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), Enrique Peñalver and 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:
Chen J, Wang B, Engel MS, Wappler T, Jarzembowski EA, Zhang H, Wang X, Zheng X, Rust J. 2014. Extreme adaptations for aquatic ectoparasitism in a Jurassic fly larva. eLife 3:e02844
[Edited to take account of John Harshman’s perspicacious critique in the comments below – thanks John!]
