31 January 2010

Deer bone soup in the sink

During last weekend's field trip for Cepaea nemoralis I also chanced upon a deer skeleton.

DeerBones

Deer bones, if not entire skeletons, are quite common in wooded areas around here (see this post for an intact deer carcass). The nice thing about last weekend's find was that almost all the major bone groups were there, some still articulated.

I took the skull, the nearby jaw bones, the pelvis and representative pieces from the spine. They were free of flesh, but I noticed later that small pieces of cartilage were present on the pelvis, although, there was no offensive odor.

Last night, I got down to cleaning the bones in the bathroom sink.

DeerBoneSoup

First, I scrubbed them under hot water using an old tooth brush, then soaked them in hydrogen peroxide overnight (yes, the deer skull soup with free radicals). I am now giving the pelvis a short soak in dilute bleach.

The sad thing was that a whole bunch of dead ants washed out of one of the jaw bones this morning. Apparently, they had a nest in there. If I had realized that sooner I would have put the bone in the backyard without disturbing the nest.

29 January 2010

How to spot a hermaphrodite

If you had no prior information about the reproductive biology of a group of animals, say, pulmonate land snails, how would you go about determining if a given species were hermaphroditic or not?

I can think of 2 ways of doing it. First, one may dissect and compare the genitalia of many individuals. If every individual is found to have the same set of reproductive organs, one may assume that they all are hermaphrodites and then try to identify the male and female parts.

Second, one may watch or separate many mating pairs and, if one is lucky and happens to see that each individual is using its penis simultaneously to inseminate its partner, one will then conclude that they all are hermaphrodites.

But what has luck got to do with it? It turns out that, even though all pulmonate snails are hermaphrodites, in some species mating may not be simultaneously reciprocal; instead, some individuals may act like "males", while others like "females". A previous posts on this subject is here.

28 January 2010

What I learned from a Charonia shell

charonia1

I believe this is a Charonia tritonis shell, one of the largest marine snails. I photographed it more than 2 years ago when I was at the Carnegie Museum of Natural History in Pittsburgh.

What especially attracted me to this shell were the numerous varices on it. A varix is a radial ridge that forms on a snail's shell when the snail stops growing temporarily. Here is one of them.

charonia2

You can see very clearly that regrowth started from under the old shell (shell growth direction was towards the left). Here is another varix, which was in the body whorl (shell growth direction was towards the bottom).

charonia3

In a couple of posts back in 2006, I discussed the alignment of the old and new shell material along a break in a shell and demonstrated that in land snails new shell always starts out from under old shell. This Charonia shell shows that this is also the case in marine gastropods. It would probably be less practical for a snail to lay new shell material on top of the existing shell, because the mantle that produces the shell is always in contact with the underneath of the existing shell.

27 January 2010

When snails were insects

Here is the title of a letter from the polymath scientist Dr. Martin Lister published in Philosophical Transactions in 1674 (vol. 9, pp. 96-99).

Lister1674

Note that the phrase "those insects" refers to snails. Yes, back then snails were insects. But that didn't mean that the pioneering scientists of the 17th century thought that snails and insects didn't differ much. Lister et al. were refined enough in that respect—but not in other respects—to know that the 2 groups were sufficiently different. But to them the word insect seems to have had a more inclusive meaning; it meant invertebrate. Therefore, snails were insects.

This usage seems to have continued at least until the end of the 18th century. For example, an anonymous compilation from 1792 titled The natural history of insects had 16 chapters on insects proper.

insects1792b

In addition, there were two chapters on spiders, scorpions, centipes, etc., and one on various worms. Finally, the last one was on snails. In 1792 snails were still insects.

insects1792a

I don't know when the word invertebrate came into use.

26 January 2010

Earthworm backlit

EarthwormBacklit
Intestine made visible for all to see.

25 January 2010

Maxwell's molecules (and species)

James Clerk Maxwell was one of the greatest physicists of the 19th century after whom the famous Maxwell's Demon was named. Today, I found one of his textbooks, Theory of heat, which was first published in 1870.

The great value of such a book, rather old as far as the current level of our knowledge is concerned, is that it opens up a portal to the mind of a great scientist and gives us clues as to how he may have developed some of his ideas.

Near the end of the book, there is an intriguing passage where Maxwell is comparing molecules, still a relatively new concept back then, to species and evolution, also a relatively new idea for that period.

The molecules of the same substance are all exactly alike, but different from those of other substances. There is not a regular gradation in the mass of molecules from that of hydrogen, which is the least of those known to us, to that of bismuth; but they all fall into a limited number of classes or species, the individuals of each species being exactly similar to each other, and no intermediate links are found to connect one species with another by a uniform gradation.

We are here reminded of certain speculations concerning the relations between the species of living things. We find that in these also the individuals are naturally grouped into species, and that intermediate links between the species are wanting. But in each species variations occur, and there is a perpetual generation and destruction of the individuals of which the species consist.

Hence it is possible to frame a theory to account for the present state of things by means of generation, variation, and discriminative destruction.

In the case of the molecules, however, each individual is permanent; there is no generation or destruction, and no variation, or rather no difference, between the individuals of each species.

Hence the kind of speculation with which we have become so familiar under the name of theories of evolution is quite inapplicable to the case of molecules.
Maxwell, it seems, was familiar with at least the basic notions of Darwin's theory of evolution.

24 January 2010

Cepaea nemoralis in the winter

The survey of Cepaea nemoralis in Maryland that we started last summer is over. But then again, I was saying that to myself back in September, but have ended up making several more field trips since then. I made one last field trip yesterday and am now ready to finish the manuscript.

This juvenile was one of the few Cepaea nemoralis I could find yesterday. It had been hibernating under the leaf litter before I disturbed it. After taking a few photos of it, I returned it to soil.

CepaeaNemoralis7

Notice in the next photo the white epiphragm sealing its aperture. I don't know of any native northeast U.S. snails that build epiphragms reinforced with calcium carbonate; the natives only use slime to seal their apertures. The morphology of the epiphragm of Cepaea nemoralis must be under genetic control. Even the captive snails make them like that.

CepaeaNemoralis8

22 January 2010

Mysterious depressions in snow

Last December's snow storm gave me a opportunities to go on snowshoeing excursions in the nearby park. The hill I climbed on the day after it snowed had still not been visited by any humans. Long and deep deer tracks were common, though.

There were also many odd-shaped superficial depressions in the snow that I could not identify. For example, these,

SnowTracks1

And also these,

SnowTracks2

However, the series of tracks in the next picture had obviously been caused by the small clump of snow visible at the end as it rolled down the slope towards the right, perhaps during a burst of wind.

SnowTracks3

I suspect all the other depressions had also been caused by pieces of wood, pine cones and other items of vegetable origin being moved around by the wind. However, in many instances, there was nothing nearby that could have caused a particular depression. Can a strong gust of wind remove a chunk of snow from the surface, drop it, pick it up again, thereby creating a depression, and finally, perhaps after repeating this process several times, disperse it without leaving any obvious traces of it?

21 January 2010

Beaver's unfinished business

Although I have seen a beaver (Castor canadensis) only once during the last 15 years or so, I know that they are quite common around here. They leave behind abundant evidence of their activities, including not only the trees they felled but also those whose trunks they gnawed on.

BeaverTree3

I photographed this young beech last weekend at a spot quite close to my house. The patches of scraped bark are telltale signs of a beaver's feeding activity. Here is a closer look that shows the marks left by the individual teeth.

BeaverTree4

If I get a chance this weekend I will check up on the same tree to see if it's still standing.

Some of the previous posts featuring beaver activities are here, here and here.

20 January 2010

Poe's snails

The Baltimore Sun reports that the mysterious person who had been leaving roses and a bottle of cognac at Edgar Allan Poe's grave site every year on the writer's birthday since 19 January 1949 didn't show up yesterday. Oh, well...

But did you know that in 1839 Poe published a book on mollusks? Yes, mollusks...snails, bivalves, octopuses and their kin. The full title of the book was The conchologist's first book: a system of testaceous malacology, arranged expressly for the use of schools, in which the animals, according to Cuvier, are given with the shells, a great number of new species added, and the whole brought up, as accurately as possible, to the present condition of the science.

Actually, Poe wrote only the preface and the introduction. The rest of the book was plagiarized, not by Poe, but by the publisher, Haswell, Barrington, and Haswell of Philadelphia, from Scottish naturalist Thomas Brown's The conchologist's text-book, embracing the arrangements of Lamarck and Linnaeus, with a glossary of technical terms published in 1833. Nevertheless, according to this site, The conchologist's first book was Poe's only book that went thru 2 editions in his lifetime.

Here are a few sentences from Poe's introduction:

Shells, too, being composed of particles already in natural combination, have not within them, like flowers and animals, the seed of dissolution. While the preparation of a specimen for the cabinet is a simple operation, a conchological collection will yet remain perfect for ages. These important circumstances being duly considered, in connexion with the universally acknowledged beauty and variety, both of form and colour, so strikingly observable in shells, it is a matter for neither wonder nor regret that these magnificent exuviae, even regarded merely as such, should have attracted, in a very exclusive degree, the attention and the admiration of the naturalist.

19 January 2010

Pedipes ovalis

Since last April I have been studying Pedipes ovalis, a little semi-terrestrial snail from Florida. They only grow to be ~3 mm long. When I first collected these snails, their affiliation confused me, but once I spotted the pneumostome (the opening of the lung) of one individual under the microscope and noticed, at the same time, that it didn't have an operculum, I knew they were ellobiids. A quick search thru Martins (1996) narrowed the genus down to Pedipes and the subsequent examination of the protconch helped me identify the species as ovalis.

An interesting characteristic of the genus is their foot, which is divided by a transverse groove into an anterior propodium and a posterior metapodium.

PedipesOvalis1

Since last summer I have also been writing 2 manuscripts about these snails. Expect more related posts in the future.


Martins, A.M.F., 1996. Anatomy and systematics of western Atlantic Ellobiida (Gastropoda: Pulmonata). Malacologia 37:163-332.

18 January 2010

Grey heron catching lunch

After photographing the dead bugs in one of the urinals in the men's room at Fletcher's Cove last Friday, I took a series of pictures of a grey heron catching and eating a fish in the Potomac River. Unfortunately, the only lens I had with me was a wide angle that went up only to 45 mm. Consequently, the pictures are not great, but they still make an informative sequence. I think.

HeronCatchinFish

In picture B the heron is striking at its prey; in C the fish it caught is visible in its beak; in D it is getting ready to swallow the fish; in E the fish is on its way down to the stomach (notice how enlarged the heron's neck appears). The fish was probably still alive as it was being swallowed.

My usual contact in matters of wildlife identification could not give me a definite id of the fish owing to the poor quality of the pictures, but thought that "a reasonable guess would be a small bass".

17 January 2010

Urinal entomology

UrinalEntomology1

Last Friday, there were 2 of these dead bugs in one of the urinals in the men's room at Fletcher's Cove along the C&O Canal. After I finished my business, I flushed, but the bugs remained. So I took out my camera and photographed them.

They appear to be some sort of stink bug (Pentatomidae).

UrinalEntomokogy2

Luckily, no one came in while I was stooping over the urinal with the camera against my face pointing inside. It would have been difficult to explain my motives.

15 January 2010

Spiraling plants

While walking past the fenced yard of a large house in Georgetown, DC today, I noticed several plants that had twisted themselves around the posts. Most were left-handed spirals or helices (left). But there was one that was right-handed (right).

SpiralingPlants

I am not much of a plant identifier and without leaves I couldn't even tell if they were all the same species. I don't know if the spiraling direction of climbing plants is determined genetically or randomly by the external circumstances. If I pass by the same spot in the spring I hope to remember to check if the right-handed plant is the same as the others.

14 January 2010

A forgotten thesis on Rumina decollata

While searching for records of the European land snail Rumina decollata from Arizona, I found a master's thesis from 1951 entitled Anatomy and life cycle of the snail, Rumina decollata.

Because of my interest in the genus Rumina, I downloaded the thesis and quickly skimmed thru it. If 2 blank pages, 2 title pages, table of contents, etc., are excluded, it's only 29 double-spaced pages. I am surprised that some one actually earned a master's degree in 1951 studying the anatomy of Rumina decollata, because Pilsbry had already published descriptions and drawings of the anatomy of the same species in the Manual of Conchology in 1905 (cited in the thesis) and then in his Land Mollusca of North America in 1946 (not cited in the thesis) and Wille had also done the same in 1915 (Jenaische Zeitschrift Naturwissenschaft 53:717-804) (not cited in the thesis).

But, anyway, here are some interesting tidbits from the thesis.

The author states that in the wild "the snails feed upon living vegetable matter". Rumina decollata is actually known to be an omnivore, eating plant matter and also preying on live snails. Here is another sentence: "The epiphragma [epiphragm] is essentially a layer of dried slime, supplemented and strengthened by the addition of calcium phosphate". It is calcium carbonate.

A noteworthy claim: "Muscular contraction and relaxation [of the floor of the mantle cavity] result in the change in size of the cavity, with resultant intake and expulsion of air". Unfortunately, nothing more is said on this and it is not explained if and how the author observed this or if she was repeating something read in the literature without giving a citation. Here is a related post.

The most useful section in the thesis is the one about the reproduction of Rumina decollata, especially the following paragraph:

There is reciprocal fertilization, that is mutual impregnation, preceded by a preparatory event in which two snails approach each other and evert the genital atrium. Copulation occurs in forty to sixty seconds. Copulation of snails in this collection began in the middle of September and continued for a period of three weeks. After copulation occurred, the snails were isolated and each was found to produce numerous clutches of eggs.
From this we can deduce that mating was in the face-to-face position* in agreement with the mating of Rumina saharica (see my paper here). Moreover, because both mated individuals laid eggs, sperm exchange appears to have been reciprocal.

Here is Plate I from the thesis with the drawings of a live snail and shells. Will the readers notice what is wrong with these drawings?

RuminaHines

The figures were reversed during printing and consequently, the shells ended up sinistral. No, the author did not happen to have chanced upon a colony of reverse-coiled snails, because she does indicate that the shell of Rumina saharica is "spirally coiled to the right", that is, her specimens were indeed dextral. Another indication that the figures were reversed is that the shell labeled "ventral" is actually showing the dorsal side and vice versa.

A paper based on this thesis was published in 1957 (Batts, J. H. 1957. Anatomy and life cycle of the snail Rumina decollata (Pulmonata: Achatinidae). Southwestern Naturalist 2:74-82). The drawings in the paper were still reversed!


*Because the snails approached each other. If they had mated by shell-mounting, one would have climbed on the shell of the other.

13 January 2010

Archaeo+Malacology Group Newsletter No. 16

The AMG Newsletter No. 16 is available here.

This issue contains articles on the mollusks found in excavations in Israel, the different survival rates of valves of the European oyster, Ostrea edulis, how the shell of the marine snail Charonia lampas can be turned into a musical instrument (presumably that is how the ancients may have also done it) and yet another paper on Papillifera bidens (=Papillifera papillaris) as well as announcements of upcoming meetings and other items of interest.

12 January 2010

A woodpecker on a cold winter day

While walking down Reservoir Road in Georgetown, DC yesterday, I noticed a couple of birds flying above me. Even to my non-birdwatcher eyes they looked unmistakably like woodpeckers, although I had certainly not expected to see woodpeckers in a residential neighborhood, especially on a day when the temperature was barely above freezing.

One of them flew across the street and disappeared, but the 2nd one alighted itself on the tree right next to me. And not only that but it also stayed there while I went into my bag, got my camera out, removed the lens cap, turned it on, guessed and then adjusted the exposure (yes, I almost always do the exposure manually) and took 3 pictures of it.

YellowbelliedSapsucker

John, who writes A DC Birding Blog, and to whom I appeal routinely whenever I can't identify a bird, recognized this one from the pictures as a yellow-bellied sapsucker. This area appears to be near the northern border of its winter range.

11 January 2010

Frozen waters

The cold spell that started in December continues unabated. Today I was at Fletcher's Boathouse at the C&O Canal near Georgetown, DC. The canal was frozen.

FrozenC&O

The building on the left is Abner Cloud House, said to be one of the oldest buildings along the C&O Canal.

To my surprise, even the nearby Potomac River was frozen. It's been that cold. But from my vintage point I couldn't tell if the ice cover extended all the way to the opposite bank.

FrozenPotomac

I wonder how Pomatiopsis lapidaria are doing.

10 January 2010

The significance of #24

chondrus24

Chondrus zebra upside down on the lid of its container.

09 January 2010

Another stupid government prohibition violated

prohibited

You may be able to tell from this picture that this sign is on the outside of a wide open space surrounded by chain-link fence. Nothing major inside is hidden from view. One could simply stand outside the fence (which is apparently not prohibited), carefully observe what's inside, walk away 2 blocks, and then take notes.

But what makes this prohibition totally absurd is that you can go into Google Earth and view every nook and cranny in the entire restricted area in high resolution.

When it comes to prohibitions, common sense is not something we can expect from the authorities. And they will never learn.

07 January 2010

The sound of a snail breathing. Pblopb!

"I have…frequently noticed that the sound, something like 'pblopb,' caused by Limnaea stagnalis opening their respiratory orifices at the surface of the water, may be heard some distance."

A.E. Boycott. 1899. Production of sound by Mollusca. Science-Gossip 6:285.

06 January 2010

Tools of philosophy

As I discussed in this post, well into the 19th century philosophy was a broad term that incorporated the physical and biological sciences in its definition. This ad I came across in a 1899 issue of the British magazine Science-Gossip shows that one could buy a philosophical instrument at least until the end of that century.

PhilosophyInstrument

Imagine how quickly you could get to the bottom of things and figure out the meaning of life if you had one of those machines.

05 January 2010

Beware of rising miasma

Over at Abnormal Interests, Duane has written about the ancient beliefs concerning the causes of diseases. The Mesopotamians may have understood that some diseases were contagious, but they also held various supernatural agencies (gods, demons, etc.) ultimately responsible for them. In the mid-1st century BCE, there was a surprisingly accurate idea that "certain minute creatures" were the causative agents of diseases; it was apparently too advanced for its times, though, and never led to anything practical.

Duane doesn't mention it, but there was also miasma, or corrupt air.

I recently read Michael W. Dols' The Black Death in the Middle East (1977). Dols writes that during the plague epidemic of the 14th century "[b]oth the Latin and Arabic authors believed that a corruption of the air, a so-called miasma, had been produced, which was visible in the form of mist or smoke, and was spreading over the land, killing all living things." He later mentions that the debate over infection versus miasma as the cause of plague "lasted until the late nineteenth century in the Middle East".

Until yesterday I was under the impression that by the end of the 19th century for Europeans the sickening influence of bad air had become a belief of the past. Then I changed my mind upon reading, on the way home in the train, the brief account of a mollusk collection expedition by a British fellow named J. Bliss in 1899. He and his companions were collecting in and around the ruins of 2 ancient cities, Magnesia ad Maeandrum and Priene, both located south of the present-day Kuşadası in western Turkey. He describes their activities in the course of a day thus (italics mine):

Stones were therefore turned over industriously, bushes searched, moss carefully picked, and walls scanned, until the declining sun, with the rising miasma, and the knowledge that a band of brigands were in the neighbourhood, warned us that we must not linger longer. Mounting our horses, we quickly traversed the twelve miles separating us from home.
We also did a snail survey in that neighborhood in 2004. The picture below was taken from Mount Mycale near sunset; the rising moon is towards the southeast. The slopes below were where Bliss did his collecting. I think I see the miasma over the horizon, which we didn't care about then and, luckily, brigands had long been a thing of the past.



J. Bliss. 1899. Molluscs in Asia Minor. Science-Gossip 5:322.

04 January 2010

Ammonicera fischeriana

Ammonicera

This marine snail shell was from a small sample of sediment that I had collected while snorkeling off the southwestern coast of Turkey back in 1997. Only recently did I begin to sort thru the sample (yes, I am that far behind). Henk Mienis of Tel Aviv University identified it from the picture as Ammonicera fischeriana.

With a diameter of 0.6 mm, it is the smallest marine gastropod I have so far seen. Apparently, they only grow to be about 1 mm or so. Ammonicera fischeriana is in the Omalogyridae, a family of very small snails. This being my 1st encounter with them, my knowledge of the family is quite limited. Hopefully, there will be more opportunities to study them in the future.

03 January 2010

Lookin’ out my back door

LookinOutMyBackDoor

Bother me tomorrow, today I buy no sorrows.
Doo, doo, doo, lookin’ out my back door.


Creedence Clearwater Revival, Lookin’ out my back door

01 January 2010

Vertigo pusilla: a sinistral snail to start off the new year

VertigoPusilla1

The readers who are versed in the study of snails will notice that the snail in the picture has a sinistral, or left-handed, shell. This is Vertigo pusilla, a land snail widespread throughout most of Europe (Fauna Europaea). This particular specimen was from Turkey, where the southern limits of the species' range may lie.

Here is a picture showing the aperture. The scale on the left is in millimeters. The shell was almost exactly 2 mm long.

VertigoPusilla2

Vertigo pusilla was described by O. F. Müller in 1774. The specific name, probably derived from the Latin pusillus, meaning tiny, is rather undescriptive in that all Vertigo species are tiny (here is Vertigo gouldi). Apparently, Müller wasn’t too impressed with the left-handedness of the shell.

The dictionary gives good as an antonym of sinister. May this be a good year for everyone.