Marstonia comalensis
| Marstonia comalensis | |
|---|---|
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| Shell of one of the lectotypes of Marstonia comalensis. Scale bar is 1.0 mm. | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Gastropoda |
| (unranked): |
clade Caenogastropoda clade Hypsogastropoda |
| Superfamily: | Rissooidea |
| Family: | Hydrobiidae |
| Subfamily: | Nymphophilinae |
| Genus: | Marstonia |
| Species: | M. comalensis |
| Binomial name | |
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Marstonia comalensis (Pilsbry & Ferriss, 1906) |
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| Synonyms | |
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clade Hypsogastropoda
clade Littorinimorpha
Marstonia comalensis is a species of minute freshwater snail with a gill and an operculum, an aquatic gastropod mollusk or micromollusk in the family Hydrobiidae. It is found in south central Texas, United States.
Marstonia comalensis is large for this genus. It has an ovate-conic, openly umbilicate shell. The penis has a short filament and oblique, squarish lobe bearing a narrow gland along its distal edge. It is well differentiated morphologically from other congeners that have similar shells and penes, and is also genetically divergent relative to those congeners that have been sequenced ( divergence 3.0–8.5%).
This species has often been confused with Cincinnatia integra.
In 1906, Henry Augustus Pilsbry and James Ferriss described this species under the name Amnicola comalensis based on six shells from Comal Creek and the Guadalupe River near New Braunfels, south-central Texas. Pilsbry and Ferriss differentiated this species from Amnicola limosa (Say) and two nomina (Amnicola cincinnatiensis [Anthony], Amnicola peracuta Pilsbry & Walker) that are currently recognized as synonyms of Cincinnatia integra (Say) by its much smaller size and noted that it further differed from the latter by its less shouldered whorls. The genus Amnicola was used at that time as "a catch-all for most American amnicoloid species that could not conveniently be placed elsewhere on the basis of their shells".Amnicola comalensis was not further treated taxonomically until Taylor (1975) transferred it to Cincinnatia without comment in a bibliographic compilation; this allocation was widely followed in the subsequent literature. During the course of a revisionary study of Cincinnatia integra, Hershler and Thompson (1996) examined several alcohol preserved collections of a snail that they identified as Amnicola comalensis and noted that it closely resembled species of Marstonia (which were then placed in Pyrgulopsis); Amnicola comalensis was subsequently transferred to Marstonia based on this unpublished work. Hershler et al. (2003) published a molecular phylogenetic analysis of the North American nymphophilines that included a specimen of Marstonia comalensis from Old Faithful Spring in Real County, Texas (ca. 180 km from the type locality), which was depicted as nested within the Marstonia clade. This was the only published record for Marstonia comalensis subsequent to its original description. Hershler & Liu (2011) redescribed Marstonia comalensis based on study of a large series of dry shell and alcohol-preserved material, most of which was collected by malacologists J. J. Landye and D. W. Taylor from 1971–1993, and provided anatomical evidence supporting its current generic allocation.
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