Tentacle #17 is out

Issue No. 17 of Tentacle, the annual newsletter of the IUCN/Species Survival Commission, Mollusc Specialist Group, edited by Rob Cowie of the University of Hawaii, is now available here, where all the previous issues can also be accessed.

This is the 3rd Tentacle issue in which I have an essay that was based on a post that first appeared on this blog. My piece titled "Will assisted colonization be a viable option to save terrestrial gastropods threatened by climate change?" is on p. 14. It is a much revised version of this post.

I decided to turn that post into an essay for the Tentacle when in early November of last year I received an e-mail from a reader who was inquiring if I would object to having my blog post cited in a manuscript in preparation.

The value of blogging in providing an outlet to test the edibility of half-baked ideas has become very clear to me now.

Posts about the previous issues of the Tentacle in which I had pieces inspired by earlier blog posts are here and here.

There are many other good articles in Tentacle #17. Download a copy now.

More secrets of slugs hidden under their mantles

Here is another installment in what is turning into a series of posts on slug development and anatomy.

Last night I dissected a specimen of Arion subfuscus, a European slug that has long been naturalized in the U.S. I cut the mantle along 3 of its edges and turned it inside out. Here is what the inside of the mantle looks like. The top border would be along the right side of a live slug.

Compare the photo with this drawing of the pallial cavity of Arion distinctus (from G. M. Barker, Naturalised terrestrial Stylommatophora [of New Zealand], 1999).


What is not visible in my photograph is the ureter that runs from the kidney alongside the rectum to the penumostome, the breathing hole. Interestingly, the kidney of Arion is shaped like a donut with the heart sitting in the hole in the middle. The membrane to the front of the kidney is the lung. It is vascularized, but the veins are not visible in my picture. The opening of the rectum, like that of the ureter, is within the penumostome.

Next, I separated the kidney from the mantle to which it was loosely attached and pushed it aside. Underneath was a secret chamber full of shiny jewels, or more accurately, granules of calcium carbonate. Those constitute the "shell" of Arion.


Yesterday's post was about how during the development of another slug, Limax maximus, many pieces of calcium carbonate appear within the mantle and eventually fuse together to form the slug's shell. In Arion the individual pieces apparently remain loose and a one-piece shell never forms. We seem to be witnessing various evolutionary steps in the disappearance of shells as slugs descended from snails.

How a slug secretly makes its shell

I am trying to learn more about the internal, vestigial shells of some slugs. Surprisingly, very little research has been done with them and there seem to be only a handful of relevant papers. In situations like this, it is often best to start from the beginning. By coincidence, or perhaps not by coincidence, the oldest original scientific paper I own, George B. Simpson's "Anatomy and physiology of Polygyra albolabris and Limax maximus" published in 1901 in the Bulletin of the New York State Museum also happens to mention the formation of the internal shell of Limax maximus during the slug's embryonic development.

Simpson describes the development of Limax maximus starting from an egg:

The body of the animal as first observed consists of a slight swelling of the upper side of the cell mass...The swelling...very soon shows a tendency to divide into two parts (pl. 24, fig. 17), the anterior part of which is the foot proper, the posterior part the mantle, shell sac, etc. Even at this early stage the embryonic shell can be observed, consisting of a few dark colored crystalline plates, not yet united.

Here is pl. 24, fig. 17:


We skip ahead a bit:

The body now rapidly develops, as shown in figures 15 and 16, plate 25. The shell has also increased in size, consisting of numerous crystalline plates, not yet unified.

Here is pl. 25, fig. 16 (the arrow I added is pointing at the shell within the future mantle):


We continue:

As development proceeds a movement of the cells takes place from the ectodermal sac into the constantly enlarging body (pl. 26, fig. 1).

Here is pl. 26, fig. 1:


It still doesn't quite look like a slug. The yellow arrow is pointing at the mantle and the red one to the shell, which, although Simpson doesn't mention it, still consists of separate pieces.

Finally, after a little bit more development, the creature starts to resemble a slug.


The right tentacle is recognizable (blue arrow) and so is the pneumostome, the breathing hole (green arrow). The shell (red arrow) still has a granular appearance; the individual plates have not fully fused yet. Simpson doesn't mention when the pieces of the shell finally unify into one piece, but, presumably, this happens at around the time of hatching.

There are 2 important pieces of information we can gather from this account:

1. The shell starts to form very early during the development of the embryo within the mantle and there it remains in adults. It is truly a vestigial structure left over from the snail ancestors of Limax.

2. The shell does not start out as a tiny bit of crystalline substance that grows bigger and bigger; instead, it is formed from the union of many bits of crystalline plates. In adult Limax maximus, the shell is a flat, elongated plate (this post has a picture of the shell). Interestingly, in some other slug genera, for example, Arion, the shell remains as a mass of granules of calcium carbonate, which makes sense as the next stage in an evolutionary sequence.

Mark your calendars: 11th Meeting of MAM

Dr. Liz Shea, Curator of Mollusks at the Delaware Museum of Natural History (DMNH) in Wilmington, Delaware, has announced that the 11th almost-annual meeting of the Mid-Atlantic Malacologists (MAM) will take place on Saturday 7 March 2009 at the DMNH.

From the announcement:

This one-day gathering is designed to facilitate contact among professional, amateur, and student malacologists who are interested in any aspect of molluscan biology. There are no dues, officers, abstracts, or publications. Meeting and parking are free of charge. Participants are encouraged to present and discuss data, compare notes on methods and problems, and catch up with colleagues and friends. Presentations (15 minutes max.) are very informal and cover topics as diverse as current research, trip reports, and collection issues.

Schedule:

0930 Museum opens & light refreshments are served.
1000 Morning presentations
1200 Break for lunch.
1300 Afternoon presentations
1600 Concluding remarks & end of session.

Additional details and contact addresses at the announcement link above.

Have you touched your fish today?

Searching for snails on a cold day

Back in November when we had our the day after Thanksgiving field trip in the Hoyles Mill Conservation Park, I flagged the locations of 5 dormant and buried Anguispira fergusoni. Yesterday, I went back to check on them.

It was a cold day; the temperature was hovering around freezing. All the small creeks running thru the park were frozen over.

Luckily I had a stable GPS signal and the coordinates measured in November also turned out to be quite accurate and so I didn't have any trouble locating the dead tree where the snails were. All of my 5 little yellow flags marking the exact locations of the buried snails were still standing.


However, I hadn't taken into account one possible complicating factor, that the soil would be frozen. It indeed was and although I could have dug into it—the snails were not very deep—I decided not to do anything forceful lest I broke the snails' shells during the operation.

According to Riddle (1981), Anguispira alternata avoids freezing of its tissues by undergoing supercooling almost down to -16 °C. Hopefully, my snails are doing the same where I left them in November. I will go back there during a warmer period.

Otherwise, it was a good trip that netted a deer skull.

Final post of this series is here.


Riddle, W.A. 1981. Cold hardiness in the woodland snail, Anguispira alternata (Say) (Endodontidae). Journal of Thermal Biology 6:117-120.

Hunting for deer skulls on a cold day

Yesterday, I went back to the Hoyles Mill Conservation Park to check up on the snails I had flagged back in November during our the day after Thanksgiving field trip.

The yellow signs posted all along the periphery of the park warned the visitors of "managed deer hunts". If they are hunting what lives in the park, that's not much of conservation, is it?


Obviously, the white-tailed deer (Odocoileus virginianus) is quite abundant around here. So, it wasn't too much of a surprise to run into some scattered deer bones soon after I entered the park.


I was excited when I also spotted the skull. Alas, its antlers had been chopped off, perhaps, by some bone-hungry scavengers. I decided it wasn't worth taking it home.


What was really surprising was to run into a 2nd skull a half an hour later. This one still had its antlers.


Just like the previous deer skull, this too had a strong sulfurous smell. Deer skin, bones, marrow or some other body part must have a high content of sulfur that gets released during decomposition. It is now soaking in a pan of hydrogen peroxide.

The left antler of this deer seems to have a malformation. Leave a comment if you can offer an explanation.


Did I say I had gone to the park to check up on snails? That will be the subject of tomorrow's post.

Unfortunately, many people fall for it

The theory that the first woman was made out of the rib of Adam - now that is quite a difficult one to believe.

David Attenborough on Charles Darwin

They might be giants—they are giants

Thanks to a Nigerian friend of the family, who visits her home country every December, I have received another batch of giant African snail shells. This lot of 6 shells are even huger than the ones she had brought back last year. Last year I had identified them as Achatina achatina, but a reader subsequently indicated that they were actually Archachatina marginata. I'll stick with that name until further notice.

For weight measurements that do not require great accuracy, I use an old, battered Ohaus Cent-O-Gram triple-beam balance that I rescued from a certain one-way trip to a garbage dump several years ago during a laboratory clean-up. Most of these guys are only a few tenths of a gram below the balance's maximum capacity of 111 g.


This one was 109.65 g. In fact, one of them exceeds 111 g.


They are also longer than the standard 15-cm span of calipers. So, how do I measure them?


I'm telling you, they are giants.

Linnaeus's folly

A while ago I got curious about how much Carl Linnaeus had said about slugs in his Systema Naturae, published in 1758. Luckily, a digitized copy was readily available. Here is Linnaeus's description of the slug genus Limax from page 652 of volume 1.

Although I don't know Latin, I have been able to create a rough translation of these words with a little help from the various online Latin dictionaries and the one I pulled out of my vest pocket. What helped me most was, of course, Linnaeus's "telegraphic" style. Correct me where I am wrong.

Corpus oblongum, subtus disco plano se promovens: Body oblong, underneath in the front(?) a flat disk.
Foramen ad latus, per quod genitalia & excrementa emittuntur: Opening on the side, through which genitalia & excrements put out(?).
Tentacula supra os quatuor: Tentacles above mouth, four.

The "flat disk" underneath is the internalized vestigial shell of the slugs in the genus Limax (also present in some other genera, for example, Deroceras). The hole on the right side that Linnaeus refers to was most likely the conspicuous pneumostome, the breathing hole. The openings of the rectum and the ureter are next to it, but the genital opening is closer to the front of the head and is normally kept closed except during mating. The picture below, originally from this post, is of a couple of mating Limax maximus. It clearly shows in the slug in the back the separate locations of the genital opening from which the penis is everted and the pneumostome, the large hole to the right of it.


If Linnaeus hadn't busied himself so much with the sex lives of plants and paid some attention to the livelier and certainly slimier sexual escapades of slugs, he certainly would have corrected his little mistake.

Squirrel tracks in snow II

Alongside those of a dog and a human, I noticed these tracks of an eastern gray squirrel in weekend's snow. The squirrel was traveling in the direction towards the top of the picture.

Because of the unique pattern they create, squirrel foot prints are among the easiest tracks to identify (rabbit tracks are somewhat similar, though).


Note that the longer prints in the front are actually those of the hind feet. The drawing below explains how a squirrel creates its track pattern.


Drawing from Anonymous. Animal Tracks, Stackpole Co., 1954.
Part I

Good riddance

The City by derf

Thumbs up for Obama

From Barack Obama's inaugural speech:

We are a nation of Christians and Muslims, Jews and Hindus—and nonbelievers.

It's good to hear a president of the U.S. acknowledge that there are nonbelievers in this country and that they are not an object of derision.

Let's hope Obama will keep up with his inclusiveness.

(Via Abnormal Interests)

Chemists do it with clamps

This picture from 1979 shows one of the old chemistry labs at our alma mater, the Boğaziçi University in Istanbul. The principal subject in the foreground is Teri Varnalı (whose name has appeared on this blog before), while yours truly is in the background behind an old (mid-1960s) Canon view-finder camera. The picture was taken by Ümit Yüksel, whose name has also been on this blog (here).

The contraption I had my camera attached to was a clampod, a makeshift monopod constructed from a laboratory ring stand (with a ring visible at its base) and a couple of clamps.


Apparently, I was attempting to photograph the lab benches cluttered with chemistry paraphernalia.


The label I had stuck on the slide has survived and the first 2 digits of the number indicate the year (i.e., 1979). The slide film I used was ORWO brand, made by a defunct East German manufacturer. We had to mail the exposed films to Germany to get them developed. The films would come back in rolls, which we would then cut into the individual exposures and slip those inside separately purchased plastic frames. The colors have help up suprisingly well.

What good is a label if it's unreadable?

I spent most of yesterday afternoon cleaning and rearranging the basement. Three categories of objects account for ~80% of the occupied space: 1. papers and books; 2. specimens; 3. empty containers (miscellaneous plastic or cardboard boxes) for future specimens.

Among the specimens are probably more than 1000 containers of snail shells, about 200 vials of alcohol specimens and about 30 containers of litter and soil samples.

Most of the latter samples are from 2003 and 2006 when I was surveying the Monocacy Natural Resources Area and Belt Woods. Some of the litter samples have already been sieved, but not yet been sorted for snail shells. Others still need to be sieved first.


Each box or bag contains a little piece of card with the station code and the collection date written on it. It is best to keep that information inside the sample container, otherwise the two could get separated. And without that information a sample would be good only for the compost pile in the backyard.

There is no guarantee, however, that what's written on the card will be readable in the future, especially if the litter was slightly damp when the lid was closed.


Luckily in this case, the end of the card where the station code was written was in better shape than the rest and after I removed some of the overlaying filamentous stuff (fungal remains?), the station code appeared: MO-53 from the Monocacy survey. I can figure out the date from my field book.


A sample saved is a sample that needs to be processed. Maybe I should have dumped it into the compost pile right away.

Istanbul street paintings and graffiti

We start off with a wall painting in the veranda of a building. Note the cat on the left.

The next picture is a real graffiti. This was on a wall along a long yokuş from the Arnavutköy district by the Bosphorus to the hills behind. Note that it's in English.


The next picture is a trafo painting the purpose of which is to beautify the front of that oversized electrical box, which is a trafo (short for transformer). Trafos are quite common throughout the city and each seems to have a different painting of some old Istanbul scene.


Note the skull and bones sign on the left. No, that was not a pirate boat in the painting. The regular readers may recognize the sign as another one of those ölüm tehlikesi, or "risk of death" warnings that have appeared on this blog before (here and here).


In this case the risk taker was, however, Deniz.

Archaeo+Malacology Group Newsletter No. 14

The AMG Newsletter No. 14 is available here.

This issue contains articles on the mollusks found in excavations in Italy, United Arab Emirates and Israel, Papillifera bidens (=Papillifera papillaris) from Carthage and abstracts of recent relevant papers, announcements of upcoming meetings and other items of interest.

Reverend Lowe's snails

Richard Thomas Lowe (1802-1874) was a British clergyman naturalist. He studied plants, fishes and snails, of course. I was at the Smithsonian's National Museum of Natural History in D.C. today and copied one of Lowe's papers on some of my favorite coastal snails, Melampus and Truncatella. The paper, titled "On the Genera Melampus, Pedipes and Truncatella: with Experiments tending to demonstrate the real nature of the Respiratory Organs in these Mollusca", came out in 1832 in the Zoological Journal.

Those were the formative years of malacology when even the broadest classifications of most of the mollusc species were debatable. Thus, in his paper Lowe was concerned with the question of whether Melampus and Truncatella were in the order Pectinibranchia or the Pulmonea. The former encompassed all the snails with gills, while the latter those with lungs. A simple dissection would have provided the answer, but "...the small size of the species, not to mention want of instruments and skill in the dissector" forced Lowe to resort to a series of experiments almost all of which involved the keeping of the subject snails in sea or fresh water or outside of water for various periods.

Not surprisingly, Lowe's experiments produced contradictory and puzzling results: both Melampus and Truncatella survived outside of water in wet containers, while when forced to remain in sea water they sometimes remained alive, sometimes died. At the end, however, he concluded that both genera were marine pectinibranchs.

Lowe didn't realize that the truth was a bit more complicated and, at the same time, much more interesting than his simple experiments could reveal. Truncatella breathes with a gill (see my dissection here), but lives its entire life on land near the sea, while Melampus breathes with a lung, lives at the edge of the sea, but enters it to reproduce via planktonic veliger larvae.

What we see in the case of Melampus and Truncatella is a mosaic-like pattern of mixed anatomies and lifestyles often observed during evolutionary transitions from one habitat to a drastically different one. The good ol' reverend was in for a surprise.


The plate from Lowe's paper showing the snails he studied: 1-7, Melampus; 8-12, Pedipes; 13-18, Truncatella.

Evolutionary freaks or new species?

Marla Coppolino sent this picture of an undescribed species of a snail-like creature with a blue shell next to her pet snails, probably a Neohelix albolabris (the bigger one) and a Mesodon thyroidus. She doesn't yet have a name for the creature, but we have already determined that it's in the family Knittedae, superfamily Craftoidea, class Woolapoda, a sister group of the Gastropoda. Marla indicates that once the new species is described, the specimen in the picture will be a yarnotype.

The next picture was from Richard Greene. It shows even a more bizarre creature: a human with the head of a snail. It's one of the drawings of the French artist J.J. Grandville from his book Les métamorphoses du jour first published in 1829.


Here is a closer look at Grandville's oddity. The bands on the shell and the black lip suggests Grandville had in mind Cepaea nemoralis when he drew his gastropodian servant.

News from the slugarium—Part 3

I am continuing with feeding trials of the 2 captive slugs, Megapallifera mutabilis. Here is one of them right after I interrupted its feeding on a piece of algae-covered beech.

The enlargement of the area in front of the slug's tail shows the teeth marks at the edge of the feeding track.


I still haven't figured out how exactly they create those marks, because I still haven't observed them feeding. As soon as I turn a light on, start opening lids and moving things around, the slugs stop feeding. The best I have done so far is the following shot. It shows the front of one slug's head. The mouth is right below the lower tentacles; it was, however, raised above the green crust of cyanobacteria.


I'll get lucky one of these nights.

Part 2

From Halicarnassus to Kyme: some coordinates for Google Earth

Via Abnormal Interests comes a link to a set of Google Earth placemarks for ~1300 Ancient Near East sites compiled by Olof Pedersén at the Uppsala University. The majority of the sites are from the Middle East and southeastern Turkey with a disappointingly few locations from the rest of Turkey.

From my own records, I will offer the coordinates of 10 archaeological sites in western Turkey that I’ve visited during snail surveys and are missing in the said compilation. The coordinates are the latitude followed by the longitude.

Kyme: 38.7594, 26.9358
A city ~19 km northeast of Phokaia. At the given link it says “Kyme (Izmir)”, which is extremely confusing, because it sounds as if those were different names of the same place. In reality, Izmir (Smyrna) is 40 km to the southeast.

Phokaia (present day Foça): 38.6676, 26.7542

Notium: 37.9925, 27.1981
Notium, also known as Notion, was a town located on a flat-topped cliff high above the Aegean Sea ~13.5 km northwest of Ephesus. It is perhaps best known by the naval battle that carries its name.

Claros: 38.0050, 27.1930
A temple site only a little more than a kilometer north of Notium. This post has a picture I took at the site.

Ephesus (theater): 37.9410, 27.3422

Euromos: 37.3741, 27.6754
This was another temple site south of Lake Bafa. Unfortunately, the Google Earth picture is of low resolution. The picture below is of the main ruins at the site of Euromos that I photographed in August 2000.

Iasos: 37.2792, 27.5840
A city in Caria.

Myndus Peninsula: 37.0567, 27.2295
This is a small peninsula at the westernmost end of the Bodrum Peninsula. The city of Myndus was located on it.

Halicarnassus (present day Bodrum): 37.0401, 27.4216 (theater); 37.0379, 27.4242 (mausoleum, or rather where it used to be).

A water closet for pipe-smoking 19th century gentlemen

I am suspecting that there has been a minor art movement behind the creation of signs for public restrooms in Turkey. However, so far it remains undeclared and rarely noticed. Nevertheless, as I noted in this post, the fruits of this creativity are not restricted to large cities but can be seen and enjoyed even in dinky towns off the beaten paths.

This sign outside the men's restroom was at a rest stop along the highway from Ankara to Istanbul last October.

One characteristic of this movement is that the men and women portrayed on the signs are almost always idealistic, unrealistic and old-fashioned characters. Probably no one looking like the man in this sign has ever entered this particular restroom. Would you say he has a late 19th century look about him? Perhaps they are expecting occasional time-travelers. More examples are in the previous post.

The favorable bias the Turkish artists must have towards smoking is also betrayed by their tendency to depict the male WC visitors with cigarettes and pipes in their mouths. A sizeable fraction of the Turkish population (males and females) smokes. But regulations restricting smoking in public places, especially in buses, for example, are being enacted. Hopefully, the future restroom signs will be a bit more contemporary and healthier looking.

Cats of Istanbul - Part 3

I had an aunt who had been born with a hearing deficit. Unfortunately, her handicap was not identified correctly when she was young; instead, she was thought to be mentally retarded, which she was not. She grew up to be self-sufficient and had a steady job for most of her adult life. Nevertheless, she lived alone in Istanbul and never had close friends. She loved cats. Cats gave her the affection and meaning that her interactions with humans couldn't provide.


The aunt did have a quirky personality. For one, she was a hoarder. Towards the end of her life, her apartment had become impassable. Once I visited the place just to take pictures (without her knowledge), which I still have. On another occasion, she requested my photographic services for a macabre and dismal project: I was to take pictures of her posing with a dead cat, her favorite who had died a few days earlier. I still have those negatives too.

I dedicate this series of pictures of cats of Istanbul to her memory.


Part 1
Part 2

More to come.

Anatomy of a breath—Part 1

Yesterday's post was on the organs inside the mantle cavity of a snail, including its lung. A quick search today of the net netted a useful open-access paper by John Maina on comparative respiratory morphology, that is, gills and lungs and what have you (Anatomical Record 261:25, 2000 pdf). Most of the information in this paper is also available in older publications, but it's good to have it all in one place in an authoritative review. This way one can cite one recent paper instead of 5 older ones.

No tissues or cells specialized in extracting oxygen from water or air have evolved. In other words, unlike, say liver cells or nerve cells, there are no specialized "lung cells" or "gill cells". This is probably because there is no need for such cells. Extraction of oxygen from an external medium is only a matter of oxygen molecules diffusing thru cell membranes and cytoplasm until they reach the point where they are needed or a circulatory system where they get bound to carrier molecules and transported elsewhere.

On the other hand, organs specialized in extracting oxygen have evolved. These are primarily gills and lungs, but there is also the tracheal system of insects.

In the simplest case (A), there is no organ specialized for gas exchange; oxygen simply diffuses in thru the cell membrane and carbon dioxide diffuses out. This is seen in very small animals that have large surface area to volume ratios; since the oxygen diffusing thru the cell surfaces is sufficient for all metabolic needs, specialized organs are unnecessary. As the body volume increases, however, the relative surface area decreases and specialized organs that concentrate blood vessels (vascularization) in pockets of increased surface area, achieved by folding or filaments, become necessary to extract sufficient oxygen from the surrounding medium. There are 2 primary groups of anatomies specializing in gas exchange: 1. organs formed as evaginations (B), e.g., gills; 2. organs formed as invaginations (C), e.g., lungs.

3 fundamental types of gas exchangers. (Inspired by Fig. 8 in Maina, 2000.)
Of course, even in organs of the type A or B, the underlying mechanism of oxygen intake is identical to that in case A: oxygen diffuses in thru the cell membranes. In addition, there are animals, including some snails, that have both gills and lungs.

To be continued...

The mantle cavity of Rumina saharica

In gastropods, the mantle cavity houses some of the vital organs, including the heart, the kidney and the gills. In pulmonates, the lungs replace the gills and the arrangements and the morphologies of the organs of the mantle cavity gain significance in the understanding of the evolutionary relationships between the different groups. Below is the mantle removed from a specimen of the land snail Rumina saharica.

The mantle cavity of Rumina saharica flipped over and turned inside out; the organs along the left-hand side in this photograph would be along the right-hand side of a live snail. Abbreviations: P, the outside opening of the pneumostome (breathing hole); MC, mantle collar (the front edge of the mantle that is fused to the top of the head in a live snail); K, kidney, V, ventricle; A, auricle (the ventricle and the auricle together make up the heart); R, rectum (its opening is within the pneumostome); L, lung. The blue dots mark the ureter, while the red dots the principle pulmonary vein.
Compare this with the mantle cavity of Rumina decollata below.


The mantle cavity of Rumina decollata from Pilsbry (Fig. 81 in LMNA, II:1, 1946). The kidney and the ureter are in blue, while the heart and the principle pulmonary vein are in green.
Note how in both species the ureter, instead of running directly towards the mantle collar, first goes down, turns around and then goes up towards the pneumostome, near which it drains to the outside. The snails with this peculiar anatomy belong to the group Sigmurethra.

I am primarily interested in the venation of the lungs of pulmonate land snails. Below is a closer shot of the lung of Rumina saharica showing some of the secondary veins covering the roof the mantle cavity.


The colorized drawing of the mantle cavity of
There will be more posts on this subject in the future. Incidentally, this was the 1st dissection I did this year.

Metallic green dung beetle on a winter day

This beetle was brought out by the rather warm temperatures (almost 20 °C/68 °F) we had back on 28 December (last year). Now, what's wrong with the last sentence? The temperature can be low or high, but there is no such thing as a warm, hot or cold temperature. Temperature is a measure of the average kinetic energy of the molecules making up the air or any other substance and so it can't be associated with a feeling such as warmth or cold.

After that digression, we return to the beetle in the photo, which has been identified by the good folks at BugGuide.net as Geotrupes splendidus, a dung beetle. In The Common Insects of North America, Swan and Papp (1972) write:

It constructs brood cells of cow dung; in the Southeast egg laying takes place in January, pupation in May.

There were no cows where I found this individual. It obviously uses the dung of other animals and appears to be active on warm days during the winter even in Maryland.

What readers think of this blog

The below are a few extracts from several score of similar e-mails, showing the esteem in which this blog is held. Additional comments at this link (p. 81). We don’t seem to get any praise from female readers, though.

“Cannot afford to miss a single post.”
John Walton, Rochester, N.Y.

“Much interested.”
E. J. Smith, Natick, MA

“Solid and valuable.”
Chas. T. Simpson, Ogalalla, NE

“Very valuable.”
Henry Vendryes, Kingston, Jamaica

“Worth the money.”
J. W. Velie, M. D., Chicago, IL
[Huh? What money?]

“It will prove of much benefit to conchologists.”
George W. Michael, Jr., Morro, CA

“Quite efficacious.”
Wm. A. Marsh, Aledo, IL

“An admirable blog.”
J. Matthew Jones, Halifax, Nova Scotia

“A perpetual surprise.”
George W. Puterbaugh, Greenfield, IN

“Convenient.”
Wm. Sutton, San Francisco, CA

“We have needed such a blog.”
J. A. Singley, Giddings, TX

“Wants an enlargement.”
H. A. Pilsbry, Davenport, IA
[Right. No, No! Doesn’t want an enlargement. It’s already enlarged enough.]

News from the slugarium—Part 2

In yesterday's post I wrote about a fallen beech tree that was covered with the feeding tracks of the slug Megapallifera mutabilis. The 2 slugs I have been keeping for about a week now happen to be the same species. So over the last weekend I decided to generate some "homemade" feeding tracks. From the fallen tree I got a nice piece of beech densely covered with cyanobacteria (green algae), put in my slugarium early in the evening and placed one of the slugs on it. This is what I had the next morning.

Interestingly, the slug formed a complete loop. It started out near the upper right-hand corner where I had placed it next to the black object (which is a piece of fecal string), crawled to the other end, turned around and crawled back to its starting point, then it stopped feeding and left the wood. Disappointingly, however, it left only a few teeth marks on the bark and those were difficult to spot (arrows).


I don't know why these slugs sometimes leave distinct marks (see the pictures in yesterday's post) and sometimes don't. Also, after discussing this with Megan, now I am not sure if those marks are made by the radular teeth or the ribs on the jaws. There will be more on that in the future.

A slug tree fell in the woods. Did it make a sound?

This American beech (Fagus grandifolia) broke at its base and fell between 28 December and 2 January in the park near my house. When I discovered it yesterday I got quite excited for 2 reasons. First, if the park maintenance people do not chop it up, and they shouldn't, because it's not blocking any paths, it will be interesting to monitor its slow decomposition over the years starting practically from day one. The tree was alive when it fell and there is at the moment only a few small sections that are already rotten.


Second, the bark is covered with the feeding tracks of the local philomycid slug, Megapallifera mutabilis. Some of the tracks were very clear: one could see the marks the teeth on the radula left as the slug was scraping off its food, cyanobacteria growing on the bark.


Here is another cluster of tracks.


Using a 10-m tape, I estimated the total length ("height") of the tree as 30 m; I couldn't get an accurate number, because the topmost branches had broken off when the tree hit the ground. According to Frank Brockman's Trees of North America (1968), the American beech grows "60 to 100 feet tall" or up to about 30 m. So this tree was about as tall as it was going to get.

Yesterday and today I spent quite some time among the branches and climbing up and down the huge trunk, which has now turned into a natural bridge across the small creek under it, all the while looking for slug tracks and photographing them. I slipped and fell a few times, but amazingly got only a minor cut on my hand. When it comes to playing with trees, I will always be a kid, especially if there are also slugs on them. What was really neat was that by following their feeding tracks I was able to get a pretty good idea of how high the slugs went up the tree.

How likely is it to find a male bdelloid rotifer?

Bdelloid rotifers (class Bdelloidea), with about 350 or so known species, are the largest group of animals that reproduce exclusively by parthenogenesis. Every individual bdelloid is a female that produces unfertilized eggs from which more females hatch and so on. There is no published record of a male bdelloid having ever been observed. Genetic studies done with a limited number of species also indicate that they have evolved without sexual reproduction (Welch & Meselson, 2000).

However, the absence of evidence is not the evidence of absence of male bdelloids. There could be some species that may have males, but for various reasons they may not have been detected so far.

About 3 weeks ago I received an interesting request from Bill Birky at the University of Arizona. He was asking everyone working with bdelloids a rough estimate of the total number of bdelloids that they have "examined without ever seeing an individual with sperm". It appears that Bill will try to come up with some sort of estimate of the likelihood that a male bdelloid may be found.

Today I finally had time to respond to Bill's request. However, I had never searched for sperm in any of them. So instead of the number of individuals without sperm, I sent him the number of individuals that were definitely female. I counted as a female those whose vitellaria or ovaries I had seen or those whom I had seen carrying or laying eggs or live embryos (some are viviparous). Fortunately, I have kept a written record of almost every bdelloid specimen I ever examined during the days I was working with them. These notes were almost always supplemented with drawings and often with photographs. So it wasn't too difficult to come up with a rough estimate of the number of definitely female bdelloids I have seen, which was 250. I am curious to know what Bill will eventually come up with.

Bdelloid rotifer Macrotrachela ehrenbergi. An experienced worker would recognize the bag-like organ (arrow) along the lower body wall as a vitellarium (the other vitellarium would be on the opposite side). This animal was, therefore, a female. The length of this specimen was about 250 μm (its foot is cut off in this picture).
I have one criticism of Bill's underlying premise, though. Let us assume there are indeed male bdelloids. Now we have 2 possibilities:

1. The external morphology of the males is roughly similar to those of the females. Therefore, when someone isolates a particular specimen using only external morphology discernible at low magnification to assure that it is indeed a bdelloid, the probability of it being a male is roughly identical to the ratio of males to females in the population from which that specimen came. In other words, the specimen selection process is not biased towards females, because males look the same. I have seen 250 females, but no males, therefore, the overall ratio of males to females must be less than 1 in 250.

2. The external morphology of male bdelloids is much different than those of the females and even an experienced worker may have difficulty recognizing them as bdelloids without a careful examination at high magnifications. Therefore, when someone isolates a particular specimen the probability of it being a male is much less than the ratio of males to females in the population from which that specimen came. Consequently, the overall "examined bdelloids" sample is highly biased towards females and the total number of females seen is meaningless for comparison purposes.


The egg of Macrotrachela ehrenbergi, about 80 μm long. What is the function of the spines on it?
I have a feeling that if there are male bdelloids they are very different morphologically from the females. They may be much smaller and even parasitic on or inside the females. Furthermore, they may appear during only certain times of the year and may have very short lifespans. Moreover, they may be present only in some species, most likely in those that live in permanent waters. These factors would all make it difficult and unlikely to spot them if they existed.

Have a Happy New Year everyday!

Several years ago I had a coworker several years my senior. She was a sweet lady who nevertheless had certain idiosyncrasies that bothered me. Once she told me she had just stopped eating milk products. The reason was that she had a doctor's appointment coming up and that she didn't want the doctor to get mad at her for not keeping her cholesterol under control. I tried to explain to her in vain that she was supposed to keep her cholesterol down for her own good not for the sake of her doctor's feelings.

On another occasion around the beginning of a new year, she had experienced a minor misfortune. That made her declare that she was afraid the rest of the year was going to be equally bad. She apparently believed that how a particular year would turn out in terms of one's personal affairs was predetermined and a bad thing happening in January was an ill omen for the rest of the year.

About a week ago I found yet another Google Book that attracted my attention. This one was called Science from an easy chair by Ray Lankester, published in 1913. The following paragraph from the book reminded me of my friend (the 1st sentence is referring to Santa Claus).

…it is not only with and for children that we make-believe at this season—we all of us, more or less, indulge in a make-believe about the New Year. As the clock strikes…at midnight on December 31st,…[a] physical change has set in—the Old Year is dead and gone, and the New Year, something tangible, which you can let in at the door or the window—has just come into being, and is there waiting for us. We are, of course, indulging in “make-believe,” for there is no New Year, with any natural, noteworthy thing to mark its commencement, starting at midnight on December 31st. New Years begin every day and hour, and it is by no means agreed upon by all nations of the earth to pretend that the 1st of January is the critical day which we must regard as that portentous epoch, the beginning of the New Year.

Lankester is absolutely right; the beginning of a new year is an entirely arbitrary nonevent in our lives. Yet, on this occasion I am also reminded of an old Turkish saying, deliye her gün bayram, the literal translation of which means that to a crazy person every day is an occasion for a celebration. So let us follow Lankester's wisdom and at the same time, be a little crazy this year and celebrate a New Year everyday!

That way, if you happen to have a misfortune one day, you won't have to worry that the rest will also be bad, because everyday will be a new beginning!