Oxyloma taxonomy

Incidentally I found a second paper on Succineidae, which is strictly spealing not Neotropical, but sufficiently interesting to warrant mentioning here. Perez et al are trying to revise the Oxyloma (Neoxyloma) species and have started with two. “The ambersnails (Succineidae), found nearly worldwide, are considered a very challenging group to classify and identify with even genus-level identifications requiring dissection. In this study, we use mitochondrial and nuclear DNA markers, shell morphometrics, and anatomical dissection to examine fresh material collected from the type localities of two nominal species in Oxyloma (Neoxyloma). We conclude from these evidence that Oxyloma salleanum (L. Pfeiffer, 1850) and Oxyloma effusum (L. Pfeiffer, 1853) are conspecific, and accordingly reduce O. effusum to the status of junior synonymy. We present a redescription of O. salleanum“.

Despite the apparent variation in shell morphology, their phylogenetic analysis point to conspecifity of both taxa. This makes it interesting to see the results of the future research, but at least it is warning that succineid taxonomy needs a thorough phylogenetic basis.

Perez, K.E. et al. 2021. A fresh start in ambersnail (Gastropoda: Succineidae) taxonomy: finding a foothold using a widespread species of Oxyloma. – European Journal of Taxonomy 757: 102-126.

Omalonyx unguis

Phylogenetics is now entering a next phase, where phylogenomics becomes more important. Belén Guzman et al. published a paper of which the abstract reads “Here we report the first complete mitochondrial genome of the semi-slug Omalonyx unguis (d’Orbigny, 1836) (Gastropoda: Succineidae). Sequencing was performed on a specimen from Argentina. Assembly was performed using Sanger data and Illumina next generation sequencing (NGS). The mitogenome was 13,984 bp in length and encoded the 37 typical Metazoan genes. A potential origin for mitochondrial DNA replication was found in a non-coding intergenic spacer (49 bp) located between cox3 and tRNA-Ile genes, and its second- ary structure was characterized. Secondary structure models of the tRNA genes of O. unguis largely agreed with those proposed for other mollusks. Secondary structure mod- els for the two rRNA genes were also obtained. To our knowledge, the 12S-rRNA model derived here is the first complete one available for mollusks. Phylogenetic analyses based on the mitogenomes of O. unguis and 37 other species of Stylommatophora were performed using amino acid sequences from the 13 protein-coding genes. Our results located Succineoidea as a sister group of Helicoidea + Urocoptoidea, similar to previous studies based on mitochondrial genomes. The gene arrangement of O. unguis was identical to that reported for another species of Succineoidea. The unique rearrangements observed for this group within Stylommatophora, may constitute synapomorphies for the superfamily”.

This paper didn’t reveal very new insights in the relationships of this species, but it nevertheless contains new phylogenomic data on this family which can be used for additional species later. Phylogenomics has great promises, but it needs freshly collected material, which limits its application in the Neotropics where local and active malacologists capable of this research are relatively scarce, and the required laboratory infrastructure is also not wide-spread. We will see what the future brings…

Belén Guzman, L. et al. 2021. The mitochondrial genome of the semi-slug Omalonyx unguis (Gastropoda: Succineidae) and the phylogenetic relationships within Stylommatophora. – PLoS ONE 16(6): e0253724.

Drymaeus on St. Kitts

Recently published, a new paper on the occurrence of Drymaeus on some of the West Indian islands. “The land snail species Drymaeus virgulatus (Férussac, 1821) is recorded in St. Kitts in the form of 21 complete or fragmented shells collected on the island in November 2019. The complete shells were collected on the backshores of South Frigate Bay and Majors Bay, while shell fragments come from naturally exposed sections of the North Frigate Bay sand ridge, where they date to the pre-Columbian period. This evidence therefore attests to the past presence of this species on the island. The absence of this taxon from recent malacological surveys points to it having been extirpated from St. Kitts. Apertural fragments of a large bulimulidae collected in the caves of Tintamarre Island, near St. Martin, are also related to this taxon, adding a second West Indian island from which this species apparently disappeared in recent centuries”.

An interesting paper which shows that the fairly recent inventory which was published in 2016 can be updated on the basis of careful studying old and subfossil shells, and archaeological sites often yield considerable gastropod material which too often remain poorly or incompletely studied by malacologists. Lenoble has proven that tailored attention can bring revealing results.

Lenoble, A. 2021. Drymaeus virgulatus, an extirpated land snail species on Saint Kitts and Tintamare Islands. – Novitates Caribaea 18: 193-206.

Patagonian Stephadiscus

New relevant literature has been scarce recently, and otherwise nothing new, there was little impetus to post. However, freshly pressed was a paper by Cuezzo et al. on a Charopidae species from Patagonia.

Their extensive abstract is as follows “

Background: Stephadiscus lyratus (Couthouy in Gould, 1846), an endemic Charopidae from southern South America, was described from few dry shells.
The distribution of this species is known on scattering occurrences, mainly from material deposited in museum collections. We provide here new information on anatomy, habitat, and microhabitat preferences and estimate the potential geographic distribution of the species to test if it is exclusively endemic to the Subpolar Magellanic Forest.
Methods: Fieldwork was carried out in the National Parks of the Patagonian Forests. Snails were photographed, measured, and dissected for anatomical studies; shells were studied with scanning electron microscopy. Estimation of the species geographical distribution (EGD) was obtained through correlative ecological niche modeling (ENM). We designed a calibration area a priori with known species points of occurrence in the Magellanic Subpolar Forests and borders of the Patagonian steppe. Seven bioclimatic variables of the WorldClim database were used. The best ENMs were calibrated and selected using a maximum entropy method with Maxent v3.3.3K through the R package “kuenm”. Candidate models were created by combining four values of regularization multiplier and all possible combinations of three feature classes. We evaluated candidate model performance based on significance (partial ROC), omission rates (E = 5%), and model complexity (AICc). From the best models obtained, a final model was transferred to a region “G” consisting of the calibration area plus the Valdivian Temperate Forests and whole Patagonian steppe, where we hypothesize that the species could be present. Finally, we obtained binary presence-absence maps. We quantified the proportion of the occurrence points and distribution range of S. lyratus in different land cover categories. To explore the degree of protection of S. lyratus’ EGD, we quantified the proportion of its distributional range within protected areas.
Results: A be-lobed kidney, a close secondary ureter, the terminal portion of the uterus forming a compact glandular mass, and the vas deferens with a dilatation are new anatomical information that distinguishes this species. Stephadiscus lyratus inhabit cold native forest areas, mainly living on or under humid logs in contact with the ground. The main constraining variables to explain S. lyratus distribution in the EGD were BIO3, BIO12, BIO6, and BIO4. The potential area of distribution obtained almost duplicates their original range (140,454 km2) extending to the Valdivian Temperate forests mainly in Chile. Natural and semi-natural terrestrial vegetation was predominant in the potential area of distribution of S. lyratus. However, only 14.7% of this area occurs within current protected areas from Argentina and Chile. The ectothermic physiological traits of this species, low dispersal capacity, and its narrow habitat requirements turn S. lyratus into a potentially vulnerable species”.

This extensive study on the ecology and potential distribution of this microsnail reveals new information on its anatomy and interesting aspects of its distribution. It also shows that Ecological Niche Modeling is now becoming more and more applied with snails and this study has interesting methodological aspects. The 20 new localities resulting from field work are a nice addition to our knowledge of this tiny species.

Cuezzo M.G. et al. 2021. Geographic distribution modeling and taxonomy of Stephadiscus lyratus (Cothouny in Gould, 1846) (Charopidae) reveal potential distributional areas of the species along the Patagonian Forests. – PeerJ 9:e11614.

Slug-eating snake

Snake meets snail, has it a happy ending? See for yourself…


It is part of the evidence that was used by Rojas-Morales et al. for their study on the feeding behaviours of two different snails species.

Their introduction is as follows: “The food animals eat and the way they obtain that food are central in species ecology (Curio, 1976; Slip and Shine, 1988). Feeding habits of snakes are of particular interest because they show remarkable adaptations for locating, capturing, subduing, and ingesting a wide array of prey (Cundall and Greene, 2000). Snakes’ diets vary within and between taxa due to evolutionary history, ontogeny, as well as differences in prey size, prey type, aspects of foraging, and microhabitat use (Greene, 1997; Cundall and Greene, 2000; Alencar et al., 2013). Detailed knowledge on feeding ecology and behaviour of several species is poorly understood, especially for neotropical species (e.g., Marques and Sazima, 1997; Alencar et al., 2013). Most of the data available about feeding behaviour of snakes comes from single observation (e.g., Rojas-Morales et al., 2017; Guedes et al., 2018a; Mario-da-Rosa et al., 2020), captivity (e.g., Braz et al., 2006; Rojas-Morales, 2013), or by encounters in the wild (e.g., Sazima, 1974, 1989; Gómez-Hoyos et al., 2015).
Among neotropical arboreal snakes, species in general such as Imantodes Duméril, 1853 and Sibon Fitzinger, 1826 show a compressed body, disproportionately slender neck, big and movable eyes, and a blunt head, making them easy to distinguish from other sympatric snakes. Other than their morphological similarity, arboreal niche, and nocturnal activity pattern (Ray, 2012), these groups have a substantially different diet. Imantodes prey mainly upon Anolis lizards (Duellman, 1978; Martins and Oliveira, 1998; Savage, 2002; Sousa et al., 2014), with frogs and amphibian eggs also recorded (Zug et al., 1979; Martins and Oliveira, 1998). In contrast, Sibon are included among the so- called “goo-eaters” (Cundall and Greene, 2000; Savage, 2002; Zaher et al., 2014), which exhibit a feeding strategy based on the consumption of small, soft-bodied invertebrates, including slugs and land snails. Goo- eaters have a specialized dentition and glandular toxins secreted by the infralabial glands to extract snails from their shells (Sheehy, 2013; Zaher et al., 2014). Sibon may also feed on annelids and amphibian eggs (Ray et al., 2012; Ward, 2016).
Imantodes cenchoa (Linnaeus, 1758) and Sibon nebulatus (Linnaeus, 1758) share a similar geographical distribution, ranging from southeastern Mexico across Central America into northern South America (Guedes et al., 2018b), inhabiting primary and second-growth forests, shrubs, and crops from sea level to 2300 m in elevation (Myers, 1982; Savage, 2002; Solórzano, 2004; Rojas-Morales et al., 2014, Missassi and Prudente, 2015). Both species are commonly syntopic in forested habitats in Colombia at elevations below 1500 m, where they are also usually one of the most frequently encountered species. We here report observations on the feeding behaviour of Icenchoa and Snebulatus from staged (with potential prey) and natural encounters in natural habitat of the northern Andes of Colombia with potential prey”.

Rojas-Morales, J.A. et al. 2021. On delicate night hunters: observations of the feeding behaviour of Imantodes cenchoa (Linnaeus, 1758) and Sibon nebulatus (Linnaeus, 1758) through staged and natural encounters (Serpentes: Dipsadidae: Dipsadinae). – Herpetology Notes 14: 714-723.

A new Auris

Simone & do Amaral recently described a new Auris: “Auris inornata is described based on samples from Guriri, São Mateus, Espírito Santo, Brazil. The new species is compared to its congeners, being mainly characterized by its small size and less sculptured shell. A brief discussion about all the species of the genus is also performed.”

Simone, L.R.L. & Amaral, V.S. do 2021. Auris inornata, a new Bulimulidae from Espirito Santo, Brazil (Gastropoda, Pulmonata). – Journal of Conchology 44 (1): 71-74.

Snails and art in Ecuador

Modesto Correoso recently published an interesting book on Ecuadorian snails and illustrations.

The book’s focus is on two persons who lived in Quito during the second half of the 19th century and shared their interest in Ecuadorian land snails: Auguste Cousin (1835-1899) and Joaquin Pinto (1842-1906). After the introduction there are seven chapters: on Pinto and scientific illustrations in malacology, a brief introduction to malacology, historical context of scientific illustration and art during the 19th century, study of an album of Cousin and illustrated by Pinto, and three chapters on the cooperation between these two men. In the annexes there is a chronology of Pinto’s work as illustratator and artist, a biography of Cousin, and a list of references.

All together it is a very nice book for which the author deserves our compliments to share with a broader public his research in historical archives and bring to light details on two persons who shared their interest in malacology during an era and a place where this was not common at all.

Correoso, M. 2020. Moluscos y al arte en Ecuador. – Casa de la Cultura Ecuatoriana, Quito, 87 [+ 2] pp., 33 figs. ISBN 978-9942-34-063-4. Available online at https://casadelacultura.gob.ec/wp-content/uploads/2021/05/Molucos-y-arte-en-Ecuador.pdf

Tomostele on Hispaniola

A paper which became online available but not yet with correct pagination is from Alvarez-Abreu et al. “The presence of alien mollusc species in an ecosystem has a negative impact on the endemic mollusc fauna and can result in economic losses. The West African land snail Tomostele musaecola (Morelet) was previously recorded from numerous localities in the Western Hemisphere. In this paper, we provide a new locality of this malacophagous snail in the Dominican Republic. The species is recorded from an urban park named Parque Ecológico Las Caobas in the province of San Cristóbal. In order to update the current distribution of T. musaecola in the Americas we examined the literature and the online database of the Invertebrate Zoology Collection of the Florida Museum of Natural History (FLMNH); when available, citizen science data were also used. A map is provided to illustrate the current distribution of the species in the Americas. The total number of records in the Western Hemisphere is 51, and 26 of them are part of this review. More studies are needed on the interaction of this species with the native land snails. Trade and planting of ornamental species in urban parks facilitate the establishment and expansion of alien molluscs.”

Given the fact that this record is from an urban area and exotic plants are present in its habitat, it seems not very surprising to find this snail in a locality hitherto not reported. Sadly, it is one more observation that underpins the name Anthropocene for our current time.

Alvarez-Abreu, O. et al. 2021. First record of Tomostele musaecola (Morelet, 1860) (Gastropoda: Eupulmonata: Streptaxidae) from the Dominican Republic and its current distribution in the western hemisphere. – Folia Malacologica 29 (2): [10 pp.] (advance online)