Nomenclature explained

Incidentally I found on the net a very useful document, explaining the use of biological (i.e. zoological) names and also of relevant articles in the ICZN Code.

Even those who are familiar with the Code can find bits of information that are enlightening. Personally I was happy to see a further explanation of Art. 11.6 which rules the names published as junior synonym (p. 68-69). As Francisco Welter-Schultes wrote to me, this is especially for malacologists a hot topic and needs further action from the Commission. But the 5th edition of the Code is only expected in 2020 or later, so in the meantime one has to cope with the situation by trying to keep nomenclature as stabile as possible.

The document can be found at http// or at


Mirror-image snails

It does not occur often, but in some groups mirror-snails do occur. Officially called eniantomorphy, there are several examples in Neotropical land snails (e.g., in Drymaeus and Corona species). Recently Richards et al. have publishe some interesting research on this phenomenon.

Variation in the shell coiling, or chirality, of land snails provides an opportunity to investigate the potential for “single-gene” speciation, because mating between individuals of opposite chirality is believed not possible if the snails mate in a face-to-face position. However, the evidence in support of single-gene speciation is sparse, mostly based upon single-gene mitochondrial studies and patterns of chiral variation between species. Previously, we used a theoretical model to show that as the chiral phenotype of offspring is determined by the maternal genotype, occasional chiral reversals may take place and enable gene flow between mirror image morphs, preventing speciation. Here, we show empirically that there is recent or ongoing gene flow between the different chiral types of Japanese Euhadra species. We also report evidence of mating between mirror-image morphs, directly showing the potential for gene flow. Thus, theoretical models are suggestive of gene flow between oppositely coiled snails, and our empirical study shows that they can mate and that there is gene flow in Euhadra. More than a single gene is required before chiral variation in shell coiling can be considered to have created a new species”.

This study of Japanese snails suggested that the mirror-images might be one species, which has implications for classification. Unfortunately, the situation with Neotropical left- and right-hand snails is less clear; while in some Corona species samples with both dextral and sinistral specimens are known, this is not the case in Drymaeus species. Thus in the latter case we even do not know which species might be siblings and potentially one and the same. This is a challenge for future (field) work!

Richards, P.M. et al., 2017. Single-gene speciation: Mating and gene flow between mirror-image snails. Evolution Letters, (advance online) DOI:10.1002/evl3.31

Dutch Caribbean Species Register

Just launched: a website which contain data on the biodiversity of the Dutch Caribbean, including – of course – the snails…

The announcement read:

‘For the first time ever, we present a complete overview of the known biodiversity (animals, plants, fungi) from the Dutch Caribbean: over 7.500 species. This online database is the result of an effort of Naturalis Biodiversity Center – the biodiversity research center and Dutch national natural history museum- to gather all relevant publications on the biodiversity and natural history of the six islands of the Dutch Caribbean: Aruba, Bonaire, Curaçao, Saba, Sint Eustatius and Sint Maarten.

We expect the species database to grow over the coming years, as Naturalis processes the results of recent expedition to e.g. Sint Eustatius, during which several species new to science were discovered.

The database contains a wide variety of information. This includes, but is not limited to: literature references, presence status per island, photos, common/local names and habitats. The checklist can be searched and filtered in several ways and can also be navigated through a taxonomic tree. Furthermore, the checklist is illustrated by a growing photo archive of over 2.000 photos of nearly 10% of the species.

Do you want to participate? We are looking for volunteer photographers with material from the area and people with knowledge of species occurring in the area. All photos and species information is validated before being published. Interested in contributing? Drop us a line at

We hope the Dutch Caribbean Species Register will prove to be a useful tool for nature conservation and biodiversity research in the Dutch Caribbean!’

Just a sample page of a snail species:

Note that you search in different ways and there are several outgoing links which you can further explore.

Deroceras in Mexico

Just published a paper by Araiza-Gómez et al. on the distribution in Mexico and phylogeny of three Deroceras species.

“This study reports the current distribution in Mexico of Deroceras laeve (Müller, 1774) and D. invadens Reise, Hutchinson, Schunack and Schlitt, 2011, both previously recorded, and the first records of D. reticulatum (Müller, 1774) in this country. The taxonomic identifications were made on the basis of morphology and DNA sequences of a fragment of the cytochrome oxidase I gene. A phylogenetic analysis by maximum likelihood was carried out in order to support the identification and to explore the association of Mexican specimens. D. reticulatum and D. invadens appear restricted to the central portion of the country while D. laeve is widely distributed. Due to the invasive and pest character of these species, it is important to know their distribution in the country and the possible risk to native fauna and crops”.

Schermafbeelding 2017-11-20 om 15.58.36

This study used only the CO1 marker and suggests that for D. laeve three subgroups may be distinguished. Further studies using other markers and phylogeographical analyses are suggested in the discussion.

Araiza-Gómez, V. et al., 2017. The exotic slugs of the genus Deroceras (Agriolimacidae) in Mexico: Morphological and molecular characterization, and new data on their distribution. – American Malacological Bulletin, 35(2): 126-133.


This cryptic code refers to the paper ‘World Scientists’ Warning to Humanity: A Second Notice’ that appeared yesterday in BioScience.

The authors have been able to mobilise more than 15,000 scientists from 184 countries across the world to endorse this paper, which gives a brief summary of major trends since the first ‘Warning’ in 1992. Still a lot remains to do, and civil-society pressure and evidence-based advocacy is needed to push (political and societal) leadership into sustainability transitions.


Any scientist that did not sign the article before the BioScience publication deadline, is invited to endorse it now after publication by visiting ( Therefore, feel free to invite any of your scientist contacts to join in now by signing the article.

The voice of world scientists is essential in driving forward progress on dealing with climate change and other critical environmental trends. Working together, we can make great progress in preserving the biosphere for the sake of humanity.


New paper

Recently pressed: a new publication on the tautonyms used by Jousseaume when describing new taxa.

We present a short biography of Félix-Pierre Jousseaume (12 April 1835-3 November 1921) and an addition to his bibliography. He published in total 138 malacological and 21 non-malacological articles or books. In the appendix additional references are listed in comparison with an earlier published preliminary bibliography. Jousseaume received many comments from other malacologists, especially for his tautonyms. Critical remarks from Weinkauff, Tryon, Woodward and Mellvill, and one comment from Jousseaume, are cited.

In total Jousseaume published 28 new species-level taxa as primary, absolute taunonyms (new genus and new species) and 24 secondary ones (22 with a new genus and 2 with a new species name). The virtual tautonyms (with almost identical genus and species names) are not discussed. However, for four taxa of Jousseaume it is unclear if the taxon is a tautonym or a virtual tautonym. In our view the problems were caused by carelessness of Jousseaume. These four taxa are discussed extensively and a conclusion is presented on the correct name. The results are shown in the tables with the original name (invariably the tautonym), source of the original name, and the present view on the taxon with the source and (explanatory) remarks”.

We already received a comment by a colleague who indicated that if Jousseaume intended a tautonym, the correct name should be the tautonym. However, the ICZN Code rules what constitutes a published name and is very strict in allowing an ‘author lapsus’. But we confess we made an oversight and published an ‘a’ where it should have been an ‘e’. As usual in taxonomy the devil is in the details…

Gemert, L.J. van & Breure, A.S.H., 2017. The tautonyms of Jousseaume: a taxonomical study. – Folia conchyliologica, 43: 10-19.

Montagu types

Oliver et al. have just published an impressive paper dealing with re-located type material of Colonel George Montagu (1753-1815).

“A complete list of new molluscan taxa introduced by Col. George Montagu (1753–1815) is presented. The available type material of these taxa are itemised and illustrated. The majority are present in the Royal Albert Memorial Museum & Art Gallery, Exeter with a smaller number in the Natural History Museum, London. The historic background of both collections is reviewed with special reference to the many non-British species spuriously introduced into Testacea Britannica and its Supplement”.

I know that locating historical collections doesn’t sound like rocket-science. but in our discipline where ‘every name counts’ it is really very helpful to have type material from our deceased colleagues available for study. And, of course, the further back in time the more difficult it becomes to locate this material and track its provenance.

In the paper also some Neotropical material turned up, quite unexpected for someone who worked on ‘Testacea Britannica’ (i.c. British shells)!

Here is his Helix detrita Montagu, 1803 not Müller, 1774. It proved to be a specimen of Drymaeus elongatus (Röding, 1789), a West Indian species…

Finally, it’s worth repeating here the last lines of their paper: “It is sad to report that those with a knowledge of historic conchology are diminising in numbers and that curatorial expertise throughout the museum sector is threatening the value and access of many collections”.

Oliver PG, Morgenroth H, Salvador A (2017) Type specimens of Mollusca described by Col. George Montagu in the Royal Albert Memorial Museum & Art Gallery, Exeter and The Natural History Museum, London. Zoosystematics and Evolution 93(2): 363-412.