R. Kapeller

European Mollusks

Systematic - Description - Distribution - Determination Key - Images - Literature

Motivation

What made me start this project?

Apart from my interest in mollusks, which I am collecting and studying since decades, my passion for nature photography and my enthusiasm for developing computer programs, the fact that I have not yet encountered a really useful, comprehensive identification tool.

Depending on whether they are printed or electronic, they all have at least some of the following disadvantages:

• Incompleteness regarding species covered
  Most determination works are limited to species that are not too rare. Complete determination works are available for limited scopes (concerning classes, habitats, geographical areas) only. This in itself would not be a disadvantage if they would be available for all scopes; but, however, they exist only for a few.
• Missing determination key
  Comprehensive, complete lists of species usually only exist in the form of checklists or databases, which, however, do not contain identification tools. Even fairly complete illustrated books lack one.
• Missing or poor descriptions
  Many identification or pictorial works have no or insufficient descriptions, so that the correctness of the result cannot be verified at the end of the identification process.
• Missing or incomplete images
  The more comprehensive an identification work is, with regard to rarer species, the more incomplete the images usually become.
• Poor quality of the images
  In many cases, the resolution of the images is so limited that important microstructural details for identification cannot be recognized. In the case of printed works in particular, the resolution is naturally limited. Often the lack of orthogonality of the images does not allow the recognition/reading of important biometric data or leads to incorrect conclusions.
• Missing, incomplete or inaccurate data on the distribution
• One-dimensional identification key
  Classic identification keys are mostly one-dimensional, so answering each question is mandatory in order to proceed. If a question cannot be answered unambiguously (e.g. because a characteristic cannot be determined from a particular specimen, or it is right at the borderline between two possible answers), one can easily end up on the wrong track.
• Ambiguous terminology, missing or only rudimentary glossary
  In the course of the identification process, as well as in the descriptions of the species, terms are often used whose meaning is not clear to the user. The correct answer to a question can also fail due to terminological misunderstandings if there is no sufficient glossary. The way of expression is very different, from simple terminology, whereby even with a term that is generally understandable in itself, it is often not clear how it is meant in relation to the object, to specific scientific terms that not only require specific knowledge, but are not always used coherently even in scientific literature.
• Missing Links
  At the end of a identification process, it is essential to verify the result. Even the best descriptions and illustrations are not always sufficient for this reason. In view of the great variability of some species in particular, it is often essential to consult further literature, or to compare with more images. Most determination works, however, lack specific recommendations for further readings. A general reference list, where you cannot see where further information/images on a specific species can be found, is not helpful.

A thorough research on the available works has shown that there are useful identification works for only a small number of limited scopes: for example, the online portal of the NHM WALES [27] for marine bivalves around the British Isles or the web-page of the Stuttgart Natural History Museum [1045] for the mollusks of Germany or the works of Glöer [4][91] for the freshwater mollusks, the latter printed only. The more comprehensive the works become, the more the weaknesses become apparent.

This is of course a very personal view from some decades of collecting and identification work and should in no way be a disparagement of the enormous work that has been done in this area so far. But outside of the scopes mentioned, I have repeatedly found that the identication of a less common species can turn into a laborious search for literature. And that's how the idea for this project came about.

Goals of the Project

The project intends to provide a comprehensive determination tool for European mollusks, avoiding the above mentioned weaknesses as far as possible. In particular:

• A database-based identification key can start from a complete list of species. It may be up to the user to include exotic species (e.g. deep sea forms) in the identification process or not. "Completeness" can, of course, only refer to the species known (published) at a given date. However, the database solution allows an addition of newly discovered species at any time.
• Digitized features, which can be both systematic features (e.g. features of certain families) and unsystematic features (e.g. dimensions, shape, color), allow both a systematic as well as an unsystematic approach, or a combination of both. It is up to the user to answer a question, thereby restricting the remaining taxa, or (in case of doubt) to leave the question unanswered; or to give a fuzzy answer (e.g. answer 2-3 of 7 possible). The more information is given, the further the matching species are cut down.
• The distribution is also included as a digitalized characteristic, so that the matching species can be restricted to those known from the particular locality.
• In many cases, users prefer browsing through a gallery of images instead of answering questions. This possibility should also exist, but with the given scope (e.g. currently 870 species of marine mussels, over 3500 species of marine snails, ...), it is not expedient to do this without any prior reduction. However, answering a few questions usually allows the species to be reduced to a manageable extent. Here, too, the user should be free with regard to the procedure.
• An exact formulation and sufficient explanation of each question is essential for a correct answer. For a better understanding, these are also supported graphically.
• Every term used that is not generally understood should be able to be looked up in a glossary, whereby clicking on the respective term leads directly to its explanation, also graphically supported.
• Particular attention is paid to the quality of the images. What do I mean by the quality of images?
  • Sufficient resolution that all details down to microscopic structures are recognizable
  • Optimized lighting that ensures that the surface texture (e.g. gloss) can be recognized and structures stand out vividly
  • All essential views (e.g. in the case of snails frontal and lateral, as well as dorsal and ventral, as far as this is useful for showing essential characteristics), in each case in an exactly orthogonal position so that biometric data can be derived
  • Exact scale
  • Exactly calibrated colors
• A major challenge of the project is to complete the images as far as possible. The starting point was my own collection, which already contains a large number of species (more than 4000), including extremely rare ones, of which there are hardly any images available. The production of further photographs of specimens that are available in the Austrian Museums is currently in progress. Furthermore, from numerous friends, authors, publishers and institutions that support the project, I have been provided with image material, so that there are already images for most species. I am confident that I will come very close to the goal of extensive completeness in the foreseeable future.
• Instead of a general reference list, a specific one is provided for each species, in which the respective sources that were considered in the construction of this database are completely listed. The sources that are recommended as further reading, especially for the purpose of verifying a determination result, are marked as such. Also, the sources that contain further images. As far as the sources are available online, links are provided, not only to the source itself, but (as far as the respective web page allows) precisely to the respective point with further information on the species.
• The database is bilingual, German, because it was originally developed in German, and English with regard to the covered area and expected users.

Orientation

When speaking of 'completeness', the orientation needs to be addressed, because there is no 'official' list of accepted species, rather it is necessary to judge the arguments in individual literature, which are not always unanimously.

In a project of this scope, it is impossible to review every single species in depth. Therefore, this database is largely based on the systematics of the Molluscabase [56] or WoRMS [29] for marine species, as these offer the most comprehensive and largely up-to-date overview. Deviations from this are always explained in detail.

Additions have been made where the original literature provides sufficient evidence for the existence of a new species and it has to be assumed that Molluscabase is incomplete on that point. This also applies to species that are listed as synonyms in Molluscabase if there is sufficient evidence for a distinct species in recent literature.

On rare occasions, species currently considered valid have been excluded as 'not valid within this identification key' when there is a lack of conclusive evidence for the existence of a new species in the original literature. In these cases, the species is listed as a synonym in the taxonomic remarks so that it can be found in the taxon search. In any case, the reason for exclusion is explained in detail. As mentioned, this was necessary in very few cases. Taxonomic discussions are not a primary goal of this project.

Covered area

The covered area is shown schematically on the title page. It includes the land area of Europe in a geographical sense, all European islands including the Atlantic archipelagos, all European coastal waters, as well as the deep seas of the Mediterranean, Arctic and North Atlantic, west to the Mid-Atlantic ridge.

In addition, species have been included that have not yet been recorded from this area, but which can be assumed to occur here or to arrive here in near future. This applies in particular to species that have migrated from the Red Sea to the Mediterranean and have already reached the southern coast of Turkey, as well as West African species that also live in deeper zones and could therefore also occur near the Canary Islands.

Structure

The database essentially contains the following elements:

• A taxon list with the following entries:
• Code: each taxon is assigned a unique code to establish relationships with the other elements, this is only handled in the background and is not displayed on the main page.
• Rank: only selected ranks (class, subclass, order, suborder, superfamily, family and species) were deliberately used in the taxon tree. Since the taxon list only serves to keep the overview in the course of the identification process, the presentation of all ranks is not necessary, moreover, it would rather impair the overview and the manageability in connection with the systematic functions.
• Name: for species consisting of genus, species and author/year.
• Taxonomic Notes: These are not shown in the taxon tree of the main page, but in the species pages. They essentially contain synonyms that are used in the literature referred to and serve on the one hand to enable them to be found with the taxon search function and on the other hand to ensure that they can be found in the literature cited. It is not a goal of this database to discuss taxonomic aspects in detail. Only in the case of divergent views in literature this is addressed briefly.
• For every taxon there are specific references (codes referring to the reference lists), a description, information about (habitat and) distribution, subspecies and variants, and references to the illustrations, all information is presented in the species pages.
• A referene list with the following entries:
• Code: each source is assigned a unique code to establish relationships with the other elements. This is shown in the left column of the reference list in the species pages, since the descriptions and other texts often contain references to these sources. These are always in square brackets and refer to this code.
• Source: author, title, citation, year. A link is appended to the source as far as available online, whereby only the word 'Link' is displayed to be clicked. The link itself is managed in the background, appended by a specific extension managed in the taxon list (but you have excess to the full link with the 'copy link' mouse function). In some cases, there is also a link to a 'License'. This is required for legal reasons, as some licenses make reference to this a condition.
• Figure: Indication of those sources that contain figures of the particular species.
• Recommendation: sources marked with 'R' are recommended as further reading.
• Descriptions:
• The descriptions are kept quite short, as there is no need to exhaustively repeat what is already covered by the digitized features or clearly seen in the figures. Rather, the description should serve to draw attention to species-typical features and to point out variabilities, as well as those features that distinguish them from similar species.
• The descriptions were compiled from the cited sources on the one hand and from own observations on the other. Particular attention was paid to a uniform terminology so that the individual descriptions can be compared. In case of conflicting data in individual sources, implausible data have been omitted, or in case of doubt, if it could not be determined which of the data are correct, both are mentioned with reference to the respective sources.
• It may appear strange that some descriptions include a long and therefore hardly readable list of criteria for distinguishing similar species. This is because there are often a large number of very similar species, most of which are narrowly endemic. You should therefore first proceed appropriately in the identification process, and in particular state the locality. These texts are then accordingly cut down in the descriptions. If you then go to a species page, you will find there the distinctive criteria for the remaining species only.
• These distinguishing criteria appended to the descriptions also serve for the identification process: if several matches remain after all questions generated from the feature list have been answered, additional questions are generated from these texts, which allow the exclusion of further species.
• Glossary:
• The glossary is also managed in the background and is not displayed as a whole. Rather, all terms in all texts contained in the glossary are marked accordingly and can be clicked directly in the text to get to the respective explanation.
• For each term there is an explanatory text and usually also an illustration. The explanatory text can contain further terms, which in turn can be clicked on.
• A feature list with the following entries:
• Feature: this is usually formulated as a question that is presented in the course of the identification process. See application notes for details.
• Feature values: each feature is assigned a table with values for the individual species. In the case of analogous features in particular (e.g. size), sometimes also with selection features, a value range is assigned, taking into account the biological range of variation of the feature in the respective species.
• Distribution data: in addition to the verbal information in the taxon list, the distribution data are also digitalized as modeled coordinates, to serve as a feature in the identification process.

Design

The design is deliberately simple and unpretentious, not (only) to underline the scientific character, but so as not to distract the eye from the essentials. Species identification in mollusks is difficult enough. Therefore the main focus was on clarity, even in the design.

Time schedule

As already mentioned on the home page, the database and identification key can currently be used for marine snails and mussels as well as for freshwater snails and mussels.

Land snails are a work in progress and are expected to go online towards the end of 2023. The other classes will then follow step by step. After completion, the first revision can be started, especially to add newly discovered species.

This schedule is a rough estimate and cannot be guaranteed. Frequently one comes across a species or group of species for which there are very controversial data, the elucidation of which can be difficult and lead to considerable delays.

Unlike some works, in which descriptions and other data are simply copied together from various sources without checking, regardless of the resulting inconsistencies, I check the data for each species carefully and try to create a consistent building.

Statistics

Some data on the current status of the database:

• Taxon database
• 9709 valid taxa, thereof
• 8611 species, thereof
• 5494 in the classes currently available online, thereof
• 5350 with detailled description and distribution data
• Literature
• 1679 sources
• 53415 references, thereof
• 41795 with link
• Images
• 8842 images of species, usually containing different views, thereof
• 4484 onw ones in high resolution, furthermore
• 519 plates
• Glossary
• 266 terms
• Determination key
• 297 general features, referring to these:
• 155440 digitalized feature values/-ranges, furthermore
• 23796 specific verbal distinguishing criteria