Monthly Archives: October 2019

El Salvador non-marine molluscs

Ignacio Agudo-Padrón has just published a short paper with a list of land and freshwater species from El Salvador. Although most data are contained in the overview by Thompson (2011), two species are listed now as a new for the territory: Bulimulus corneus (G.B. Sowerby I, 1833) and Orthalicus maclurae Martens, 1893.

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The paper is illustrated with several photographs of live snails (Drymaeus discrepans (G.B. Sowerby I, 1833) above) and the species list contains 30 names, based on an inventory made by the government of El Salvador in 2016.

Reference:
Agudo-Padrón, I., 2019. Los moluscos no marinos ocurrentes en El Salvador, América Central: una breve revisión panorámica introductoria de su actual conocimiento. – Bioma (El Salvador), 5: 48–53.
Thompson, F.G., 2011. An annotated checklist and bibliography of the land and freshwater snails of México and Central América. – Bulletin Florida Museum Natural History, 50(1): 1–303.

Photo of the day (181): Rabdotus

Bill Frank and Harry Lee added to their site a record and photo of a live Rabdotus dealbatus (Say, 1821), the so-called Whitewashed Rabdotus.

218rab
This snail was found on grass stalks at the base of a limestone cutting, during light rain, between mile 58 and 59 markers along Interstate 840, Rutherford Co., Tennessee on 7 October 2019 (shell height 14 mm).

Left-right chirality

Dextral and sinistral coiling shells are well known throughout the molluscan phylum, but the genetic mechanism was unresolved so far. Abe & Kuroda have recently published  a paper which answers the question.

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Their abstract reads “The establishment of left-right body asymmetry is a key biological process that is tightly regulated genetically. In the first application of CRISP/Cas9 to a mollusc, we show decisively that the actin-related diaphanous gene Lsdia 1 is the single maternal gene that determines the shell coiling direction of the freshwater snail Lymnaea stagnalis. Biallelic frameshift mutations of the gene produced sinistrally coiled offspring generation after generation, in the otherwise totally dextral genetic background. This is the gene sought for over a century. We also show that the gene sets the chirality at the one-cell stage, the earliest observed symmetry-breaking event linked directly to body handiness in the animal kingdom. The early intracellular chirality is superseded by the intercellular chirality during the 3rd cleavage, leading to asymmetric nodal and Pitx expression, and then to organismal body handedness. Thus, our findings have important implications for chromophogenesis in invertebrates as well as vertebrates, including humans, and for the evolution of snail chirality”.

This is a breakthrough that has importance beyond malacology. While it sheds light on the occurrence of sinistrality in certain groups (e.g. Clausiliidae), it doesn’t completely answer the question why it occasionally (or with different frequency) is found found in other groups of snails. Is it just a mutation or is there more at play?
Anyway, since sinistrality is also found in some Neotropical groups, this is an interesting paper.

Reference:
Abe, M. & Kuroda, R., 2019. The development of CRISP for a mollusc establishes the formin Lsida1 as the long-sought gene for snail dextral/sinistral coiling. – Development, 146: dev175976 (7 pp.).

J.L. Staid-Staadt revisited

Just published: a paper dealing with the French malacologist and palaeontologist Jean Louis Léon Staadt (1886-1969), also known as John L. Staid or J.L. Staid-Staadt (hereafter JLS). The first time I came across his name was when preparing a manuscript about the Bravo collection (Mogollón & Breure, 2008). He was the main European correspondent of Bravo. But little was known about this person, except a short paper by a fellow-Dutchman who had visited him shortly before his death.

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During one of my visits to the Paris museum the large collection of JLS was noticed, incorporated in the general collection. Virginie Héros kindly made me aware of documentation, which appeared to be detailed notes by JLS handwritten in ‘year books’. Unfortunately they are not complete; some years are missing and they end in 1940. The details intrigued me as they gave insight not only in the contact network of JLS, the financial aspects of building a collection in the period 1920-1940, but also about the person of JLS. What initially still remained enigmatic was the time he had spent in England, where he adopted the name John L. Staid. During a visit in London I was able to trace his former house, some of his activities and also recovered that he was married twice there.

Besides the biographical details, the paper gives a bibliography, list of new taxa, a list of eponyms, and in the Appendices a verbatim transcription of the summaries from JLS’ year books, and a list of contacts and correspondents.

References:
Breure, A.S.H., 2019. Obsessed with shells: John L. Staid-Staadt (1886-1969) as a life-long and ardent collector. – Folia Conchyliologica 50: 5-74. Link
Mogollón, V. & Breure, A.S.H., 2008. José Julián Bravo (1874-1927), a hitherto unknown conchologist from Peru. – Basteria, 83: 601-613.