Revision of the Nassariidae (Gastropoda, Neogastropoda) of the malacological collection of the Museu de Ciències Naturals de Barcelona

Resumen

Revisión de los Nassariidae (Gastropoda, Neogastropoda) de la colección malacológica del Museu de Ciències Naturals de Barcelona
Se ha revisado el conjunto de muestras de Nassariidae integradas en la colección malacológica del Museu de Ciències Naturals de Barcelona. Se han analizado individualmente los ejemplares de cada muestra, se han contado y se ha corregido la determinación taxonómica en aquellos casos en los que ha parecido justificado, actualizándose la nomenclatura. En aquellas muestras que contenían una mezcla de especies distintas, se han creado nuevas muestras, de manera que cada una de ellas contenga un único taxón. Con independencia de la anotación existente en las etiquetas originales, a cada muestra se le ha asignado una región biogeográfica. Finalmente, se ha valorado el conjunto de la colección de Nassariidae con relación al número de muestras, al número de especies y a la distribución geográfica de las mismas.

Palabras clave: Nassariidae, Revisión taxonómica, Biogeografía

Abstract

Revision of the Nassariidae (Gastropoda, Neogastropoda) of the malacological collection of the Museu de Ciències Naturals de Barcelona
The entire set of samples of the Nassariidae integrated in the malacological collection of the Museu de Ciències Naturals de Barcelona has been reviewed. For all the samples, the number of individuals has been counted, each shell has been revised individually, and the taxonomic determination has been corrected in those cases in which it seemed justified, updating the nomenclature. For those samples containing a mixture of different species, new samples have been created so that each sample contained a single species. Regardless of the annotated in the original labels, one biogeographical region has been assigned to each sample. Finally, the Nassariidae collection has been valuated as a whole regarding the number of samples, the number of species and its geographical distribution.

Key words: Nassariidae, Taxonomic revision, Biogeography

Resum

Revisió dels Nassariidae (Gastropoda, Neogastropoda) de la col·lecció malacològica del Museu de Ciències Naturals de Barcelona
S’ha revisat el conjunt de mostres de Nassariidae integrades a la col·lecció malacològica del Museu de Ciències Naturals de Barcelona. S’han analitzat individualment els exemplars de cada mostra, s’han comptat i se n’ha corregit la determinació taxonòmica i actualitzat la nomenclatura en aquells casos en què ha semblat justificat. En aquelles mostres que contenien una barreja d’espècies diferents, s’han creat noves mostres, de manera que cadascuna contingui un sol taxó. Amb independència de l’anotació existent a les etiquetes originals, s’ha assignat una regió biogeogràfica a cada mostra. Finalment, s’ha valorat el conjunt de la col·lecció de Nassariidae amb relació al nombre de mostres, al nombre d’espècies i a la distribució geogràfica d’aquestes.

Paraules clau: Nassariidae, Revisió taxonòmica, Biogeografia

Introduction

The malacological collection of the Museu de Ciències Naturals de Barcelona was created at the same time as the museum. The promoters were molluscan shell collectors, thus establishing the initial malacological fund of the institution. Other legacies from collectors or other entities were added during the early periods of the Museum functioning and successively. As for the marine molluscs, they are highlighted those of Francesc Martorell, who donated the foundational funds for creating the museum, Joan Rosals, Baltasar Serradell, Artur Bofill, Manuel Chia and Joan-Baptista d’Aguilar-Amat as numerous collections.

During this period, exchanges and probably acquisitions were performed through contacts with certain European malacologists and from other places. Moreover, it was observed certain collection campaign that was promoted by the Museum; usually near the coastal areas. However, it was not observed any material from scientific expeditions of naturalist prospecting in far seas unlike in other museums as those in Madrid, Paris or London. Nevertheless, numerous samples have been gathered until forming the whole malacological collection found currently. Since the beginning, this approach has determined the composition and structure of the collection.

The Museum activity was significantly diminished during the long post-war period (from 1939 to the 1970s), and although considerable performances on the malacological collection were attained, such as rearrangements, taxonomic reviews, changes in the procedure of the specimens display, etc., the contributions were scarcer. It was not until the last decades of the 20th century when significant legacies were added to the collection, especially those of Lluís Gasull and Joan Rosal, encouraging somehow the beginning of cataloguing of the entire malacological collection and the computerization of its contents. This work was continued for years according to the staff’s availability at every stage.

Currently, this work is achieved, the consulting and access to the collection contents is precise and rapid, and the new contributions are perfectly integrated. It was at this point when the author was especially interested to initiate the review on the Nassariidae family presented below.

This review has allowed, as a first impact, publishing descriptions of two new species of the genus Nassarius (Gili, 2015).

Material and methods

The preliminary point was the selection of samples containing the Nassariidae through the database screening of the entire malacological collection of the Museum. Each sample has been studied by reviewing its contents. The number of specimens was counted and each one was individually observed with the aid of stereomicroscope when required.

In each sample, the specific determination of its label was assessed and modified if needed. In this aspect, the Cernohorsky works (1975, 1981 and particularly 1984) were taken as initially guide, but also using subsequent works and reviews listed in annex 1.

Annex 1. Main bibliography used in the determination of the species. Anexo 1. Principal bibliografía utilizada para la identificación de las especies.

For those cases containing specimens of two or more species, new registered lots were created so that each sample contained a single species. Some forms which are currently considered as different species, but at the time were deemed as a single species, or simple varieties of a species, were segregated. In other cases, the specimens that have been segregated in new samples were different species that moreover were from different geographical regions. The same procedure was performed on those specimens that did not belong to the Nassariidae family but were mixed together. For each sample, it was recorded the specimen’s morphologic features or colour pattern as well as its state of preservation.

In order to assess the contents of the collection regarding the different geographical sources, each sample was assigned to one of the biogeographical regions commonly used in marine malacology (annex 2). This was performed if the source was specified or not. When the source was deemed to be erroneous, it was assigned to the biogeographical region where the species is really located. In certain cases, owing to its uncertain source, there was certain ambiguity for designating the sample to a single region, therefore sorting those localities where it probably exists.

Annex 2. Biogeographic regions considered in the review. Anexo 2. Regiones biogeográficas consideradas en la revisión.

The scientific nomenclature of the species has been updated, and indicating the full name of the genus, as well as the complete name of the author and the year of publication, following the standards, recommendations and current trends within this field. Generally, in this review, the names of the varieties were not preserved or considered. Special caution has been devoted to the taxonomic identification from labels printed with the name Museo de Biología de Barcelona. In this context, it is quite common to read apparent subspecific names that in fact are only varietal forms that did not meet the biological concept of subspecies. The current practice in taxonomy eliminates  such subspecific levels. However, certain subspecies that are properly described and assigned to their corresponding geographic regions were considered.

No subgeneric division was used, since in the Nassariidae family it has not been reached any satisfactory subgeneric subdivision scheme with a minimum of ambiguity and a maximum of consensus.

In the taxonomic determination, it was always intended to reach to the species. In spite of the state of preservation of the specimens in certain samples did not permit it without any significant risk of error. In these cases, the open nomenclature (Bengstom, 1988) was applied but avoiding misuse of the particle ‘sp.’, which did not provide any information on which species the author had focused on, which forms he questioned or with which morphologies he carried out the comparison. Whereas, the use of the particle ‘cf.’, to indicate the resemblance of a doubtful form to a certain species, provides further information. Regarding the species names and years of publication, an aspect entailing certain discrepancies among the authors, the criterion of Cernohorsky (1984) was mainly followed.

All the collected information was entered into a datasheet and processed in order to describe thoroughly the collection. The resulting report and associated inventory have been put in hands of technical staff of the Invertebrate non-Arthropods department of the Museu de Ciències Naturals de Barcelona.

Many specimens of several samples were measured for a better knowledge and characterization of the species; moreover, pictures of several specimens were taken.

Results and discussion

As a first result of the review performed, the number of studied samples is detailed in table 1 and the taxonomic distribution of the species in table 2.

Table 1. Summary of the number of studied samples. Tabla 1. Resumen del número de muestras estudiadas.

Table 2. Taxonomic distribution of the species. Tabla 2. Distribución taxonómica de las especies.

The overall number of living Nassariidae species is not definitively established. The assessment of the validity of certain forms differs according to the authors; some identified them as ‘valid species’, whereas others considered them synonyms. On the other hand, new species are regularly described while exploring poorly sampled places, or studying thoroughly certain groups. Cernohorsky (1984) considered there would be about 319 valid species. However, since that period, certain names that Cernohorsky (1984) considered as synonyms have been established as valid species, and they have been described more than twenty new species. Therefore, it is does not seem very bold to consider that the number of species of such family is about 360 currently.

From this viewpoint, the overall number of Nassariidae species identified in the collection of the Museu is not considered very significant; about 1/3 of the whole existing, approximately. However, from the qualitative perspective, there are taxonomically interesting forms regarding their size, colouring, ornamentation, or their variability; or because they enabled us a direct assessment of the entity of certain synonyms and the identification of new species.

Characteristics of the collection

The Nassariidae collection is mainly formed by empty shells deriving from living animals or dead collected shells, although a certain proportion had remnants of the soft tissue and occasionally preserving the operculum. Just a pair of samples included operculums without shells exclusively.

An outstanding fact is the presence of the types of two species, Nassarius absconditus Gili, 2015 (holotype and two paratypes) and Nassarius rainbowae Gili, 2015 (holotype), based on the material of the collection.

The materials state of preservation is rather varied; from complete shells, preserving their original colour, to very discoloured and damaged shells. The specimens were not preserved for their conchological aesthetic ‘perfection’, but with the criterion of establishing their source locality for enabling the scientific study. Thus, in many samples it is preserved a large number of material without prioritizing its condition, or a single or few specimens although their shells are rather impaired. It is not always relied on the presence of the protoconch, therefore in certain cases, it may hinder the specific determination of the material. Discolouration is due to sun exposure in those cases where the shells were collected on the beach, or have been kept under aggressive conditions for the pigments or shell material, in other cases.

Another important fact to note is that most of the original labels of the sample were preserved including those with nomenclature modifications or other type that might have been added overtime. On the other hand, the information of such labels is rather limited regarding the precise geographical locality that sometimes is not recorded, as the dates of the collection, data concerning the habitat, or methods of obtaining. Certain collectors specified the dates although the majority omitted them; concerning the habitat (depth, type of community, nature of bottom, accompanying species, etc.) just few samples included certain indication; and the method of collection was not specified in any sample.

As for the geographical locality, it is quite generic, indicating the name of a country or a province, a sea or an ocean. However, in some samples there is a significant ambiguity regarding such aspect. In some cases, the label indicates a locality but the specimens belong to a species never cited in such area. In other samples that contain a single specimen, there are two or more labels with different geographical localities. On the other hand, there are samples with two specimens of different species deriving from different regions with just one geographic locality on the label (see annex 3 for more details on uncertain geographic origins).

Annex 3. Some cases with uncertain geographic origin. Anexo 3. Algunos casos con origen geográfico incierto.

As specified above, the limitations indicated are the result of how the collection was formed and the vicissitudes endured overtime; the former collecting was not cultivated in such aspects and perhaps the staff who handled the collection lacked training and, as for the malacological trading, it is unusual to consider such significant facts for the scientific study.

Considering the above stated, the Nassariidae of the Museum’s collection has mainly a taxonomic utility. As in some Mediterranean species there are a significant number of specimens, therefore in such cases, they could be used for studies of population and of variability. Perhaps they may have certain significant historical viewpoint thus allowing us to study the changes endured by the populations of certain species, mainly those concerning our geographical area, or to verify their longevity or disappearance. It should be considered that many of the samples were collected about 100 years ago and during such period, the changes and transformations occurred in many places have been significant or drastic.

Previous reviews of the collection

During the study period, it was detected that several actions were performed on the original samples, such as modifications in the determinations of the species, grouping and subdivision of samples, etc.

Modifications in the species nomenclature were detected from the several labels that were added to the original ones. In many of the cases, it was not an exact transcription of the original, but  a taxonomic interpretation of the sample’s contents or an adjustment of the nomenclature according to the trends of that time, and frequently adding the name of variety. Owing to that many samples had an identification number of the initial collection, and these numbers were preserved in the new labels, it was able to detect the division of some original samples into two or more samples (see annex 4).

Annex 4. Certain cases of segregation and grouping of samples. Anexo 4. Algunos casos de segregación y agrupación de muestras.

At some point, several samples had been grouped into a single one, occasionally, from different geographical sources. This has been detected because some of the samples had several original labels of one collection, or from different collections, with different specific names but were considered as synonyms (see annex 4).

In some cases, it has been detected the simultaneous exclusions and groupings of several samples. This was observed in those cases where it was intended to distribute the specimens of a species of various collections in new homogeneous samples regarding the varieties of species under consideration (see annex 5).

Annex 5. Taxonomic modifications with or without grouping or segregations. Anexo 5. Modificaciones taxonómicas con o sin agrupaciones o segregaciones.

In some samples, there is indication that it was the author of a specific review, since there was an added label with his name.

Distribution of the samples by biogeographic regions

The following table (table 3) shows the number of samples assigned to each of the malacological regions considered. In annex 2 the concrete geographic space included in these regions is given.

Table 3. Number of samples assigned to each of the malacological regions considered. Tabla 3. Número de muestras asignadas a cada una de las regiones malacológicas consideradas.

As perceived in table 3, the samples distribution according to the region is rather uneven and is not related with the number of species identified in each of them. The Lusitanian region (region 3) accumulates more than 71% (71.08) of overall samples and, within this region, samples of the Mediterranean province (3a) represent 61.20% of the whole. On the other hand, the Indo-Pacific region (region 6), the second with largest number of samples, accumulates almost only 19% (18.84). In contrast, the number of Nassariidae species living in the Indo-Pacific region is larger than the number of Lusitanian species. Regarding the material of the collection studied, it was observed that 71% of the Lusitanian samples contained only 16% of the species, whereas the number of species identified in the Indo-Pacific region represents 55.2% of the whole, just with 19% of the samples. It is observed, with more poor proportion, the Caribbean (region 10), with 3.22%, and the Californian (region 13), with 1.58% of the samples. The remaining biogeographical regions represent individually lower percentages of the whole, and ranged about 5.2% globally.

Taxonomic outcomes

In table 4 the complete list of species identified is given with specification of the number of samples where each one is located, the total number of specimens, and the corresponding geographical regions according to the numbers assigned in table 3.

Table 4. List of species identified is given with specification of the number of samples where each one is located, the total number of specimens, and the corresponding geographical regions according to the numbers assigned in table 3. Tabla 4. La lista de las especies identificadas se acompaña del número de muestras localizadas, el número total de especímenes y las regiones geográficas correspondientes de acuerdo con los números asignados en la tabla 3.

Since many species are found in more than one region, in annex 6 species are grouped by biogeographical regions to facilitate consultation.

Annex 6. Identified species grouped by biogeographic regions. Anexos 6. Especies identificadas agrupadas por regiones biogeográficas.

Acknowledgements

I would like to sincerely thank the Museum’s staff for the attention received and, particularly, both Dr. Francesc Uribe, curator of non-arthropod invertebrates, and Dr. Miguel Prieto, documentalist, for their support and courtesy.

References

Bengston, P., 1988. Open nomenclature. Palaeontology, 31(1):  223-227.

Cernohorsky, W. O., 1975. The taxonomy of some West American and Atlantic Nassariidae based on their type-specimens. Records of the Auckland Institute and Museum, 12: 121-173.

– 1981. Revision of the Australian and New Zealand Tertiary and Recent species of the family Nassariidae (Mollusca: Gastropoda). Records of the Auckland Institute and Museum, 18: 137-192.

– 1984. Systematics of the family Nassariidae (Mollusca: Gastropoda). Records of the Auckland Institute and Museum, 14: 1-356.