Tag Archives: venezuela

Why photo identifications remain tricky

With the increasing ease for using social media, a larger group of people become interested in putting a name to a shell. Some call this ‘citizen science’ as they think it is a means to involve the interested general public with e.g. taxonomic work. Others see it as a harmless pastime that nobody bothers. I think neither of the two is correct.

Internet can be a great help and for taxonomy it definitely is a great resource. Think alone of the Biodiversity Heritage Library (BHL), where a multitude of sources are becoming available and are made accessible for everyone. The means are there but does this mean that everybody can pick up a shell and compare it to literature found on the internet without good knowledge of the group concerned and the relevant area? I have strong doubts.

There are a lot of pictures of snails and shells on the internet with a proper locality. However, a specific locality alone does not qualify for a proper identification. Often characteristics of the species are concealed in the picture and different views are needed to know which species (singular or plural) might be concerned. Many times photos are good enough for making a correct guess of the genus concerned, but inadequate for a correct identification at the species level. Either because the photographer didn’t take the view(s) needed for a good comparison with figures in the literature, or the specimen wasn’t full-grown which prevents from showing the required characteristics needed for a correct identification.

My basic stand is field photographs are unsuitable for identifications, unless 1) full details are available on the locality and habitat, 2) proper care has been taken to photograph the shell (or snail) from such sides that all characteristics for identification are visible. Two caveat are immediately clear here: if the animal is still present it may obscure some of the characteristics needed for identification, and it may need a basic knowledge of the family concerned to know which views are needed to enable a specialist to put a name to a shell.
Thus the baseline is: photo identifications remain tricky, and personally I’m especially wary when it comes to lesser known species or species from lesser known areas.

This having said, today an example from Venezuela. It is taken from the blogpost of Ignacio Agudo-Patron who, if I’m correctly following the links, did not have the shell at hand himself but has put a name to pictures taken by one of his ‘Facebook friends’.

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On first view this looks reassuring: a rather specific locality (“San Juan”, Dept. Sucre, Venezuela) and specific habitat information (premontane humid forest). There is even a reference to literature (my 2009 paper on the snail fauna of Venezuelan Guayana). Under the pictures in the blogpost is the identification “Plekocheilus (Eudolichotis) sp.”, which seems proper to me. However, the summary page of his post gives as identification “Plekocheilus (Eudolichotis) aff. gibber (Oberwimmer, 1931)”. While these pictures were taken in northern Venezuela at relatively low altitude, Oberwimmer’s taxon lives in southern Venezuela at more than 2000 m. It seems totally implausible to me that these pictures represent this species. Instead I think it is one of the coastal area species (P. (E.) distortus, and its allies) which are currently insufficiently known in their variation, distribution and relationships to allow a quick-and-dirty identification via photographs. After all, despite some scant literature, Venezuela is still one of the lesser-known areas in the Neotropics when it comes to snails.

A new Tudora from Venezuela

In the most recent number of Basteria Hovestadt published a short paper on the Peninsula de Paraguaná in Venezuela, describing a new Annulariid species: Tudora paraguanensis. The new species is the first record of Tudora from the South American mainland, and although the collected specimens are regarded as ‘subfossil’, it cannot be excluded that the finding of living specimens is possible.

schermafbeelding-2016-12-17-om-11-29-41

Reference:
Hovestadt, A. A new Tudora (Gastropoda, Hypsogastropoda, Annulariidae) from Peninsula de Paraguaná, Venezuela. – Basteria, 80:149-151.

Venezuelan land snails

The following report was found on Facebook, with land snails data from NE Venezuela, a region for which hardly reliable data exist in literature.

 

foto van Ignacio Agudo.
foto van Ignacio Agudo.
foto van Ignacio Agudo.

Ignacio Agudo aan Moluscos del Caribe/ Moluscos do Caribe/ Caribbean Mollusks

… NEW UPDATING DATA ( III ) — ABOUT RECENT AND SUB-FOSSIL CONTINENTAL SNAILS (MOLLUSCA: GASTROPODA: CAENOGASTROPODA & PULMONATA) OF ARAYA PARISH, SUCRE STATE, NORTHEASTERN VENEZUELA, SOUTHERN CARIBBEAN REGION: A “PRELIMINARY” FIELD BALANCE !

Total of seventeen (17) verified species (thirteen (13) terrestrial — two (2) non-native/ exotic — and four (4) freshwater forms — one non-native/ exotic), found in “xerophytic environments” of the parish until “December 2016”, distributed in fourteen (14) genus and nine (9) families.

Important to highlight that, in addition to the three (3) other specifically native aquatic/ limnic forms, all the thirteen (13) native terrestrial species so far detected in the region “contradictorily” correspond to own forms of environments/ humid forest ecosystems ……….

_@/”
SYSTEMATIC RELATIONSHIP:

– Family HELICINIDAE Férussac, 1822
Helicina tamsiana (Pfeiffer, 1850)

– Family NEOCYCLOTIDAE Kobelt & Möllendorff, 1897
Poteria fasciatum (Kobelt & Schwanheim, 1912)

– Family AMPULLARIIDAE Gray, 1824
Pomacea glauca (Linnaeus, 1758)
Marisa cornuarietis (Linnaeus, 1758)

– Family LYMNAEIDAE Rafinesque, 1815
Pseudosuccinea columella (Say, 1817)

– Family PLANORBIDAE Rafinesque, 1815
Drepanotrema lucidum (Pfeiffer, 1839)

– Family ORTHALICIDAE Albers, 1860
Bulimulus cacticolus (Reeve, 1849)
Bulimulus constrictus Pfeiffer, 1841)
Bulimulus krebsianus Pilsbry, 1897
Drymaeus multilineatus (Say, 1825)
Oxystyla abducta (Shuttleworth, 1856)
Oxystyla maracaibensis (Pfeiffer, 1899)
Plekocheilus (Eudolichotis) distortus (Bruguière, 1789)

– Family ODONTOSTOMIDAE Pilsbry & Vanatta, 1898
Biotocus (- Tomigerus) cumingi (Pfeiffer, 1849) [according to Simone, 2006: Biotocus cumingi]

– Family SUBULINIDAE Fischer & Crosse, 1877
Beckianum beckianum (Pfeiffer, 1846)
Subulina octona (Bruguière, 1798)

– Family ACHATINIDAE Swainson, 1840
Achatina (Lissachatina) fulica (Bowdich, 1822)


The adjective ‘native’ which is used here, should be considered with care. E.g., the Subulinid and Achatinid species have been introduced, and also Drymaeus multilineatus has probably been introduced in the past. The list contains thus several species which originate from elsewhere, which is no big surprise as the locality is at the coast.

Apart from some minor errors (Bulimulus and Drymaeus belong to the family Bulimulidae; Oxystyla should be Orthalicus, abducta = obductus), this is information from a country with comparably hardly good information in the malacological literature.

Photo of the day (149): Plekocheilus

Philippe Kok very kindly shared some additional photographs of living Plekocheilus snails from tepuis in Venezuelan Guayana.

The first picture was taken at night on Auyán-tepui in the Chimantá massif. It is a very yellow coloured specimen of P. (Eurytus) mundiperditi Haas, 1955. This species is well known from this area and may be found on several of the tepuis in this massif.

The second snail was found on Uei-tepui, also known as Cerro El Sol, an isolated mountain-top south-east of Roraima. This tepui was hitherto malacologically terra incognita, but the photo is interesting in several aspects. First, this appears to be P. (E.) sophiae Breure, 2009, which was until now only known from Yuruani-tepui, NW of Roraima. Secondly, this shell has had a severe ‘life accident’ as shown by the upper part of the last whorl near the peristome; looks like a repaired shell after a predator attack (mammal??). Finally, the colour pattern at the penultimate whorl is peculiar (lighter and darker spiral bands), but has been observed in other species as well; this may be due to either a genetic defect regulating the colour pattern genes or may have been induced by another damage of the shell (on the side not shown here).

More information on this group may be found via this link: http://bit.ly/IOYgok

Plekocheilus mundiperditi Plekocheilus sophiae

Venezuelan tepuis – their caves and biota

The Venezuelan tepuis have long been a mysterious place and geologists only recently have begun to explore the caves inside these mountains made up by sandstones. Some years ago geologists and speleologists from Czech and Slovakia set out to Chimantá massif, together with local counterparts. They explored the immense caves that are present and brought several novelties for science home. Among them some snails, collected on special request.

Now the scientific results have been compiled in a book: Venezuelan tepuis – their caves and biota (Aubrecht et al., 2012). Originally scheduled for end 2011, officially dated for 2012, it only now appears in 2013. Thanks to the determined editors, Roman Aubrecht and Jan Schögl, they succeeded in the end. A paper version of the book will appear “later (perhaps in March)“.
This book contains parts on Cave systems in Churí and Roraima tepuis, and Faunistical investigations of Pantepui biogeographical region. The chapter on the malacofauna is a review of all known species, with new data on the anatomy of some and phylogenetic results on Plekocheilus species.
My contribution on the malacofauna is slightly ‘outdated’ (so to speak); my recent paper published in Basteria (Breure, 2012) was written after the deadline for this book was closed. And another paper is in the pipeline. This subject remains intriguing for me…

References:
Aubrecht, R., Barrio-Amorés, C.L., Breure, A.S.H., Brewer-Carías, C., Derka, T., Fuentes-Ramos, O.A., Gregor, M., Kodada, J., Kovácik, L., Lánczos, T., Lee, N.M., Liscák, P., Schlögl, J., Smida, B. & Vlcek, L., 2012 [2013]. Venezuelan tepuis – their caves and biota. – Acta Geologica Slovaca, Monograph, Comenius University, Bratislava: pp. 1-168. Available at http://geopaleo.fns.uniba.sk/ageos/archive/monograph/aubrecht_et_al_2012_monograph.pdf (NB: 163 Mb).
Breure, A.S.H., 2012. Living in isolation: Plekocheilus (P.) philippei spec.nov. from Venezuelan Guayana (Gastropoda, Amphibulimidae). – Basteria 76: 101-106.

Modeling on Giant African Snail invasion

An Argentinan group of colleagues has elaborated the potential areas where the Giant African Snail (GAS) might occur or invade (Vogler et al., 2013). Using the same methodology as Borrero et al. (2009), they have detailed now the potential distribution areas for all South American countries. The abstract reads:

The best way to reduce problems related to invasive species is by preventing introductions into potentially susceptible areas. The purpose of this study was to create distribution models for the invasive gastropod Achatina fulica Bowdich, 1822 in South America in order to evaluate its potential geographic distribution and identify areas at potential risk. This mollusc, considered one of the 100 world’s worst invasive alien species, is the focus of intense concern due to its impact on agriculture, human health, and native fauna. We tested two commonly used ecological niche modeling methods: Genetic Algorithm for Rule-Set Prediction (GARP) and Maximum Entropy (MaxEnt). Models were run with occurrence points obtained from several sources, including the scientific literature, international databases, governmental reports and newspapers, WorldClim bioclimatic variables, and altitude. Models were evaluated with the threshold-independent Receiver Operating Characteristic (ROC) and Area Under the Curve (AUC). Both models had consistent performances with similar areas predicted as susceptible, including areas already affected and new potentially susceptible areas in both tropical and temperate regions of South America.

This new study is more detailed and much more elaborated than Borrero et al. (2009), and uses two modeling methods, (A) GARP and (B) Maxent, of which the latter is generally performing best in comparative studies. The relevance of presenting country maps for potential distribution of this species in each South American country is clear: the responsible authorities now have a handle to focus their attention to areas most under threat. Generally, the Amazon basin is most infected or theathened, but certain areas in Ecuador, Colombia and Venezuela are across the Andes but have already been invaded. The following table shows that none of the South American countries can escape to the threat of GAS, although there are gradual differences.

References:
Borrero F.J. et al., 2009. Into the Andes. Three new introductions of Lissachatina fulica (Gastropoda, Achatinidae) and its potential distribution in South America. – Tentacle 17: 6-8.
Vogler, R.E., Beltramino, A.A., Sede, M.M., Gutiérrez Gregoric, D.E., Nuñez, V. & Rumi, A., 2013. The Giant African Snail, Achatina fulica (Gastropoda: Achatinidae): using bioclimatic models to identify South American areas suspectible to invasion. – American Malacological Bulletin 31: 39-50.

New land snail from Venezuelan tepui

Venezuelan tepuis are a fascinating environment for land snails, and several new species have been described during recent years. Material from tepuis previously unexplored for their malacofauna comes in occasionally. Earlier this year Phillippe Kok (Free University, Brussels) showed some material from Angasima tepui, and one of the species appeared to be new to science.

Schermafbeelding_2012-12-26_om

This new species was named after its collector, Plekocheilus (P.) phillippei; the holotype is RBINS MT2576. The anatomy (genitalia, radula) is also described.
0schermafbeelding_2012-12-26_om

Reference:
Breure, A.S.H., 2012. Living in isolation: Plekocheilus (P.) philippei spec.nov. from Venezuelan Guayana (Gastropoda, Amphibulimidae). – Basteria 76: 101-106.