30 November 2005

Shop for some invertebrates

Don’t miss the 3rd performance of the venerable Circus of the Spineless at Urban Dragon Hunters. And while you are there buy some spiders, bugs and snails for everyone who’s been good this year.

Mammalian Species

From the web page for the Mammalian Species:

“Mammalian Species is published regularly by the American Society of Mammalogists with 25-30 new accounts issued each year. Each account summarizes the current understanding of the biology of a single species, including systematics, distribution, fossil history, genetics, anatomy, physiology, behavior, ecology, and conservation. The accounts vary from 2-14 pages.”
PDF files of the first 739 accounts, from the Waterhouse's Leaf-nosed Bat (Macrotus waterhousii) to the Baja California Sur Deer Mouse (Peromyscus eva) are FREELY available here.

Duh! I wasn’t even aware of this publication until yesterday. Each account is a treasure trove of authoritative information for a particular species, including a list of references for further research. If I read one account a day, I would be reading these for the next 739 days and by then there would be new ones posted. So many species, so little time...

Wied’s Long-legged Bat from Mammalian Species No. 62

29 November 2005

Kind of an obscure film meme

The idea for this meme came in an e-mail from tony g of milkriverblog. I can probably come up with many obscure, yet good films, but for the time being, I am going to suggest the following 3.

The mad adventures of Rabbi Jacob. 1973. When I was growing up in the 1960s in Turkey, a series of action-mostly comedy Fantomas films starring the late French comic Louis de Funès were among my favorites. This is one of his later films and I consider it one of the funniest and most sophisticated slapstick comedies ever made. Louis de Funès plays a bigoted, racist, anti-Jewish Frenchman, who, for whatever reason (it's been a while since I last saw the movie), has, not only some terrorists, but also the police after him. He manages to elude them only by impersonating a famous rabbi who has just arrived from New York. Now, of course, he must visit the Jewish neighborhoods of Paris and do the things a rabbi would do. One hilarious scene follows another until the end when our reluctant "rabbi" learns his lesson. I've seen this film twice; the 1st time was in Turkey in the mid-70s and the 2nd time was in a dinky little movie theater in Soho, Manhattan in the mid-80s. Now I just might get a DVD of it. French with English subtitles. I wish I could understand French just for this film.

The late Alec Guinness was one of my favorite actors. The next 2 are his films.

The man in the white suit. 1951. This film isn't so much obscure as it is mostly forgotten. Alec Guinness plays a chemist who synthesizes an indestructible fiber ("a copolymer of amino acids and carbohydrates") that also repels dirt. Convinced that he has solved the world's laundry problems, he tailors himself a suit from his fiber and goes out into the world hoping for fame and fortune. But the rest of the world thinks otherwise. Not just chemistry fans, but all science fans should like it. It has weird laBORatory equipment, boiling mixtures and plenty of explosions. It is truly a classic. Beware of future remakes, watch the original!

Chemist at work, synthesizing trouble

Edwin. This was apparently a TV movie released in 1984. I don't know if it was ever broadcast in the U.S. I taped it in the late 80s in Ann Arbor from a Canadian station broadcasting from Windsor. It's about a retired judge (Alec Guinness) who suspects his neighbor and close friend (Paul Rogers) of having "rogered" his wife (Renée Asherson). After their son, Edwin, whom we see only for a moment, visits them for lunch, the question turns into who Edwin's real father is. The 2 men bicker endlessly until finally the wife reveals her secret and relieves both men in a surprising twist. There are only 3 "old" characters in the film, which takes place during 1 day and in the same place. Although that may sound boring and depressing, this is a rather pleasant little film with many subtle jokes. Normally, I don't watch and when I watch, I don't care for movies like this. But this one has ended up being one of my favorites. Perhaps because acting is very good and because it doesn't have a "moral of the story" at the end, at least not a traditional "Judeo-Christian" one.

Alec Guinness 30 years later, seeking justice in his household

28 November 2005

Coffee grounds have spoken, but what the heck did they mean?

To help save trees in a meager way, I use a gold coffee filter instead of paper filters. The gold filter, however, lets thru the finest grains. This results in my coffee being slightly thicker, before the suspended grains settle down on the bottom of the mug. But, I have gotten used to it, and besides, it reminds me of the traditional Turkish coffee.

Coffee tasseography, the reading of one's fortune from the patterns created by the coffee residue left on the bottom of his/her fincan, the small traditional mugs used for Turkish coffee, was routinely practiced in Turkey. However, I don't think anyone took his/her fortune told from wet coffee grounds seriously; this was done more for amusement than for serious future planning.

Nevertheless, when I noticed this pattern on the bottom of my mug recently, I was convinced that I was destined to visit a mountainous country, perhaps Nepal to climb the Himalayas, and started packing. But my wife took a peek at the bottom of my mug and predicted instead that I was going to buy a double humped camel. These conflicting interpretations created confusion and put everything on hold.

We are now waiting for the future to unfold itself in a more conventional way, a second at a time.

27 November 2005

Painted Lady (Vanessa cardui)

The Painted Lady (family Nymphalidae) is a widely distributed species, present on all continents except Australia and Antarctica. In the U.S., its range overlaps a similar species, the American Lady ( Vanessa virginiensis). The 2 species can, however, be easily distinguished from each other1, especially when good photographs are available. The lower surfaces of the hindwings of the American Lady have 2 large eyespots, while those of the Painted Lady have 5 spots that are clearly visible in the picture above. The upper forewings of the Painted Lady have a large semicircle or circle forming from the black markings (arrow in the picture below). This feature is lacking on the wings of the American Lady. Furthermore, the upper forewings of the latter species have a small white spot on orange. Firefly Forest Blog has a picture of an American Lady identifying these characteristic spots.

1. Glassberg, J. Butterflies through Binoculars. The East. Oxford U. Press. 1999.

26 November 2005

Saturday's beer review: SkullSplitter from Scotland

This is a dark brew with a creamy texture. It has a strong—slightly sweet—flavor, but a light aroma. (Does that make sense?) I didn't think it was bitter (I don't care much for bitter beers).

SkullSplitter is brewed by the Orkney Brewery, on Orkney off Scotland, UK. The guy on the label is pretending to be Thorfinn Hausakluif, aka Skull Splitter, the Viking Earl of Orkney ca. 1000 AD.

SkullSplitter's alcohol content is 8.5%, slightly higher than most ordinary beers. Drink too many of these and your skull will split the next morning.

Other comments on SkullSplitter

The previous beer review was Dead Guy Ale.

25 November 2005

A happy survivor

"All that we can do, is to keep steadily in mind that each organic being is striving to increase in a geometrical ratio; that each at some period of its life, during some season of the year, during each generation or at intervals, has to struggle for life and to suffer great destruction. When we reflect on this struggle, we may console ourselves with the full belief, that the war of nature is not incessant, that no fear is felt, that death is generally prompt, and that the vigorous, the healthy, and the happy survive and multiply."

Charles Darwin, On the Origin of Species

Butterflies with damaged wings are common. Their wings may be damaged by predators, other butterflies during courtship or territorial fights, and perhaps even by strong winds and heavy rainstorms. The ability of butterflies to fly with wings missing chunks demonstrates that their wings are larger than the minimum size required for flight. Although it must be costly to grow larger wings, they are an indispensable safety mechanism. I have written about an example of a similar "over-adaptation" in land snails that can survive without water for periods much longer than they normally experience in the wild.

This Wood Nymph (Cercyonis pegala), with its wings literally falling apart, was a real survivor. Obviously, it had gone thru a lot. But it could still fly and it wasn't done yet. It was nectaring, perhaps to take care of one last unfinished business.

May its genes live long and evolve!

24 November 2005

It was 146 years ago today

"I am fully convinced that species are not immutable; but that those belonging to what are called the same genera are lineal descendants of some other and generally extinct species, in the same manner as the acknowledged varieties of anyone species are the descendants of that species. Furthermore, I am convinced that Natural Selection has been the main but not exclusive means of modification."
Charles Darwin On the Origin of Species

On this day in 1859, Charles Darwin's On the Origin of Species was published in London.

Don't forget to give thanks to Darwin today for letting us stand on his shoulders.

Darwin's study at Down

More information on Darwin's writings and evolution:

Charles Darwin's writings on the web

Darwin Digital Library of Evolution

Darwin and Natural Selection

23 November 2005

Beaver's luck or the lack thereof

I photographed this tree about 12 days ago. The characteristic teeth marks left on the wood indicated that the perpetrator was a beaver (Castor canadensis). But for whatever reason, the beaver had left its job unfinished.

Imagine my surprise yesterday, when I passed by the same spot and noticed that the beaver had returned and finished chopping the tree. When I saw where the tree had fallen, though, I couldn't help but laugh. After all that trouble, the beaver still couldn't get its tree.

22 November 2005

Sister Tillie's good ol' thesaurus

This is one of the oldest books I have. I bought it many years ago for $3 in a used bookstore in New York. The covers are slightly damaged and some of the pages are loosening. But otherwise, and considering that it's almost 130 years old, it's in pretty good shape. I hope I will be as healthy when I am 130.

Inside, there is a dedication probably to the original owner of the book.

It reads
"...... the crown[?]
Dear Sister Tillie
December 2nd - 1878"

I cannot figure out the first word of the first line. The first 3 letters appear to be i-n-i and the last 2 are e-d. There are only 16 entries starting with "ini" in my huge Random House Dictionary, but none makes sense in this context. I think the last word of the same line is "crown".

In the thesaurus, the words are numbered, and presented in a hierarchical classification rather than alphabetically. You can see below that even in the smallest groupings, the words are not alphabetized. Instead, they follow each other somewhat subjectively based on their meanings. For example, "Intrinsicality" comes before "Extrinsicality". But there is an alphabetical index that lists every word and its number.

Despite these shortcomings and its age, however, this could still be a useful book. There is also a long list of foreign words and expressions. Why evolution was considered "motion in a reverse cycle", I don't understand, though.

21 November 2005

Snail shell terminology 4

Arrows point at the columella of Albinaria anatolica, a clausiliid land snail from southern Turkey.

The columella is the central axis inside a snail's shell around which the shell spirals. The columella forms from the innermost walls of the whorls. The columella is hollow. On the bottom of the shell, the columella may open to the outside as the umbilicus or, if the snail has determinate growth, it may be covered by the edge of the lip in the adult snail.

To be continued...

Snail shell terminology 1
Snail shell terminology 2
Snail shell terminology 3

19 November 2005

Papers read this week

Musical accompaniment: Philip Glass: Etudes for Piano, vol. I.

Villalobos et al. 1995. Life cycle and field abundance of the snail Succinea costaricana (Stylommatophora: Succineidae), a tropical agricultural pest. Rev. Biol. Trop. 43:181-188.
Besides detailed information on the reproduction, development and lifespan of this land snail, the paper also offers some tidbits of interesting facts. For example, the authors report that these snails can reproduce without mating. (Other species of succineids had previously been reported to do so.) This presumably involves selfing, which means that a snail uses its own sperm to fertilize its own eggs (remember, they are hermaphrodites). They also note that one captive snail that had lost its entire shell was able to regenerate another one. Moreover, the authors measured the crawling speed of their snails. Mean speed of 8 juveniles "over horizontal moist filter paper" was 16.2 mm/min. If the snails could maintain that speed for 1 hour, they would travel only about 97 cm, barely a meter. They are slow, aren't they?

Ramos, et al. 2004. Overcoming an evolutionary conflict: Removal of a reproductive organ greatly increases locomotor performance. PNAS 101:4883-4887. Free Full Text
Male spiders in the genus Tidarren are much more smaller than females (see photo below from the original paper). However, the males' pair of pedipalps (appendages in front of the head), used for sperm transfer, are disproportionately large. Males remove one of these large pedipalps before maturing. To test the hypothesis that such large pedipalps might interfere with locomotion and that their removal facilities locomotion, the authors compared maximum speed and endurance of male spiders before and after pedipalp removal. Their results show that pedipalp removal increases both maximum speed and endurance. This is an example of an evolutionary conflict: a structure evolved for one function, in this case, pedipalps for reproduction, impairing other vital activities, in this case, locomotion. And this appears to have led, as the authors note, to the evolution of a novel behavior: removal of one pedipalp.

This guy certainly needs penis, or rather pedipalp enlargement.

Blackstone, et al. 2005. H2S Induces a Suspended Animation-Like State in Mice. Science 308:518.
When mice breathe small amounts of hydrogen sulfide (80 ppm), their metabolism is reversibly inhibited and their body temperature lowered. For example, after 6 hours, their metabolic rate dropped by ~90%. The authors speculate that hydrogen sulfide-induced suspended animation might be useful for various medical conditions (in humans, not mice), such as trauma and during surgery.

18 November 2005

A fuzzy bird

I don't consider myself a birder, although I do have a couple of bird books and I can identify some of the common birds. Nevertheless, I try not to miss a chance to photograph a bird, especially if I can't identify it.

This was one of those occasions about a month ago in Black Hill Regional Park, Montgomery Co., Maryland, when I saw this bird wading in a quite shallow part of the lake. Unfortunately, it was kind of dark, the bird was far and my camera's optical zoom magnifies only up to 3X. So, I turned on the digital zoom, but that only created more noise.

The picture on the left may give an idea of the hunting ground of the bird. In the background there is a male Mallard (Anas platyrhynchos). From the appearance of the bird, I suspected it was some kind of sandpiper. Luckily, the park office puts out a brochure listing all the bird species that have been recorded in the park (mine dates from 1996). Out of the 7 species of plovers and sandpipers listed, I am guessing that this was either a Solitary Sandpiper (Tringa solitaria) or a Spotted Sandpiper (Actitis macularia).

I will be getting a better camera.

17 November 2005

Some questions on terrestrial mollusks

What is the highest altitude at which live land snails have been collected? Land snails live at many high altitude mountains, including the European Alps and the North American Rocky Mountains. I wouldn't be surprised to find land snails at any altitude provided that the location is free of ice and snow for at least 2-3 months a year.

Are there any sinistral slug species? Despite the external apparence of a slug that may give the first impression that its body is symmetric, all slugs species that I know of have their breathing holes and genital openings on the right sides of their bodies. In that respect, they are like dextral snails. And just as one occasionally encounters a sinistral specimen of a snail species that is normally dextral, one may occasionally find a sinistral slug that has its breathing hole and genital opening on the left side of its body1. Moreover, there are many snail species that are normally sinistral. Are there also normally sinistral slug species?

Most (all?) sinistral snail species have shells that are taller than they are wide. Slugs have evolved from snails. Although some slug species have completely lost their shells, many species still have a small external or internal vestigial shell. There are also so-called semi-slugs, snails with shells that are much smaller than their bodies and into which they cannot withdraw. The shells of semi-slugs are always wide, not tall. This suggests that slugs have descended from snails with wide shells. And since sinistral snail species with wide shells are rare (absent?), this may be the reason why there are no normally sinistral slug species, or if there are any, why they are rare.

What is the smallest land snail species? The smallest North American land snails are probably Punctum minutissimum and Guppya sterkii. Pilsbry gave the diameters of shells of P. minutissimum as 1.5 mm or less and those of G. sterkii as 1.2 mm. The largest G. sterkii shells I have measured were 1.3 mm wide. The smallest European land snails may be Punctum pygmaeum and Truncatellina claustralis. The shells of the latter species are 1.5-1.8 mm long. Vagvolgyi2 noted that "Some species of the genus Ptychodon reach only 1 mm as adults, Charopa 1.2, Pronesopupa 1.3". Back in August, I had a post on miniaturization in animals and Tim Pearce commented that some adult diplommatinid land snails could be as small as 0.7 mm long. But I think this information, which came from a 1938 publication, needs to be confirmed with more recent work.

Who discovered that pulmonate snails are hermaphrodites? All pulmonate snails are hermaphrodites. I have written about the American naturalist Thomas Say, who, in an 1818 paper, gave dimensions for “male” and “female” pulmonate snails. Twelve years later, in his American conchology3, Say wrote that the snails in the then catchall genus Helix were hermaphrodites. It seems that sometime during the first decades of the 19th century it became established that pulmonate snails were hermaphrodites. I have done some searching and asked around, but haven’t found out who first figured out that pulmonates were hermaphrodites. Was it Lamarck?

Are live land snails or their live eggs being transported over long distances by the winds? There are numerous records of live land snails that have been found on migrating birds, but in 1965 Rees4 wrote that "Direct evidence for the transport of minute snails [by hurricanes and tornadoes] is not yet forthcoming". Ten years later, Vagvolgyi2 speculated that very small land snails can be transported by air currents. But I am not aware of a published record of live land snails, their eggs, or even empty shells, that have been collected high enough above the ground to eliminate local wind-blown transport.

1. Reise et al. 2002. A sinistral specimen of the terrestrial slug Arion lusitanicus. Malakologische Abhandlungen 20:247-252.
2. Vagvolgyi, J. 1975. Body size, aerial dispersal & origin of the Pacific land snail fauna. Systematic Zoology 24:465-488.
3. Say, T. 1830. American conchology: or, Descriptions of the shells of North America. New Harmony, Indiana.
4. Rees, W.J. 1965. The aerial dispersal of mollusca. Proc. Malac. Soc. London 36:269-282.

15 November 2005

Artist's conception of a self-portraiture between parallel mirrors

Extra noise was added in Photoshop.

Land snails of Turkey: Lauria cylindracea

Lauria cylindracea from the vicinity of Kuşadası, Turkey.

This small species was described by da Costa in 1778. The taxonomic placement of the genus is uncertain; it was put in Pupillidae by Kerney & Cameron1, and in Orculidae by Schileyko2.

Differing descriptions in the literature may perhaps be explained by Kerney & Cameron's note that L. cylindracea is a variable species. According to them, "An angular tooth is normally present, linked to the top of the outer lip...In juveniles there is also a columellar lamella..." Schileyko, on the other hand, states that "Armature of adult shells represented by only two teeth: parietal and columellar lamellae; besides, angular tubercle may [be] present as well." The teeth in the aperture of the adult shell below agree with Schileyko's description.

Lauria cylindracea from Istanbul, Turkey. Arrows point to parietal (left) and columellar (right) lamellae. This shell was 3 mm long.

Lauria cylindracea is a widely distributed species with records from western Europe, including England, Germany, Denmark, Sweden and also Crimea, Caucasus, Turkey and northern Africa.

1. Kerney, M.P. & Cameron, R.A.D. 1979. A Field Guide to the Land Snails of Britain and North-west Europe. Collins.
2. Schileyko, A.A. 1998. Treatise on Recent Terrestrial Pulmonate Molluscs. Part 1. Ruthenica, Supplement 2.

14 November 2005

Cyclops in the forest

Ever since reading at Firefly Forest Blog about aspen eyes, markings on the trunks of quaking aspens (Populus tremuloides) that uncannily resemble eyes, I have been paying more attention to the trunks of trees around here. A few days ago, while taking a walk in Black Hill Regional Park, my usual prowling ground, I noticed that beech trees (Fagus grandifolia) too have eyes, although theirs are not as noticeable as those of aspens, mainly because they lack the dark colored "iris" in the eyes of the latter.

The eyes on the trunks of quaking aspens mark the spots where branches used to be before they got self-pruned. The stub left behind in the "pupil" of the eye in the above picture shows that beech eyes also form at the locations of former branches.

12 November 2005

Papers read this week

Tonite's musical accompaniment: Édouard Lalo: Symphonie espagnole.

Albert, A.Y.K. & Schluter, D. 2005. Selection and the origin of species. Current Biology 15:R283-R288.
A useful paper that discusses in a relatively simple language some key concepts of evolutionary biology, including natural selection, sexual selection, allopatric and sympatric speciation. Also discussed is one step speciation in plants, which creates a new plant species literally in a single step as a result of chromosome doubling. Apparently, it is a common process in plants.

Keiper, J.B., Walton, W. E., & Foote, B. A. 2002. Biology and ecology of higher Diptera from freshwater wetlands. Annual Reviews of Entomology 47:207–232.
Among the common inhabitants of wetlands (bogs, fens, swamps, marshes and floodplains) are flies (Diptera). The larvae of most of these flies seem to feed on decaying plant and animal matter, although some prefer live plants. The larvae in one family that interests me most (the Sciomyzidae), however, specifically feed on freshwater mollusks (bivalves and snails) and terrestrial mollusks (snails and slugs).

The following 2 papers deal with Bergmann's rule, which, according to Ernst Mayr1, is that "races from cooler climates in species of warm-blooded vertebrates tend to be larger than races of the same species living in warmer climates". Before proceedings further, however, we need to remind ourselves of Mayr's cautionary statements elsewhere2: "Generalizations in modern biology tend to be statistical and probabilistic and often have numerous exceptions...The so-called laws of biology are not the universal laws of classical physics but are simply high-level generalizations."

Yom-Tov, Y. & Yom-Tov. 2004. Climatic change and body size in two species of Japanese rodents. Biological Journal of the Linnean Society 82:263–267.
To test the hypothesis that global warming may have been causing the skulls of warm-blooded vertebrates to become smaller (if Bergmann's rule applied), the authors measured the skulls of 2 species of Japanese rodents, the specimens of which had been collected continuously throughout much of the 20th century. The specimens had been collected on Honshu Island, where the mean annual temperature increased by 1.53°C between 1900 and 1990. There were, however, no significant relationships between any of the measured skull characters of either species and mean maximum or minimum annual temperatures in the year of collection.

Laugen, A.T., Laurila, A., Jönsson, K.I., Söderman, F. & Merilä, J. 2005. Do common frogs (Rana temporaria) follow Bergmann’s rule? Evolutionary Ecology Research 7:717-731.
The authors wanted to know if Bergmann’s rule applied to the frog Rana temporaria, which is a cold-blooded animal. They measured body sizes of frogs across a 1600-km long latitudinal gradient in Scandinavia. According to their results (Fig. 2, below), the mean body size increased from south to mid-latitudes and declined thereafter. They conclude that "although there is considerable geographic variation in mean body size of R. temporaria, this variation does not conform with Bergmann’s rule."

1. Mayr, E. 1970. Populations, Species and Evolution (p. 197). Harvard University Press.
2. Mayr, E. 1988. Toward a New Philosophy of Biology (p. 19). Harvard University Press.

11 November 2005

Snail shells are made of this

Yesterday, an inquisitive mind prowling the Internet using the search string "what are land snail shells made of" ended up on this blog. I don't think that question was specifically addressed on this blog before. Therefore, we must answer it now.

Land snail shells are made of calcium carbonate. Well, that's the quick and simple answer. In reality, however, nothing that evolution has ever created can be explained away so simplistically. And snail shells are no exception. So, here is a slightly more detailed answer.

Snail shells are indeed made of mostly calcium carbonate, but that's not all they contain. They also contain small amounts of protein. Basically, the shell consists of calcium carbonate crystals organized within a matrix of protein. But the reality is still more complicated than that. Calcium carbonate crystallizes in 2 principal forms, aragonite and calcite, and what form is present in a particular shell may depend on several factors. For example, the crystal type in the shell of the land snail Helix pomatia is normally aragonite, but calcite has also been found in repaired areas of shell1. The shells of many marine snails and bivalves normally contain calcite.

Moreover, the shells of many aquatic as well as land snails are covered on the outside by a hard, skin-like layer of protein that is called the periostracum. Geerat Vermeij in his book A Natural History of Shells2 has a discussion on how the periostracum of marine snails, sometimes growing quite thick, helps protect the underlying shell from dissolving, especially in cold water in which the solubility of calcium carbonate increases.

Here is a simple way to demonstrate that the composition of snail shells is mostly calcium carbonate. When calcium carbonate (CaCO3) dissolves in any common acid, carbon dioxide (CO2) is generated. So, for example, the dissolution of CaCO3 in acetic acid (CH3COOH) can be represented as follows.

CaCO3 + 2CH3COOH ----> Ca(CH3COO)2 + H2O + CO2

Calcium acetate (Ca(CH3COO)2) is soluble in water and that's why a shell placed in acetic acid will eventually completely dissolve away. What happens to carbon dioxide? It bubbles out of the solution. And that's how one tells—by noticing the bubbles forming on the surface of the shell—that the shell is made of calcium carbonate.

In fact, a geologist's standard test for calcium carbonate is to place a drop of dilute hydrochloric acid (HCl) on a rock suspected of containing calcium carbonate (for example, limestone or marble or even a conglomerate containing calcium carbonate besides other minerals). If bubbles form in the drop of acid, the rock contains calcium carbonate.

But don't take my word for it. Try it yourself and be amazed. If you have a shell, a piece of marble or a limestone pebble from your yard, put a drop of vinegar, which is about 5% acetic acid, on it and look for bubbles. Moreoever, if you have powderized limestone and if you drop a bunch of it in a glass of vinegar, you will get a violent reaction with lots and lots of bubbles. Do it in your parents' kitchen, just don't tell them that you read it on Snail's Tales.

1. Saleuddin, A.S.M. & Wilbur, K. M. 1969. Shell regeneration in Helix pomatia. Canadian Journal of Zoology 47:51-53.
2. Vermeij, G. J. 1993. A Natural History of Shells. Princeton University Press.

10 November 2005

Prospecting for backyard snails: Vertigo pygmaea


Several species of snails and slugs live around my house. One of these is the tiny Vertigo pygmaea that lives on and near the rocks that we use to build walls around flower beds. The average V. pygmaea shell in my backyard is 1.9 mm long. Because they are so small and have brown shells, they are hard to spot on rocks (and even harder on soil) unless you look very carefully.

The picture above shows 2 adults and a juvenile V. pygmaea that I found on the side of a large rock. You can see a close up of the 2 adults on the left. When the weather is dry these snails aestivate on the sides of or underneath the rocks. Sometimes you may see the same snail at the same spot for several days in a row.

Vertigo pygmaea is a widespread species. It is present throughout most of Europe and northeastern America. The genus itself is holarctic being present in North America, Europe and Asia. Pilsbry1 noted that fossil Vertigo had been recorded from the Eocene (~50 Myr ago) of Wyoming.

I have written about Vertigo gouldi, a close relative of V. pygmaea. The Vertigo species are distinguished from each other by the shapes and dimensions of their shells, the shell surface microsculpture and the number and positions of the teeth in the aperture. The picture below shows the teeth in the aperture of an empty V. pygmaea shell from my backyard.


1. Pilsbry, H. 1948. Land Mollusca of North America, II:2, p. 943.

08 November 2005

Puzzling Wednesday

[I know it's not Wednesday yet, but I wanted you people to have a head start.]

You are to have an important meeting in Manhattan, New York at a certain time on a certain day with a person whom you don't know and have never seen. But you both have an esoteric insignia that will enable you to recognize each other. Unfortunately, you lose contact with the person before a meeting place was picked and now you have no way of reestablishing contact. (This puzzle dates from long before e-mail and cell phones.) Nevertheless, on the designated day at the designated time, you decide to be at some public place in Manhattan where you think the other person is most likely to be.

Where would you go to maximize your chances of meeting the other person assuming that the other person is also trying to find you? Assume that there had been no mention of a suitable meeting place between the 2 of you.

In the original puzzle1, the purpose of the meeting was not specified. However, the nature and purpose of the meeting could easily affect the selection of a meeting place and increase the chances of two people finding each other.

Now, where would you go if the meeting was about…

an archeological expedition to Egypt?

a research project about the microscopic animals that live in large ponds?

a new international organization to foster peace among countries?

Obviously, there are no correct answers to this puzzle, but, any number of possible, and rather subjective, answers.

I will post some answers of mine tomorrow nite in comments.

1. Modified and expanded from puzzle #12 in Mosteller, F., Fifty Challenging Problems in Probability. Dover Publications, 1965.

07 November 2005

Moon, Venus and neighbor's house

Taken on 5 November 2005, around 19:30 with an Olympus Camedia C-5000; exposure was 4 seconds at f8 with sensitivity at ISO 320; "developed" in Photoshop.

Free-access science journals on the Internet 5

New Zealand Journal of Marine and Freshwater Research 1967–2002

New Zealand Journal of Zoology 1994-2002

Journal of General Physiology Free content after 12 months, starting at 1918

Journal of Ethnobiology and Ethnomedicine A new electronic journal

The Searchable Ornithological Research Archive (SORA) Free access to old issues of 8 journals of ornithology (birds, folks, birds!) [Appreciations to tony g from milkriverblog for bringing this to my attention.]

EJOS - Electronic Journal of Oriental Studies – “…an electronic journal devoted to Arabic, Persian and Turkic studies in their widest sense”

Previous posts with links to free-access science journals:

Free-access science journals on the Internet

Free-access science journals on the Internet 2

More free books ‘n stuff!

Free-access Journals and newsletters on insects and their relatives

05 November 2005

Papers read this week

I consider the writing of these posts about the papers I've recently read a good mental exercise, forcing me to go over the papers, re-read parts of them and try to distil out what I find significant in them.

Martens, K., G. Rossetti, D. J. Horne. 2003. How ancient are ancient asexuals? Proceedings of the Royal Society, Biological Sciences 270:723-729.
In a recent post on rotifers, I mentioned that bdelloid rotifers are the largest group of asexual animals. A less speciose group that is also asexual is darwinuloid ostracods (family Darwinulidae). Ostracods are microscopic crustaceans with a pair of carapaces resembling clam shells. Thanks to their carapaces that fossilize well, they have an extensive fossil record. In those species that have males, male carapaces can be distinguished from female carapaces by 3 morphological criteria: lack of a brood pouch, position of muscle scars and size dimorphism (dimensions of male and female carapaces differ). The authors analyzed fossil carapaces of a darwinuloid ostracod, Alicenula leguminella, from about 145 Myr ago and found that all the individuals were females. They also reconsidered published accounts of fossil male darwinuloids and rejected them, concluding that these ostracods have been reproducing asexually for about 200 Myr.

I have a deep interest in the evolution of terrestriality among animals, especially invertebrates. Here's a couple of papers more or less related to that topic.

K. Martens, P. De Deckker, G. Rossetti. 2004. On a new terrestrial genus and species of Scottiinae (Crustacea, Ostracoda) from Australia, with a discussion on the phylogeny and the zoogeography of the subfamily. Zoologischer Anzeiger 243:21-36.
Another paper on ostracods. This is cool, because there are terrestrial ostracods, something I didn't know before I read this paper. They apparently retain a film of water within their carapaces and breath thru that water. The appendages of terrestrial species have been modified by evolution to enable them crawl on land.

Fratini, S., M. Vannini, S. Cannicci & C.D. Schubart, 2005. Tree-climbing mangrove crabs, a case of convergent evolution. Evolutionary Ecology Research 7(2): 219-233.
Several species of semi-terrestrial crabs in the family Sesarmidae climb mangroves. These crabs have a number of common morphological characters and therefore have been assumed to have descended from a common ancestor. The authors derived a phylogeny for these crabs based on their mitochondrial DNA sequences. Their results suggest that tree-climbing species are not as closely related to each as previously thought and that their arboreal lifestyle evolved in at least 3 independent lineages.

And now for something completely different...

Graham, L.A. & P. L. Davies. 2005. Glycine-rich antifreeze proteins from snow fleas. Science 310: 461.
Snow fleas are tiny wingless insects (family Poduridae) that may be seen in winter on the surface of the snow. Not surprisingly, they produce antifreeze proteins to resist freezing. The authors isolated 2 antifreeze proteins from a species of snow flea and determined its partial amino acid sequence, which was rich in glycine. They note that the snow flea antifreeze proteins do not resemble the antifreeze proteins of moths and beetles, which are rich in another amino acid, threonine. It appears that the ability to produce antifreeze proteins evolved independently in different groups of insects.

03 November 2005

Prospecting for snails during lunch break

Exploring the neighborhood for natural history specimens and photographic subjects during my daily walks has become a passion. Last Thursday my walk took me to a local “community” park in College Park. Such places, ordinarily with paved parking lots, regularly cut grass and well-spaced trees with very little leaf litter and almost no deadwood, offer few suitable habitats for ground-dwelling animals. Fortunately, however, I chanced upon a relatively young tree that nevertheless had a large hole thru its base. Tree holes usually harbor snails and other critters and this one was no exception.

In the hole under the wind-blown leaves covering the soil, I found 2 juvenile specimens of Mesodon thyroidus, a common eastern native. As you can see in the picture, this tree was next to a parking lot. Normally, I wouldn't have expected to find any snails in that hole. But what probably made a difference in this case was that the hole was facing a small patch of 2nd growth forest a few meters away. The snails had probably migrated over from the forest.

In previous posts (here and here), I had pictures of adult M. thyroidus shells showing how the lip partially covers the umbilicus. I also mentioned before that in juvenile shells the umbilicus is always open. Thus, being a juvenile, the pictured snail had an open umbilicus. Also notice that the internal organs show thru the semi-transparent shell.
Later on, in a narrow strip of forest separating the “urbanized” park from a small stream, I found, next to a piece of rotting wood, another species of land snail: Ventridens ligera, another native that is perhaps even commoner than the former species. But it refused to come out of its shell for a photo-op.

02 November 2005

Meanwhile, back at Belt Woods

A big mother at Belt Woods. This one is a tulip poplar with yours truly next to it.

Taking advantage of the unusually warm days we‘ve been having, I went back to Belt Woods last Sunday to do more snail collecting.

There are two sections of forest at Belt Woods. One is the so-called South Woods that has never been logged and the other, and the larger, is North Woods, which was selectively logged in 1975 and 1985. The old growth South Woods has the tallest tulip poplar (Liriodendron tulipifera) trees in Maryland and some of the tallest in the eastern U.S.

On Sunday, I explored North Woods for the first time. As you can see in the photo above, some of the trees that were spared the chain saws are truly big and obviously old.

As for snails, there were plenty. During my last trip, I found and photographed some Triodopsis that I still haven’t identified definitely. One of last Sunday’s pleasant discoveries was another species of Triodopsis. This one is T. fallax. I will have more about this species in a future post.