31 March 2010

December 4, 1703: Leeuwenhoek lets his imagination run wild

In a letter1 to the Royal Society of London written on December 4, 1703, Dutch microscopist Antony van Leeuwenhoek (1632-1723) gave an account of his microscopical examinations of sand grains. Leeuwenhoek starts off by declaring that no 2 sand grains are identical:

I remember I have formerly affirmed of Sand, that you cannot find in any quantity whatsoever two Particles thereof, that are entirely like each other, and tho perhaps in their first Configuration they might be alike, yet at present they are exceeding different...
Having established that basic fact, he goes on to give descriptions and drawings of several sand grains he had observed with his microscope. One particular grain was exceptional:
In the said Sand, which is describ'd by GHIKL, you may see not only, as it were, a ruined Temple, but in the corner of it GHI appear two images of humane shape, kneeling, and extending their Arms to an Altar, that seems to stand at a little distance from them...
Here is Leeuwenhoek's drawing of the sand grain with a temple:

What is curious is that Leeuwenhoek offers no explanation whatsoever of how an image of a temple complete with worshipers could have been on a tiny sand grain that he had randomly selected from among numerous grains. It is also not clear if he believed what he thought he saw was a real image or some cracks and lines on the sand grain that resembled the picture of a temple.

He may very well have believed that there was an actual temple drawing on that particular sand grain. This is supported by his conclusion that all sand grains had been created when earth was created:
From these Observations, I imagined that almost all the Sand on the whole Earth have preserved the figure that was given to it at the Creation...and so have remained what they were originally; saving that by their frequent collisions with other bodies their first figure may be something impaired...
His phrase "first Configuration" in the opening quote from his letter, therefore, refers to the shapes of sand grains "at the Creation". Thus, it is perhaps expected that Leeuwenhoek was not too surprised to find sacred images etched on sand grains left over from his god's handiwork.

Obviously, Leeuwenhoek didn't understand that sand continuously forms from the disintegration of rocks.

1Part of a Letter from Mr Anthony van Leuwenhoek, F. R. S. concerning the Figures of Sand. Philosophical Transactions 1704 24:1537-1555.

30 March 2010

Beaver's tale

In their 2003 book The Beaver, Müller-Schwarze & Sun call the beaver's (Castor canadensis) tail a "multipurpose tool" and list its functions:

1. To support the beaver's body when it's cutting a tree.
2. To help the beaver maneuver in the water.
3. To slap on the water to signal danger.
4. To store fat.
5. To regulate heat loss to the surroundings.

If we were to rate a single-function organ, like the eye, on a scale from 1 to 5, we could perhaps give it a 4.5, if not a 5. Our eyes are pretty damn good at doing what is required of them. Granted, they may develop various illnesses, become near- or far-sighted and even blind, but when our eyes are healthy, and most of the time they are, we can see quite well with them. In any case, evolution couldn't have come up with an organ impervious to failure.

But, if we were to rate the individual functions of a multi-function organ like the beaver's tail, would we be able to give each function a rating of 4 or higher? In other words, could a multi-function organ be as good at each of its functions as a single-function organ, like the eye, is at its one function?

The problem is that when an organ has evolved to perform more than one function, the morphological and physiological requirements of all of those functions may interfere with each other. Such conflicts may then result in what are known as evolutionary trade-offs: the organ evolves to become less good at one particular function so that it can also become mediocre at one or more additional functions. The resulting multi-function organ evolves to be good at performing multiple functions but it may not be as good at performing any one of those functions as it would be if it had evolved to perform only that function.

One way evolution can overcome this problem is to have a given function performed by multiple organs. The net result is that the overall performance of a given function then obtains a high rating, say a 5. This mechanism also provides insurance: if one of the organs is disabled, its functions can still be performed, albeit now slightly less efficiently, by other organs.

So, going back to the beaver's tail, how good is it in performing each of its functions and does the beaver have other organs that function at least some of the tail's functions?

29 March 2010

Leeuwenhoek's snails

In a letter1 to the Royal Society of London written in 1697, Dutch microscopist Antony van Leeuwenhoek (1632-1723) gave an account of his observations of snail eggs. The eggs had been brought to him by a friend of his for Leeuwenhoek to determine which animal they belonged to. Leeuwenhoek failed to get the eggs to hatch on several occasions before it dawned on him that they needed to be prevented from drying. After he started keeping the eggs in moist soil, he was fascinated to see "Horn Snails" coming out of them2.

Leeuwenhoek identified the snails as "wine-yard snails" and noted that the diameter of their eggs was "almost the Fifteenth Part of an Inch", about 1.7 mm. An internet search for "vineyard snail" came up with 2 species: Helix pomatia and Cernuella virgata. Other snail species have probably also been called vineyard snails. The exact identity of Leeuwenhoek's snails may forever remain a mystery; one that doesn't really need a solution.

What I thought was the most significant part of Leeuwenhoek's letter was his conclusion regarding snail reproduction:

Therefore we see (as it is said before) that the generation of the Wine-yard Snail happens by Eggs, the old Opinion is consequently to be laid aside, viz. That the Snails come forth by the spoil'd and rotten Leaves of Trees, and that the Leaves of Trees, left on the Ground, produce Snails.
Leeuwenhoek then went on to provide a rational explanation for the origin of the spontaneous generation myth he had just knocked down:
But we shou'd rather think, that when we in Autumn leave the Leaves of trees lying on the Ground, the Eggs of Snails lying in the Earth these Leaves lye, are better defended from the hard Cold, than those which lye where no Leaves are.
A simpler and more reasonable explanation is that snails seem to come out of leaf litter because many species live and reproduce in leaf litter.

Note that Leeuwenhoek acknowledged that it had already been stated that snail reproduction took place via eggs. But he didn't bother to give a citation. Such lax acknowledgment of prior authority seems to have been a common practice at that time.

I don't know who was the 1st to figure out how snails reproduced.

1Part of a Letter of Mr. Anthony van Leeuwenhoeck, Dated Delft, Sept. 10. 1697. Concerning the Eggs of Snails, Roots of Vegetables, Teeth, and Young Oysters
Philosophical Transactions 1695-1697 19:790-799.
2By "horns" he was probably referring to the snails' tentacles.

26 March 2010

How creationism once crippled progress

Yesterday afternoon I finally finished reading F.J. Cole's History of Comparative Anatomy from Aristotle to the Eighteenth Century. As discussed in this post, an underlying theme of the book is that the main purpose of comparative anatomy is to help find which organs may be homologous between different species.

The early anatomists did occasionally notice homologous organs between otherwise very different species. For example, Belon in the mid-16th century compared the human and bird skeletons and noted what he thought were the homologous bones in the 2 types. However, neither he nor any of his successors could make heads or tails of their findings. They could not, for example, explain the puzzling anatomical relatedness of certain "fishes", such as dolphins and whales, to terrestrial mammals. Cole writes:

We thus see that Belon demonstrated the importance of comparative studies as early as 1555, but the significance of the homologies then disclosed was not recognized by himself, or by Goethe, pondering similar facts, over two hundred years later. The lapse of time therefore had left the situation almost unchanged...Descriptive anatomy had served its purpose, and could do no more.
However, the early anatomists were not totally lost and they did have an underlying rationale of sorts. Cole explains:
...community of structure might be established between two organs without the inference being drawn that they were historically related. Such community was often regarded as evidence of design in the sublime scheme of the Creation, in which case organisms were as independent of each other as are the variations on a theme in a musical composition...
But why would an intelligent designer have put mammals in the sea? Such questions were, however, not allowed. Therefore, creationism was, and still is, a cul de sac. Creationism, by its very nature, did not allow for speculation outside its narrow limits and could not lead to understanding. Once the dead end was reached, all progress necessarily came to a halt. Cole continues:
Progress depends on the influence of some energizing and integrative speculation, sound or unsound, which is sufficiently bold and provocative to attract supporters and opponents, eager to investigate its validity. Without such a stimulus the observer is for ever groping in the dark for the switch he cannot reach.
Eventually, a new road was found and the cul de sac was completely avoided and left behind.
We know now that the theoretical basis of comparative anatomy is the genetical history of animals, or in other words the principle of evolution.
Cole’s book dates from 1949. Creationists are still and will always be groping in the dark.

25 March 2010

Vertigo pusilla in Turkey

In this post back in the fall of 2008 I had an account of myself searching for micro snails in Turkey a few weeks earlier. That post also had a link to a video of me in the field.

The snail species I collected that day included Vertigo pusilla and Euconulus fulvus. When I subsequently realized that the specimen of the sinistral Vertigo pusilla I had found was the 3rd ever record of that species from Turkey, I wrote up a short paper about it, which came out today*. You may download a pdf version of the paper from here. The paper has color pictures of Vertigo pusilla and Euconulus fulvus.

*Örstan, A. 2010. A new record of Vertigo pusilla from Turkey. Triton 21:27.

24 March 2010

Leech breach: it's Hirudo verbana

In this post I wrote about the leeches I had seen at an exhibit at the Delaware Museum of Natural History (DMNH) in Wilmington, Delaware earlier this month. Here is one of those leeches.

At that time, the identity of the leeches was a mystery to me. Subsequently, one reader commented that they were either Hirudo verbana or Hirudo medicinalis. The latter is the "medicinal leech" that is still used to get rid of excess blood in certain medical conditions.

Today I came across a paper* from 2007 that gives the following picture to distinguish between the 2 species.

Fig. 1 from Siddall et al. 2007.

The patterns on the leech I photographed match those on Hirudo verbana.

According to the cited paper, molecular data demonstrate that leeches marketed as Hirudo medicinalis are actually Hirudo verbana. For details read the paper; it's available freely.

*Siddall et al. 2007. Diverse molecular data demonstrate that commercially available medicinal leeches are not Hirudo medicinalis. Proc. R. Soc. B 274:1481-1487. pdf

23 March 2010

This is not a blog post about René Magritte

This evening the message board in the train was displaying the message that there was no message. You can see it in the picture below, the best I could get of a dimly lit moving target with an iPhone camera.

Is this a variation on Magritte's This is not a pipe? The obvious resolution of the paradox—if that was indeed what it was—Magritte presented is that his object is not a pipe but a painting of one.

But a "No message" display is a message, is it not? It is informing us that there is no message. Therefore, it is a message.

I suppose when there is no message to display, the message board could simply be turned off. But then the passengers will not know if the display is broken or turned off because there is no message to display.

Is it possible to convey the information that there is no information to convey without actually conveying any information?

22 March 2010

On the slow progress of biology

I am still reading F.J. Cole's History of Comparative Anatomy from Aristotle to the Eighteenth Century. Our subject now is the Dutch anatomist Jan Swammerdam whose magnum opus Biblia Naturae was 1st published in 1738, 58 years after Swammerdam died. Nevertheless, Cole writes that when the book came out it was "not yet out of date".

In the 17th and the 18th centuries the progress of science was much slower than it is now. But even then, certain key discoveries were made and published by different scientists independently and within a few years of each other. Cole mentions several examples. For example, the technique of injecting colored liquids or waxes into veins to make them more visible was apparently discovered and rediscovered several times between 1651 and 1666 by Harvey, Swammerdam and others. So there was indeed competition between the scientists and rapid progress in some areas of science. On the other hand, microanatomy of animals—the main subject of Swammerdam's book—wasn't practiced by many and Swammerdam's skills at it were apparently difficult to match even decades after his death. Thus, his findings were still fresh when they were published belatedly.

Even now, in our age of rapid progress in many areas of science, certain fields of biology still rely on decades old publications. That is because we know very little about the life histories, behaviors and anatomies of most of the hundreds of thousands of species that are out there. In a paper I just published on the reproductive biology of the snail Oxyloma retusum, the oldest reference I cite is from 1935; that is from 75 years ago. Despite certainly not being up to par with today's standards, it is still a relevant publication.

In short, it is not surprising to me that the much delayed publication of Swammerdam's Biblia Naturae in the 18th century had not made it obsolete. The descriptive biology will always return to the old masters even when they are only good for knocking down.

21 March 2010

Spring peeper in my hand

Two recent daytime expeditions to photograph the spring peepers (Pseudacris crucifer) inhabiting a wetland-like area not too far from my house produced several sound recordings of their incessant calls, but no photos. I failed to see a single frog, although the snails co-inhabiting the place didn't escape my attention. So last night I followed Fred Schueler's advice, donned my headlamp and rubber boots and went out at dusk.

The frogs were calling all around me as I squatted at the edge of the swampy area with camera in hand. For many minutes I looked and looked at the spots brightened by my headlamp, but just couldn't see a frog. I was puzzled about how they could be so noisy and invisible at the same time. Just as frustration was setting in, I finally noticed the inflated vocal sac of one, my 1st spring peeper sitting by a skunk cabbage.

Once I knew what they looked like and how small they were, I started spotting them left and right. Eventually, I even caught one and held it in my hand long enough for a few shots. The picture below will give you an idea of an adult frog's size.

And here is one of the recordings I made with my iPhone. Against the background cacophony of countless frogs, you will hear the peeping of one Pseudacris crucifer.

Call of the spring peeper

19 March 2010

I see the snails but where are the frogs?

Since about the beginning of this week when the weather suddenly warmed up frogs have been broadcasting their loud cacophonies. A certain species lives in a flooded area near a creek not too far from my house. I have recorded their calls and got a possible identification: spring peepers (Pseudacris crucifer). For confirmation, I figured I needed their pictures. So late this afternoon I took my camera, put on my rubber boots and entered the swamp.

Frogs were everywhere; I knew that because they were deafening me with their calls. For about 40 minutes I searched for them to no avail; not one made itself visible to me. They are supposed to be small, only about 2 to 3 cm long. So I was looking very carefully. But instead of tiny frogs, I kept picking up even tinier snails from among the plant litter in the water. First, there was this succineid, probably a juvenile Oxyloma retusum, a land snail of wet places. Compare it to the size of my thumb.

Then there was this aquatic species. Let my finger be a scale for its length.

It didn't have an operculum. So it was a pulmonate, possibly a Fossaria species. It was actually hard to see it when it was crawling on the debris matching the color of its shell.

All the while the frogs kept up with their shrill. But my eyes, obviously programmed to see snails, could not see them.

I will continue my quest tomorrow afternoon.

18 March 2010

Message from the sidewalk


Happy Sring! No, wait, there is a p in there. Happy Spring!

17 March 2010

A face on the train


This was a part of a larger panel.


These are pictures LXXI & LXXII in the boxcar graffiti series. Boxcar mini-graffiti LXVII, LXVIII, LXIX & LXX are here.

16 March 2010

Slug weighing operations resume

In this post I introduced an ongoing research project involving the eastern North American slug Megapallifera mutabilis. Basically, we are trying to deduce the population cycle of this species by monitoring the sizes of the slugs during a year.

Last weekend's rains and the sudden rise of the temperature were the signals I had been waiting for to start this year's data collecting. I was able to go out to the park near my house for about 45 minutes this morning to search for slugs. Luckily, I found and weighed 3 of them.


Here is a preliminary graph showing the slug weights toward the end of the fall and near the beginning of the spring.

Red dots are for 2009; blue squares are today's data. The X-axis is not to scale.

It appears that the largest slugs that are present early in the fall die off before the winter comes (compare the weights of the slugs in the picture in the previous post with that of the slug in the picture above). However, adults do survive the winter and they will probably start mating pretty soon.

Updates may be provided.

15 March 2010

How I escaped from a one-way train that wasn't going to stop at my station


This evening at the station I noticed the crowd was larger than usual. That often means that the trains are running late. I took this picture of the train when it finally showed up and got on it a few minutes later. As I was moving down the aisle looking for an empty seat, I heard the conductor's announcement: "The next station is Point of Rocks".

In a span of a few microseconds a train of thoughts rushed thru my mind: Point of Rocks is the station after Germantown; This isn't my usual train, because the trains are running late; I am on one of those occasional trains that don't stop in Germantown where I get off; There is no return train at this hour; If I go to Point of Rocks it will be very, very difficult for me to get home.

After another nanosecond of indecisiveness—as if that was necessary—I turned back, scampered down the aisle and entered the space between the 2 cars. I felt the jerk of the train and thru the doors that were still open saw the platform below move. Then the conductor blocked my way—it's not safe for passengers to be there while the train is moving. To be sure, I asked, "Do you stop in Germantown?" He said, "No" and radioed the engineer while the train doors closed.

The train went a few meters and stopped. The doors opened. I jumped on the platform yelling a "Thank you" at the conductor. He yelled back, "The next train stops in Germantown".

I was lucky. Point of Rocks is 24 miles from Germantown and the trains in the opposite direction don't start running until early in the morning.

14 March 2010

Forget the snails, worry about the idiotic newspapers there are still around

A peculiar article appeared in the Orlando Sentinel on 11 March about the potential threat the giant African snails (Achatina sp.) may pose to agriculture and human health in Florida. The article has since been repeated verbatim by at least 1 other paper (Los Angeles Times).

I am not sure what exactly the "news" is in this "news" article. It is already illegal to bring into the U.S. not just giant African snails, but any species of live snail without a permit. And the USDA inspectors routinely inspect for snails the cargo that is being imported into the U.S. in Florida and elsewhere. There is nothing new so far as import regulations are concerned. Moreover, the article doesn't say if any Achatina has recently been found in the wild in Florida. Nor does the article mention if there has been any recent confiscations of snails at U.S. borders. There may well have been some. But the article doesn't say that.

So what's the point of publishing an "empty" article like this other than as an excuse to sell ads?

Are we still lamenting the ongoing decline and the eventual and unavoidable demise of the newspaper industry? Oh, I can't wait for that day to come! We won't be losing much, believe me.

Appreciations to C. Christensen for bringing this to my attention.

12 March 2010

Maybe a fox jaw—I don't know


This pair of jaws are from a field trip back in January during which I also found a deer skeleton. Each jaw is about 9 cm long. Both are missing the incisors and the canines.

I found them in a hedgerow on one side of which was a farm field and on the other side a hill leading up to a residential building. I am suspecting that they belonged to either a small fox or a small dog. Raccoons seem to have a more curved lower jaw. I don't have enough expertise to tell the lower jaw of a fox from that of a dog. In fact, it may not be possible to reliably distinguish the 2 species from each other only from lower jaws unless large samples are available to do a statistical comparison.

10 March 2010

Slugs of Book Hill

A neighborhood of Georgetown in Washington, DC is called Book Hill where there is a hill with a small park on it.


I had passed by the park several times before, but only this afternoon did I get a chance to take the steps to the top of the hill. There were 5 or 6 beech trees in the park. Whenever I am near a beech I can't help myself from checking its trunk for feeding tracks of slugs. Sure enough, on a couple of the beeches I saw what I believe were slug tracks.


Now we know there are slugs in Book Hill Park, but I don't what species they may be.

Excuse the quality of the photos. They were taken with the camera of my iPhone.

09 March 2010

Stenacme floridana: what was Pilsbry thinking?

In 1945, the great Henry Pilsbry, who was then about 83 years old and still very active, described a new family, a new genus and a new species of what he thought was a pulmonate marine snail from Florida: Stenacme floridana, family Stenacmidae.

This was a small, about 6 mm long, snail. Because it had an operculum, Pilsbry first thought it was prosobranch, or a gill-breathing snail. Then, he changed his mind.

It was not until I examined the radula that it became clear that we had a member of the Pulmonata. It is one of the very few pulmonates, like Amphibola, having an operculum.
Pulmonate snails breathe by means of a lung and the majority of them do not have an operculum; they lost it during their evolution from an ancestor that, nevertheless, had one. We know that the ancestor of the pulmonates had an operculum, because the adults in only one pulmonate genus, the amphibious Amphibola carry an operculum and the embryos in the pulmonate family Ellobiidae, also amphibious, go thru an operculated stage during their development. Based solely on the radula morphology of his specimens, Pilsbry thought he had a new family of operculated pulmonates.

But when Pilsbry dissected specimens of his new snail, he saw that they had a well-developed gill in their mantle cavity. His paper even includes a drawing of Stenacme's gill.

Pilsbry's drawings of a live
Stenacme floridana and its opened mantle cavity showing the gill.

Pilsbry was confronted with clear evidence that something was amiss with his taxonomic interpretation. But he still believed he had a pulmonate snail. He called the snail's mantle cavity the "lung cavity" and its gill a "secondarily developed gill".

All pulmonate gastropods, including the operculated Amphibola (see, Pilkington et al. 1984), have a pneumostome, the opening to the otherwise sealed lung inside the mantle cavity. The pneumostome of a live snail is relatively easy to observe, because it periodically opens and closes for gas exchange with the atmosphere.

If Stenacme floridana was a pulmonate, it should have had a pneumostome. This little fact seems to have slipped Pilsbry's mind; he makes no mention of seeing a pneumostome either in live or dissected snails.

Stenacme floridana is in fact a gill-breathing marine snail. This was established in 1958, a year after Pilsbry died, by Robertson & Oyama. The species, now called Alexania floridana, is in the family Epitoniidae.

How did the master Pilsbry, who had ruled the world of malacology for many decades, make such a gaffe? Had old age clouded his mind and his eyes? Had he grown too powerful and peerless and unjustifiably moved beyond criticism? Perhaps, the answer is all of the above and more.

In his long obituary of Pilsbry, H.B. Baker wrote:
...he positively was pained by the exposure of occasional real errors, such as those caused by faulty optics (inadequate microscopes or, when he grew oldest, his own tired eyes).
Baker also noted that Pilsbry's co-workers sometimes let his errors remain uncorrected, because, otherwise, "his feelings would have been hurt".

It seems that in the world of scientific research it is never too safe to leave everyone else behind.

Baker, H.B. 1958. Nautilus 71:73.
Pilkington et al. 1984. Journal of the Royal Society of New Zealand 14:327.
Pilsbry, H.A. 1945.
Nautilus 58:112.
Robertson, R. & Oyama, K. 1958.
Nautilus 72:68.

08 March 2010

Heartless leeches

After last Saturday's MAM meeting at the Delaware Museum of Natural History, Megan P. and I stopped by the museum's ongoing exhibition Attack of the Blood Suckers. Megan had heard that there were leeches.

We found the leeches in a large aquarium tank. In the dimly lit hall, they looked rather drab. But the flash of my camera revealed their true colors.


Here is another one that was mostly out of the water. Despite being aquatic creatures, leeches apparently do leave the water occasionally and voluntarily. Is this one a different species than the previous one?


According to the information panel below the tank, leeches don't have hearts. But they have an anus.


Leeches are, of course, sanguivorous; they feed on the blood of other animals. We left wondering what they were feeding the ones at the exhibit. There were lots of little kids around.

Note added 24 March 2010: I have now identified the leech in the photo as Hirudo verbana. See this post for details.

07 March 2010

Bootleg transactions of the 12th MAM meeting

The 12th meeting of the Mid-Atlantic Malacologists took place yesterday at the Delaware Museum of Natural History (DMNH) in Wilmington, Delaware. The number of attendees, only 17, was unusually low. Most malacologists had apparently not woken up from their winter slumber yet.

Here are the speakers in the order they spoke, and the not-more-than-two sentence summaries of their talks.

  • Paul Callomon (Academy of Natural Sciences, Philadelphia): A new collated facsimile reprint by Richard E. Petit of George Perry's Arcana, originally published in 1811.

  • Tim Pearce (Carnegie Museum of Natural History, Pittsburgh): Attempts to correlate the activities of land snails with wheather conditions.

  • Adam Baldinger (Museum of Comparative Zoology, Harvard University): The ongoing renovations in the Department of Malacology at the Museum of Comparative Zoology.

  • Adam's talk was followed by a long discussion on collection arrangement, management and databasing.

  • Robert Robertson (Academy of Natural Sciences, Philadelphia): Sexual dimorphism in the marine gastropod superfamily Phasianelloidea, including the genera Tricolia variabilis, Gabrielona and Phasianella.

  • Liz Shea (DMNH): Stomach content analyses of meso- and bathypelagic squids from western North Atlantic using CO1 DNA barcodes.

  • GiantSquid
    Here is a giant squid catching a fish.

  • Aydin Örstan (Carnegie Museum of Natural History, Pittsburgh): The behavior of the intertidal snail Batillaria minima during low tide.

  • Liz Shea (DMNH): Dissection of a giant squid she participated in last November.

  • In addition, Megan Paustian (University of Maryland) presented a poster about the competition (or the lack thereof) between the native and non-native slugs Philomycus carolinianus and Arion subfuscus, respectively.

    Once again, I will take this opportunity to thank to Liz Shea, the curator of mollusks at the DMNH and Leslie Skibinski, the collection manager, for organizing this wonderful meeting and also for providing access to the collections. I am already looking forward to next year's meeting.

    Poster readers.

    The bootleg transactions of the 11th MAM meeting are here.

    05 March 2010

    MAM meeting will be tomorrow

    The 12th meeting of the Mid-Atlantic Malacologists (MAM) will take place tomorrow, 6 March 2009, at the Delaware Museum of Natural History in Wilmington, Delaware.

    More information is available at the museum link above.

    Barring a last minute change of plans, I am hoping to be at the meeting tomorrow. That means I need to get back to work and finish putting together the slides for the talk I want to give.

    04 March 2010

    Mating Helix

    In her long and useful paper on the biology of the land snail Helix lutescens, Elżbieta Koralewska-Batura describes the initial stages of mating as follows.

    ...two of them assume a vertical position and remain in further contact through their mouths, tentacles and raised anterior parts of their feet. The snails are supported on posterior parts of their feet and on their shells, most often stuck in concavities in dense herbaceous vegetation. Almost all the surface of their soles adheres closely, and the gonopores* widen.
    All Helix species seem to go thru the same pre-mating stages of behavior. I had a chance to photograph a couple of mating Helix in October 2008 in Turkey.


    The snails' vertical positions indicate that they had just started their courtship. When I took this picture, they were slightly disturbed by my intrusion into their affair and hence withdrawn their tentacles. Unfortunately, I was with a group of people and could not afford to stop and watch the rest of the process at leisure. I hope I will see and photograph more next time.

    *Genital openings.

    Koralewska-Batura, E. 1999. Helix lutescens Rossmässler, 1837 (Gastropoda: Pulmonata: Helicidae) Its structure, biology and ecology.
    Folia Malacologica 7:197-240. Abstract

    03 March 2010

    Oxyloma paper finally published

    About 8 years in the making, my paper on the reproductive biology and the annual population cycle of the land snail Oxyloma retusum came out in the current issue of the American Malacological Bulletin a few days ago. You may download a pdf version of the paper from here.

    Succineids are interesting snails and I will probably work with them again when and if opportunities arise in the future.

    One of the past posts on Oxyloma retusum is here.

    02 March 2010

    A new snail blog on the block

    Our friend and fellow malacologist Rob Dillon, with whom I co-authored a paper last year on the malacological work of Charles Darwin, has just started a blog. Rob specializes in the freshwater gastropods of North America and his blog is called exactly that: Freshwater Gastropods of North America.

    For years, Rob has been sending out at irregular intervals e-mail posts on various subjects related to freshwater snails. His topics have ranged from arcane taxonomic problems to urgent conservation issues. Luckily, he's made his blog retroactive so that his posts dating back to 1998 are now all there.

    If you have any interest in freshwater gastropods, Rob's blog should be on your reading list.

    01 March 2010

    A tale of universal parsimony

    In Karel Čapek’s Tales From Two Pockets there is a detective captain Dr. Mejzlik who appears in a few of the tales. In one of them, while he and the historian Divisek are trying to solve what they think is a murder mystery from 1465 using only a handful of historical facts and a clue from a tombstone, Mejzlik explains their "basic rule of methodology":

    Now first of all, any hypothesis we advance must take into account all of the known facts; nothing, not even the slightest circumstance, can be allowed to contradict it. In the second place, these facts must be arranged into a single, continuous action; the simpler, the more contained and connected the action, the more likely that things happened exactly that way and not otherwise.
    What Čapek had his character espouse is, of course, the general methodology of all scientists, including what may be called the principle of parsimony, which presupposes that when everything else is equal, the simplest theory among competing theories is likely to be the correct one.

    Čapek's stories date from the late 1920s. In 1992, Peter Atkins wrote in Creation Revisited:
    The only clue we have at the outset is that the final answer will almost certainly be one of extreme simplicity, for only the perfectly simple can come into existence while all agents asleep (or are not there). This suggests that we should examine the universe for the footprints of its underling simplicity.
    Atkins was also trying to solve a mystery, albeit one that is a bit more grandiose: the creation of the universe. Nevertheless, the basic methodology of both scientists is the same and reduces to the perception of the simplest that can explain the most.

    Mejzlik would have approved of Atkins' method. However, although Mejzlik solved Divisek's mystery, Čapek hints at the end of his tale that the duo hadn't followed "proper scholarly methodology". Perhaps, what they lacked was sufficient data. Then again, scientists trying to explain historical events rarely ever have enough information, but must often rely on statistical reasoning. It seems that we can not be sure of the causations of even the simplest happenings.