by Matthew Cobb
Just out in eLife, an Open Access journal that aims to rival Science and Nature, is this fantastic fossil of an aquatic fly larva from the Chinese mid-Jurassic (around 165 MY ago), published by Chen et al. Soft-bodied animals rarely fossilise well, but the Chinese fossil-hunters have been able to find three of these fossils, exquisitely preserved. The beast is called Qiyia jurassica – Chen et al write: ‘Qiyia is from the Chinese ‘qiyi’ meaning bizarre; jurassica is a reference to the Jurassic age of the fossils.’
Here’s the ‘holotype’ (ie the one they made their taxonomic descriptions on the basis of, and in this case the best of the three fossils) (click to see the full size photo). This is Figure 1 from the paper and the scale bar in A is 5mm.
Panel D shows the amazing preservation of an odd structure, which they interpret as ‘a thoracic sucker with six radial ridges, unique in insects’. Here’s a hi-res picture of the six ridges (again, click to see it in all its glory). Will you look at this? It looks like it has been preserved in alcohol!
The authors think these ridges – which they suspect are modified prolegs (fly maggots don’t actually have legs) were covered in a thin layer of skin forming a sucker that would have enabled the maggot to hang onto a prey’s smooth flesh, so that its bitey mouthparts (D and E in the figure above) would then be able to suck the blood of their prey.
On the basis of a detailed anatomical description, the authors conclude:
This combination of primitive and derived features demonstrates that Q. jurassica is a stem lineage representative of the Athericidae (water snipe flies), a family sister to the more familiar horse flies (Tabanidae).
The spiracles on the sides of the maggots indicate that these were air-breathing (this is typical of dipteran maggots – even larvae that spend their whole life in the water, such as rat-tailed maggots or mosquito larvae, breathe air rather than dissolved oxygen in water, which requires gills). They also have two structures at the rear, which may have been used for water-breathing, or for dealing with salt. So, it had a sucky thing and bitey mouthparts and it lived in water. The authors state:
Suckers are widespread in aquatic ectoparasites such as leeches, fish lice, and lampreys (Kearn, 2004) which require more suction power to avoid becoming dislodged; other aquatic ectoparasites without attachment organs embed themselves in skin or muscle, such as cyclopoid copepods (anchor worms) (Kearn, 2004). In addition to the sucker, the stiff, upward directed bristles and apical hooks on the prolegs (Figure 1F) are also specialized attachment structures. These morphological adaptations provide compelling evidence that Q. jurassica adhered to a host as an ectoparasite, providing further specialization for a dense, watery habitat.
And what were they eating? Well the fossil beds at Daohugou are full of fossil salamanders, so the authors suggest that they were sucking the blood of Jurassic salamanders. Here’s a reconstruction of the beast. The head end is at the left, with the sucker on the ventral surface of the thorax. The mouthparts are at the far left:
And here’s an imaginary view of what it might have looked like, attached to an oddly-cheery-looking salamander:
One of the things that is interesting about the fossil, apart from its stunning detail, is that it pushes the origins of blood-sucking further back. In an accompanying piece (also open access, hooray), Ricardo Pérez-de la Fuente point out that ectoparasitic blood-sucking (i.e. sitting on the outside and sucking), evolved several times over in the insects, as shown in this figure (our maggot is bottom left, with the star shape, meaning its precise affinities aren’t known):
As to what the adult fly might have looked like, here are two modern representatives of the Athericidae and the Tabanidae, respectively:
(Atherix ibis, from Wikipedia, photo by Hechtonicus
Tabanus spp, by Dennis Ray, from Wikipedia.
This stupendous set of fossils shows that there are amazing things to be discovered in the earth, and in particular in China. We are living through an amazing period in palaeontology!
Reference:
[Edited to take account of John Harshman’s perspicacious critique in the comments below – thanks John!]
I had only to read the title to know it was a missive from Matthew Cobb. Fascinating information and soon to be a major motion picture.
Creepy crawly.
“(click to see the full size photo)”
There doesn’t seem to be a clickable link on the first photo.
I think you may have mistaken the mouthparts. The “thoracic sucker” isn’t mouthparts; it’s a sucker on the thorax. Are those perchance modified legs?
The mouthparts are apparently E (and inside the white rectangle in D).
Ooh, they are:
“The most notable structure of these newly discovered fossils is the ridged thoracic sucker which is a unique evolutionary adaptation among holometabolous insects. The round sucker has six radial ridges which are considered to be highly modified thoracic legs (Figure 2D).”
Mea maxima culpa, John. Serves me right for trying to write this too quickly. I have edited the post to take account of your points. Many thanks – MC
You’re welcome, but I think you still have it wrong. The sucker isn’t supposed to be modified prolegs (which are abdominal structures) but actual legs. At least that’s what the paper claims.
Are there truly no fly larvae with legs? (I don’t know of any, but there’s a lot I don’t know.) Are there fly larvae with thoracic prolegs?
As awesomely preserved this find is, it forever grosses me out that insects have modified or unmodified leg parts as mouth parts. I don’t know why this has grossed me out over the decades, it just has.
You have modified gill arches as mouth parts. And I expect you hold your fork with a modified foreleg.
Yes, they do say *legs*, which seems odd to me as, like you, I didn’t think that fly larvae had properly jointed legs (and the watersnipe fly maggots linked to by Mark Sturtevant below don’t have joined legs). So I’ve e-mailed a couple of the authors and asked them… Watch this space!
I have to say that the photos look like legs: they’re highly sclerotized and seem to be jointed (especially visible in the one on the left in D). Is this a reversal of the suppression of larval legs seen in most (all other?) flies?
I got a mail back from Bo Wang, who seems to agree with me: “I think the sucker is made of six prolegs. As far as I know, the thoracic prolegs are reduced or absent(?) in tabanaform larvae.” So a) the paper should have said ‘prolegs’ rather than legs (so they are sclerotised structures, but *not jointed*). This only makes the fossil more bizarre, and highlights that this early form contains aspects that do not fit with a simple ‘tabanaform’ identification.
I was taught, while earning my entomology degree, that fly larvae are not considered to have true thoracic legs. I know of no exception to this. A quick check on the internet turned up no indication of true legs in fly larvae. I do not regard myself to have sufficient authority to say that I am sure of this.
Many fly larvae, especially aquatic species, can have thoracic and/or abdominal appendages that are labeled as prolegs. These ‘false legs’ seen in many other kinds of insect larvae. Black fly and midge larvae, for example, have a weird, flexible appendage under their thorax that is used for gripping. These seem to be is regarded to be a pair of thoracic prolegs that are bilaterally fused. Some illustrations that you can find label them as a ‘leg’, but perhaps that is meant to be informal.
In my experience, prolegs are neither sclerotized nor jointed, yet that’s what we seem to have here.
Thanks for confirming, though, that thoracic prolegs are a thing.
Cool info.
That salamander looks just like my axolotly, Rose! (Axol Rose.)
https://www.flickr.com/photos/101506315@N08/14191795961
I misspelled axolotl and the photo link is shite…let’s try that again:
https://www.flickr.com/photos/101506315@N08/14191795961/
Wonderful life! One quibble: “Panel D shows the amazing preservation of the mouthparts” — the sucker is a thoracic structure, very plausibly interpreted as an attachment organ. But not mouthparts! The mandibles, shown as long, sharp and channeled, were used to penetrate and feed on fluids, as in many dipteran larvae.
I’m only surprised that modern tabanids haven’t entered this niche — to me their larvae seem to parallel free-living leeches.
I also tend to quibble about the “giant Cretaceous fleas” — There are reasons to believe that these were one of several mecopteran-like groups to evolve similar ectoparasitic lifestyles. …which to me is all the more wonderful!
Terrific, thanks for sharing this! The preservation is simply amazing. (Queue the creots saying it’s faked …)
But not by humans. Satan!
I think you can just see a fishhook in B.
Matthew Cobb – “…and in particular in China. We are living through an amazing period in palaeontology!”
China because palaeontology relatively recent there? Or Chinese focussing on it currently?
Probably some of both of those, but also because of some regions with geological / environmental / ecological histories that were favorable for fossilization. There are of course regions like that around the globe but China’s are relatively new to main stream scientific investigation. Probably been known / exploited by locals for hundreds of years.
China has vast, open areas with fossil-rich beds from the Jurassic and Cretaceous. Lots of beautifully preserved fossils of primitive birds and feathered dinos are coming out of there, for example. The government also seems pretty good at supporting paleontology research, as these fossil beds are a world treasure, and the government understands good PR when it sees it.
Cool. How long has China been conducting this intensity of research?
Decades. At least from the 1980s’, and possibly further.
China was pretty much closed to Westerners following the Communist takeover in 1949 until Nixon’s “ping pong diplomacy” in the early 1970s. For some of us, that counts as “relatively recent”.
Here’s an article on the history and prospects of palaeontology in China. I didn’t read it all, but a few points it may or may not cover:
Students don’t get to choose their specialties, they’re assigned to a field of study by a central bureaucracy. This seems crazy, but that’s the way China has done things for millennia.
Building, deforestation, massive earthworks and road-building schemes open up lots of geology, and China is (tectonically speaking) the scum swirling around the plughole of Pangaea, with huge diversity of sediments and ages.
Numerous fossil museums have been built and filled with vast numbers of display specimens from the various Jurassic and Cretaceous Conservat-Lagerstätten, a significant proportion of which are composites or fakes.
Data on geological context data are often poor because the collectors are mostly moonlighting farm labourers who sell through (black market) dealers.
The quite small number of researchers in these institutions necessarily concentrate on the very best specimens, like those above and the huge numbers of feathered dinosaurs discovered since the 1990s.
Biology question:
It was claimed somewhere that they found a large amount of those maggots, that the habitat was devoid of fishes and that is why the suckers had time to evolve. Suckers are not seen on heavily predated animals, as I understood it.
So why didn’t those salamanders establish themselves in the maggot eating niche?
Perhaps there were other things easy enough to eat and the cost to the salamanders imposed by the maggots was not significant enough to favor selection for eating the maggots. Or maybe the maggots didn’t taste good, i.e. chemical deterrent. Or maybe the salamanders derived some benefit from the maggots that outweighed or neutralized the cost.
Here are some pix of modern watersnipe fly larvae. From this, one can see that their preliminary identification to family seems reasonable. BugGuide
More on the biology of modern species. The larvae live in fresh water, including streams. They use their well developed prolegs (P1, P2… in the above pix) to hang on in a current. I am not sure if I buy that the spiney anterior end in the fossil species means they were ectoparasites. Those could also be used for getting a grip, especially if this species is attached to substrates in strong currents.
Some modern species are blood feeders as adults, which is interesting. Would like to learn about the gut contents of the fossils. Even better would be to find a fossilized host with larva attached.
Fantastic fossils. You can even see what look like fine trichome hairs on the body. Amazing.
Reasonable suggestions, except that kind of fine preservation is definitely not consistent with strong currents. They would have to have washed a long way downstream (or be living in a habitat for which the novel adaptation was useless) to settle in completely still, anoxic water with only the finest sediment.
Blood-sucking adult Tabanidae = Horse-flies, March flies. Bastards.
Good points! I do not always take the clues about taphonomy into account.
That is stunning preservation – detail down to 10s of microns, maybe finer. It almost looks 3d ?
No? Oh well. It’s not the tuffaceous siltstone that’s the problem. It’s that they describe them as surface impressions – strongly implying that they’ve looked for a 3rd dimension.
OTOH, if those beds contain early-formed concretionary nodules … “to the field-research-mobile, Batman! Let’s go!”