Checklist for Hispaniola

Just published: an extremely useful addition to our knowledge of Caribbean malacology: “The annotated checklist on the extant terrestrial mollusks from Hispaniola Island based on literature from 1758 to 2020 is here presented. We report 612 taxa distributed in three subclasses, 129 genera and 39 families. The most representative families are Annulariidae with 26 genera and 233 species, and Urocoptidae with 14 genera and 104, respectively. As more information is produced from the different families reported, these numbers can vary considerably”.

This text-only document contains the original reference to the island, the depostories of type material when known, the type locality, and a reference to the paper on which the current status has been based. Very useful indeed.

Reference:
Espinosa, A. & Robinson, D.G., 2021. Annotated checklist of the terrestrial mollusks (Mollusca: Gastropoda) from Hispaniola Island – Novitates Caribiaea 17: 71-146.

New Sultana from Peru

Freshly pressed: “A new species of Sultana Shuttleworth, 1856 is described from North of Peru, Sultana hidalgoi n. sp. presents clear differences with all the previously described species of Sultana within Peru and South America, and also a well-delimited area of distribution. Sultana (Metorthalicus) marahonensis (Albers, 1854) being the closest species geographically, although conchologically, the new species is more similar to Sultana (Metorthalicus) labeo (Broderip, 1828) and Sultana (Metorthalicus) vicaria (Fulton, 1896)”.

This species is described from northern Peru, Yambrasbamba District. Holotype in the Madrid museum. These large snails can hardly be overlooked when in the right area, but require some expertise and reference material to identify. Given the limited distribution it may be a short-range endemic, which need appropriate conservation action to prevent its untimely extinction.

Reference:
Vega-Luz, R., 2021. A new Sultana Shuttleworth, 1856 (Pulmonata: Orthalicidae) from Peru. – Malacologia Mostra Mondiale 110: 7-9.

Snails and flatworms: a nasty combination

A large review paper was recently published by Gerlach et al. on this topic, also relevant in part of the Neotropics.

Their abstract is: “Since 1955 snails of the Euglandina rosea species complex and Platydemus manokwari flatworms were widely introduced in attempted biological control of giant African snails (Lissachatina fulica) but have been implicated in the mass extinction of Pacific island snails. We review the histories of the 60 introductions and their impacts on L. fulica and native snails. Since 1993 there have been unofficial releases of Euglandina within island groups. Only three official P. manokwari releases took place, but new populations are being recorded at an increasing rate, probably because of accidental introduction. Claims that these predators controlled L. fulica cannot be substantiated; in some cases pest snail declines coincided with predator arrival but concomitant declines occurred elsewhere in the absence of the predator and the declines in some cases were only temporary. In the Hawaiian Islands, although there had been some earlier declines of native snails, the Euglandina impacts on native snails are clear with rapid decline of many endemic Hawaiian Achatinellinae following predator arrival. In the Society Islands, Partulidae tree snail populations remained stable until Euglandina introduction, when declines were extremely rapid with an exact correspondence between predator arrival and tree snail decline. Platydemus manokwari invasion coincides with native snail declines on some islands, notably the Ogasawara Islands of Japan, and its invasion of Florida has led to mass mortality of Liguus spp. tree snails. We conclude that Euglandina and P. manokwari are not effective biocontrol agents, but do have major negative effects on native snail faunas. These predatory snails and flatworms are generalist predators and as such are not suitable for biological control.”

Their conclusion is already clear for some time, but is nevertheless a sad one. The problem is of course that once introduced, these alien species are nearly impossible to eradicate. So the best strategy is prevention and think twice before you start with a biological enemy.

Reference:
Gerlach, J. et al., 2020. Negative impacts of invasive predators used as biological control agents against the pest snail Lissachatina fulica: the snail Euglandina ‘rosea’ and the flatworm Platydemus manokwari – Biological Invasions: 1-35 (advance online). https://doi.org/10.1007/s10530-020-02436-w

Subfossil fauna of Tintamarre Island

Just received, a paper by Bochaton and colleagues, on this island in the Caribbean. “Although there is an increasing amount of subfossil data available that documents the effects of past human impact on the biodiversity of the West Indies, many islands remain poorly documented, if at all. The palaeontological study of an assemblage of terrestrial mollusc shells and bone remains recovered on the surface level of two cave deposits, Trou de Souris 1 and 4, provides the first data on the past biodiversity of Tintamarre Island (northern Lesser Antilles). The results indicate the presence of at least six vertebrate taxa and a possible six terrestrial snail species that are no longer present on the island. As it was not possible to excavate the deposits from which these assemblages were collected, we currently lack a chronological framework to interpret the collected data. However, based on phenomena observed from several other islands in the Lesser Antilles, we propose several hypotheses linking the local extinction of these species to human activity on Tintamarre throughout the last few centuries”.

This is an interesting paper as we have some (sub)fossil material from Guadeloupe which can be compared to their results. To be continued…

Reference:
Bochaton, C. et al., 2020. Initial observations of the subfossil fauna from Tintamarre Island (Anguilla Bank, Lesser Antilles). – Quartenaire 31(4): 327-340.

Phylogeny of Scolodontidae

Recently published, a paper by Calcutt et al. on Solaropsidae, of which the abstract reads “The classification of terrestrial sundial snails has a long and contentious history; they have been diversely classified in Camaenidae, Pleurodontidae, Polygyridae, and also in their own family, Solaropsidae. Two genera have been recently removed from Solaropsidae (Polygyratia Gray, 1847 and Ridleya Ancey, 1901), but the status of its 3 remaining genera (Solaropsis H. Beck, 1837, Olympus Simone, 2010, and Psadara K. Miller, 1878) is still uncertain. We have sequenced 4 mitochondrial and nuclear markers of species belonging to those 3 genera and included them in a phylogenetic framework of all helicoid snails (Sagdoidea and Helicoidea). Our analysis supports a monophyletic Solaropsidae within Sagdoidea, as well as its internal division into Solaropsinae and Caracolinae. Solaropsis and Psadara are both paraphyletic and include the monotypic Olympus. Thus, we consider the latter 2 genera synonymous with Solaropsis. We also present a summary of the fossil record of the family, excluding from it the genus Hodopoeus Pilsbry & Cockerell, 1945 (now classified in Labyrinthidae) and discussing the paleobiogeographic history of Sagdoidea and of early branches of Helicoidea. Finally, Epiphragmophoridae (formerly a subfamily of Xanthonychidae) is supported as a distinct family-level clade within Helicoidea”.

This paper, which was presented at the CLAMA virtual conference a few months ago, solves a persistent problem of uncertainty at the genus level of this group. As usual in phylogenetic studies, some species needed to solve outstanding questions could not be sampled and further research should try to solve these. Nonetheless, a leap forward for this group.

Reference:
Calcutt, J. et al., 2020. Phylogenetic relationships and classification of Solaropsidae (Gastropoda: Stylommatophora). – Archiv für Molluskenkunde 149(2): 181-193.

New Scolodonta from Argentina

Miquel & Santin recently published a paper about alien snails, describing also a new species from Argentina. “Ten taxa belonging to seven families of land gastropods are reported from a garden in Villa Adelina (Buenos Aires Province, Argentina). One of them is a species new to science, here described as Scolodonta enigmatica n. sp. (Scolodontidae). The genera Pristiloma, Subulina (Achatinidae Subulininae) and Glyphyalus (Oxychiilidae) are recorded for the first time in Argentina. The following species, already known from Argentina and common in gardens, are reported for the first time in Villa Adelina: Cecilioides (C.) acicula (Ferussaciidae), Allopeas gracile, Opeas pumilum (Achatinidae Subulininae), Paralaoma servilis (Punctidae), Hawaiia minuscula (Pristilomatidae) and Zonitoides arboreus (Zonitidae). The sources of these introductions are unknown”.

Four new records for Argentina, of which one species new to science, is a good score (or a bad one if you view it from the point of introductions). The new species is compared to various other species and its a natomy and variation within the Scolodontidae is described. Also from some other species anatomical details are presented.

Reference:
Miquel, S.E. & Santin, R.A., 2020. New records of alien land gastropods in Argentina, with the description of a new species of Scolodontidae (Mollusca: Pulmonata: Stylommatophora). Molluscan Research: 1-11 (advance online). https://doi.org/10.1080/13235818.2020.1836720

Aestivation strategy

Barrientos published last year in a less well-known journal a paper on the aestivation strategy of land snails. The abstracts reads “Introduction: Many land molluscs survival strategies are still poorly understood or have not been even reported, especially in the Neotropics. Methods: I collected 25 adult Tikoconus (Tikoconuscostarricanus from Reserva Forestal Río Macho, Costa Rica. I kept the specimens for 8 days in terrariums to film their behavior. Objective: To analyse the behavior of T. costarricanus, with emphasis on its strategies to survive drought and probably also predation. Results: This snail has at least three unusual behaviors that probably help them reduce dehydration and may be escape from enemies and avoid diseases: hanging upside down like bats, falling and grooming. During aestivation, they compress the body and hang upside down from leaves, like bats hang from perches. They attach to the underside of leaves with mucus from a caudal gland. Disengagement is done with vigorous shell rotations and foot twisting in contorting sequences, and can be done as reaction to direct sunlight, and probably to avoid predators and parasites. They groom their own shell, shell lappets and foot, an unusual behavior among land snails. This species feeds mainly on epiphyllous mosses, algae and lichens, occasionally adding arthropod eggs and carrion. Egg laying is similar to other euconulids and valloniid snails. Conclusions: Aestivating hanging upside down is a drought avoiding trait described here for the first time and is also a new function for the caudal gland mucus. Leaf detaching is done by a contortion sequence of shell rotations and foot twisting; its complexity and duration varies according to the leaf side where the snail is located”.

The paper includes interesting observations on the biology and ecology of Tikoconus costaricensis, and supplements data on snails dangling from mucus threads previously published in literature.

Reference:
Barrientos, Z., 2020. A new aestivation strategy for land molluscs: hanging upside down like bats. – UNED Research Journal 12(1): e2802 (13 pp.).

Microhabitat selection Tikoconus

Just published a paper by Barrientos about a Costa Rican euconulid. The abstract is as follows: “Introduction: The integument of terrestrial mollusks is highly susceptible to dehydration; there- fore, microhabitat selection, seasonality and behavior around the day are crucial to their survival. However, they are still poorly understood, especially for tropical montane wet forest species. Objetive: To analyze activity patterns and microhabitat selection on shrubs of the land snail Tikoconus costarricanus, according to season, daytime and weather. Methods: I conducted the study near “El llano” water dam in a tropical montane wet forest in Costa Rica. I observed daily activity of T. costarricanus, during the rainy and the dry season on a 2 km long trail. I observed 167 specimens and made 781 observations in total. I took note of: season, time, activity, weather, temperature and relative humidity inside the forest, and part of the leaf and height where snails were. Active snails had optical tentacles extended. I analysed daily rainfall data from a nearby meteorological station. Results: This species can be found mainly on understory leaves between 1.1 and 2 m above the floor. They are active the day around during the whole year. Only 24 % of the snails were on the upper side of leaves, but 92 % of them were active. The following behaviors were season dependent: activity peaks, leaf side selection according to daytime and weather, quantity of snails aestivating and vertical distribution. During the dry season, I found more active snails in rainy and cloudy days. During the rainy season I found more active snails in sunny days. During rainy season light hours, active snail percentage on the upper side of leaves decreased with rainfall increase, while in the dry season decreased with temperature increase and relative humidity decrease. During night hours of both seasons, the number of snails on the upper side of leaves decreased considerably in relation to active snails, especially in the rainy season. This snail aestivated on the underside of leaves during periods shorter than 21 h, mainly around noon and afternoons during the dry season. High humidity in this forest allowed snail activity around the day at any season. However, this species aestivated when moisture reached the lowest values, mainly, around noon and in the afternoons in the dry season. The rainfall pattern during the rainy season light hours explains the specimen decrease on the upper side of leaves, but in the dry season it is better explained by the temperature increase and the decrease in relative humidity. During dark hours, the almost complete snail absence on the upper side of leaves during the rainy season is explained if the effect of canopy drip produced by rain and dew condensed on leaves is added to the rain pattern. The situation is slightly different in dark hours of the dry season, in this case, snail decrease on the upper side of leaves is explained by canopy drip from dew and fog precipitation. Seasonal difference in vertical distribution may be a way to avoid rain and rain splash out on the soil. Conclusions: Moisture, temperature, rain, and canopy drip from dew, fog and rain, affect behavior and substrate selection of small terrestrial mollusks that inhabit shrubs in wet tropical rainforests”.

Another excellent study by this researcher on the biology of Neotropical snails. Although other species from tropical montane wet forests might show different behaviour, I guess the pattern will largely follow the observations here presented.

Reference:
Barrientos, Z., 2020. Microhabitat selection, and seasonal and daily activity of the snail Tikoconus costarricanus (Stylommatophora: Euconulidae) in tropical montane wet forest understory. – Revista de Biología Tropical, 68(4): 1131-1142.

New Cuban land snail

Cuba is a mega-diverse malacological ‘paradise’ and relatively well-studied, not the least by the continuous efforts of Cuban malacologists. Quite remarkably a new species was found, classified even in a new genus, by Hernandez et al. Their abstract reads “A new genus and species of Cepolidae is described from the Island of Cuba: Plagiosimilis gibarensis gen. et sp. nov. It is classified in Cepolidae based on the following diagnostic characteristics of the family: dart apparatus consisting of a dart sac with a pedunculated gland on its apical side, both covered by a sheath; at the base of the dart apparatus there are two accessory glands; absence of a diverticulum. The specimens from the new genus come from the northern part of the Holguin province in the vicinity of the town of Gibara and live in special habitat dominated by Tillandsia plants. Shell with the rounded last whorl, circular umbilicus and strongly reflected lip distinguishes conchologically the new genus. The reproductive system and the shell differ from the other genera, although have a certain similarity with the genera Plagioptycha and Hemitrochus.”

As you see its always possible to find something unexpected, even in a country that is so well-studied as Cuba.

Reference:
Hernandez, M. et al., 2020. A new genus and species of cepolid from Cuba. – Ruthenica 30(3): 155-164.