Monthly Archives: May 2011

Photo of the day (122): Drymaeus

Michal Minas commented on a previous post (# 121) with a link to this picture of a Drymaeus species, taken at Uxmal, Yucat??n, Mexico. It is probably D. serperastrus (Say, 1830).

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The picture was made by Maximilian Paradiz and posted in a Photostream on Flickr containing mostly pictures of amphibian and reptiles (http://bit.ly/lM4gVx). One of which is this snail eating snake (Sibon sanniola (Cope, 1866), the Yucat??n snail-eater or Pygmee snail-sucker), which I now add to my list of snail predators.
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New paper

Today a new paper was published. It is entitled “Annotated type catalogue of the Orthalicoidea (Mollusca, Gastropoda) in the Royal Belgian Institute of Sciences, Brussels, with descriptions of two new species”, and was published in Issue 101 of ZooKeys. URL: http://bit.ly/k6UBuR  doi: 10.3897/zookeys.101.1133

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The abstract reads:
The type status is described of 57 taxa from the superfamily Orthalicoidea in the collection of the Brussels museum. Two new species are described: Stenostylus perturbatus spec. nov., and Suniellus adriani spec. nov. A new lectotype is designated for Thaumastus alausiensis Cousin, 1887. New combinations are: Bostryx borellii (Ancey, 1897); Bostryx carandaitensis (Preston, 1907); Protoglyptus mazei (Crosse, 1874); Kuschelenia (Vermiculatus) sanborni (Haas, 1947). New synonymies are established for the following nominal taxa: Orphnus thompsoni var. lutea Cousin, 1887 = Kara thompsonii (Pfeiffer, 1845); Orphnus thompsoni var. nigricans Cousin, 1887 = Kara thompsonii (Pfeiffer, 1845); Thaumastus nystianus var. nigricans Cousin, 1887 = Drymaeus (Drymaeus) nystianus (Pfeiffer, 1853); Orphnus thompsoni var. olivacea Cousin, 1887 = Kara thompsonii (Pfeiffer, 1845); Orphnus thompsoni var. zebra Cousin, 1887 = Kara thompsonii (Pfeiffer, 1845). 

Furthermore it it is interest that the complete collection of Cousin was rediscovered, which is an important historical source for land and freshwater molluscs from Ecuador.

A garden as laboratory

Wonderful to have your own backyard as laboratory. Gerard van Buurt’s garden acts as one, now he recently transplanted there some specimens of Drymaeus elongatus.

Today he sent me some pictures of a specimen on a cactus. In the first picture you can clearly see that there are several patches (of lichen? fungi?) growing on the plant. 

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In the second picture (taken the next day) you can see within the red circle signs of what might be attributed to snail grazing. 

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The real challenge would be to see the snail actually eating, but this animal seems to be truly nocturnal. Even in a backyard’s laboratory that may be a bit of a stretch for the voluntary observer…

Thanks Gerard, for sharing these pictures.

Metrics

For those people who love metrics (and there are definitely more metrics lovers now than e.g. 30 years ago), there is a website who provides an interactive graphical interface of all names published in Zoological Record (http://bit.ly/iVILER). You can choose to display new (sub)species named in any specific year, up to higher taxa, while at the same time you can choose on the left-hand side in the screen any taxonomic group down to superfamily level.

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Apparently 1975 and 2010 have been very productive years in malacology, in this case for the Stylommatophora.But, hey… let me check something I have some knowledge of. Selecting the Orthalicoidea as group to display, the number of new taxa in 1975 still is very high. And I can assure you, it wasn’t me who is behind this number… Actually, I don’t think it was a remarkably productive year for Orthalicoid papers either. Perhaps it is linked to the definition of Orthalicoidea, which admittedly have changed a bit (and probably will do so in the years to come)… Anyway, I have no clue where these 329 new (sub)species come from.

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Fieldwork Peru (8)

Marjan van Hulsel is back from Peru and spent two days in Leiden to discuss her observations.

Without any analyses of the material, it is clear that the following preliminary conclusions can be reached:
– In Laraos region, the ‘cork-skrew’ shells were only observed on a South-facing slope  exposed to the winds blowing up the Río Cañete valley.
– Two Bostryx species exhibiting these morphs we found allopatrically on this slope; B. imeldae was only present on the upper part, B. zilchi on the lower part of the slope.
– in Tembladera region, carinated and ‘normal’ Scutalus species were found sympatrically, which relatively few hybrid specimens mixed.
– in the area where both species were most abundant, S. baroni was relatively more frequent on the upper part of the slope, and S. cretaceus relatively more frequent on the lower part.

Further analyses of the many data collected may start to give some clues on this phenomenon, but undoubtedly will also present more questions.

Some other observations:

Some shells showed probably signs by predation. However, no actual predation was observed and it remains unknown what animal may have caused this. BTW: note the thick mucus remnants on spots where snails possibly have been inactive for prolonged periods.
Scutalus species not only occur here on the rocks, but also on trees and cacti. This movie  shows that they can reach heights which are usually associated with arboreal snails. The highest altitude above the ground where Marjan observed a Scutalus cretaceus was 5 m!
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Finally, some pictures of snails; the longer you look, the more you see…

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Snail food

A recent mail thread with Gerard van Buurt set me on the track of the food of snails. Particularly, Gerard was wondering what Drymaeus elongatus might be eating, observing it on the stems of Guaiacum officinale in his garden in Willemstad, Cura??ao. Since on these stems no fungi or lichens are visible – known as snail food – we tried to find any literature reference to Orthalicoid snail food based on field observations.

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A reference to Tardigrada (see http://bit.ly/ma0dXx; Glime, 2010) in the faeces of Bulimulus guadalupensis made us wondering to what extent these water bears may contribute to the food of snails. The reference appeared to be a description of a new species of Tardigrades, which happened to be found alive in the faeces of this Bulimulus species in San Juan, Puerto Rico (Fox & Garcia-Moll, 1962); only 2.1% of the specimens was reported as infected by this water bear species, and we concluded that this is probably insignificant as food source, although Fox & Garcia-Moll state that “Tardigrades were found in snail feces at will in 1953, 1959, 1960 and 1961, which argues against the idea of occasional fortuitous occurrence”. 

Regarding other Drymaeus species, I could only find a summary in Bledsoe (1977), summarising literature research on D. dormani, and reporting that no lichens were eaten but “a possibility that the snails may eat the spore normally found on the tree trunk”.

That leaves us with bewildering little hard data on the food of these animals. And the quest for more field observations.

References:
Bledsoe, M.E., 1977. Biological studies on the citrus tree snail Drymaeus dormani (Binney), and the citrus rust mite Phyllocoptruta oleivora (Ashmead), as well as the effect of different acaricides on the citrus rust mite. Ph.D. thesis, University of Florida. Available at http://bit.ly/m15XOw
Fox, I. & Garcia-Moll, I., 1961. Echiniscus molluscorum, new Tardigrade from the feces of the land snail Bulimulus exilis (Gmelin) in Perto Rico (Tardigrada: Scutechiniscidae) – Journal of Parasitology 48: 177-181.
Glime, J.M., 2010. Bryophyte ecology, vol. 2. Chapter 5-2. Tardigrades reproduction and food. Michigan Technological University, available online at http://bit.ly/jqGvh9 (accessed 14 May 2011).