28 June 2010

Truncatella subcylindrica, I presume

One of the coastal snail species I was able to find yesterday at a rocky beach on the western coast of Turkey near Çeşme was this Truncatella subcylindrica. As far as I know one species of Truncatella exists in the entire Mediterranean and it is this species. The range of the species extends all the way north to the southern coast of England.


It's not a very good picture, but you can see the snail's snout, 2 short tentacles and eyes as well as the yellow operculum at the top of the back of its foot. The shell of the snail is only about 4 mm long.

25 June 2010

Lindholmiola lens after the rain

It is unusual to encounter active snails during the summer months in western Turkey. The normally hot and dry Mediterranean summer rules out all land snail activities that involve the protruding of a snail's body outside its shell. But last Wednesday, a violent thunderstorm and a subsequent day long rain drenched the soil enough to activate at least some of the snails temporarily. In fact, I found this Lindholmiola lens and another one crawling under a rock on damp soil the next day.


This is a common and often abundant land snail species in western Turkey. It also seems to be more opportunistic than others when it comes to taking advantage of sudden and unexpected weather events.

20 June 2010

Island snails

Since about 2000, we’ve been surveying the land snails of a group of small islands in Turkey. In preparation for my current trip there, recently I tallied up the species we have so far collected. Here is a graph showing the number of species found on each island as a function of island surface area (km2).

These types of graphs are customarily done using log units, but our data come closer to a straight line when plotted in ordinary numbers. Island C is clearly an outlier. The main reason for the smaller than expected number of species on island C is probably that I was the only one who collected there on one occasion, while at least 2 people have collected on each of the other islands on multiple occasions.

Revisiting island C to add 4 or 5 more species to its snail fauna is on top of my list of things to do in Turkey.

14 June 2010

A shrimp that looks like a snail shell

A tiny shrimp, Vercoia interrupta, only about 6 or 7 mm long, seems to have evolved to resemble a snail shell in its superficial, external appearance (Anker, 2010).

Photo of live Vercoia interrupta (by Guido Poppe) from Anker (2010).

Anker notes that the shrimp “remarkably resembles a dead and encrusted cerithiid shell, more specifically that of Cerithium rostratum G.B. Sowerby II, 1855, which is common in the area”. New sightings of this species, previously known only from southern Japan, come from the central Philippines.

Thanks to the reader Andrew Broome for bringing this paper to my attention.

Anker, A. 2010. A second finding of Vercoia interrupta Kim & Fujita, 2004 (Crustacea, Decapoda, Crangonidae), a remarkable shrimp imitating dead snail shells. Raffles Bulletin of Zoology 58:27-30. pdf

13 June 2010

Second tick of the year refuses to let go

I pulled, the little sucker hung on. Look how it was lifting my skin up. It must have really liked my blood. Eventually I prevailed and got it out. And in the process I squished the life out of it. But here it is gorging itself with its mouth buried deep inside my skin moments before death came from above in the form of a pair of blue tweezers.

It was yet another deer tick (Ixodes scapularis). Here was the 1st tick of the year.

11 June 2010

Alas, no coitus tonight

Imagine my surprise and delight yesterday morning when, while looking for slugs, I instead came upon a Bipalium adventitium crawling about on the wet trunk of a beech.

This was near the spot where I had found another one of these land planarians in May 2009. Obviously, these planarians, which are believed to have been introduced to North America from eastern Asia, have established themselves in the wild and are here to stay.

After taking a few pictures of the planarian, I put it in a container and brought it home. This morning I put it and the one I've been keeping since last September in a wet petri dish. The planarians in the genus Bipalium are known to mate1, that is reproduce sexually, and then produce cocoons containing offspring. However, not much seems to have been published about their reproductive biology. So I was hoping to gain some carnal knowledge from these slimy beasts.

After almost 12 hours of confinement and numerous encounters, I don't think the 2 have mated yet. One problem is I don't quite know how I can tell when 2 planarians are mating. And how long does their mating last? There were several occasions when the 2 were on top of each other, but I didn't notice anything unusual that would have indicated they were copulating.

But at least they seemed to be enjoying each other's company, if they have such feelings.

Observations will continue and updates may be posted.

1Ogren & Sheldon. 1991. Ecological observations on the land planarian Bipalium pennsylvanicum...Proc. Penn. Acad. Sci. 65:3-9.

10 June 2010

Do Cochlicopa lubrica aggregate?

This is the 4th post in this series about the snails, Cochlicopa lubrica, on my garage door. As long as the snails are there, I will write about them.

The question I have had in my mind is this: is the distribution of the snails on the garage door random or is there a tendency of them to be near each other, in other words, to aggregate?

What is meant by aggregation could be tricky to conceptualize. My garage door is 240 cm long and 210 cm high. If there were 1000 snails on it, they would have no choice but to aggregate to some extent. On the other hand, the distribution of 1000 snails placed randomly on the garage door could be distinguished by using appropriate statistical tests from that of the same number of snails piled on top of each other in one corner. In the 1st instance, there would be no aggregation; in the 2nd instance, there would indeed be aggregation.

So, on 2 occasions within the last 12 days, I have measured the location of each dormant Cochlicopa lubrica on my garage door*. Because I also marked the location of each snail with a number, I know that each snail moved between the 2 sets of measurements. Therefore, there were no duplicate measurements. However, one problem I have is that there aren't that many snails on the garage door; during the 1st set of measurements, there were 36 snails and during the 2nd set 24. Therefore, unless the snails have a very strong tendency to stay close to each other, it may be difficult to see clear spatial patterns. Here are 3 of the snails I photographed tonight. Was their distribution random or not?

I don't have time to run any statistical tests tonight. But here is one simple analysis of the combined data from 2 days. This graph shows the distributions of the heights of the snails above the ground (in 20 cm increments).

Most snails remain below 120 cm. I don't know why they tend not to climb higher. This tendency to stay close to the ground increases their chances of being near each other or their chances of aggregating.

To be continued...

Part 3 was here.

*No, I didn't have anything better to do with my time. Besides, I was having fun.

08 June 2010

A mute and a dwarf

Thank you Vasha!

07 June 2010

Starchy feast in the backyard

Here is a picture of several slugs and one isopod feeding on a slice of stale bread discarded in the backyard several nights ago following a rainstorm.

The slugs were probably Arion subfuscus, while the isopod may have been Philoscia muscorum. Meanwhile, a Limax maximus was making a meal of another piece of bread.

This is one way to get rid of the kitchen waste. But disposal via gastropods is slow; several days later today, the bread slices were still there with only small chunks missing.

06 June 2010

Bunny Rabbit Lawn Care, Inc.

After the brief but intense thunderstorm came and left early this afternoon, this little rabbit appeared on our front yard. I grabbed my camera, slowly opened the front door, stepped partially out and started photographing it as it was munching away.

Initially I assumed the rabbit would prefer the miscellaneous weeds, including clover and dandelion, that outnumber the regular grass throughout the lawn.

But a closer examinations of the photos later showed that it was actually eating grass stalks. You can see one sticking out of its mouth in the next photo.

As long as it is eating whatever is growing in the lawn and keeping everything short, I am not complaining.

04 June 2010

The earthworm that didn't get eaten while getting eaten

The terrestrial planarian Bipalium adventitium that has been the star of several posts since September 2009 and which also provided enough experimental data for a note in Tentacle #18 is still alive and well. I have no idea when it was born. I found it near the end of September; it is now at least about 8 months old. I also don't know how long the natural average lifespan of this species is. I feed it an earthworm about once a month. I also don't know how often and how much it would eat in the wild. Maybe may feeding regime is sort of a dietary restriction that is extending the planarian's life.

Anyway, the other day I put a small earthworm in the planarian's container, closed the lid and left. About a half an hour later when I returned, I saw the worm crawling on the dead leaves covering the bottom of the container. But it looked strange: it was shorter and its posterior end ended rather abruptly instead of being pointed the usual way.

The planarian, on the other hand, was in a corner with its pharynx everted over an earthworm that it was in the process of consuming. So what seems to have happened was this: the planarian had seized the worm, but the latter apparently amputated its back half and crawled away, while the less fortunate half became food for the planarian.

The pinkish segment under and to the left of the planarian's head is a piece of the earthworm and the whitish tissue on the left covering what seems to be the rest of the worm is the planarian's everted pharynx.

The worm survived the predator's attack by letting a part of itself get eaten. After I realized it was a true survivor, I returned the worm to the yard whence it had come. Hopefully, it has regenerated its missing half and will soon be passing on its good genes to its offspring.

This is part 6 in this series of posts about Bipalium adventitium.

03 June 2010

Apex down or apex up—that is the question

One citation led to another and the terminal find was a 1918 paper from Science titled "Concerted behavior of terrestrial mollusks" by someone named T. C. Stephens. The subject was the snail Cochlicopa lubrica of which the author had collected 125 dormant individuals from the door of a laboratory building in Iowa. The author summarized his findings and conclusions thus:

...all exhibited precisely the same orientation, viz., the apex of the shell pointed downward...It seemed to the vriter that so many of these snails being found together, and with similar orientation, was a fact inviting explanation, which, however, he is unable to furnish...And while I am unable to explain the behavior of these snails, I am inclined to look upon it as a sort of concerted action.
There are 2 separate questions here: 1. Why do some species of snails aggregate? 2. Why do snails always have their apexes pointing down (or apertures pointing up) when they become dormant on a vertical or near vertical surface? As far as I know, orientation with the apex down is not specific to Cochlicopa lubrica and is displayed by all snail species regardless of shell shape (tall or wide).

To make sure things hadn't changed since Stephens' observations in 1915, I went out this afternoon and examined the Cochlicopa lubrica that have been dormant on my garage door. All 27 snails I could see had their apexes pointing down. Some snails were more or less vertical (for example, #20), while others were tilted (for example, #32), but with their apexes always below their apertures. Here are the 2 examples.

After all these years, we still don't know why some snail species tend to aggregate (there are probably multiple reasons). But I can offer an answer to the 2nd question. The pull of the gravity probably has something to do with the orientation of a snail on a surface. If a snail were dormant with its shell pointing up parallel to a vertical surface, the shell would have a tendency to flip down. This would either break the seal between the aperture and the wall and the snail would fall off or the snail would have to spend energy to keep its shell pointing up. Therefore, on a vertical surface, the apex-down orientation seems to be more natural and more economical than the opposite orientation. It follows that in the absence of gravity the orientations of dormant snails on a vertical surface should be random.

Part 4 in this series is here.

02 June 2010

Helix cornea and other taxonomic headaches from 111 years ago

I spent about an hour today synonymizing 2 lists of land snail species that had been collected in western Turkey in 1899. I didn't actually attempt to come up with a synonymy for each species; I only wanted to know what species the author of the paper had collected. The problem was that the author apparently didn't have much experience with the species of his study area. So his lists are peculiar mixtures of those species expected from the area and those that are not.

For example, one recorded species was Vitrea koutaisiana Mousson, now called Oxychilus koutaisianus and known only from northeast Turkey. It is possible that the range of the species was wider 100 years ago. But the more likely explanation is that a similar species common in the author's study area in western Turkey, possibly O. cyprius, was misidentified.

Another example was Clausilia messenica now known as Albinaria nivea. According to AnimalBase, A. nivea lives in the Pelopónisos region of Greece, but not in Turkey. There are 3 Albinaria species that are presently known from the study area. Which of those did the author find? The only way to find out is to go the same location and search for snails, which is something I intend to do this summer.

Sometimes taxa that were thought to be separate species in the past are now lumped under one name. For example, among the species listed by the author were H. virgata and H. variabilis, which are now considered to be synonyms with the former being the primary one.

As taxonomists continuously refine their understanding of the evolutionary relationships between different taxa, species get shuffled around between genera and consequently, their accepted names change. Only a small fraction of the names given to newly described species in the 18th and 19th centuries still remain in use. The only 2 examples from the lists I was working with are the snail species Linnaeus called Helix lucorum and Helix pomatia in 1758. They still go by those names, although the latter does not live in Turkey. Another case of geographically misplaced misidentification. But what was the 2nd Helix species the author had?

One troublesome name in one of the lists is Helix cornea. Again, according to AnimalBase, there have been 2 taxa by that name. One is a terrestrial species Draparnaud described from France in 1801 and which is currently not referrable to a known species. The other is the freshwater species now known as Planorbarius corneus (Linnæus, 1758). Which one did the author find? He provides a clue: the snails were attached to the plants growing in the fields. Therefore, they were land snails. But what on earth was the terrestrial Helix cornea?