Tag Archives: literature

New records of Chilean snails

Based on a small collection already made in 1982, Araya et al. have just published a paper on the snail fauna near Antofagasta.

New records for Bostryx holostoma (Pfeiffer, 1846), Pupoides minimus (Philippi, 1860), Stephacharopa calderaensis Miquel & Araya, 2013 and an unidentified charopid species are presented on the basis of specimens collected near the city of Antofagasta, in northern Chile. This is the first record for S. calderaensis after its description, extending its known distribution about 350 km northwards. Details on the protoconch of B. holostoma are presented for the first time, and this species extends its distributional range 145 km southwards. The microhabitat of these species in litho-refugia may explain the presence of these minute terrestrial mollusks in hyper arid northern Chile, further highlighting the need of additional studies of this neglected fauna”.

Especially the protoconch structure of Bostryx holostoma is interesting, as this reveals a spiral structure which is not present in other Chilean Bostryx species. As unpublished DNA results of species from this genus from different countries reveal, this genus may well be polyphyletic.

Reference:
Araya, J.F. et al., 2017. New records of terrestrial mollusks (Gastropoda: Stylommatophora) from Antofagasta, northern Chile. – Revista Mexicana de Biodiversidad, 88: 769-772.

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New Carychium species

Recently Jochum et al. published on Carychium species from the Nearctic and Neotropical regions, i.e. southeastern U.S.A., Belize and Panama. This add substantially to the known distribution of this genus in Central America.

The abstract reads: “Three new species of the genus Carychium O.F. Müller, 1773, Carychium hardiei Jochum & Weigand, sp. n., Carychium belizeense Jochum & Weigand, sp. n. and Carychium zarzaaeJochum & Weigand, sp. n. are described from the Southeastern United States, Belize and Panama, respectively. In two consecutive molecular phylogenetic studies of worldwide members of Carychiidae, the North and Central American morphospecies Carychiummexicanum Pilsbry, 1891 and Carychium costaricanum E. von Martens, 1898 were found to consist of several evolutionary lineages. Although the related lineages were found to be molecularly distinct from the two nominal species, the consequential morphological and taxonomic assessment of these lineages is still lacking. In the present paper, the shells of these uncovered Carychium lineages are assessed by comparing them with those of related species, using computer tomography for the first time for this genus. The interior diagnostic characters are emphasized, such as columellar configuration in conjunction with the columellar lamella and their relationship in context of the entire shell. These taxa are morphologically described and formally assigned their own names”.

They used micro-CT scanning to make the inner shell structures visible, which is an excellent and non-destructive way of doing.

Reference:
Jochum, A. et al., 2017. Three new species of Carychium O.F. Müller, 1773 from the Southeastern USA, Belize and Panama are described using computer tomography (CT) (Eupulmonata, Ellobioidea, Carychiidae). – ZooKeys, 675: 97-127.
[open access: https://zookeys.pensoft.net/article/12453/]

Adaptive significance of arboreality

Seaki et al. (2017) have recently published the results of a field experiment in which they tested the survival advantages of living in a tree.

Arboreality has evolved in a wide range of taxa, but its adaptive significance has rarely been examined in natural ecosystems. Euhadra brandtii sapporo is an arboreal land snail distributed in a restricted area of Hokkaido, Japan. We hypothesized that arboreality provides the species with significant survival advantages, which we tested via field observations and experiments. A monitoring census showed that E. b. sapporo hibernates in winter in the ground litter, climbs into the canopy in early spring and returns to the ground in late autumn. This seasonal movement appears to be effective for escaping from predation by ground-dwelling carabine beetles, whose activity was high during the summer based on a pitfall-trap census. Manipulative field experiments were conducted to compare survival rates in arboreal and ground-dwelling environments. We collected 120 E. b. sapporo individuals in summer and tethered 40 in tree canopies and 80 on the ground; half those on the ground were covered by baskets to prevent predation by large animals. The survival rate after 11 days was highest in the canopy, followed by that on the ground with a basket and was lowest on the ground without a basket. Predation was the main cause of death, but some died from other causes. Similar results were obtained in autumn, except for higher survival rates of the ground treatments. Analyses of carbon and nitrogen isotope ratios suggest that the land snail uses epiphytic lichens and mosses as food resources. In conclusion, arboreality has a marked advantage in reducing mortality in E. b. sapporo and is probably supported by food availability as well”.

This seems a very well-conducted experiment which may have more general significance for other snail families with arboreal members around the world.

Reference:
Saeki, I. et al., 2017. Adaptive significance of arboreality: field evidence from a tree-climbing land snail. – Animal Behaviour, 127: 53-66.

 

Geometric morphometric study on Cuban Cerion

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.

Reference:
Miller, J.P., 2016. Geometric morphometric analysis of the shell of Cerion mumia (Pulmonata: Cerionidae) and related species. – Folia Malacologica, 24: 239-250.

Cecilioides in Argentina

Diaz et al. recently published a new record of an introduced species for Argentina. “Cecilioides acicula (Müller, 1774), family Ferussaciidae, is native to the Palaearctic region but has been dispersed around the word by human activity. Here, we report the presence of this introduced species in La Plata city, Buenos Aires province, Argentina. This snail is largely subterranean and frequently is found in old graves in association with skeletal remains. Our samples were collected from sediments from the Municipal Cemetery of La Plata, Buenos Aires province, Argentina”.

Reference:
Diaz, A.C. et al., 2017. First record of Cecilioides acicula (Müller, 1774) (Mollusca: Ferussaciidae), from Buenos Aires province, Argentina. – CheckList, 13(2): 2096.

Predation by land planarians

Land planarians are increasingly been reported as predators of land snails, and several reports have been summarised by Cseh et al. (2017), as well as presenting new data.

“The food preference of Obama anthropophila Amaral, Leal-Zanchet & Carbayo, 2015, a species that seems to be spreading across Brazil’s human-modified environments, was investigated. Extensive experiments led to the conclusion that the generalized diet of this species may have facilitated its dispersal. The analysis of 132 feeding records of 44 geoplaninid species revealed a tendency for closely related species to feed on individuals from similar taxonomic groups, suggesting that in this group behavioral evolution is more conserved than phylogenetic diversification”.

The paper supplies a table with the known prey animals of land planarians.

Reference:
Cseh, A. et al., 2017. Observations on food preference of Neotropical land planarians (Platyhelminthes), with emphasis on Obama anthropophila, and their phylogenetic diversification. – Zoologia (Curitiba), 34:e12622

An overlooked designation

Taxonomy of fossils and recent species sometimes intertwines as demonstrated by a new publication of Kadolsky.

A nice update for the correct names of the Hispaniolan malacofauna.

Reference:
Kadolsky, D., 2017. On the type species of the genus Galactochilus Sandberger, 1875, with a review of the identity of Helix cornumilitare Linnaeus, 1758 and of its misidentifications (Gastropoda: Helicoidea). – Archiv für Molluskenkunde, 146: 97-110.