Detailed structure of a blowfly proboscis

rjlittlefield · Post by **rjlittlefield** » Sat Mar 03, 2012 7:08 pm

This blowfly proboscis is some work in progress that I thought you might be interested in.

First image, almost full frame at 10X so subject field roughly 2 mm high. Shot with Nikon CFI60 10X NA 0.25 objective, StackShot focus step 5 microns, 198 frames, Zerene Stacker PMax.

Crop from the above.

Crossed-eye stereo, most of a full frame at 50X on sensor, about 0.4 mm height. Shot with Nikon CF Plan 50X NA 0.55 inf/0 EPI ELWD (8.7 mm), focus step 1 micron, 113 frames.

Crop from above.

One thing that interests me about this image is the striking difference in anatomy from what's shown at http://www.sciencephoto.com/media/369670/enlarge.

Someplace I've read that some flies have teeth on their proboscis to help rip up meat. Is that what we're seeing here in those long forked structures? Do they tuck down into the groove between the lobes when the proboscis is fully expanded while feeding?

--Rik

Cactusdave · Post by **Cactusdave** » Sun Mar 04, 2012 1:23 am

Very interesting images. The X50 is a terrific image at such high magnification. I must look at this subject again in a mounted slide of the proboscis. The 'toothed' forked structures will of course be lying flat , but it should be possible to see them, and I can't say I've noticed them before.

Craig Gerard · Post by **Craig Gerard** » Sun Mar 04, 2012 1:34 am

It would appear to me the fly turns that particular appendage inside out when chomping but for reasons of aerodynamics retracts and tucks it away when not required, as displayed in the SEM image.

Those 50X images are outstanding!

Craig

Harold Gough · Post by **Harold Gough** » Sun Mar 04, 2012 1:49 am

Excelllent images.

As the food is +/- liquid, a wet surface might pick up a lot of dust, etc in flight. Perhap another reason for folding it away?

Harold

Peter M. Macdonald · Post by **Peter M. Macdonald** » Sun Mar 04, 2012 3:56 am

Rik,

Have a look at http://www.biodiversitylibrary.org/bibliography/1160 where you can download B. Thompson Lowne's comprehensive study of blowfly anatomy. It might date from the 1890s, but it is still the best. The book is "The anatomy, physiology, morphology and development of the blow-fly (Calliphora erythrocephala) A study in the comparative anatomy and morphology of insects"

Two volumes, sunning to over 850 pages. The external anatomy of the proboscis is in Volume 1 and the internal anatomy and rather more on the physiology is in Volume 2. Superb drawings. Now if only Thompson Lowne had been able to take couloured stacks and process them in ZS...

Peter

Harold Gough · Post by **Harold Gough** » Sun Mar 04, 2012 4:05 am

The book is also available here:

http://www.general-books.net/search.cfm ... pson+Lowne

Harold

Cactusdave · Post by **Cactusdave** » Sun Mar 04, 2012 5:37 am

I have located the same area on an old Victorian mounted slide of the blowfly tongue by Amos Topping, and it is an interesting comparison. If you are interested Rik, I could post a couple of images here or in a separate thread.

Edit: I have now created a new thread for these images in the 'Photography through the microscope' section http://www.photomacrography.net/forum/v ... hp?t=16216

rjlittlefield · Post by **rjlittlefield** » Sun Mar 04, 2012 12:50 pm

Peter & Harold, enormous thanks for the references! Seems that what I'm looking for is on page 145, Fig.31, note 4, "A pseudotracheal vessel and the prestomal teeth and folds", with further discussion on page 146. (I live in awe of people who can construct illustrations like this based on flying the focus knob up and down.)

Cactusdave, yes I'd love to see comparable images. Let's put them in a separate thread. That'll keep things straight and make it more obvious how to view side-by-side by opening two browser windows.

One more reference is to Tony Thomas's two-part article in Micscape magazine, HERE and HERE (Sept & Oct, 2011). Proboscis photos are in the 2nd part. The prestomal teeth there look much different from what I have and what's illustrated by B. Thompson Lowne.

--Rik

Peter M. Macdonald · Post by **Peter M. Macdonald** » Sun Mar 04, 2012 1:14 pm

See page 401 in volume 2 for the use of these structures when the fly is feeding on solids. Seems that they help to get the digestive juices into the food. Now, that is impressive observation on the "tongue" of a live fly.

rjlittlefield · Post by **rjlittlefield** » Sun Mar 04, 2012 1:52 pm

Ah yes, page 401...

When, however, the insect feeds on solids, the oral sucker is applied by its edges to the food, and the pseudo-tracheae distribute the salivary secretion of the lingual glands over the anterior surface of the sucker ; this dissolves the food, assisted, perhaps, by the disintegrating action of the stomal teeth, which, as Suffolk [58, p. 339] remarked, leave lines upon the food material ; and the fluid, with small particles in suspension, is drawn into the oral cavity. Under these circumstances, as I formerly suggested [62], the pseudo-tracheae probably conduct it into the prestomum and mouth and act as strainers.

As an aside, I can't help mentioning that I did not have to re-type those words. The entire document has been very well OCR'd, so all I had to do was copy/paste from the PDF file.

The fact that it's OCR'd also means that it's searchable. (What a treat!) However in this case I missed page 401 earlier because I had looked for "prestomal" per the description on pages 144-146, rather than "stomal" as used on page 401. I'm pretty sure these are talking about the same structures though, because searching on "teeth" finds nothing else that makes sense. The index entry is "Teeth of proboscis, 146".

By the way, while searching for "teeth" I also ran into page 394, where there is a description of the pseudo-tracheae. The description is accompanied by Plate XXIII, "Details of oral lobes", which contains a couple of nice photographs. The text notes that "The figure is taken from a very beautiful photograph which Dr. H. M. Wright, of Sidney, N. S. Wales, has kindly sent me; it was taken by him with one of Powell and Lealand's latest apochromatic objectives." Pretty dang impressive for a book whose cover page says 1893-95 !

--Rik

rjlittlefield · Post by **rjlittlefield** » Sun Mar 04, 2012 3:45 pm

For those who cannot see stereo, here's a small rotating version (animated GIF).

--Rik

rjlittlefield · Post by **rjlittlefield** » Sun Mar 04, 2012 9:29 pm

In response to an offline question...

This specimen was killed by being placed in a small plastic container in a home freezer. It was kept in the freezer for several days, then removed from the freezer and had some chance to dry (several hours) before all the shots posted above were completed.

What you're seeing is undoubtedly far from a lifelike appearance. In some sense, it's fortuitous that the fly died in this posture at all. As described in B. Thompson Lowne's book (page 139):

The proboscis is an erectile organ. It is flaccid and folded on itself when not in use, but is capable of being rendered rigid by the injection of air into the extensive tracheal sacs which lie in its cavities. When at rest the only rigid parts are the fulcrum, the prelabrum and the theca. The two lateral halves of the flaccid stomal disc are folded together, so that the stomal surface is concealed.
...
When the proboscis is in use, it is projected from the head capsule, and rendered stiff by the injection of air into its tracheae. Its varied movements are brought about by the action of muscles; the flaccid proboscis is also folded and withdrawn into the head capsule by means of retractor muscles.

So, what we see here appears to be a proboscis in an unnatural position, neither fully rigid from injected air nor fully retracted by muscular action. Still, it's a handy position for seeing the anatomy.

The reason I say it's fortuitous "in some sense" is that I collected and treated in the same manner multiple specimens of several species. I was expecting all of them be about equally easy or difficult to deal with, but in fact 6 out of 7 of the blowflies ended up in this position, while almost all of the others ended up in unusable fully folded positions. So really, what's fortuitous is that this highly studied fly happens to die in a position that makes the study easy. At least I assume that's fortuitous -- if the early investigators were particularly interested in the proboscis, then it could be causal!

--Rik

Harold Gough · Post by **Harold Gough** » Mon Mar 05, 2012 12:13 am

rjlittlefield wrote:I live in awe of people who can construct illustrations like this based on flying the focus knob up and down

Me too! I once had to do it for the (dissected out) three-level mouthparts of a springtail. It was the Holotype of a new species I had found and the only entire specimen known and it was in a genus where species are defined by the detail of such structures. These days, when I look at whole collembolan under a microscope, I sometimes struggle to clearly see diagnostic characters and would not contemplate drawing the smaller ones!

Harold

seta666 · Post by **seta666** » Mon Mar 05, 2012 3:43 am

Very nice shot!! Love the structures seen and the overall clarity; you made me want to catch a fly to try it myself ;-)
Regards

Planapo · Post by **Planapo** » Mon Mar 05, 2012 4:59 am

Great photos, Rik!
Love the stereos, another outstanding example where they help so much to grasp the real morphology.

--Betty