From so simple a beginning

Evolution and Biodiversity

Category: aggression

Gaping display

24 October 2022 /

Sarcastic fringehead impresses with giant upper jaw

sarcastic fringehead can open its mouth extraordinary wide

Males of the blenny Neoclinus blanchardi, the sarcastic fringehead, can open their mouths extraordinary wide. They perform their gaping display for nothing but impressing each other, Watcharapong Hongjamrassilp and colleagues show.

It is an amazing scene when Neoclinus blanchardi fully opens its mouth. A huge membrane becomes visible, consisting of palate and cheeks. It is vividly coloured and has a yellow margin.

In English, the fish is called sarcastic fringehead; it lives along the coast of California. It was already known that males, that have a larger mouth than females, impress each other with it. Now, Watcharapong Hongjamrassilp and colleagues show that they perform their elaborate display for that purpose exclusively.

Wrestling

The sarcastic fringehead can open a large mouth thanks to an upper jaw that is enlarged compared to related fish species and that grows longer than the rest of the body. Its posterior part is unossified and flexible and extends beyond the head. The jaw is connected to the skull in such a way that it can be rotated laterally.

As said, males signal by gaping to scare off each other. A successful male manages to occupy an empty snail shell or a rock crevice in which he hides with only his head protruding. He tries to attract a female. When she likes him, she will lay eggs in his shelter. He fertilizes the eggs and takes care of them until the young hatch. When another male invades his territory, he approaches him, performing the gape display.

The intruder either retreats immediately, or he persists and returns the display. Then the males clash and push each other with the open mouths pressed together. The bigger a male is, the wider his gape. The smallest usually loses, sometimes after the victor had bitten him.

Apparently, suitable shelters are so scarce that the fish has developed a special weapon to defend its place.

Missed opportunity?

But the sarcastic fringehead’s exaggerated gape would also be impressive enough to scare away predators, Hongjamrassilp thought. Or enticing enough to seduce females. He scuba-dove into the water and conducted experiments in the laboratory to see whether this happens.

It did not. If a predator looms, the sarcastic fringehead chases it away by burst swimming. And when a female shows up, he rapidly shakes his head side to side to arouse her interest. He keeps his amazing mouth closed in both cases.

A missed opportunity, you might say.

Willy van Strien

Photo: Neoclinus blanchardi in its shelter. Magnus Kjaergaard (Wikimedia Commons, Creative Commons CC BY-SA 2.5)

This video shows the gaping display

Sources:
Hongjamrassilp, W., Z. Skelton & P.A. Hastings, 2022. Function of an extraordinary display in Sarcastic Fringeheads (Neoclinus blanchardi) with comments on its evolution. Ecology, online Octobre 6: e3878. Doi: 10.1002/ecy.3878
Hongjamrassilp, W., A.P. Summers & P.A. Hastings, 2018. Heterochrony in fringeheads (Neoclinus) and amplification of an extraordinary aggressive display in the Sarcastic Fringehead (Teleostei: Blenniiformes). Journal of Morphology 279: 626-635. Doi:10.1002/jmor.20798

Peaceful together

24 December 2019 /

Dangerous bullet ant and defensive bee tolerate each other

the bullet ant Paraponera clavata and a stingless bee tolerate each other

The bullet ant is not a friendly animal, the stingless bee defends its nest fanatically. Still, these two fighters live smoothly together, Adele Bordoni and colleagues report.

Just like honey bees, stingless bees are social insects. They construct their nest in a cavity, but are unable to dig out their own cavity. So, they exploit an existing one, and they often choose a bigger nest of other social insects, for instance termites. This offers a convenient home, because the host guarantees a proper nest climate.

stingless bee Partamona testacea builds its nest in an ants' nestThe small stingless bee Partamona testacea, which occurs in the Amazon in South America, builds its nest in an ants’ nest. That may be the nest of harmless fungus growing leaf cutter ants, but they also inhabit nests of the bullet ant Paraponera clavata, as Adele Bordoni and colleagues report. A weird choice at first sight, because the bullet ant is not quite friendly.

Large jaws

The bullet ant will aggressively attack as soon as it feels threatened. Its sting is known to be one  of the most painful experiences you can have in nature. In addition, it hunts for insects, which it preys upon, and it has large jaws. If you also realise that the bee is much smaller, you would expect it to avoid the nest of bullet ants. But instead, it enters it to make a home.

And things are going well, Bordoni shows. In the lab, the researchers placed a bullet ant and a bee together in a petri dish. The fierce ant behaved only a little aggressively and did not attack the bee. If the bee was from a nest within the ant’s nest, the ant was even less aggressive. Biting and stinging were highly uncommon.

Resin

Conversely, stingless bees also are tolerant. They defend their colony fanatically, as the researchers observed at an ants’ nest with inhabiting bee colony; the bullet ant builds its nest at the base of a tree. When they introduced an ant at the bees’ nest entrance, bee workers grabbed that ant, dragged it deeper inside the nest and covered it with resin, so that it was not able to move anymore.

But a bullet ant will not enter a bees’ nest voluntarily. An ant may pass the entrance, where always bee guards are present to deter invaders. And then the bees will not attack. When a bullet ant passes by, the guards were seen to retreat and to reposition when the ant was gone. When the ant passing by and the bee are from different ants’ nests, the bee guards reposition faster; in that case, they are a bit more vigilant.

Protection

Apparently, the dangerous bullet ant and the defensive stingless bee Partamona testacea recognize each other as familiar species, and they also discern individuals of an associated nest from foreigners. They probably know each other’s body odour. They live smoothly together without bothering each other, and it is to the bees’ advantage that the ants protect and defend their nest; maybe, the bees participate in nest defence with their vigilant guards.

Willy van Strien

Photos:
Large: Paraponera clavata. Graham Wise (Via Flickr. CC BY-NC-ND 2.0)
Small: nest entrance of Partamona testacea ©Giorgia Mocilnik

Source:
Bordoni, A., G. Mocilnik, G. Forni, M. Bercigli, C.D.V. Giove, A. Luchetti, S. Turillazzi, L. Dapporto, & M. Marconi, 2019. Two aggressive neighbours living peacefully: the nesting association between a stingless bee and the bullet ant. Insectes Sociaux, online November 30. Doi: 10.1007/s00040-019-00733-9

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