the Namib Desert are sparsely covered with grasses and shrubs. Therefore, the beetles cannot remain in the shade all the time but must venture out onto the open sand.

Fatal temperature

That sand is often very hot. The surface temperature can reach as high as 70°C. Namib Desert beetles must be able to withstand this.

It helps that the animals stand high on their legs, with their bodies a centimeter and a half above the surface. It’s 10 to 15 degrees cooler there. But they would still quickly overheat in the sun, Roberts calculates. Male beetles heat up 6 degrees Celsius per minute from the sun’s radiation, females 4 degrees. When they walk or run, the exertion adds another degree. An animal that starts with a comfortable body temperature would reach 50°C within minutes and succumb, because that temperature is fatal.

But this doesn’t happen. That is: as long as the animal keeps running.

High speed

The researchers managed to measure the beetles’ body temperature using a tiny thermometer attached to a long wire. A beetle standing still in the sun – they tested this on dead animals – does indeed warm up quickly. But a running beetle cools down, as it turned out.

A Namib Desert beetle runs at a speed of almost 1 meter per second. That is fast for its size. It maintains this speed for 50 seconds on average, covering over 40 meters.

The researchers theorized that the air passing over its body during such a sprint takes heat away. The flattened body dissipates heat easily. Air flowing past removes more heat than solar radiation and exertion add, resulting in the beetle cooling down. Lab tests confirmed this idea.

The Namib Desert beetle is, as far as we know, the only animal that loses heat by running as fast as it can in the sun when there is no wind. A few insects are known to cool down by flying, the authors write, following the same principle.

Willy van Strien

Photo: Namib Desert beetle Onymacris plana. Lidine Mia (Wikimedia Commons, Creative Commons CC BY-SA 4.0)

Source:
Roberts, C.S., E.L. McClain, M.K. Seely, D. Mitchel, V.L. Goodall & J.R. Henschel, 2025. Beetling the heat – the diurnal Namib Desert beetle Onymacris plana cools by running. Journal of Experimental Biology 228: jeb250379. Doi:10.1242/jeb.250379

Fish without males

15 July 2025 /

Amazon molly is a sexual parasite

In Amazon molly, only females exist.

All Amazon mollies are female. A female mates with a male of another species—and then gives birth to daughters that are clones of herself. What sustains this sexual parasitism? Waldir Berbel-Filho and colleagues solve a piece of the puzzle.

The tropical fish Poecilia formosa, the Amazon molly, has a peculiar sex life. The species consists only of females that reproduce asexually: they produce daughters that are genetic copies of the mothers. However, a female must mate with a male to initiate the development of the embryos. Since there are no males of their own species, she will mate with a male of a related species. His sperm triggers the development of her eggs, but his genetic material (DNA) is sidelined. He does not contribute to the genetic make-up of the offspring.

Amazons thus sexually parasitize males of other species. Researchers like Waldir Berbel-Filho and his colleagues are puzzled by how this situation can persist.

Hybrid

The Amazon molly is a freshwater fish averaging about 5.5 centimetres in length that lives in southern Texas and northeastern Mexico. The species is a hybrid, resulting from a single mating event of a male Poecilia latipinna (sailfin molly) and a female Poecilia mexicana (shortfin molly). These parental species are the ‘hosts’ on which the Amazones sexually parasitize.

Where Amazon mollies live, typically only one of the parent species is found, either the sailfin molly or the shortfin molly. The silvery-gray females of all three species look quite similar, but they differ in body shape: the shortfin molly is longer and thinner than the sailfin molly, and its shorter dorsal fin is inserted more posteriorly. Amazon mollies are intermediate in body shape between the two parental species, but their shape varies across locations.

Miracle

Hybridization occurred 100,000 to 200,000 years ago, meaning that the Amazon molly has gone through approximately 500,000 generations.

That’s a miracle. Because male sailfins and shortfins that mate with an Amazon do not sire any offspring, you’d expect them to learn to distinguish between an Amazon molly and a female of their own species and avoid mating with an Amazon molly. But if they would mate only with females of their own species, the Amazon molly can’t reproduce and becomes extinct.

In addition, the Amazon molly competes with its parental species for food; the fish mainly eat algae and small insects. And because Amazons only have daughters, their populations can grow twice as fast as those of the parental species, which produce equal numbers of sons and daughters. The Amazons could therefore displace the parental species, but then, due to a lack of males, they also perish.

Body shape

It seems like a hopeless situation. To explain why Amazon mollies still manage to survive, Berbel-Filho investigated three possibilities.

First possibility: to attract males, Amazons in each location most closely resemble females of the parental species that is present there. So, where they coexist with sailfin molly, they resemble female sailfin molly, and where they coexist with shortfin molly, they resemble female shortfin molly. In other words, they deceive males through mimicry.

Second possibility: to diminish competition for food, Amazon mollies differ from females of the parental species that they coexist with. If that parental species is sailfin molly, they resemble female shortfin mollies, and vice versa. The underlying idea is that a different body shape is associated with a slightly different diet, so that species with different body shapes at least have some of the available food for themselves, and the species can coexist.

Third possibility: the shape variation of Amazon mollies is random and independent of the parental species with which they occur.

Detailed measurements showed that the second possibility is correct. Amazon mollies are less similar in body shape to females of the parental species with which they coexist. The conclusion is that Amazons do not displace the locally present parent species through food competition, although it still needs to be proven that a difference in body shape indeed reduces competition for food.

Waste

But then there is the other danger: the danger that males of the parental species won’t mate with Amazons. The difference between females in each location helps males distinguish the sexual parasite from their own species. Previous research has shown that males indeed mate more often with females of their own species. So how does the Amazon molly manage to survive?

There is no clear answer to that yet. It could be, I think, because females differ on average. The fish vary in body shape, and there is some overlap between females of the local parental species and Amazons. If males were so choosy as to avoid any mating with an Amazon, they would also reject some females of their own species and miss out on paternity. If the amount of sperm they produce isn’t limiting, they’d be better off wasting some sperm to the wrong females than losing fertilisation opportunities with good ones.

Willy van Strien

Photo: Amazon molly, Poecilia formosa. ©Tyler Reich

Sources:
Berbel-Filho, W.M., M. Tobler, T. Reich, A. Eghbalpour, M.J. Ryan, K. Heubel, F. Garcia-De León & I. Schlupp, 2025. Converging or diverging? Shape coevolution between a sperm-dependent asexual and its sexual hosts. Proceedings of the Royal Society B 292: 20250432. Doi: 10.1098/rspb.2025.0432
Riesch, R., M. Plath, A.M. Makowicz & I. Schlupp. 2012. Behavioural and life-history regulation in a unisexual/bisexual mating system: does male mate choice affect female reproductive life histories? Biological Journal of the Linnean Society 106: 598-606. Doi: 10.1111/j.1095-8312.2012.01886.x
Riesch, R., I. Schlupp & M. Plath, 2008. Female sperm limitation in natural populations of a sexual/asexual mating complex (Poecilia latipinna, Poecilia formosa). Biology Letters 4: 266-269. Doi: 10.1098/rsbl.2008.0019

Victims of own defence

11 June 2025 /

Assassin bug Pahabengkakia piliceps hunts bees with their own weapon

Pahabengkakia at the entrance of nest of stingless bees

The assassin bug Pahabengkakia piliceps specializes in capturing stingless bees. To do so, it uses the resin with which the bees defend their nest, Zhaoyang Chen and colleagues show.

To protect their nest against small predators such as ants, beetles and spiders, workers of the stingless bee Trigona collina apply drops of plant resin around the nest entrance and guard bees keep an eye on the entrance. The defence is adequate: unwanted visitors are trapped in the resin and can be eliminated. But one predator is unaffected and even sabotages the system: the assassin bug Pahabengkakia piliceps. It uses the resin to catch the bees themselves, Zhaoyang Chen and colleagues write.

The stingless bee Trigona collina lives in Thailand and China. It establishes colonies in cavities in termite nests, soil, trees or, sometimes, walls of buildings. A nest is surrounded by a wall and accessible through a thin tube of wax and resin.

Sticky

The assassin bug Pahabengkakia piliceps goes to this entrance tube and smears its front and middle legs with resin that the bees have deposited there for defence. Remarkably, the bees do not interfere. With the sticky legs raised, the bug then can grasp bees that approach it – and that are faster than it – immobilize them, take them to its hiding place and pierce them with its stylet (rostrum) to suck their haemolymph (insect blood).

But it is not the stickiness of the resin alone that helps him capture bees, Chen discovered. When, in an experiment, he smeared resin on the hind legs and abdomen of an assassin bug instead of the front and middle legs, the bug was less successful in capturing bees. But the guard bees approached it just as fanatic. Why?

Aromatic

The researchers show that resin on an assassin bug emits more volatile substances, and is therefore more aromatic, than resin droplets at the nest entrance. This is because resin that is evenly spread on a moving animal dries out less quickly.

And the strong resin smell works as a lure. It is also released when an animal ends up in a resin droplet and struggles to get loose, a signal to the guards to go for it. The smeared predatory bug imitates that struggle and in doing so, it attracts bees that it can then easily catch with its sticky front and middle legs. It uses the bees’ resin as a tool for its own purpose: to obtain food.

He uses the bees’ defence weapon against them.

Specialist

There are other assassin bugs that catch their prey with sticky legs, but they are not as specialized as Pahabengkakia piliceps, which only has a few species of stingless bees on its menu. Not only does it catch bees with their own weapon, but sometimes it also lays eggs in the bee nest. The young bugs (nymphs) that emerge from these are not recognized as foreign by the hosts because their body shape resembles that of bees. They feed on the brood of the bees and on adult workers in the nest.

Defence mechanisms of Trigona collina can’t get a grip on the specialized predator Pahabengkakia piliceps.

Willy van Strien

Photo: assassin bug Pahabengkakia piliceps at the entrance of a bee nest. © Zhaoyang Chen

Hunting Pahabengkakia piliceps on YouTube

See also: a generalist sticky assassin bug

Sources:
Chen, Z., L. Tian, J. Ge, S. Wang, T. Chen, Y. Duan, F. Song, W. Cai, Z. Wang & H. Li, 2025. Tool use aids prey-fishing in a specialist predator of stingless bees. PNAS 122: e2422597122. Doi: 10.1073/pnas.2422597122
Jongjitvimol, T. & W. Wattanachaiyingcharoen, 2007. Distribution, nesting sites and nest structures of the stingless bee species, Trigona collina Smith, 1857 (Apidae, Meliponinae) in Thailand. The Natural History Journal of Chulalongkorn University 7: 25-34. Doi: 10.58837/tnh.7.1.102916
Wattanachaiyingcharoen, W. & T. Jongjitvimol, 2007. First record of the predator, Pahabengkakia piliceps Miller, 1941 (Reduviidae, Harpactorinae) in the stingless bee, Trigona collina Smith, 1857 (Apidae, Meliponinae) in Thailand. The Natural History Journal of Chulalongkorn University 7: 71-74. Doi: 10.58837/tnh.7.1.102921

Rain call

5 June 2025 /

Chaffinch warns mate if nest is in danger

The chaffinch's rain call is a specific alram call

With his rain call, a male common chaffinch warns its partner of predators that threaten eggs and young, Léna de Framond and colleagues show.

A common chaffinch not only can produce its song with the characteristic flourish at the end, but also an often-melancholic sounding ‘rain call’. This call has nothing to do with coming rain. What does it mean, Léna de Framond and colleagues wondered.

It is a peculiar call, different from the other calls that the common chaffinch (Fringilla coelebs) has in its repertoire. Only a male calls this call; he repeats it every few seconds and continues to do so for minutes. He calls only during the breeding season and from his territory. And, as in songs, there are dialects, or local differences, which means that the call is partly learned. Its function, De Framond writes, was not known until now.

Playback

There are several possible functions. The rain call, like the song, could be a way to charm a female or to defend the territory and scare off rivals. It could serve as a warning signal to other birds when a predator appears. Or it could be a form of communication between male and female.

To find out which of the three possibilities applies, the researchers did playback experiments in a forest. First, they let male chaffinches listen to the chaffinch’s song, his rain call or, as a control, the song of a blackbird. They noted how each male finch responded to the sound offered: did he sing or call, or did he become aggressive.

In another experiment, they played the sound of a predator or the song of a blackbird with increasing intensity to see if that would elicit the rain call. As enemies they chose the Eurasian sparrowhawk, which hunts adult chaffinches and sometimes grasps young, and the carrion crow, which does not attack adult finches but plunders nests. In both playback experiments they noted whether a female or another male was nearby. In addition, they observed the spontaneous behavior of finches.

Nest in danger

These experiments and observations provided clarity about the function of the rain call: the second possibility – that it is an alarm signal – is the correct one. But it is not a general alarm signal. It is specifically aimed at the partner and warns her when the nest is in danger.

This result is consistent with the fact that the male guards and defends territory and nest, while the female builds the nest, incubates the eggs and raises the young; he helps with feeding them, but she does most of the work. And to complete the story: when dad calls the rain call, the young fall silent so as not to attract the attention of nearby predators.

The rain call is often heard. Apparently, life is not without worries for a chaffinch family.

Willy van Strien

Photo: Male common chaffinch. Membeth (Wikimedia Commons, Creative Commons, public domain CCO 1.0)

The rain call of common chaffinch on YouTube

Source:
Framond, L. de, R. Müller, A. Comin & H. Brumm, 2025. Decoding the chaffinch “rain” call: a female-directed alarm call? Behavioral Ecology, online 4 May. Doi: 10.1093/beheco/araf039

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