Newly discovered fungus species manipulates cave spiders
The newly discovered fungus Gibellula attenboroughii infects cave spiders and forces them to help spread its spores, Harry Evans and colleagues report.
Animals that are infected with parasites may behave like zombies. The parasite manipulates their behaviour so that they cooperate to their own demise, to the benefit of the parasite. The ability of parasites to do this is amazing; it shows that they are able to control their host’s nervous system. There are multiple examples, as you will see in the category manipulation; they are gruesome tales.
Also some parasitic fungi do it. Gibellula attenboroughii, named for the renowned wildlife documentary filmmaker David Attenborough, is a newly found parasitic fungus that lives in spiders. Harry Evans and colleagues describe this species.
The researchers discovered the fungus Gibellula attenboroughii in an abandoned gunpowder store in Ireland, growing on the orb-weaving cave spider Metellina merianae. This European spider lives in caves, hollows, and cellars, where it hides near its web. But a fungal infected spider, it turns out, leaves its safe place and settles on the ceiling or wall near the entrance, where air circulates. It becomes covered with fungal mass and special spore-bearing fungal threads and dies. Air currents take up the fungal spores and disperse them.
Spore dispenser
The fungus has thus transformed the spider into a spore disperser. We already knew this type of manipulation. Notorious are fungal species of the genus Ophiocordyceps that infect carpenter ants (of the genus Camponotus). A sick ant is often forced to leave the nest, make its way onto the vegetation next to an ant trail, and bite down; the jaws lock, and the ant dies. A kind of mushroom grows out of its body, producing fungal spores. The dead ant’s location is favourable for spreading to new victims.
Fungi are known that infect spiders and turn them into a spore dispenser in a similar way. The recently discovered fungus species Gibellula attenboroughii is specific to cave spiders. It is remarkable that a pathogen can spread among these spiders, which live isolated, in contrast to ants. Besides the orb-weaving cave spider, the fungus also infects the European cave spider, Meta menardi, a larger species.
Sources:
Evans, H.C., T. Fogg, A.G. Buddie, Y.T. Yeap & J.P.M. Araújo, 2025. The araneopathogenic genus Gibellula (Cordycipitaceae: Hypocreales) in the British Isles, including a new zombie species on orb-weaving cave spiders (Metainae: Tetragnathidae). Fungal Systematics and Evolution 15: 153–178. Doi: 10.3114/fuse.2025.15.07
Hughes, D.P., J.P.M. Araújo, R.G. Loreto, L. Quevillon, C. de Bekker & H.C. Evans, 2016. Chapter eleven. From so simple a beginning: the evolution of behavioral manipulation by fungi. Advances in Genetics 94: 437-469. Doi: 10.1016/bs.adgen.2016.01.004
The eyespots of a spicebush swallowtail caterpillar protect the animal from hungry birds – but only when the caterpillar is concealed, Elizabeth Postema shows.
An older caterpillar of the spicebush swallowtail butterfly Papilio troilus has an appealing swollen head with two eyespots. It is obvious that these eyespots serve to deter predators. But they do so only under special conditions, Elizabeth Postema writes.
The swallowtail occurs in North America; the caterpillars live on leaves of trees and shrubs such as sassafras and American tulip tree. A common predator of caterpillars is the black-capped chickadee (Poecile atricapillus), a tit species.
Frightening
A spicebush swallowtail caterpillar sitting openly on a leaf is visible; it is green, but in a slightly different shade than the leaf. The eye spots make it even more conspicuous. That is why a caterpillar hides during the day to escape detection by hungry tits and other predators. Lying on the midrib of a leaf with its head turned towards the tip, it exudes silk. The silk dries and shrinks, forcing the leaf to fold around the caterpillar.
But what is the use of eyespots to a hidden caterpillar? Postema assumed that these eyespots are important when a bird peers into a leaf roll or picks it open. It will then suddenly see a snout with two eyes – an imitation of a snake – and be startled by it. Two eyespots that suddenly appear, the idea is, have a completely different effect than two eyespots that are continuously visible from far away.
Caterpillars of modelling clay
She tested this hypothesis with artificial caterpillars. She made hundreds of green caterpillars of modelling clay with and without eyespots and attached them to tree leaves, which she then folded around the caterpillar or not. So, there were four experimental groups: visible caterpillar without eyespots, visible caterpillar with eyespots, hidden caterpillar without eyespots and hidden caterpillar with eyespots. After five days, she looked for her artificial caterpillars and checked whether they showed bite marks from birds.
As expected, she discovered that a leaf roll offers protection. Caterpillars that were sitting on a leaf in the open were attacked more often than caterpillars that were hidden.
Eye spots did not help the visible caterpillars: tits did not care. But caterpillars in a leaf roll – which were already safer – were even better off with eyespots. Eye spots made the chance of an attack smaller. Postema’s assumption appears to be correct.
The conclusion is that spicebush swallowtail caterpillars protect themselves by combining eyespots with a refuge, so that the ‘eyes’ suddenly pop out in the event of acute danger.
Young caterpillars have no eyespots, but use a different defense strategy: predators overlook them because they are brown and resemble bird droppings.
Willy van Strien
Photo:
Large: caterpillar of spicebush swallowtail Papilio troilus. NCBioTeacher (Wikimedia Commons, Creative Commons, Public Domain)
Small: adult spicebush swallowtail. Robert Webster (Wikimedia Commons, Creative Commons CC BY-SA 4.0)
Source:
Postema, E.G., 2024. Eyespot peek-a-boo: Leaf rolls enhance the antipredator effect of insect eyespots. Journal of Animal Ecology, online December 25. Doi: 10.1111/1365-2656.14232
Red-cheeked cordon-bleu male shows his ability to collect nesting material
A red-cheeked cordon-bleu often holds a grass stem in its beak during courtship. It chooses the longest object it can get, Masayo Soma and colleagues found.
A male and female red-cheeked cordon-bleu work on their relationship continuously. They sing and dance for each other; dancing entails simply hopping up and down. Song and dance play a role in mutual mate selection and serve to strengthen the pair bond afterwards; a courtship session rarely results in copulation. Couples are close and male and female raise young together.
The red-cheeked cordon-bleu (Uraeginthus bengalus) is a songbird that lives in sub-Saharan Africa. It belongs to the estrildid finches, a group of species of which most have beautiful colour patterns. Many species strengthen the pair bond, like the red-cheeked cordon-bleu, with song and dance during which they may hold a grass stem. Males hold a stem during dance more often than females.
Previous research had shown that species performing a stem-holding display are mainly species in which males work intensively on building the nest. Many species of estrildid finches make a nest of grass; the males have the task of collecting the nesting material, while females remain on the nest and weave in the stems that were brought in. This is also the case in red-cheeked cordon-bleu.
The idea is therefore that a male holds a grass stem in his beak while dancing to show that he is well able to perform his task. For females, handling a grass stem does not have that meaning.
The longest
That idea is now gaining additional support. Because if a male intents to advertise his nest material collecting ability by performing nesting material holding display, a long stem is more convincing than a short one. And indeed: a long stem is preferred, red-cheeked cordon-bleus showed in choice tests. The birds, which are about 13 centimetres long, were offered strings of 5, 10 and 20 centimetres. They mostly chose a string of 20 centimetres. If they picked up a short string, they immediately threw it away.
The researchers did similar experiments with the star finch (Bathilda ruficauda, synonym Neochima ruficauda), an estrildid finch from northern Australia and also a grass nest builder, and got the same result.
The story is not yet complete. For instance, the researchers do not know whether a bird that displays with a long grass stem will get a better partner or be more successful in maintaining the pair bond. Moreover: it is not clear whether long stems are preferred for nest building. If not, then handling a long stem would serve to embellish the display rather than to prove collecting ability.
Willy van Strien
Photo: red-cheeked cordon-bleu (Uraeginthus bengalus). Carlos Vermeersch Santana (Wikimedia Commons, Public Domain)
See also: blue-capped cordon-bleu (Uraeginthus cyanocephalus), closely related to red-cheeked cordon-bleu, performs tap dance
Sources:
Soma, M., M. Nakatani & N. Ota, 2025. Choice of props for courtship dancing in estrildid finches. Scientific Reports 15: 219. Doi: 10.1038/s41598-024-81419-6
Soma, M., 2018. Sexual selection in Estrildid finches, with further review of the evolution of nesting material holding display in relation to cooperative parental nesting. The Japanese Journal of Animal Psychology, 68: 121-130. Doi: 10.2502/janip.68.2.2
Theridiosoma gemmosum catapults its web to passing prey
A Theridiosoma gemmosum female does not wait for a mosquito to fly into her web. If she hears one approaching, she strikes her web at it, Sarah Han and colleagues write. The mosquito cannot escape.
Most female spiders that construct a web, feed on the insects that have flown into it. But Theridiosoma gemmosum takes a different approach: this spider catapults her web at a passing prey, usually a mosquito, to capture it.
If she did not, such a mosquito would escape the web. A mosquito flies with its front legs extended forward, and as soon as the legs touch a spider’s web, the mosquito reverses its flight and the spider misses her prey. But Theridiosoma gemmosum is ahead of this avoidance strategy by taking action when she hears a mosquito coming close, Sarah Han and colleagues show.
Theridiosoma gemmosum belongs to the ray or slingshot spiders (Theriodiosomatidae), small spiders that use their web as a catapult. Theridiosoma gemmosum is only a few millimetres in size. The web is also small, and it is difficult to find one. The species is widely distributed in wet environments such as river banks and swamps in the northern hemisphere.
Ready to strike
A slingshot spider makes a planar orb web, spins a thread from the centre and attaches the end to a twig. Then she sits in the middle of the web, grabs the centre with her four back legs and the anchor thread with her four front legs. By letting her front legs run over the thread, she stretches the web a few centimetres; the web becomes cone-shaped and is now ready to strike. The spider, sitting on top of the cone, holds the loose piece of thread between front and back legs with her pedipalps (the ‘boxing gloves of spiders).
And then she waits until a flying insect passes the base of the cone. If this happens, she releases the thread; the web snaps back, the spider whizzing backwards with it. The more the web was stretched, the more powerfully it shoots back. If it hits the unfortunate passer-by, the spider has captured her prey; the insect sticks to the threads and cannot escape. Otherwise, she immediately picks up the thread to tighten the catapult again.
Sound
The researchers wondered what exactly made the spider release her web. They conducted experiments in which they tethered a mosquito to a paper strip, in such a way that it could make normal flying movements. They moved it towards a web of Theridiosoma gemmosum. High-speed camera footage shows that the spider shoots its web at lightning speed at a mosquito when it is within reach, but before it touches it with its front legs and realizes the danger.
How does a slingshot spider perceive that a mosquito is within reach? Not with her eyes: the spider does not see sharply and, moreover, she is facing away from the mosquito. But she has special long hairs on the hind legs that sense the airborne vibrations caused by the wing beats. Moreover, the vibrations propagate over the threads of the web, and she detects that too. From the combination of this information, she probably infers where a mosquito is.
There is another piece of evidence that slingshot spiders respond to sound: they shoot their webs also at the snap of a finger or at the sound of a tuning fork. This does not produce any result, but apparently, slingshot spiders take every chance.
Sources: Han, S.I. & T.A. Blackledge, 2024. Directional web strikes are performed by ray spiders in response to airborne prey vibrations. Journal of Experimental Biology 227: jeb249237. Doi: 10.1242/jeb.249237 Alexander, S.L.M. & M.S. Bhamla, 2020. Ultrafast launch of slingshot spiders using conical silk webs. Current Biology 30: R928-R929. Doi: 10.1016/j.cub.2020.06.076
Heart cockle accommodates algae that require light
The shells of heart cockles (Corculum cardissa) have many transparent windows on their sun-facing side for the benefit of resident algae. The windows have a special structure, Dakota McCoy and colleagues show.
Shells need to be hard and sturdy to protect the mollusk inside. It is a simple function and usually there is nothing special about a shell, apart from the diversity in shapes and colours. But the shells of heart cockles (Corculum cardissa and other species) are remarkable: they contain a large number of transparent windows, orderly arranged. They are there for a reason: they transmit sunlight to the unicellular algae that live within the mollusk. Dakota McCoy and colleagues investigated shape and function of the windows.
But why are algae living in shellfish in the first place?
Algae, like plants, are able to capture carbon dioxide from air to synthesize sugars with the use of sunlight in a process called photosynthesis; the sugars are the basis for energy and building materials. The nutrients that algae and plants need are chemical elements such as nitrogen, phosphorus, and calcium, which they incorporate into complex carbon compounds such as proteins and DNA, carrier of genetic information. Animals are dependent on photosynthesis; they must feed to obtain energy and building materials. Or…..
…. they can accommodate algae, so that they have sugars at their immediate disposal and do not have to feed.
Tiny windows
Some bivalves use this alternative opportunistically. And there are two groups that can only live with algae: the giant clams (Tridacninae, including the large Tridacna gigas) and many heart cockles (Fraginae). They house unicellular algae in fine branches of their intestinal tract. The algae provide sugars in exchange for a safe living place and probably also nutrients.
A prerequisite for successful cooperation is that the algae have access to sunlight. The hosts, which are partially buried, must ensure this. They live in shallow water, where sunlight penetrates to the bottom. Giant clams often keep their shells open, so that the animal is bathed in sunlight. Heart cockles have a different solution. Their shells remain closed, but the algae receive light through minuscule windows in the sun-facing side of the shells.
The researchers wanted to know more about the structure of these windows and examined those of the heart cockle Corculum cardissa.
Optic fibres
The shells of Corculum cardissa consist of aragonite, a calcium compound (calcium carbonate, CaCO3) that forms planar crystals that are crossed in orientation.
The windows have a different microstructure: here, the aragonite forms fibres instead of planar crystals. Each window is a bundle of cables consisting of parallel aragonite fibres that runs perpendicular to the shell surface. The cables transmit light, just like glass fibre cables. Fibre optic cables are exceedingly rare in nature, and cable bundles have never been found before.
Experiments show that the sun-facing shell sides – the windowed sides – transmit colours of sunlight that are important for photosynthesis; on average 31 percent of these colours passes through. In contrast, for ultraviolet light, which is harmful to animal tissue and algae, this percentage is only 14. The sand-facing shell sides transmit hardly any light.
Some individuals have a microlens beneath each window, also consisting of aragonite, which condenses the incoming light and focuses it deeper in the tissue, where the algae are. That completes the design.
You wouldn’t make it up: shells with windows. But it exists.
Willy van Strien
Photo: the sun-facing side of heart cockle Corculum cardissa. Ria Tan, Wildsingapore, via Flickr. Creative Commons: CC BY-NC-ND 2.0
Sources: McCoy, D.E., D.H. Burns, E. Klopfer, L.K. Herndon, B. Ogunlade, J.A. Dionne & S. Johnsen, 2024. Heart cockle shells transmit sunlight to photosymbiotic algae using bundled fiber optic cables and condensing lenses. Nature Communications 15: 9445. Doi: 10.1038/s41467-024-53110-x Kirkendale, L. & G. Paulay, 2024. Photosymbiosis in Bivalvia. Treatise Online no. 89: Part N, Revised, Volume 1, Chapter 9. Doi: 10.17161/to.v0i0.6568
Nest mound of Globitermes sulphureus provides a stable indoor climate
Periods of severe drought, periods of heavy rain: a nest mound of the termite Globitermes sulphureus withstands it all. That is thanks to its three-layered structure, Chun-I Chiu and colleagues show.
The savannahs of Thailand are bone dry in winter while the wet summer season brings an extreme amount of rain: a challenging climate. But the termite Globitermes sulphureus prospers, thanks to nest mounds that protect the colonies in the underground nests beneath them. The mounds persist, the animals neither desiccate nor drown, but always enjoy a pleasantly high humidity level in their nest. This has to do with a clever piece of architecture, Chun-I Chiu and colleagues conclude from various measurements.
Like ants, termites live in large colonies, but they are not related to ants; they are related to cockroaches. A termite colony has a king and queen that produce offspring, and workers and soldiers of both male and female sexes. The queen, that has to produce a huge amount of eggs, is much larger than the other termites.
Stability
The mound above a nest of Globitermes sulphureus may look a little plump, but it is a complex structure. It consists of three layers each of which contributes in its own way to the stability of the mound and to the favourable internal climate in the nest.
The thin outer layer consists of plate-like elements of hard material. The animals make it from sand or soil particles, hence it has the same colour as the soil on which it stands. This layer prevents moisture from escaping from the nest, which is very important during dry periods. Underneath this layer, there is a thicker middle layer of irregularly shaped, stuck-together pieces with cavities in between that are also made of soil particles. This layer is waterproof and can withstand pressure, for example when raindrops hit it. It makes the mound robust.
The inside of the mound, the third layer, clearly differs from the outer layer and the middle layer. It is filled with rounded, smooth pellets in which a lot of fibrous organic material is incorporated, such as cellulose from plant remains. This layer is redder in colour than the other two, and it is the most porous one. Like a sponge, it absorbs water vapour that the termites exhale, holds it and releases it at a low rate. This layer forms a water reservoir with which humidity can be maintained at a high level.
Repair
Has the mound to be repaired after damage, the termites work from the outside inwards. Within a few hours, they are fixing the outer layer, after weeks the outer layer and middle layer are ready. The repair of the inner layer takes more time. The researchers think that this is because the animals must collect material that is less easy to find.
Source: Chiu, C-I., K. Attasopa, S. Wongkoon, Y. Chromkaew, H. Liao, K-C. Kuan, P. Suttiprapan, I. Guswenrivo, H-F. Li & Y. Sripontan, 2024. Three‐layered functionally specialized nest structures enhance strength and water retention in mounds of Globitermes sulphureus (Blattodea: Termitidae). Environmental Entomology, online 9 October. Doi: 10.1093/ee/nvae093
The first fungus gardens, adaptations, and innovations
Ted Schultz and colleagues link the emergence of ant farming to an asteroid impact and the domestication of the fungal crop to a period of strong climate change.
You can forage for food, but you can also grow it to make sure it is available. About 250 species of ants from South, Central, and North America do the latter, growing a fungus in their nests for food. The evolutionary history of this ant-fungus relationship was largely known. Now, Ted Schultz and colleagues compare the evolutionary tree of fungus-growing ants with that of cultivated fungus varieties and refine the picture.
The fungus-growing ants have a common ancestor that started agriculture. This happened 66 million years ago in wet tropical forests of South America. Shortly before that, an asteroid had hit Chicxulub in Mexico with enormous consequences. Dust in the atmosphere blocked sunlight for months, plants died and many species of plants and animals, including dinosaurs, became extinct.
But fungi that live on dead material, such as fallen leaves, flourished, and some ants took advantage of this. They could not digest organic material themselves, but they allowed a mushroom-like fungus that could do the job to grow in their nest by providing it with detritus. The fungus broke down the material, and the ants consumed breakdown products as well as fungus. All 250 species of ants that currently have a fungus garden in their nest descend from these pioneers.
Soon, ants picked up a second mushroom-like fungus. Virtually all cultivated fungus varieties today – and there are several hundred of them – descend from these two early crops.
Domestication
From the beginning, the farming ants could not do without their crops; they would starve. But conversely, the fungi did not need the ants. They also lived outside ant nests, and fungal crops exchanged genetic material with their wild relatives. Outside they formed mushrooms, within ant nests the ants prevented this and only allowed fungal threads to grow. This is known as lower ant agriculture. Today, roughly a hundred species of ants exist that practice lower farming, with many semi-wild fungal varieties.
But it did not stop there. At some point, there were ants that domesticated their crop. That means that the cultivated fungus became dependent on the grower and can no longer live in the wild. And it produces nutrient-rich food bodies especially for the ants, the so-called gongylidia. These ants and their fungi are inseparable, and a young queen that wants to establish her own colony does not leave the maternal nest without a piece of fungus garden between her jaws. This is called higher ant agriculture.
This agricultural transition only occurred when lower ant agriculture had already existed for 36 million years, now about 27 million years ago. Why didn’t it happen earlier, and why did it suddenly happen then?
Global cooling
The researchers point at the so-called Terminal Eocene Event 33.5 million years ago that preceded the transition. The Earth cooled down rapidly and many species became extinct, although the extinction was not as massive as 66 million years ago. In South America, part of the wet tropical forests made way for landscapes that were seasonally dry, such as savannas.
Some of the fungus-farming ants moved to drier areas. The fungi in their nests retained the same growing conditions, but they lost contact with wild relatives, which lived in wet forests only. Because the cultivated fungi no longer exchanged genetic material with their wild relatives, the ants could select freely for characteristics that were beneficial to themselves, and not necessarily to the fungus. And so, a domesticated crop developed.
Innovation
Finally, 18 million years ago, a new form of higher ant farming appeared: there were fungus growers that started to provide their gardens with pieces of fresh leaves instead of leaf litter. These leaf-cutter ants form complex colonies of millions of individuals; they manage to keep their gardens in perfect order. They all grow the same fungus species, Leucoagaricus gongylophorus, a descendant of the very first fungus with which ant farming ever started.
Schultz does not mention whether there was a special reason for these ants to switch to fresh leaves as a substrate for their fungus. There are now more than fifty species of leaf-cutter ants.
Alternative agriculture
Two other agricultural systems branched off from lower ant agriculture. About 30 million years ago, a group of ants switched to growing fungi in unicellular form – that is: a yeast – instead of in multicellular thread form (there are unicellular and multicellular fungi). This is remarkable, because the mushroom-like fungi of which the cultivated crops are derived grow exclusively in multicellular form. Even the fungi cultivated as yeast never occur in yeast form in the wild.
And 21 million years ago, another group of fungus growers exchanged the usual mushroom-like fungi (from the family Agaricaceae) for coral fungus species (from the family Pterulaceae), which do not break down leaf litter, but wood.
Would there be a reason for these two shifts also? It would be great if a reason was found.
Sources: Schultz, T.R., J. Sosa-Calvo, M.P. Kweskin, M.W. Lloyd, B. Dentinger, P.W. Kooij, E.C. Vellinga, S.A. Rehner, A. Rodrigues, Q.V. Montoya, H. Fernández-Marín, A. Ješovnik, T. Niskanen, K. Liimatainen, C.A. Leal-Dutra, S.E. Solomon, N.M. Gerardo, C. R. Currie, M. Bacci, Jr., H.L. Vasconcelos, C. Rabeling, B.C. Faircloth & V.P. Doyle, 2024. The coevolution of fungus-ant agriculture. Science 386: 105-110. Doi: 10.1126/science.adn7179 Branstetter, M.G., A. Ješovnik, J. Sosa-Calvo, M.W. Lloyd, B.C. Faircloth, S.G. Brady & T.R. Schultz, 2017. Dry habitats were crucibles of domestication in the evolution of agriculture in ants. Proceedings of the Royal Society B 284: 20170095. Doi: 10.1098/rspb.2017.0095 De Fine Licht, H.H., J.J. Boomsma & A. Tunlid, 2014. Symbiotic adaptation in the fungal cultivar of leaf-cutting ants. Nature Communications 5, 5675. Doi: 10.1038/ncomms6675 Schultz, T.R. & S.G. Brady, 2008. Major evolutionary transitions in ant agriculture. PNAS 105: 5435-5440. Doi: 10.1073_pnas.0711024105 Villesen, P., U.G. Mueller, T.R. Schultz, R.M.M. Adams & A.C. Bouck, 2004. Evolution of ant-cultivar specialization and cultivar switching in Apterostigma fungus-growing ants. Evolution 58: 2252–2265. Doi: 10.1111/j.0014-3820.2004.tb01601.x
White-bearded manakin with rich territory is more successful
A territory with plenty of food is a valuable asset for a male white-bearded manakin.The easier he finds food, the more time he spends on courtship display and the more females will visit him, as Luke Anderson and colleagues show.
In the white-bearded manakin, Manacus manacus, males contribute nothing to the care of the offspring. They occupy a territory in the vicinity of two to dozens of other males and try to attract as many females as possible and seduce them to mate. Females do the rest: after they have selected a male and copulated, they build a nest without help, incubate the eggs and raise the young.
Males with a territory that is rich in the fruits that they eat receive more female visits than males in a place with less food, Luke Anderson and colleagues discovered.
Costly courtship display
The white-bearded manakin, a small songbird, lives in forests in tropical South America. Like in many of the other 55 manakin species, the black-and-white males display spectacular courtship behaviour to attract females during the breeding season. Some males are much more successful than others.
A male possesses a territory in which he has cleared a court – a piece of ground of 15 to 90 centimetres in diameter, surrounded by saplings – down to the bare soil. Clean ground is safe, because a dangerous snake is perceived immediately. Moreover, the male stands out with his show. He puffs out his beard feathers, utters his call and leaps up and down between stems and the ground at lightning speed, his wings snapping and whirring. He can sustain this energetically costly show for up to half a minute at a time.
The olive-green females do best to choose a male of good genetic quality, to maximize the chance to produce successful offspring. An important criterium by which females can judge the quality of males is their courtship performance. The more intense the courtship is, the stronger and healthier the performer will be.
Uneven playing field
But now, Anderson writes that some white-bearded manakin males have an advantage by possessing a rich territory. The birds eat mainly ripe fruits, and territories differ greatly in fruit availability, his research in Ecuador shows. Males with a rich territory have to spend hardly time looking for food and are in good condition, he assumed. And indeed, as camera observations showed: the richer a territory was, the more time its owner spent on his shows.
And the more time a male spent displaying, the higher the frequency of female visits, thus the more reproductive success he had.
So, the displaying males are rivals on an uneven playing field; males with a rich territory are at an advantage. Is courtship performance then an honest signal of their quality?
Competition
It would be an dishonest signal if it is a coincidence whether a white-bearded manakin male occupies a rich territory, his quality having nothing to do with it.
But probably, the males have to compete for the best place, and the highest quality male will obtain the richest territory where he can spend much time on courtship display. In this case, the courtship performance is an honest signal for females to assess male quality.
The birds deposit the seeds of the fruits they eat back into their territory. In this way, places with fruiting plants will continue to exist. Males are long-living and can occupy the same territory for up to eleven years.
Willy van Strien
Photo: White-bearded manakin male. Félix Uribe (Wikimedia Commons, Creative Commons CC BY -SA 2.0)
Sources: Anderson, H.L., J. Cabo & J. Karubian, 2024. Fruit resources shape sexual selection processes in a lek mating system. Biology Letters 20: 20240284. Doi: 10.1098/rsbl.2024.0284 Cestari, C. & M.A. Pizo, 2014. Court cleaning behavior of the white-bearded manakin (Manacus manacus) and a test of the anti-predation hypothesis. The Wilson Journal of Ornithology, 126: 98-104. Doi: 10.1676/13-032.1
A female desert locust spends more than two hours to lay a batch of eggs in the hot sand of the Sahara.Usually, a male is sitting on her back, acting as a sunshade, Koutaro Ould Maeno and colleagues write.
Desert locust females produce about a hundred eggs at a time. They drill their abdomens into the sand and then sit still for more than two hours on average while the eggs leave her body. If they do the job during daytime, they must endure the scorching heat. How does the insect cope with that, Koutaro Ould Maeno and colleagues wondered.
They studied the behaviour of desert locusts, Schistocerca gregaria, in Mauritania during the so-called gregarious phase, when the animals live in groups. Males gather at leks during the day to attract females and copulate.
Possessive behaviour
After mating, a female stores the sperm; one mating provides enough sperm for several egg-laying sessions. A male invests a lot in mating, as it takes him hours. To ensure that she actually uses his sperm, he usually continues to guard her until she has laid eggs, keeping rivals away. This possessive behaviour limits her freedom to choose another partner, but in return she is not harassed by other males.
And it turns out to have still another advantage.
Most females lay their eggs at night, but some wait until the next morning. They avoid predators that are active during the cool night. But another danger is looming: it gets dangerously hot. Desert locusts can withstand much heat, but a temperature of 55°C or more is fatal, and it can get that hot in the sun. This is where the guard helps. When a female lays eggs, he sits on her back and functions nicely as a parasol, the researchers write.
Probably, this is also the case in a mating couple.
Cooler
Females that oviposit during the day cool down a bit because their abdomen extends into the ground; it is less hot there than at the surface. In addition, the researchers now show that an egg-laying female with a male on her back is cooler than a female without a guard. She is also cooler than the sand.
The guard himself also gets less hot than the sand because he is at a greater distance from the ground. When males attract females at a lek, they stand as high on their legs as possible to avoid overheating. In addition, the animals position themselves in such a way that they catch a minimum of solar radiation.
Desert locusts can live gregariously; then they gather, multiply rapidly and can become a plague that eats almost everything that is green, moving fast and far. But in dry periods they are solitary and occur in small numbers; the animals then live longer.
Willy van Strien
Photos: Large: mating couple of desert locust. Adam Matan (Wikimedia Commons, Creative Commons CC BY-SA 3.0) Small: ovipositing desert locust female without guarding male. Christiaan Kooyman (Wikimedia Commons, Creative Commons, public domain)
Sources: Maeno, K.O., S. Ould Ely, S.A. Ould Mohamed, M.E.H. Jaavar, A.S. Benahi & M.A. Ould Babah Ebbe, 2024. Mate-guarding male desert locusts act as parasol for ovipositing females in an extremely hot desert environment. Ecology e4416, online 15 September. Doi: 10.1002/ecy.4416 Maeno, K.O., S. Ould Ely, S.A. Ould Mohamed, M.E.H. Jaavar & M.A. Ould Babah Ebbe, 2023. Thermoregulatory behavior of lekking male desert locusts, Schistocerca gregaria, in the Sahara Desert. Journal of Thermal Biology 112: 103466. Doi: 10.1016/j.jtherbio.2023.103466
Florida carpenter ant workers treat leg wounds effectively
Injured leg?In the Florida carpenter ant, Camponotus floridanus, nestmates treat the patient to prevent lethal infections.If it is useful, they amputate the leg, Erik Frank and colleagues write.
With a wound on a leg, a worker of the Florida carpenter ant, Camponotus floridanus, would have only a small chance to survive if it were not for her nest mates that come to the rescue. To prevent infection, they lick the wound clean and often amputate the leg, significantly increasing the survival chance, Erik Frank and colleagues show. This care is frequently needed because colonies of this ant species fight each other intensively.
The researchers tested the ants’ medical skills by making a small cut in the leg of workers. They then injected a saline solution containing a deadly bacterium, Pseudomonas aeruginosa, into the wound. Infected ants were placed either in isolation or in a nest where two hundred workers were available.
Bitten off
Most of the ants that sat alone after infection succumbed to the injuries. But when placed in a nest, most ants did survive thanks to the care of nest mates. What care they provided turned out to depend on where the wound was.
If the infected wound was on the upper leg, usually one of the nest mates intervened drastically and bit off the leg at the top. If the wound was on the lower leg, this did not happen; instead, workers licked the wound thoroughly clean. In both cases, helpers chose the treatment that was most effective, as became clear in experiments with infected wounds in which the researchers amputated the affected leg.
Bacterial load
If they amputated a leg of an ant with a wound on the upper part, then her chance to survive was as high as it was in the case of amputation by nestmates. But if they removed a leg with an injury on the lower part, it did not help: most patients died. The treatment that the ants apply in that case, extensive cleaning, is much more effective.
Why is amputation only helpful for an infection in the upper leg?
Whether an ant will survive an infection depends on how quickly the bacteria are able to spread through the body: the higher the bacterial load, the higher the mortality. The bacteria spread via the hemolymph, the insect version of blood, which flows through the legs in channels.
In the upper leg, these channels are narrower than in the lower leg, so that bacteria are less likely to enter the hemolymph. Also, the upper leg has much more muscle mass than the lower leg, and blood is pumped around by muscle movements. If the upper leg is affected, circulation is slowed down much more than if the lower leg is affected, impeding the spread of bacteria.
Time enough
Consequently, when the upper leg is affected, ants have enough time to perform an amputation, which takes forty minutes at least, before the bacteria have spread. But timely amputation is unfeasible with an infection in the lower leg. Then cleaning is the best way to help a victim.
The ants also amputated the leg if the researchers injured the upper leg but injected a sterile saline solution instead of a solution with bacteria. That makes sense, because under natural conditions, in the ants’ nest, such a wound is most likely to become infected. The workers err on the side of caution.
The Florida carpenter ant is the only animal species known to apply amputation to treat conspecifics in case of injury.
The researchers previously discovered that also workers of the Matabele ant from Africa, Megaponera analis, treat infected wounds of nestmates. They do so by administering antibiotics from glands on their backs that produce a mix of antimicrobial substances. The Florida carpenter ant does not have such a built-in pharmacy. For this ant, cleaning and amputation are good alternatives.
Source: Frank, E.T., D. Buffat, J. Liberti, L. Aibekova, E.P. Economo & L. Keller, 2024. Wound-dependent leg amputations to combat infections in an ant society. Current Biology, 2 July online. Doi: 10.1016/j.cub.2024.06.021
