Monthly Archives: July 2011

Project Noah

Project Noah stands for Networked organisms and habitats. It is meant as a tool that you can use to explore and document wildlife and harness the power of citizens scientists. See for more details on what how to can participate.

Looking up ‘snail’ under Organisms I found this picture taken at Ecuador, Loja of a transparent shell, seemingly a shell-less snail. Very peculiar! Being so transparent, it’s hard to identify it other than “Helix-like” which is as good as a shot in the dark.
Another one is this ‘Blue Rainforest Snail’ (my own words) from Costa Rica, Lim??n Prov.: Drymaeus sulphureus (Pfeiffer, 1857). It’s my favorite on the Project Noah site.
There are a lot of unidentified species on the site and probably most of them have been spotted near rural areas. Still it is a way to raise awareness for the flora and fauna around you and may serve an educational purpose.

Find out more about Project Noah and the behind it at and explore the site. There are apps for your mobile phone available if you want to join in using modern technology.

Conservation status of some Brazilian species

Two recent papers of Ignacio Agudo give details on invasive species and the conservation status of freshwater and terrestrial mollusks in Santa Catarina State, Brazil.

In the first paper, 12 exotic terrestrial molluscs were assessed and nine are considered as invasive species: Pallifera sp., Limacus flavus, Limax maximus, Lehmannia valentiana, Deroceras leave, Lissachatina fulica, Bradybaena similaris, Cornu aspersa, and Zonitoides arboreus. The spatial distribution in the State is presented.

The second paper 19 terrestrial mollusks are listed for the region, of which 7 are according to IUCN Red List criteria should be considered as “Vulnerable” and 6 “In Danger”. The paper discusses the general conservation status and threats to these species. Also freshwater and marine species are included in the listing.

Agudo-Padr??n, I., 2011. Exotic molluscs in Santa Caterine’s State, Southern Brazil region (Mollusca, Gastropoda et Bivalvia): check list and regional spatial distribution knowledge. – Biodiversity Journal 2: 53-58. 
Agudo-Padr??n, I, 2011. Threathened freshwater and terrestrial molluscs of Santa Catarina State, southern Brazil (Mollusca, Gastropoda et Bivalivia): checklist and evaluation of regional threaths. – Biodiversity Journal 2: 59-66.


Ten things

Last week Jeff Nekola (Univ. of New Mexico, Albuquerque) gave a seminar at NCB Naturalis, entitled “The ten things every macroecologist should know about land snail biodiversity”. Although based on an extensive survey of more than 1500 North American sites, representing more than 400 taxa (mainly microsnails) and over a half million specimens, the main points of his talk may be inspirational to Neotropical malacologists too.

1. North American faunas are dominated by minute species (< 5 mm dimensions)
More than half of the taxa and over 80% of the individuals found in his survey belonged to these truly ‘micro-snails’. Comparative data about Neotropical faunas are largely unknown, but my guess is that the trend could be the same. This would imply that much taxonomic work still needs to be done focussing on micro-snails.
2. Community composition is largely related to soil architecture and moisture
The majority of taxa had a clear preference for either a ‘duff’ or a ‘turf’ habitat. In the former the grass roots layer is limiting the distribution of snails, in the turf habitat the moisture plays an important role. In the Neotropics, the macro-snails are only partially soil-based (e.g. Bulimulus) and arboreal species may be regulated by other factors than soil moisture. 
3. Acidic habitats are an important biodiversity reservoir
More than half of the North American species has been observed in at least one acidic site. Thus, contrary to intuitive ideas, snails may also be encountered in acidic habitats. They are usually under-sampled and may appear rare.
A nice example of this phenomenon are the snails from Venezuelan tepuis. It is likely that under such conditions snails use plants as their main calcium source.
4. Land snail species coexist at very small spatial scales
Even a small quadrat usually holds a significant percentage of the total land snail richness. A consequence of high levels of microsympatry is that land snails often have exceedingly high intercept and low slopes to their Species Area Curves.
A notion during the discussion was that snail occurrence can be very patchy, one you have found the spots where they flourish you may easily find them.
5. Communities display extraordinary levels of eveness
This organizing principle can be illustrated with dominance-diversity curves from closed-canopy forests.

6. Composition along environmental gradients becomes more similar to the north
Regional species richness varies with latitude and may be deconstructed into four categories: Alpha (within site), Beta (additional species found only in different habitat), Gamma (additional species found only in other examples of the same habitat), Beta/Gamma (additional species found only in both the same and different habitat types in region). Alpha increases with latitude, Beta decreases, and the geographic turnover (Gamma + Beta/Gamma) again increases with latitude.
My gut feeling says it is roughly the same for Neotropics, but this is clearly a topic for any interested ecologist.
7. Body size range tends to decrease with increasing latitude
Large species increase in abundance towards the equator. Of the areas investigated North America show a decrease of smallest species towards the pole, while these increase in Europe and New Zealand.
In the Neotropics small shelled species probably also become more abundant towards the pole, as relatively larger species drop off.
8. Range size is inversely correlated with body size
The most likely explanation is that small snails are much more likely to uniparentally reproduce and to be passively dispersed by birds, mammals, and wind, compared to larger species. 
9. Species richness and abundance are decoupled at regional and continental scales
At regional scales and above, more large species and fewer small species exist than is expected from the number of individuals alone. The decoupling of richness and abundance across the body size spectrum becomes more pronounced with decreasing latitude.
10. Speciation may be driven by global – not local – factors
Phylogenetic research of Vertiginidae lead to the insight that phylogenies are not geographically segregated; Eurasian species are no more divergent from North American species than North American species are from each other. Species-level branch-lengths appear to be inversely correlated with latitude. An analysis of diversification rates showed an remarkable increase around 7 myBP, which may be correlated with a global shift from C3 to C4 grasses.

This was a very insightful seminar and inspirational at the same time.

New papers

Today two new papers were published in Basteria. One is an addition to the Bibliography of Cuban terrestrial Mollusca that was published last year. The other is the introduction of a replacement name for a Helicina species that was described from Colombia in 1977.

Further details may be found on the Publications page on my Snail Site (link above).


CLAMA summary

Roberto Cipriani, President of the Asociaci??n Latinoamericana de Malacolog??a (ALM), has sent around a brief summary of the Congress. 

The conclusions of the seven official symposia held during the congress have not been added; however, it may be that some of them may follow in a later stage. 
The next CLAMA congress will be in Mexico, M??rida in 2014. 

Determinanda (4): Helicarionidae (?)

Another picture similar to the last one in this series and one first inspection it may be confused. Both species have a caudal horn, but this is a distinctive morphological characteristic for different genera. Communis opinio among the persons consulted was this could be a member of the Helicarionidae. This is an Asian family and one would think it may have been introduced; however, Adrián González spotted this snail in northern Ecuador in primary forest. So frankly, we don’t have a clue yet what it is.

In general, microsnails from northern South America are ill-studied and it seems that nobody has closely looked to these groups since Horace Burrington Baker in the 1920s, when he mainly published on material from northern Venezuela.


Snail dispersal by birds

There have been some previous reports on snail dispersal suggested by means of birds (e.g. Gittenberger et al., 2006). Now Japanese biologists have studied the survival rate of snails digested by birds and found a surprising 15% for the micro-snail Tornatellides boeningi (Wada et al., 2011). In this case they explain the dispersal of this snail within an isolated island in the Ogawasama group in the western Pacific.

It may be noticed that the example of Wada et al. relates to micro-snails. If larger species are at stake, it would be more likely that only juveniles may be digested. Hence the rate of success during the establishing phase after a successful dispersal is expected to be lower than in the case of adults, as the juveniles first need to mature before they start to reproduce.

However, this is an interesting result as it could explain long distance dispersal and establishment (LDDE) events more easily. Of course this will be related to the migration route of birds, the speed of flying and the duration of the passage in the digestive channel of the birds. In the case described by Wada et al., the snails were evacuated 30-40 minutes after digestion, which makes the distance a bird can travel meanwhile rather limited. The alternative to explain longer distances seem to be attachment of egg capsules to bird legs.

It is all a matter of chance, but if time is long enough chances for such events are more than zero.

Cadée (1988, 2011) described estuarine species (Hydrobia ulvae) passing the digestive system of waterfowl. This is an operculate species, but the reported survival rate is similar to Tornatellides: 13-16%. 
Cadée, G.C., 1988. Levende wadslakjes in bergeend faeces. – Correspondentieblad Nederlandse Malacologische Vereniging 234/244: 443-444.
Cadée, G.C., 2011. Hydrobia as “Jonah in the whale”: shell repair after passing through the digestive tract of shelducks alive. – Palaois 26: 245-249.
Gittenberger, E., Groenenberg, D.S.J., Kokshoorn, B. & Preece, R.C., 2006. Molecular trails from hitch-hiking snails. – Nature 439: 409.
Wada, S., Kawakami, K. & Chiba, S., 2011. Snails can survive passage through a bird’s digestive system. – Journal of Biogeography (Early View; doi:10.1111/j.1365-2699.2011.02559.x).