SNAIL'S TALES

Stuck between leftists and libertarians

2009-07-13T18:50:00.000-04:00

According to the World's Smallest Political Quiz, I am a centrist, right at the corner.

Darwin was a malacologist!

2009-07-13T09:32:00.000-04:00

Although I don’t work with freshwater snails and don’t know much about them, I happen to belong to the mailing list of a group of researchers interested in freshwater gastropods of North American (FWGNA) run by Rob Dillon of the College of Charleston. At irregular intervals, Rob e-mails to the group members his always informative and entertaining essays on various aspects of the taxonomy, ecology and biology of North American freshwater gastropods (archive). His essay of 25 February 2009 was about Charles Darwin’s interest in freshwater mollusks. Upon reading Rob’s piece, I remembered this post of mine from 2005 about Darwin’s experiments with land snails when he was trying to understand their dispersal mechanisms.

A few days later, I conceived the idea of combining Rob’s essay with my blog post in one article about Darwin’s work with mollusks in general. Rob liked the idea and I started working on it. I finished the first draft towards the end of March and sent it to Rob. He made some revisions and sent it back to me; I made a few more revisions and then sent the manuscript to Mollusc World, the magazine of the Conchological Society of Great Britain and Ireland.

Our joint effort, titled Charles Darwin the malacologist, recently got published in the July issue of Mollusc World. You may download a pdf version of the paper from here.

Darwin was truly a versatile biologist. The scope of his interests and the depths of his knowledge relative to what was known during his time are amazing.

What to do with missionaries

2009-07-12T08:56:00.000-04:00

Red Meat by Max Cannon
But do give them each a glass of wine.

Smile, you are on trike-cam!

2009-07-10T18:17:00.000-04:00

I had been meaning to attach my old camera to the front of my Greenspeed Anura to take pictures while riding. This afternoon I finally had a chance to do it. Because the camera's remote receiver is in the front, I had to turn the camera towards the back or at least sideways to be able to operate it with the remote from where I was sitting. Here is the camera attached to the front of the trike.

The exposure was set at auto, which often selected otherwise unacceptably slow shutter speeds, resulting in blurry pictures with double images, especially when I was going fast on bumpy paths. Here is shaky self portrait.

But when I was travelling slow on smooth roads, the results were better.

Here is a picture of the trike with the camera.

I have uploaded more pictures on facebook.

Where do dead birds go? — Part 16

2009-07-09T19:11:00.000-04:00

Sometimes they just stay there, like this dead catbird I photographed the other day by the side of a road. It was probably a hit-and-run victim.

Or, like these remnants of undoubtedly what was once a bird. I've been passing by them on a path on my way to and from the train station every work day for about a month.

For whatever reason, there seems to be quite a bit of interest out there in figuring out what happens to birds after they die. A Google search using the phrase "where do dead birds go" returned 11,200 hits*. I have already provided an answer in this post.

The moral of today's post is that anyone who spends a lot of time walking, while paying attention to what's on the ground, is bound to see plenty of dead birds, in addition to other types of expired creatures, for example, salamanders.

*In comparison, when I searched for "where do dead rats go", I got only one hit. I don't know if there are more rats or birds, but birds, being more visible than rats, obviously create more interest.

Another well hidden tree frog

2009-07-08T21:22:00.000-04:00

This is a gray treefrog. But is it Hyla versicolor or H. chrysoscelis? Apparently, the 2 species can be distinguished only from their calls. I need to get a sound recording device and then go out there one night to record their calls.

I photographed this individual in the park near my house. The previous well hidden treefrog from the same location was the subject of this post.

That's my speeding car, all right

2009-07-07T17:05:00.001-04:00

I got photographed doing 38 mph in a 25 mph zone in DC and had to pay a $50 fine. I had a right to request a hearing and then go to court, but do I really want to waste my time with all of that? And what was I going to tell the judge? The 25 mph limit is too low for that road, your honor. I am sure you realize that this is just a gimmick for the DC Government to take more money from the citizens. So why don't you give me a break?

Would he/she have felt sorry and waived the fine?

Hermaphrodite parent and child reunion

2009-07-06T17:33:00.000-04:00

Both of these slugs, Megapallifera mutabilis, were from the same tree. So it is likely that the larger slug is the mother or father of the juvenile.

In the wild and in captivity, this species enters pools of water to regain water lost during its daily feeding excursions on tree trunks.

It was 5 years ago today

2009-07-04T20:38:00.001-04:00

Time flies when you are procrastinating. I mentioned in this post back in December of last year that I was working on the material collected during a land snail survey we had done in Turkey early in the summer of 2004. I am still not finished, because after December I took a long break and worked on other stuff. I am now back at it and I intend to finish sorting all the specimens by the end of the year.

Imagine my pleasant surprise today when a bag of shells I picked randomly had the date of 4 July 2004. It seems like it was only, well, 5 years ago.

D51 was a pretty rich station with about 22 species. In the picture you can see a couple of long and narrow Bulgarica shells near the center and a couple of white Albinaria puella to the right. The tall white shells near the top are Zebrina cosensis, while the large, flat ones are Oxychilus samius. The tubes are holding the smaller shells.

One interesting non-snail specimen that was in the bag was this insect larva.

It appears to be a drilid larva (becaue it is hairy). The larvae of the beetles in the family Drilidae are predators of land snails. Surprisingly, I don't seem to have written about drilids before. But there is a summary of a paper I once wrote about them on this page. It was one of the first 2 papers I wrote on snails. One of these days I am going to scan it and turn it into pdf.

A belated celebration of the Evolution Day

2009-07-03T13:53:00.000-04:00

This year is the 151st anniversary of the historic session of the the Linnean Society in London on 1 July 1858 when Charles Darwin’s and Alfred Russel Wallace’s independently developed ideas on evolution by natural selection were made public for the first time.

Darwin had been developing his ideas for 20 years, but before that day he had revealed them only to a few close friends and correspondents, including the American botanist Asa Gray. Wallace, on the other hand, had come up with his version of natural selection, very much similar to that of Darwin's, several months earlier while doing fieldwork in the Malay Archipelago and communicated it to Darwin in a now famous letter*.

The presentation at the Linnean Society was initiated with a letter of introduction by Darwin’s close friends Charles Lyell and Joseph D. Hooker, opening with the words:

My Dear Sir, -- The accompanying papers, which we have the honour of communicating to the Linnean Society, and which all relate to the same subject, viz. the Laws which affect the Production of Varieties, Races, and Species, contain the results of the investigations of two indefatigable naturalists, Mr. Charles Darwin and Mr. Alfred Wallace.

This was followed by the reading of extracts from an unpublished essay Darwin had written in 1844, part of his 1857 letter explaining his ideas to Gray and the manuscript Wallace had sent to Darwin.

Why not celebrate this great idea today and everyday? Read a book on evolution, teach someone about evolution, visit a natural history museum or take a hike in the woods or go to a sea shore to witness the products of evolution. And don’t forget to remember Darwin and Wallace, for, after all these years, their idea remains indefatigable.

Hooray to the bearded guys! Pictures of Darwin (left) and Wallace are from the Linnean Society.

*According to the Darwin Correspondence Project, Wallace's letter and unpublished manuscript are missing.

Helix aspersa from San Diego

2009-07-02T18:14:00.000-04:00

A friend at work walked into my office today with a plastic water bottle containing a live snail. It was a gift* for me picked up by her husband yesterday in San Diego, California.

I am tentatively identifying it as Helix aspersa (Cantareus aspersus), an introduction from Europe. It was found with several others in a flower bed at a hotel, an unlikely place to find native local species. It is a juvenile with a soft, still not-reflected lip. First, I though it was a Helix aperta, a species I am not familiar with, but now I am leaning towards the former.

The snail still hasn't fully come out of its shell. It appears moribund, actually. Could it be suffering from jet lag? I hope it will recover and grow to become an adult so that I can be certain of its identity.

*It was the same couple who brought back Littorina littorea for me from Bar Harbor, Maine.

Purple poop

2009-07-01T17:55:00.000-04:00

This purple stain surrounding what appears to be a deposit of bird ordure was on my deck yesterday.

What had this bird eaten?

My botanical knowledge, especially when it comes to identifying plants from their seeds, is pitifully poor. Any ideas?

Depth of field, f-numbers and diffraction (or how to take a rotten photograph)

2009-06-30T16:40:00.000-04:00

In Handbook for Scientific Photography (1977), Alfred A. Blaker wrote:

As the substage diaphragm is closed, the depth of field increases (as when you close the diaphragm of your camera lens)...However, diffraction of light by the edge of the diaphragm increasingly impairs the image resolution until the image becomes "rotten."

He was explaining how to take pictures thru a microscope using a camera back and the substage diaphragm he was referring to is the one under the stage of a microscope. One encounters a similar diffraction effect when using a camera with a lens to take closeup* pictures. Blaker explained this in another book, Field Photography (1976):

...at significant magnifications the choice of f-number is...nearly always a matter for compromise between depth of field needs and the resolution of fine detail in the image. At very small apertures, diffraction of light at the diaphragm edge reduces resolution.

The bottom line is that the smallest aperture will give you the greatest depth of field, but not the best resolution†.

Here are some tests I did with my Olympus 35 mm Zuiko lens on Olympus E-500. In this case, the object was a flat wood surface and so the depth of field was not an issue. Notice the decrease in sharpness as I increased the f-stop (decreased the aperture diameter).

Click on the image to view a bigger version. These are unretouched images. Some image quality was lost because I had to compress the composite picture before I could post it here.
The decrease in sharpness going from f5.6 to f11 is almost not noticeable. Even f14 would be acceptable for some purposes. But ordinarily, I avoid the apertures above f14.

Here is another example; shots of a flower bud of trumpet vine at f5.6 and f22, again with the 35 mm lens. There is a definite loss of resolution at f22.

But now let's compare the overall images.

At f5.6 with diffused sunnlight:

And at f22 with flash light:

The one at f22 has a much wider depth of field and the overall loss of resolution due to diffraction is not noticeable at this magnification. Therefore, we follow Blaker's advice and compromise and chose between depth of field and resolution. If we want a wide depth of field despite the loss of overall sharpness, we decrease the aperture; if we want a sharp focal point amidst blurry surroundings, we increase the aperture. How you take a picture depends on what you want the picture to look like and what you will do with it. In many cases, there is no right or wrong photograph as long as the image is not too rotten.

*Blaker's definitions of closeup photography as photography at image magnifications of actual size or less and photomacrography as photography at image magnifications greater than actual size are arbitrary and pointless.
†Don't confuse this with the pixel resolution of a digital camera.

Snail Poster Museum Official Hiking Laboratory

2009-06-29T13:34:00.000-04:00

Or, official hiking shoe museum garden path snail poster. Or, cat fortune house laboratory hiking shoe.

Today’s temperate silliness has been inspired by a webpage by Charles H. Bennett. As Bennett notes, English speakers can create arbitarily long and yet meaningful chains of nouns even when starting from just a handful of appropriate words. Bennett gives an example of 2 noun loops of 5-4 words joined in a figure 8. Here is my example of 3 joined noun loops of 5-2-5 words.

You can start at any word and go in either direction to obtain a meaningful sentence of any number of words. Admittedly, some sentences may be a bit more meaningful than others, but none is grammatically wrong. Note that the word official, both a noun and an adjective, adds more variety to the endless possibilities.

Cat hiking shoe museum poster snail.

Official hiking laboratory house fortune cat hiking shoe museum garden path snail poster museum official hiking laboratory house fortune cat hiking official museum poster snail path garden...

Grazing slugs and the evidence they leave behind

2009-06-28T16:15:00.000-04:00

The northwest wall of the house receives sunlight filtered by trees and bushes and thus remains wet longer than the more southerly sides; it is a perfect habitat for cyanobacteria (blue-green algae). If it weren't for the resident slugs, a thick jungle of microscopic proportions would long have developed on the siding.

Slugs love the green stuff and on warm, humid days come out to graze on it. Here is an Arion subfuscus with its feeding track behind it.

There are a variety of tracks on the wall. Some are more elaborate than others. I suspect different species are involved.

This one reveals the marks of the individual teeth of the radula that does the scraping.

I am curious to know if I can tell the species apart from their feeding tracks. Updates will be posted.

Weight lifting snails

2009-06-26T17:26:00.001-04:00

Anyone who has tried to pick up a snail crawling on a smooth surface like a sidewalk or glass may have noticed that snails can have quite a tenacious grip. One way to measure how strongly a snail can hold onto a surface is to measure how much weight the snail can lift.

To collect some relevant data, I put together a crude apparatus consisting of a small plastic bottle taped to 2 glass microscope slides. I can increase the weight of the apparatus by adding objects, usually coins, into the bottle. The snail is placed on the upper slide. After it attaches its foot on the glass, I hold its shell and lift it up, at the same time starting a stopwatch. I selected 5 seconds as an arbitrary minimum time necessary for a lift to count as successful.

This Cepaea nemoralis carried, in addition to the apparatus itself, 3 quarters and 1 dime, or a total of 41.3 grams for 39 seconds.

That weight will be more meaningful once I express it in relation to the surface area of the snail's foot. I haven't had a chance to do that.

Keep in mind that a snail does not not actually hold onto a surface using muscle power; its grip results mainly from the functioning of the sole of its foot like a sucker. Parker* wrote in 1911:

As means of attachment snails secrete a bed of mucus, and use the foot as a sucker. Both methods are commonly employed by the same species, but in a given form one method is usually developed much in excess of the other. For instance, in Helix pomatia, Limax maximus, and other allied species, the moist surface of the expanded foot will stick with some tenacity to glass. But if such an animal be allowed to creep its length over a glass surface and thus spread a bed of mucus on which it can rest, it will be found to have multiplied the strength of its attachment many times. The mucus adheres to the glass and the surface of the foot to the mucus very much more powerfully than the foot alone can adhere to the glass.

I have noticed it is somewhat difficult to obtain reproducible results. There may be some habituation involved. If the snails are picked up too frequently, they appear to start letting go off the surface more easily.

*G. H. Parker. 1911. The mechanism of locomotion in gastropods. Journal of Morphology, 22:155-170. pdf

Catbird in the backyard with something in its beak

2009-06-25T17:21:00.000-04:00

I have been seeing a catbird* (Dumetella carolinensis) in the backyard. There must be a nearby nest in the vicinity close to the house†. Their name comes from the distinctive cry uttered with an open mouth as in the picture below. It is supposed to sound like a meow, but to me, it sounds more like a long, high-pitched me.

The funny thing was every time this bird flipped its tail down, it would dip in the bird bath. But, otherwise, I did not see the bird enter the water.

When the tail is lifted up, the reddish coverts under the tail become visible (according to the books, they are "chestnut" colored). There must be some evolutionary significance to their color and display.

At one point during this photo session, I saw the bird with something in its beak. But I just can't tell what it was. What do catbirds usually eat?

*The full name is gray catbird, although neither of my bird books lists catbirds of any other color.
†That was an exercise in redundancy.

Marissa confronts Mittens (from behind a screen)

2009-06-24T21:29:00.000-04:00

Remember Mr. Mittens, one of our neighbors' cat? He is still around and he still comes to our door whenever he wants to go in his house. The other morning he was on our porch again, hoping we would walk him him over to his house and let him in, something we don't do when his owners are home.

Marissa happened to be sitting by the kitchen window and looking outside. The 2 cats watched each other for a while. There was some growling. That's when I lowered the window to prevent anyone attempting to pass thru the screen. Luckily, cats haven't figured out how to tunnel across barriers a la electrons.

Melongena corona dives

2009-06-23T21:07:00.000-04:00

Back in April when I was in Florida, I did some simple seashore experiments to investigate the behavior of the common intertidal snail Melongena corona. At low tide the snails usually bury themselves in the wet sand. My experiments consisted of removing the snails from their holes, placing them elsewhere on the sand or on rocks and then watching them. Here is one that I transplanted on a flat, wet rock surrounded by water.

A few minutes later the snail came out of its shell, slowly crawled to the edge of the rock and...

As usual, the video was made by stitching together sequential shots.

Bipalium adventitium — Part 1

2009-06-22T18:21:00.002-04:00

And now for something completely different: the land planarian Bipalium adventitium.

I found this critter a few weeks ago in the park near my house. As usual, I was looking for slugs and snails and there was this planarian crawling around the roots of a tree.

The fully stretched animal—they have very flexible bodies—was ~8 cm long.
Although Libbie Hyman described this species using the specimens collected in Pasadena, California (Hyman, 1943; pdf), it is believed to have been introduced to North America originally somewhere from eastern Asia. Here are the 3 exotic Bipalium species found in the U.S.

From Ducey et al. 2007. Southeastern Naturalist 6:449.
Bipalium adventitium preys on earthworms. Mine ate one earthworm I had put in its container, but I wasn't around to take its pictures during the process. Subsequently, it produced 3 egg cocoons. If it were a native species, I would have released it back into the wild. But, and despite the fact that it is more or less a naturalized alien, I decided that the best thing to do was to preserve it in alcohol for posterity.

More will be in Part 2.

Nest sharing birds

2009-06-21T09:09:00.000-04:00

This is a continuation of Friday's post about a large stork nest in Turkey. At the end of that post I noted that there were many small birds congregated around the storks' nest. The reader Tristram Brelstaff, who writes the blog Life and Opinions, asked in his comment if the little birds were nesting in the underside of the storks' nest. After I re-examined the original photos, I realized that that was indeed what was going on.

Here is the evidence. First, another picture of the storks in their nest. The red arrow on the left is pointing at one of the small birds. I suspect it is either some sort of sparrow or a swallow, perhaps a sand martin (bank swallow, Riparia riparia).

The green and yellow arrows are pointing at additional individuals. That those are birds is indicated by the yellow arrow. Look at it closely. Now look at the same spot in the next picture. The object in the hole is missing.

The blue arrows are pointing at the holes tunneling into the storks' nest. There are several others. They all appear to be bird nests. What we have here is a giant communal nest. My sister has remarked: "Yes, they live in an apartment building. The storks are in the penthouse".

More white stork pictures from Turkey

2009-06-19T17:21:00.002-04:00

My sister, whose stay in Turkey since last September is about to end, sent these stork pictures earlier today. She took them on the way to the city of Aydin (yes, the city named after me).

As I mentioned in this post, the white storks (Ciconia ciconia) get special treatment in Turkey. They are almost never harassed and their nests are left alone even if they reach an enormous size like the one in these pictures. One wishes that all other wild animals received the same respect.

I can't tell what those small birds are, but they seem to be attracted to the storks' nest. (See the follow-up post for more.)

Previous bird pictures from Turkey also sent by my sister are here and here.

James Barbut and his mating slugs

2009-06-18T16:25:00.000-04:00

Free access to old books on the Internet (primarily thru Google Books, the Internet Archive and the Biodiversity Heritage Library) has saved me not only many trips to libraries, but also money and time I would have otherwise spent at photocopy machines.

James Barbut was a British painter and naturalist who was active in the 1780s; he published 2 books, one on insects and the other on Vermes or worms, which, back then, included all other invertebrates.

That's more or less everything we know about Barbut.

A little more than a year ago, while searching Google Books for the occurrences of the name of the slug Limax maximus, I discovered a full copy of Barbut's worm book* The genera Vermium exemplified by various specimens of the animals contained in the orders of the Intestina et Mollusca Linnaei. In his book, Barbut had a few pages of information on the 4 slug species he knew of, including a brief but surprisingly accurate explanation of how they mate. As I was reading that section, it dawned on me that Barbut's account was one of the earliest published descriptions of the aerial mating of Limax maximus.

Subsequenly, I turned all of that into a short paper that came out in the March 2009 issue of Mollusc World, the magazine of the Conchological Society of Great Britain and Ireland. My copy arrived only a few days ago.

A pdf version of the paper is here.

Barbut's Limax maximus.
I will appreciate receiving any further biographical information on James Barbut.

*An earlier edition is available at the Biodiversity Heritage Library.

3 books from the bookstore that sells used books

2009-06-17T17:00:00.002-04:00

Yesterday and today I attended a workshop at the U.S. Pharmacopeia in Rockville, Maryland. During one of the lunch breaks, I took a walk to the nearby Second Story Books. Bookstores that sell old books for profit tend to overprice their wares, often remaining oblivious to the fact that many 19th and early 20th century books are now available for free either on Google Books or the Internet Archive. Luckily, in this store everything was 25% off and I ended up getting 3 books at quite reasonable prices.

Julian Huxley's classic Problems of Relative Growth was originally published in 1932. I had already photocopied some pages from it. Now I have the entire thing, albeit it's a 1972 reprint. That one was $2.25. In Search of Nautilus by Peter Ward (1988) looked interesting and the price, $4.5, was good.

I bought the 3rd book, The Orientation of Animals by Fraenkel & Gunn (1961), for $3, mainly to read the chapter titled Variation in behaviour. I have lately been intrigued by certain variations in the behaviors of snails and slugs and thought that the ideas in this book could provide some relevant background. On the other hand, they are likely to be obsolete. But, still...

Probably a five-lined skink...

2009-06-16T16:21:00.000-04:00

...but I am not sure. I photographed this creature along the Billy Goat Trail last Saturday. It was probably at least ~20 cm long.

It is either the common five-lined skink (Eumeces fasciatus) or the broad-headed skink (Eumeces laticeps). According to Amphibians and Reptiles of Delmarva (White & White, 2002), the 2 species may be distinguished by their numbers of certain facial scales.

Figure 17 from Amphibians and Reptiles of Delmarva.
This particular individual had 4 upper labial scales, which would make it a five-lined skink. But only 1 postlabial scale is visible in the photo. So, either the 2nd postlabial isn't visible or this is an unusual specimen. Based on its coloration, it's a male (of either species).

Yes, I am surprised too that I could get so close to it before it finally ran away.