31 October 2006

30 October 2006

Why is this snail hairy?

pustuloides1

This snail, a native of eastern U.S., is known as Lobosculum pustuloides, although it may not actually belong to that genus (family Polygyridae). For today, however, I will ignore its uncertain taxonomic placement and instead discuss the hairs that cover its shell.

The hairs grow out of the periostracum, the thin skin-like layer that covers the outside of the shell. There are several species of land snails that have similar hairy shells. For example, in the U.S. the species in the genus Stenotrema, also in Polygyridae, too have hairy shells.

What are the hairs for?

To answer that question, Pfenninger et al. (2005) studied the members of the European land snail genus Trochulus. Their analyses show that the habitats of the Trochulus species with hairy shells tend to be wetter than those of the species with hairless shells. They also did some tests that showed that on a wet leaf surface a larger minimum force was necessary to move hairy shells than hairless shells. So they speculate that the hairs help the snails stick to wet surfaces such as the leaves of plants that they apparently climb when they are feeding. It is not clear to me, however, why the snails' already sticky feet and slime wouldn't be strong enough to secure them to the plants they are on.

Would their findings apply to L. pustuloides and the other hairy U.S. snails? These snails seem to spend most of their time in the litter or on rotting trunks on the ground. I don't think they are in any danger of falling down from places high above the ground.

One possibility not considered by Pfenninger et al. is that the hairs may have an antipredatory function. They may, for example, deter the carnivorous snail Haplotrema concavum that drills thru the shells of its victims if it can't fit its head thru their apertures.

pustuloides2
Lobosculum pustuloides is a small snail. The shell of this particular adult was 4.2 mm across.



Markus Pfenninger, Magda Hrabáková, Dirk Steinke, Aline Dèpraz. 2005. Why do snails have hairs? A Bayesian inference of character evolution. BMC Evolutionary Biology 5:59 (4 November 2005). pdf

29 October 2006

The young and the old

Last weekend at Belt Woods, I walked thru a section of the reserve that was clear-cut several years ago. The forest has since been regenerating, but the appearance of the forest was so different than that of the old-growth section where the trees are believed to have never been cut that I decided to post pictures here.

The first picture shows the regenerating 2nd growth forest.

youngforest

Here, all of the trees are young, have narrow trunks and their stands are dense. On the ground there is very little deadwood; what is there consists mostly of small branches. Because the canopy formed by the young trees is not very extensive, plenty of sunlight reaches the ground.

Compare this with the below photo of a typical scene from the old-growth forest.

oldforest

The old-growth forest (and in general, any old enough 2nd growth forest) is characterized by huge trees (in addition to younger ones) that are more widely spaced as well as a large amount of rotting wood on the ground. Also when the canopy is fully developed, especially in the summer before the leaves start to fall off, very little sunlight gets thru to the ground.

One additional and important characteristic of old forests is the thick layer of litter or humus consisting of rotting leaves and wood and other plant parts mixed with animal remains that covers the ground. This litter layer provides habitats and food for many small animals and fungi. Young forests growing on heavily disturbed soil, such as an abandoned farm field, lack this litter layer and it may take many years before enough of it accumulates.

27 October 2006

Friday nite's beer review: Pyramid Apricot

pyramid

Ever since I had my first wheat beer back in the spring, I've become a fan of them. Pyramid Apricot is also an unfiltered wheat beer, but in this case, the characteristic wheat beer flavor is accentuated with a nice apricot aroma. I enjoyed this beer with some hazelnuts and chocolate covered pecans. I wish I had another bottle.

Pyramid Apricot is brewed by the Pyramid Breweries and this site has more info about this particular brew.


Index to the Snail's Tales' Beer Reviews

25 October 2006

Land snail dispersal

Dispersal of the proverbially slow land snails over suitable habitats is an interesting topic. Whilst the ranges of some species, such as Zoogenetes harpa, naturally extend across several continents, others are restricted to smaller areas.

Yesterday, I read a short paper by Baur and Baur titled "Dispersal of the land snail Helicigona lapicida in an abandoned limestone quarry" (Malak. Abh. 24:135-139, 2006).

The authors released 300 marked adult snails of the said species in a limestone quarry and then monitored the dispersal of those snails over a 2-year period. Although the recovery rates of the marked snails were low, 16.7% after 1 year and 4.0% after 2 years, the results do provide a general estimate of how far and how quickly this species disperses.


Fig. 1 from Baur & Baur, 2006. Arrows indicate median displacements.

Median dispersal was only 1.7 m 5 months after release, but increased to about 6.4 m after 2 years. These results roughly agree with the measured dispersal rates of other species of land snails. However, smaller species in general tend to move less within a given period than do larger species.

If we assumed that the measured dispersal rate of H. lapicida was constant over a long period and there was a continuous limestone habitat, the approximate median dispersal of the snails would be 32 m after 10 years, 320 m after 100 years and 3200 m after 1000 years. You get the idea. Dispersing barely 3 km over a thousand years isn't much of a dispersal. Over geologically long-enough periods other factors, for example, the movements of the continents, also come into play. Of course, we also have to take into account assisted dispersal facilitated by winds, animals, etc.

24 October 2006

Helicodiscus parallelus revisited

Hparallelus1

This is the land snail species Thomas Say described twice under different names, the first time as Helix lineata and the second time as a freshwater snail with the name Planorbis parallelus. I already discussed this in a previous post.

Hparallelus2Here is a live Helicodiscus parallelus I found in Belt Woods recently. The diameter of this snail's shell was 3 mm. As Pilsbry, citing E.S. Morse, noted in Land Mollusca of North America (1948), H. parallelus is "blind" in that it doesn't have visible eye spots at the tips of its upper tentacles.

Say didn't give figures of his specimens. I don't know if anyone published figures of this species before Amos Binney did, as Helix lineata, in 1857 in volume 3 of his Terrestrial Air-Breathing Mollusks of the United States etc. However, Binney's drawing showing the shell from the side doesn't look like a typical H. parallelus. The spire is too high and the aperture is too descending. Compare Binney's drawing, reproduced below, with my photographs of shells here and in my previous post.

BinneyHparallelus2

23 October 2006

Boxcar graffiti XXXII

boxcar32


Index to the Snail's Tales boxcar graffiti pictures

The thing that was crawling up my leg

tick

Yesterday, I did some more exploring and collecting in Belt Woods. A few minutes after I entered the forest, I found this tick on my pants. It was crawling up my leg slowly and deliberately, the way ticks always do, looking for a passage thru my clothing to my skin.

This is a female deer tick (Ixodes scapularis). Although their name suggests that they may be specialized to feed on deer, according to this source, the larvae of this tick feed on a wide variety of mammals and birds, primarily on white-footed mice (Peromyscus leucopus).

Thomas Say described this species in 1821 (full text). He didn't give a type location, but stated that the species was "rather common in forests, and frequently found attached to different animals."

22 October 2006

2 stories about eating pigs

I am not Moslem. But because I am originally from a predominantly Moslem country and because I have a Turkish name, as opposed to, say, a Jewish or Armenian name, people who don't know me (and sometimes those who know me) often assume that I am Moslem. I also eat pig meat occasionally.

Several years ago I had a Palestinian colleague at work who was a devout Moslem. And to my annoyance, he assumed I was one too. One year during Ramadan, he showed up in my office with a Ramadan calendar that he wanted to give me as a gift. I figured it would be rude to reject his gift, but at the same time if I had accepted it would have only reinforced his self-formed opinion about my being a Moslem. And who knows what else he had in mind? I refused the calendar, he insisted that I take it, I refused, he insisted. Finally, he gave up and left.

Some time passed. It was now December and the office was having the annual holiday party. I went to the room where all the good foods where and got in line. The Palestinian guy was next to me in the line. I looked at the table and saw that they had the usual cold cuts of turkey, roast beef and ham. So, I decided to shake this guy up a bit. When it was my turn I announced my culinary choice rather loudly: "I think I will have some ham today!" I noticed the Palestinian guy glancing at me briefly as I was reaching out for the ham. He never bothered me with his calendars again.

In 1842 some Polish refugees were given a small bit of land in the Ottoman Empire to the east of Istanbul, where they erected a village. To this day the village is known as Polonezköy, which means "Polonez Village" and sounds as if the residents are Polynesian rather than Polish.

The village is now a tourist attraction with several good restaurants. Last July when we were in Istanbul, my cousin Mete took me and Tim Pearce there one day for lunch (and for snail collecting afterwards in the surrounding forests). We had been eating Turkish food for 2 weeks, so I wanted to try some Polish food, something that I don't get to eat often. Besides the usual borscht soup, the menu had only 2 Polish sounding entries. The name of one of them also had the word "pork" (spelled as it would be in English) in it. When I inquired about it, the first thing the waiter did was to warn me that it had pig meat in it.

The borscht soup was fine, but the "pig" meat, which was in the form of some sort of stew, was tough and chewy. I didn't quite like it, but finished it nevertheless. Later, when I complained to the waiter about it, he said (in Turkish, of course) "Oh, that's because that wasn't a farm grown pig, that was a wild boar". Apparently wild boars are quite common in the nearby woods and they are hunted down for the Polish restaurants.

I llike good ham, but I don't think I will eat wild boar meat again.

polonezköy
Lunch at Polonezköy. From left: Tim, Mete, Aydin

19 October 2006

Welcome to my neighborhood

MYPLACE2

This is a satellite photo from Google Earth of where I live. The red arrow points to my house. To the north and about a 5-minute walk away is Black Hill Regional Park, my usual prowling ground; diagonally cutting it is a long utility clearing for buried gas(?) pipes. To the west is the northeast tip of Little Seneca Lake, a reservoir created in the early 1980s by damming Little Seneca Creek. The creek itself is obscured by the trees; what is visible is another utility clearing running alongside the creek.

Drop by sometime, we'll go explore the woods.

18 October 2006

Mmm…shit

snailsonpoop1

In his 1934 review of British land mollusks, Boycott discussed their diets and noted that the "partly digested vegetables of rabbit and sheep dung are much appreciated." So he probably would not have been surprised if he had observed with me these mollusks, a Deroceras reticulatum and a Ventridens ligera, feeding on a pile of what was most likely dog poop on a sidewalk late this afternoon.

The sidewalk where I came upon this spectacle was bordered by a forest on one side and a narrow grass strip on the other. The introduced D. reticulatum is quite common around here. They live in backyards of houses, fields and at the edges of forests, whereas the native V. ligera is primarily a forest dweller. In this instance, both species probably came out of the woods, but whether they chanced upon this particular food item while crossing the sidewalk or were attracted to it by its smell, I don't know and I don't intend to carry out experiments to find out.

snailsonpoop2

Interestingly, Chatfield, in her 1976 review of the diets of European snails and slugs, made no mention of them feeding on feces.

A previous post featured an A. subfuscus eating a dead earthworm.

REVISION made 19 October: The original post identified the slug as an Arion subfuscus. Subsequently, Tim Pearce e-mailed me his opinion that the pictured slug can't be an Arion, because its breathing pore is in the back half of the mantle (in Arion the pore would be in the front half of the mantle). He also suggested that it is probably a Deroceras reticulatum. He was correct. I hadn't paid attention to the location of the pore, but instead relied on the slug's color, which is a shade of brown common in A. subfuscus.


Boycott, A.E. 1934. Habitats of land mollusca in Britain. Journal of Ecology 22:1-38.
Chatfield, J.E., 1976. Studies on food and feeding in some European land molluscs. Journal of Conchology 29:5-20.

God is still dead

Last Sunday, 15 October, was philosopher Friedrich Nietzsche’s birthday (in 1844). Nietzsche, one of the most influential thinkers of the last few centuries, is best known for the statement "God is dead" from an 1882 book.

More information on Nietzsche and his works is available at the Stanford Encyclopedia of Philosophy and Wikipedia and Freethought of the Day.

In a brief comment I recently left at Natalie Bennett’s blog Philobiblon, I stated my opinion that the apparent power of religion in the U.S. is more of a manifestation of its “death struggle” than anything else.

Today, Reuters is reporting that several books with atheistic themes have recently been in the best-seller lists in the U.S. (Of course, with the usual and "mandatory" idiotic defense of religion, this time offered by a Timothy Larsen.)

Have we finally come to a turning point?

16 October 2006

Shoveltuskers

While visiting the Delaware Museum of Natural History (DMNH) last Friday, I had a chance for a peek at an exhibit on ice-age mammals that was to open Saturday. Included in the exhibit were remains of mammoths and mastodons, extinct relatives of modern elephants, that lived in North America until the end of the last Ice Age, 10,000 years ago.

Besides the familiar mammoths etc., there was one other group of animals that I had never seen or heard of before: shoveltuskers. The picture below shows the lower jaw of one shoveltusker. Look at the size of that thing relative to the TV screen on the upper lefthand corner.

shoveltusker1
The museum display identified the owner of this fossil jaw as Britt's Shoveltusker (Amebeledon britti)

Unlike the cylindrical tusks of an elephant, the 2 tusks of a shoveltusker were considerably flattened and emerged from the lower jaw next to each other, forming a huge spatula-like structure (see the picture below). What exactly the shoveltuskers did with their peculiar tusks is open to speculation.

shoveltusker2

The exhibit, called TUSKS!, will be at DMNH until 7 January 2007. More info is available at the museum site.

shoveltusker3

15 October 2006

It's a snail eat snail shell world

After almost a year-long break, I resumed my survey of the land snails of Belt Woods, possibly the only tract of old growth forest left in eastern Maryland. (Previous posts on Belt woods are here and here.) The trees in an approximately 45-acre section of Belt Woods are believed to have never been cut. Yesterday, I spent about 3 hours there looking for snails.

Snail shells and the egg shells of most snail species are made out of calcium carbonate. That means that snails need calcium in their diet. In forests of eastern U.S. where there are no limestone or marble rocks and the soil is low in calcium, the snails get some, if not most, of their calcium by eating other snails' shells.

One common species that I have frequently found in the process of eating empty snail shells is Ventridens ligera. I encountered 2 such individuals yesterday. On both occasions, the snails were in damp, loose soil under pieces of wood or tree bark. The first V. ligera (picture below) had consumed most of the body whorl of the partially empty shell of another V. ligera. The red arrows point at the remaining jagged edges of the body whorl.

Vligera3

In the second picture you can see what is left of the shell of another V. ligera covering the aperture of a live V. ligera. The snail was apparently eating the shell from the inside.

Vligera4

As far as I know, V. ligera is not carnivorous. So they wouldn't normally attack other snails, including conspecifics; they probably eat only empty shells or the shells of dead snails.

These observations have 2 implications:

1. Consumption by snails is one of the significant factors that determine the life span of empty shells in areas otherwise low in calcium.

2. Missing sections of snail shells may not necessarily have been the result of a predatory attack, but may instead have resulted from post-mortem consumption by other snails.

13 October 2006

How I survived the flesh-eating beetles on Friday the 13th!

Today I was at the Delaware Museum of Natural History (DMNH) in Wilmington, Delaware. I spent most of my time working in their library. But the highlight of the day was when Jean Woods, the curator of birds, took me to see the "beetle room".

This is where they keep millions of hungry dermestid beetles that could devour an adult human in less than 5 minutes. Well, okay, I am exaggerating a little bit. They use the beetles, especially their larvae, to clean animal carcasses, especially those of birds, so the bones can be added to the museum's collection. The beetles were in a large box that you can see in the picture below.

dermestidbox1

When there are no carcasses that need to be cleaned they feed the beetles dead gulls. There was one in the process of being eaten. So, you can imagine what this room smelled like. Jean was apparently used to it, but I couldn't stand it for more than a few seconds at a time. I kept pretending I had to change the lenses of my camera so I could step outside to get fresh air (this room, although it is attached to the museum building, has a separate entrance that opens directly to the outside).

dermestidbox2

The pictures below show adult dermestid beetles (left) and a larva (right). The largest larva I saw was about 1 cm long.

dermestids

And here are some deer bones that were cleaned by the beetles. They do a pretty good job.

deerbones

So, next time you are visiting DMNH (it is a nice museum, by the way), if you feel like being grossed out, go find Dr. Woods and maybe she will take you to see the flesh-eating beetles...

Here is an old post on dermestid beetles that live in my basement!

11 October 2006

Another beaver dam and a possible beaver print

Whilst exploring the muddy banks* of Little Seneca Lake, I came upon a couple of peculiar prints in the mud. Here is a photo of one.

Beaver print?

Is this the foot print of a beaver (Castor canadensis)? I don't think it is a goose or a duck print, because a bird wouldn't have left such a deep impression, would it?

My suspicion that those prints belonged to a beaver was strengthened about a half an hour later when I literally walked into this beaver dam (yes, I was wading in the creek, looking for snails). The small creek flowing thru the dam is the 10-Mile Creek that empties into Little Seneca Lake near the northwest corner of Black Hill Regional Park in Montgomery County, Maryland.

Beaver Dam across 10-mile Creek

I estimated the length of the dam as 5 m. I will return to check up on the future activities of the beavers. I wonder where their lodge is.

*I guess I should have said "shores", for normally streams have banks, lakes have shores.

Previous posts on beavers and their dams:

Beaver's luck or the lack thereof

A beaver dam

Beaver's dam and lodge

Beaver's dam is no more

10 October 2006

The new English

Whilst deleting some old e-mails this morning, I found one from November 2000 that had this joke in it. It is stil funy (viz apologis to ur German frinds).

To : All members of Her Majesty's Government

In accordance with popular opinion throughout Britain, but to the surprise of some of our foreign neighbours, the commissioners for European Union have recently announced that agreement has been reached to adopt English as the accepted language for European communications rather than German, the other language which had been under consideration. This is seen as a great boost for our country.

As part of the negotiations, Her Majesty's Government did concede that on occasion the English spelling had some room for improvement and a five-year phased plan has been accepted for the introduction of what will become known as EuroEnglish (Euro for short).

In the first year the letter "s" will be used instead of the soft "c". Sertainly, sivil servants will reseive this news with joy. Also the hard "c" will be replased by the letter "k". Not only will this klear up konfusion, but typists akross the kountry will be delighted as keyboards kan have one less letter.

There will be growing publik enthusiasm in the sekond year, when the troublesome "ph" kombination will be replased by the letter "f". This will make words like "fotograf" twenty per sent shorter.

In the third year, publik akseptanse of the new spelling kan be expekted to get to the stage where more komplikated amendments are possible. Governments will enkourage the removal of double letters, as these have always been a deterent to akurate speling. Also, al wil agre, that the horible mes of silent "e"s in the languag is disgrasful and they wil be exterminated.

By the fourth year the new vision wil be klose to fulfilment when the "th" kombination is replasd by the leter "z", "w" is replasd by "v" or "m" depending on sirkumstanses and "qu" by ze easier to pronouns "kv". By zen peopl vil aksept mizout kvestion ze final steps.

During ze fifz year ze unesesary "o" vill be dropd from vords kontaining "ou", and similar zings vud of kors be aplid to ozer kombinations of leters.

By ze end of ze fifz yer ven ze master plan is komplet, al pepol vill be hapy mit zis vay of speaking and riting and ve vil hav a ruzlesly efisiant languag and riten styl. Zer vill be no trubl or difikultis und evrivun vil find it ezi tu understand ozers.

Ze drem vil finaly kum tru and ve kan say mizout kvestion zat ve hav vays of making yu talk.

Boxcar graffiti XXVIII & XXIX

boxcar28


boxcar29


Index to the Snail's Tales boxcar graffiti pictures

09 October 2006

Land snails of Turkey: genus Sprattia

Sprattia is a genus of land snails (family Clausiliidae) endemic to southern Turkey. The genus was named after the British Admiral T. Spratt who visited southern Turkey in the 1840s and collected the snail shells that were later used by the German malacologists Pfeiffer and Boettger to describe many new species and genera (for example: Boettger, O. 1883. On new Clausiliae from the Levant, collected by vice-admiral T. Spratt. Proceedings of Zoological Society, London 324-343.)

At the last revision 8 species were known (Nordsieck, H. 2004. Stuttgarter Beitr. Naturk. Ser. A, Nr. 670:1-28). Without going into a discussion of the taxonomic standings of all those subspecies Nordsieck seems so fond of describing, the map below presents the approximate known range of every taxa.

SprattiaRange
Based on Nordsieck (2004), but color coded for your viewing pleasure. Each small square represents a 10x10 km UTM square.

The ranges of most taxa seem rather small, although further collecting will undoubtedly expand some of the ranges. The apparent gap in the south-center of the map may also be a result of inadequate collecting rather than the scarcity of Sprattia in that area.

What struck me as especially odd is the interjection of the ranges of S. aksoylari and S. sowerbyana sowerbyana in between the 2 subspecies S. beycola beycola and S. beycola medoroides. Did the ancestral "beycola" population break into 2 subspecies after its range was invaded by those 2 species?

In 1997, our Turkish malacologist friend Zeki Yıldırım described S. sowerbyana aksoylari (Yıldırım, M. Z. 1997. Turkish Journal of Zoology, 21:219-221). In his 2004 paper Nordsieck determined that this taxon was a separate species, S. aksoylari.

Zeki and I just published a note concerning the holotype of Sprattia sowerbyana aksoylari. You may download a pdf copy from here.

Sprattia aksoylari
The holotype of Sprattia sowerbyana aksoylari, now at the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania, U.S.A. (CM73333).

07 October 2006

Thursday afternoon in the park

redtaildhawk1

When I first came upon this scene it took me a few seconds before I convinced myself that it was not a person but a big bird "sitting" at the park bench. Although the pictures, taken with the digital zoom of a small camera left much to be desired, a friend was later able to identify the bird as a young red-tailed hawk (Buteo Jamaicensis).

redtaildhawk2The hawk let me approach it a little bit before flying to the top of a nearby tree, where a small—but, brave—bird started harassing it. Eventually, the hawk flew away followed by the small bird.

When I returned to the scene about 15 minutes later, I noticed a group of noisy crows flying from one tall tree to another. I suspected the hawk had come back and the crows were mobbing it. Sure enough, soon I spotted the hawk on a tree surrounded by the crows. I was able to get the picture below before the hawk left the scene again.







redtaildhawk3

Most birds of prey, despite being skillful and feared hunters, never seem to get any peace from the smaller birds. At Words & Pictures, Roger B. mentions having watched a pair of choughs teasing a peregrine falcon. If you haven't the slightest notion what a chough is or how to pronounce it, read his post.

06 October 2006

Friday nite's beer review: Ayinger von Aying

ayinger

What I am enjoying tonite is a reddish-brown, and if that's what the prefix "alt" in "altbairisch" means, top-fermented brew from Aying, Bavaria (the actual color is lighter than it looks in the picture). It has a nice flavor reminiscent of the wheat beers that I have reviewed (Franziskaner and Hefeweizen). Unlike those wheat beers, however, this one is filtered (not that the turbidity bothers me). It is only slightly sweet and there is no bitter aftertaste.

Ein gutes Bier, ja?


Index to the Snail's Tales' Beer Reviews

05 October 2006

Pictures from high above 5: West Gilgo Beach

I am not too fond of flying, but one thing about flying that I do enjoy is the opportunity to take pictures of landmarks from airplane windows and the challenge to try to identify them later.

Here is a shot I took last June as my flight from Washington D.C. was approaching the JFK Airport in New York from the Sea.

WestGilgoBeach

It was easy to find the same place on Google Earth. I rotated the photo from Google Earth (below) so that its orientation is approximately the same as that of my photo. (North is in line with the top edge of the rotated photo.)

googlegilgo

It turns out that this is the town of West Gilgo Beach. The map below is from MapQuest. The red star on the left marks the JFK.

Mapquestgilgo

Finally, I believe those white objects along what appear to be 2 parallel piers towards the center-left of my photo are docked boats. See the enlarged detail below. Curiously, they seem to be missing in the Google photo.

boats


Previous pictures from high above:

1. Pentagon
2. Potomac River
3. San Francisco saltworks
4. San Francisco Steinberger Slough

04 October 2006

Goodbye little cloud, we hardly knew you

cloudseries1

Ever since I read The Cloudspotter’s Guide, I have been paying more attention to clouds. Many cumulus clouds, created by warm and moisture-laden air rising over sun-drenched geological features, such a sunny hill, however, have rather short lifespans. They could be hanging there in the sky one moment and gone the next as this series of photos of a tiny cumulus I took a couple of days ago show.

cloudseries2

The entire lifespan of this one was barely 3 minutes. If I had more time I would create a time-lapse video like Henry did over at Webiocosm.

03 October 2006

Withdraw or die!

The intertidal snail Batillaria minima was the subject of a post back in June. Long-time readers of this blog may recall that deep retractibility of land snails into their shells and the resulting conclusion that they build oversized shells have been the subjects of several posts (for example, here).

While photographing B. minima one day last June, I also tested their retractibility into their shells. During that process, I noticed that many snails had repair scars on their body whorls. This observation led to a quick study, which has just been published in No. 14 of Triton, the Journal of the Israel Malacological Society. You can download the pdf version from here.

In summary, the study demonstrated is that some B. minima survive the attacks of a predator, because the snails can withdraw to a position about a quarter of a whorl behind their apertures, which is possible because they have oversized shells. This led to a more general conclusion:

"From an evolutionary point of view, a snail would build an oversized shell only if the protection and other possible advantages offered by such a shell compensate for the extra time, energy and material required to build and maintain it. In B. minima, the vital antipredatory function of the oversized shell provides the necessary
compensation."


Note: Some time after I submitted this manuscript, I found a paper (Dudley, Nautilus, 94:162-164, 1980) about the comparison of the frequencies of repair scars on B. minima and Cerithium lutosum. The paper did not discuss retractibility.

02 October 2006

Throw food!

snappintrtl

I photographed this large snapping turtle (Chelydra serpentina) in the C&O Canal last June. It was floating next to the bank of the canal with its mouth open, probably hoping that one of the plump kids watching him would slip and fall into its jaws. Un/Fortunately, that didn't happen.

Once I was swimming cross turtle creek
Man them snappers all around my feet
Sure was hard swimming cross that thing
with both hands holding my ding-a-ling-a-ling

Chuck Berry, My Ding-A-Ling