Marstonia comalensis
Encyclopedia
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
, USA.
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 congener
s that have similar shells and penes, and is also genetically divergent relative to those congeners that have been sequenced (mt
COI
divergence 3.0–8.5%).
This species has often been confused with Cincinnatia integra.
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); Amnicola comalensis was subsequently transferred to Marstonia based on this unpublished work.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.
. The original collections of Marstonia comalensis are worn shells having the appearance of drift material. It is possible that Marstonia comalensis became extinct at Comal Springs when
this water body temporarily dried in 1964; it is also possible that the shells of this species which have been found at this site were washed downflow from extant populations in the headwaters of the Guadalupe River
.
Records published by Hershler & Liu (2011) considerably expanded the geographic range of Marstinia comalensis, which lives in springs and fluvial habitats spread among four river basins in south-central Texas. Almost all of these localities are on the Edwards Plateau
. Records indicate that Marstonia comalensis was historically distributed in the upper portions of the Brazos River
, Colorado River (Texas)
, Guadalupe River (Texas)
and Nueces River
basins, south-central Texas
. The species has been live collected at only 12 localities and only two of these have been re-visited since 1993.
Hershler & Liu (2011) were unable to confirm a previous report by Cable & Isserhoff (1969) of this species from a drainage canal near Galveston Bay
.
Hershler & Liu (2011) also analyzed previously published molecular data to evaluate the genetic divergence
and phylogenetic relationships of Marstonia comalensis, whose geographic range is broadly disjunct
relative to other members of the genus.
is ovate-conic with 4.5–5.5 whorls
. The height of the shell is about 2.6–4.6 mm. Protoconch
is near planispiral, slightly tilted, initial 0.75–1.0 whorl strongly wrinkled. Teleoconch whorls are weakly convex, often narrowly shouldered, rarely having subsutural angulation. The sculpture
of strong collabral growth lines, later whorls having numerous weak spiral striae. The aperture
is pyriform or ovate. Inner lip complete across parietal wall in larger specimens, usually narrowly adnate, rarely slightly disjunct; usually thin, sometimes slightly thickened apically; columellar shelf absent or very narrow; outer lip thin or slightly thickened, orthocline or prosocline. Umbilicus is open but small.
The operculum
is thin, amber
, narrowly ovate, multispiral with eccentric nucleus. The last 0.25 whorl is sometimes frilled on outer side; inner side having well developed rim near outer edge. The attachment scar border is sometimes weakly thickened near the nucleus.
is brown, distal lips are pale and foot is pale. Pallial roof has black pigment bands along edges of ctenidium
and dorsal edge of genital duct; visceral coil pale except for black pigment on testis. Ctenidium is positioned a little in front of pericardium. There are 24-25 ctenidial filaments, that are broadly triangular with lateral surfaces ridged. Osphradium
is narrow, positioned slightly posterior to middle of ctenidium.
Radula
has about 36 well-formed rows of teeth. Central teeth are about 38 μm wide with convex cutting edge. There are 3-8 lateral cusps. Central cusp are pointed or hoe-shaped, parallel-sided proximally or tapering throughout. There are 1-3 small basal cusps. Basal tongue is U- or V-shaped, about as long as lateral margins. Lateral tooth face is rectangular. Central cusp is pointed or hoe-shaped. There are 2-5 lateral cusps (inner) and 3-7 (outer). Outer wing is broad, flexed, with about 140% length of cutting edge. Basal tongue weakly is developed. Inner and outer marginal teeth both have 14-21 cusps and basally positioned rectangular wing.
Hypobranchial gland
is large, overlapping rectum and part of genital duct, thickened alongside kidney. Style sac is longer than remaining portion of stomach, posterior stomach have small caecal appendix.
Reproductive system
: Testis is large (1.75 whorls), composed of compound lobes, broadly overlapping stomach anteriorly. Seminal vesicle is opening near anterior edge of testis, composed of a few thickened coils, positioned along ventral side of anterior 33% of testis. Prostate gland is small, pea-shaped, with about 50% of length in pallial roof. Anterior vas deferens opening from antero-ventral edge of prostate gland, section of duct on columellar muscle straight. Penis is large, base rectangular, inner edge without folds. Penial filament is short, narrow, tapering, oblique. Lobe is rather medium-sized, squarish, oblique. Terminal gland is narrow, usually transversely positioned along outer edge of lobe, less frequently horizontal, sometimes borne on short stalk. Penial duct is narrow, near outer edge, almost straight. Penial filament has black internal pigment core along most of length.
Ovary is small (0.75 whorl), composed of simple, stalked lobes. It is slightly overlapping stomach anteriorly. Female glandular oviduct and associated structures are as follows: Coiled oviduct is narrow, vertical. Bursa copulatrix is small, ovate, horizontal, about 50% overlapped by albumen gland. Bursal duct is longer than bursa, narrow, opening from distal edge, partly embedded in albumen gland proximally, entirely embedded distally, junction with common duct well in front of posterior wall of pallial cavity. Seminal receptacle is small, pouch-like, positioned near ventral edge of albumen gland slightly anterior to bursa copulatrix. Albumen gland is largely visceral. Capsule gland composed of two distinct tissue sections. Genital aperture a terminal slit.
It can be distinguished from Marstonia gaddisorum by its less convex shell whorls, distinctive pallial roof pigmentation, larger number of cusps on the inner side of the lateral teeth and on the outer marginal teeth, larger penial lobe, narrower terminal gland, and smaller overlap of the bursa copulatrix by the albumen gland.
If differs from Marstonia lustrica by its smaller prostate gland, smaller penial lobe, narrower penial filament, straight anterior vas deferens, partly imbedded (in albumen gland) bursal duct, and larger seminal receptacle.
It differs from Marstonia ogmorhaphe by its smaller size, broader shell, smaller prostate gland, straight anterior vas deferens, and smaller bursa copulatrix.
(2009) ranking, but found not to warrant listing owing to insufficient information. The data by Hershler & Liu (2011) suggest that the conservation status of this snail needs to be re-assessed.
Freshwater snail
A freshwater snail is one kind of freshwater mollusc, the other kind being freshwater clams and mussels, i.e. freshwater bivalves. Specifically a freshwater snail is a gastropod that lives in a watery non-marine habitat. The majority of freshwater gastropods have a shell, with very few exceptions....
with a gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
and an operculum
Operculum (gastropod)
The operculum, meaning little lid, is a corneous or calcareous anatomical structure which exists in many groups of sea snails and freshwater snails, and also in a few groups of land snails...
, an aquatic
Aquatic animal
An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...
gastropod mollusk or micromollusk
Micromollusk
A micromollusk is a descriptive term for a shelled mollusk which is extremely small, even at full adult size. The word is usually, but not exclusively, applied to marine mollusks, although in addition, numerous species of land snails and freshwater mollusks also reach adult size at very small...
in the family Hydrobiidae
Hydrobiidae
Hydrobiidae, common name mud snails, is a large cosmopolitan taxonomic family of very small freshwater snails and brackish water snails that have an operculum, aquatic gastropod mollusks in the clade Littorinimorpha.- Distribution :...
. It is found in south central Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
, USA.
Marstonia comalensis is large for this genus. It has an ovate-conic, openly umbilicate shell
Gastropod shell
The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage...
. 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 congener
Congener
Congener has several different meanings depending on the field in which it is used. Colloquially, it is used to mean a person or thing like another, in character or action.-Biology:In biology, congeners are organisms within the same genus...
s that have similar shells and penes, and is also genetically divergent relative to those congeners that have been sequenced (mt
Mitochondrion
In cell biology, a mitochondrion is a membrane-enclosed organelle found in most eukaryotic cells. These organelles range from 0.5 to 1.0 micrometers in diameter...
COI
Main subunit of cytochrome c oxidase
Cytochrome C and Quinol oxidase polypeptide I is main subunit of cytochrome c oxidase complex.Cytochrome c oxidase is a key enzyme in aerobic metabolism. Proton pumping heme-copper oxidases represent the terminal, energy-transfer enzymes of respiratory chains in prokaryotes and eukaryotes...
divergence 3.0–8.5%).
This species has often been confused with Cincinnatia integra.
Taxonomy
In 1906, Henry Augustus PilsbryHenry Augustus Pilsbry
Henry Augustus Pilsbry was an American biologist, malacologist and carcinologist, among other areas of study. He was a dominant presence in many fields of invertebrate taxonomy for the better part of a century...
and James Ferriss
James Ferriss
James Henry Ferriss was an amateur conchologist. According to Henry Augustus Pilsbry, Ferriss was "the fore-most of American landshell collectors... as a collector he has probably never been surpassed."...
described this species under the name Amnicola comalensis based on six shells from Comal Creek and the Guadalupe River
Guadalupe River (Texas)
The Guadalupe River runs from Kerr County, Texas to San Antonio Bay on the Gulf of Mexico. The river is a popular destination for rafters and canoers. Larger cities along the river include New Braunfels, Kerrville, Seguin, Gonzales, Cuero, and Victoria...
near New Braunfels, south-central Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
. 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
Whorl (mollusc)
A whorl is a single, complete 360° revolution or turn in the spiral growth of a mollusc shell. A spiral configuration of the shell is found in of numerous gastropods, but it is also found in shelled cephalopods including Nautilus, Spirula and the large extinct subclass of cephalopods known as the...
. The genus Amnicola
Amnicola
Amnicola is a genus of very small freshwater snails which have an operculum. Amnicola species are aquatic prosobranch gastropod mollusks in the family Amnicolidae according to the taxonomy of the Gastropoda ....
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
Cincinnatia
Cincinnatia is a genus of very small freshwater snails that have an operculum, aquatic gastropod mollusks in the family Hydrobiidae, the mud snails.-Species:Species within the genus Cincinnatia include:...
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
Marstonia
Marstonia is a genus of freshwater snails with a gill and an operculum, aquatic gastropod mollusks in the family Hydrobiidae.-Distribution :Species in the genus Marstonia are distributed in springs, streams and lakes in eastern North America...
(which were then placed in Pyrgulopsis
Pyrgulopsis
Pyrgulopsis is a genus of freshwater snails with a gill and an operculum, aquatic gastropod mollusks in the family Hydrobiidae.- Etymology :The name Pyrgulopsis is composed from Pyrgula and opsis = aspect of.- Shell description :...
); 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.
Distribution
The type locality is Comal Creek, near New Braunfels, Comal County, TexasComal County, Texas
Comal County is a county located on the Edwards Plateau in the U.S. state of Texas. In 2010, its population was 108,472. Its seat is New Braunfels.Comal County is part of the San Antonio Metropolitan Statistical Area.-History Timeline:...
. The original collections of Marstonia comalensis are worn shells having the appearance of drift material. It is possible that Marstonia comalensis became extinct at Comal Springs when
this water body temporarily dried in 1964; it is also possible that the shells of this species which have been found at this site were washed downflow from extant populations in the headwaters of the Guadalupe River
Guadalupe River (Texas)
The Guadalupe River runs from Kerr County, Texas to San Antonio Bay on the Gulf of Mexico. The river is a popular destination for rafters and canoers. Larger cities along the river include New Braunfels, Kerrville, Seguin, Gonzales, Cuero, and Victoria...
.
Records published by Hershler & Liu (2011) considerably expanded the geographic range of Marstinia comalensis, which lives in springs and fluvial habitats spread among four river basins in south-central Texas. Almost all of these localities are on the Edwards Plateau
Edwards Plateau
The Edwards Plateau is a region of west-central Texas which is bounded by the Balcones Fault to the south and east, the Llano Uplift and the Llano Estacado to the north, and the Pecos River and Chihuahuan Desert to the west. San Angelo, Austin, San Antonio and Del Rio roughly outline the area...
. Records indicate that Marstonia comalensis was historically distributed in the upper portions of the Brazos River
Brazos River
The Brazos River, called the Rio de los Brazos de Dios by early Spanish explorers , is the longest river in Texas and the 11th longest river in the United States at from its source at the head of Blackwater Draw, Curry County, New Mexico to its mouth at the Gulf of Mexico with a drainage...
, Colorado River (Texas)
Colorado River (Texas)
The Colorado River is a river that runs through the U.S. state of Texas; it should not be confused with the much longer Colorado River which flows from Colorado into the Gulf of California....
, Guadalupe River (Texas)
Guadalupe River (Texas)
The Guadalupe River runs from Kerr County, Texas to San Antonio Bay on the Gulf of Mexico. The river is a popular destination for rafters and canoers. Larger cities along the river include New Braunfels, Kerrville, Seguin, Gonzales, Cuero, and Victoria...
and Nueces River
Nueces River
The Nueces River is a river in the U.S. state of Texas, approximately long. It drains a region in central and southern Texas southeastward into the Gulf of Mexico. It is the southernmost major river in Texas northeast of the Rio Grande...
basins, south-central Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
. The species has been live collected at only 12 localities and only two of these have been re-visited since 1993.
Hershler & Liu (2011) were unable to confirm a previous report by Cable & Isserhoff (1969) of this species from a drainage canal near Galveston Bay
Galveston Bay
Galveston Bay is a large estuary located along the upper coast of Texas in the United States. It is connected to the Gulf of Mexico and is surrounded by sub-tropic marshes and prairies on the mainland. The water in the Bay is a complex mixture of sea water and fresh water which supports a wide...
.
Hershler & Liu (2011) also analyzed previously published molecular data to evaluate the genetic divergence
Genetic divergence
Genetic divergence is the process in which two or more populations of an ancestral species accumulate independent genetic changes through time, often after the populations have become reproductively isolated for some period of time...
and phylogenetic relationships of Marstonia comalensis, whose geographic range is broadly disjunct
Disjunct distribution
In biology, a taxon with a disjunct distribution is one that has two or more groups that are related but widely separated from each other geographically...
relative to other members of the genus.
Shell description
The shellGastropod shell
The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage...
is ovate-conic with 4.5–5.5 whorls
Whorl (mollusc)
A whorl is a single, complete 360° revolution or turn in the spiral growth of a mollusc shell. A spiral configuration of the shell is found in of numerous gastropods, but it is also found in shelled cephalopods including Nautilus, Spirula and the large extinct subclass of cephalopods known as the...
. The height of the shell is about 2.6–4.6 mm. Protoconch
Protoconch
A protoconch is an embryonic or larval shell of some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod...
is near planispiral, slightly tilted, initial 0.75–1.0 whorl strongly wrinkled. Teleoconch whorls are weakly convex, often narrowly shouldered, rarely having subsutural angulation. The sculpture
Sculpture (mollusc)
The sculpture of a mollusc shell is the three-dimensional ornamentation on the outer surface, as distinct from the basic shape of the shell itself or colouration. Sculpture may be concave as well as convex. Sometimes it has microscopic detail. Sculpture refers to the calcareous outer layer, not the...
of strong collabral growth lines, later whorls having numerous weak spiral striae. The aperture
Aperture (mollusc)
The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where part of the body of the animal emerges for locomotion, feeding, etc....
is pyriform or ovate. Inner lip complete across parietal wall in larger specimens, usually narrowly adnate, rarely slightly disjunct; usually thin, sometimes slightly thickened apically; columellar shelf absent or very narrow; outer lip thin or slightly thickened, orthocline or prosocline. Umbilicus is open but small.
The operculum
Operculum (gastropod)
The operculum, meaning little lid, is a corneous or calcareous anatomical structure which exists in many groups of sea snails and freshwater snails, and also in a few groups of land snails...
is thin, amber
Amber
Amber is fossilized tree resin , which has been appreciated for its color and natural beauty since Neolithic times. Amber is used as an ingredient in perfumes, as a healing agent in folk medicine, and as jewelry. There are five classes of amber, defined on the basis of their chemical constituents...
, narrowly ovate, multispiral with eccentric nucleus. The last 0.25 whorl is sometimes frilled on outer side; inner side having well developed rim near outer edge. The attachment scar border is sometimes weakly thickened near the nucleus.
Anatomy
The cephalic tentacles are pale, except for black eyespots. SnoutSnout
The snout, or muzzle, is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw.-Terminology:The term "muzzle", used as a noun, can be ambiguous...
is brown, distal lips are pale and foot is pale. Pallial roof has black pigment bands along edges of ctenidium
Ctenidium
Ctenidium may be:* Ctenidium , , a comb-like gill, part of the respiratory system of gastropods and bivalves* Ctenidium, , a row of peg-like spines in some insects...
and dorsal edge of genital duct; visceral coil pale except for black pigment on testis. Ctenidium is positioned a little in front of pericardium. There are 24-25 ctenidial filaments, that are broadly triangular with lateral surfaces ridged. Osphradium
Osphradium
The osphradium is the olfactory organ in certain molluscs, linked with the respiration organ.The main function of this is to test incoming water for silt and other possible food particles.It is used by all members of the Genus Conus....
is narrow, positioned slightly posterior to middle of ctenidium.
Radula
Radula
The radula is an anatomical structure that is used by molluscs for feeding, sometimes compared rather inaccurately to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus...
has about 36 well-formed rows of teeth. Central teeth are about 38 μm wide with convex cutting edge. There are 3-8 lateral cusps. Central cusp are pointed or hoe-shaped, parallel-sided proximally or tapering throughout. There are 1-3 small basal cusps. Basal tongue is U- or V-shaped, about as long as lateral margins. Lateral tooth face is rectangular. Central cusp is pointed or hoe-shaped. There are 2-5 lateral cusps (inner) and 3-7 (outer). Outer wing is broad, flexed, with about 140% length of cutting edge. Basal tongue weakly is developed. Inner and outer marginal teeth both have 14-21 cusps and basally positioned rectangular wing.
Hypobranchial gland
Hypobranchial gland
The hypobranchial gland is a glandular structure which is part of the anatomy of many mollusks, including different families of gastropods, and protobranch bivalves...
is large, overlapping rectum and part of genital duct, thickened alongside kidney. Style sac is longer than remaining portion of stomach, posterior stomach have small caecal appendix.
Reproductive system
Reproductive system of gastropods
The reproductive system of gastropods varies greatly from one group to another within this very large and diverse taxonomic class of animals...
: Testis is large (1.75 whorls), composed of compound lobes, broadly overlapping stomach anteriorly. Seminal vesicle is opening near anterior edge of testis, composed of a few thickened coils, positioned along ventral side of anterior 33% of testis. Prostate gland is small, pea-shaped, with about 50% of length in pallial roof. Anterior vas deferens opening from antero-ventral edge of prostate gland, section of duct on columellar muscle straight. Penis is large, base rectangular, inner edge without folds. Penial filament is short, narrow, tapering, oblique. Lobe is rather medium-sized, squarish, oblique. Terminal gland is narrow, usually transversely positioned along outer edge of lobe, less frequently horizontal, sometimes borne on short stalk. Penial duct is narrow, near outer edge, almost straight. Penial filament has black internal pigment core along most of length.
Ovary is small (0.75 whorl), composed of simple, stalked lobes. It is slightly overlapping stomach anteriorly. Female glandular oviduct and associated structures are as follows: Coiled oviduct is narrow, vertical. Bursa copulatrix is small, ovate, horizontal, about 50% overlapped by albumen gland. Bursal duct is longer than bursa, narrow, opening from distal edge, partly embedded in albumen gland proximally, entirely embedded distally, junction with common duct well in front of posterior wall of pallial cavity. Seminal receptacle is small, pouch-like, positioned near ventral edge of albumen gland slightly anterior to bursa copulatrix. Albumen gland is largely visceral. Capsule gland composed of two distinct tissue sections. Genital aperture a terminal slit.
Similar species
Marstonia comalensis has a closely similar shell and penis to some of its congeners, but can be differentiated from them in these ways:It can be distinguished from Marstonia gaddisorum by its less convex shell whorls, distinctive pallial roof pigmentation, larger number of cusps on the inner side of the lateral teeth and on the outer marginal teeth, larger penial lobe, narrower terminal gland, and smaller overlap of the bursa copulatrix by the albumen gland.
If differs from Marstonia lustrica by its smaller prostate gland, smaller penial lobe, narrower penial filament, straight anterior vas deferens, partly imbedded (in albumen gland) bursal duct, and larger seminal receptacle.
It differs from Marstonia ogmorhaphe by its smaller size, broader shell, smaller prostate gland, straight anterior vas deferens, and smaller bursa copulatrix.
Habitat
Marstonia comalensis lives in cold water springs near their sources, and slack water riverine habitats. It has been most commonly found on mud, aquatic vegetation and dead leaves.Conservation
This species was included in a recent federal listing petition (2007) based on its critically imperiled (G1) NatureServeNatureServe
NatureServe is a non-profit conservation organization whose mission is to provide the scientific basis for effective conservation action. NatureServe and its network of natural heritage programs are the leading source for information about rare and endangered species and threatened ecosystems in...
(2009) ranking, but found not to warrant listing owing to insufficient information. The data by Hershler & Liu (2011) suggest that the conservation status of this snail needs to be re-assessed.