Another paper just published in the ‘end-of-the-year-stream’ is by Harasewych & Tenorio.
Their abstract reads: “Morphometric analyses of shell shape of living specimens of Cerion inhabiting San Salvador Island segregate samples into two primary phenotypes, one inhabiting the western and southern coasts of the island, the other the eastern and much of the northern coast. These are concordant with phenotypes identified in prior morphometric studies. Lectotypes are designated for Cerion watlingense Dall, 1905; C. inconspicuum Dall, 1905; C. inconspicuum lacunorum Dall, 1905; and C. coloni Bartsch, 1924. The lectotype of Cerion watlingense Dall, 1905 falls within the western and southern phenotype, and is the oldest name available for this taxon. The lectotype of Cerion coloni Bartsch, 1924, a validly introduced, but previously unrecognized taxon, and the holotype of Cerion rodrigoi Gould, 1997 both fall within the group containing the east coast populations, with Cerion coloni Bartsch, 1924 being the oldest available name for this phenotype. A third, previously unrecognized phenotype, represented by a single inland population, is morphologically similar to the lectotype of Cerion inconspicuum Dall, 1905, which is the oldest available name for this phenotype. The geographical distribution and chronological succession of these phenotypes since the late Pleistocene is reviewed in the context of both the single and multiple colonization models for the arrival of Cerion on San Salvador, and the evolutionary and taxonomic corollaries of each model are discussed”.
An interesting paper which shows that morphometric analysis may be needed when the morphology and distribution are seemingly entwined. The study of Cerion, which has intrigued many authors, has been elucidated with a thorough discussion of both the morphological and distributional aspects of the species of this island.
Harasewych, M.G. & Tenorio, M.J., 2018. The genus Cerion (Gastropoda: Pulmonata: Cerionidae) on San Salvador [Watling Island], Bahamas: a geometric morphometric analysis of shell morphology. – The Nautilus, 132 (3-4): 71-82.
In a not so current journal, a new species of Cerion was just described from Cuba.
“Cerion milerae sp. nov. is described from the type locality Punta Bejuquera, Gibara, Holguín province, Cuba. It is compared conchologicaly with Cerion paucicostatum paucicostatum, Cerion paucicostatum harringtoni and Cerion caroli aedilii. Anatomically it is compared with Cerion paucicostatum paucicostatum. With its description the number of species known from Cuba is increased to 148 and to 35 the number of species and subspecies known from Holguín province. An extensive survey in the zone showed that Cerion milerae sp. nov. is microlocalized, associated to Bayhops (Ipomoea pes-caprae), in sandy substrate”.
Suárez, A., 2018. Especie nueva de Cerion (Mollusca: Pulmonata: Cerionidae) de Holguín, Cuba. – Novitates Caribaea, 12: 43-48.
Recently a study by Jonathan Miller came to my attention about Cuban Cerion species. Morphometric studies are becoming more popular, but the methodology may not be familiar to the readers and can be challenging to perform.
The abstract reads: “Cerion mumia is a complex of eight subspecies distributed along the north coast of Cuba from Pinar del Rio to Camaguey provinces. The geometric morphometric analysis presented here was aimed at identifying patterns of shell shape variation to test the hypothesis of colonisation through land bridges during the Eocene-Oligocene. C. mumia cuspidatum, the easternmost population, was similar in shape to the subspecies from the north coast of Havana, but showed morphometric differences suggesting allopatric speciation followed by dispersal. The shells from the west were more globose than those from Havana or the east, which tended to be more cylindrical, as shown by the thin-plate spline analysis. As a result of the morphometric analysis I propose to elevate C. noriae comb. nov. and C. wrighti comb. nov. to species rank and to include C. noriae hondanum comb. nov. as a subspecies of C. noriae comb. nov. I report a second locality of C. noriae comb. nov. at Playa Santa Fe formation from the late upper Pleistocene. Geometric morphometric techniques are useful in species identification through comparing new samples with type material”.
The author collected his shells in the field, photographed them in situ and released them afterwards. Therefore, as far as I understand, no vouchers are available in a museum collection of the material studied. This might be a challenging procedure and may hamper the repeatability of this study. Otherwise this seems a nice study with as outcome that this species group may be split into three species with disjunct distribution along the Cuban north coast.
Miller, J.P., 2016. Geometric morphometric analysis of the shell of Cerion mumia (Pulmonata: Cerionidae) and related species. – Folia Malacologica, 24: 239-250.
Freshly pressed…. In the latest number of The Festivus that I found this morning in our library, González et al. have a paper on Cerion from Cuba. “The exceedingly polytypical genus Cerion (Röding, 1798), with around 91-92 species described for Cuba is still poorly studied. The urgent need of more studies related to ecology, genetics, environmental components, morphology, conservation status plus a serious taxonomic evaluation of the genus in the archipelago is more than evident. The present paper reviews the narrow-range Cerion taxa that occur in the coastal zone of the Holguin province, in northeastern Cuba, including comments on each taxa. Additional observations related to other taxa from the same geographic coastline area are included to reinforce the importance of further research studies that the authors believe need to be conducted”.
The paper comprises data on 15 taxa (species or subspecies) with adequate (although somewhat darkish) photographs of each taxon, and two plates which facilitate comparisons.
González, A., Fernández, A., Lajonchere, L.A. & Berschauer, D.P., 2017. Narrow-range taxa of Cerion (Mollusca: Cerionidae) in the northeastern province of Cuba. – The Festivus, 49 (1): 3–17.
Harasewych and his team have focused on different aspects of the Cerionidae, but have now added a phylogenetic paper with state-of-the-art technique. “The complete mitochondrial genome of the neotype of Cerion incanum (Leidy, 1851) was sequenced using high-throughput sequencing and found to be a circular genome 15,117 bp in length with a GC content of 34.3%. It is the largest mitogenome presently known in Stylommatophora, with the difference in size due primarily to intergenic regions and to a lesser extent to larger sizes of individual genes. Gene content is identical to that of other stylommatophorans, but differs in having the tRNA-Gln gene situated on the major coding strand. Gene order of C. incanum was similar to that in Helicidae, differing in the regions between COX1 and NADH5, and between tRNA-Ser2 and tRNA-Ile. The potential origin of replication was located in a 50-bp noncoding region between COX3 and tRNA-Ile. Phylogenetic analyses using Bayesian inference and maximum-likelihood analyses of nucleotide data for all protein-coding and large and small ribosomal genes resulted in a well-resolved tree. This tree was similar to trees derived from nuclear or a combination of nuclear and mitochondrial genes, differing from previous phylogenetic reconstructions based on mitogenomes in the placement of Hygrophila. The phylogenetic position of Cerionidae as sister taxon to Helicoidea is consistent with previous findings after allowing for more limited taxon sampling in the mitogenome tree. The mitogenome tree is sufficiently populated to refute the inclusion of Cerionidae in Clausiloidea, as advocated by some authors, but at present lacks the representatives of the Orthalicoidea or Urocoptoidea needed to resolve more precisely its relationships with those taxa”.
The last sentence of their abstract is intriguing, and in Leiden we had hoped to be able to contribute to this knowledge by supplying data from a Bulimulus and a Drymaeus species. However, the PCRs have failed and the project has been dropped.
González, V.L., Kayal, E., Halloran, M., Shresta, Y. & Harasewych, M.G., 2016. The complete mitichondrial genome of the land snail Cerion incanum (Gastropoda; Stylommatophora) and the phylogenetic relationships of Cerionidae within Panpulmonata. – Journal of Molluscan Studies: 1–9 (advance access doi:10.1093/mollus/eyw017).
And another post by Richard Goldberg on Cerion….
To stay in the Cerionid flow…. Richard Goldberg recently has posted on his Facebook account a series of summarizing texts on Cerion species from the Bahamas, of which I reproduce here three.