''Marstonia comalensis'' is a species of minute
freshwater snail
Freshwater snails are gastropod mollusks which live in fresh water. There are many different families. They are found throughout the world in various habitats, ranging from ephemeral pools to the largest lakes, and from small seeps and springs ...
with a
gill
A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...
and an
operculum, an
aquatic gastropod
The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda ().
This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...
mollusk
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...
or
micromollusk
A micromollusk is 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 ...
in the family
Hydrobiidae
Hydrobiidae, commonly known as mud snails, is a large cosmopolitan family of very small freshwater and brackish water snails with an operculum; they are in the order Littorinimorpha.
Distribution
Hydrobiidae are found in much of the world, ...
. It is found in south central
Texas
Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
, United States.
''Marstonia comalensis'' is large for this genus. It has an ovate-conic, openly umbilicate
shell
Shell may refer to:
Architecture and design
* Shell (structure), a thin structure
** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses
** Thin-shell structure
Science Biology
* Seashell, a hard ou ...
. 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 (
mt COI divergence 3.0–8.5%).
This species has often been confused with ''
Cincinnatia integra
''Cincinnatia'' is a genus of very small freshwater snails that have an Operculum (gastropod), operculum, aquatic animal, aquatic gastropod molluscs in the family Hydrobiidae, the mud snails.
Species
The genus ''Cincinnatia'' is currently Monoty ...
''.
Taxonomy
In 1906,
Henry Augustus Pilsbry
Henry Augustus Pilsbry (7 December 1862 – 26 October 1957) 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 centu ...
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
New Braunfels ( ) is a city in Comal County, Texas, Comal and Guadalupe County, Texas, Guadalupe counties in the U.S. state of Texas known for its German Texan heritage. It is the county seat, seat of Comal County. The city covers and had a popula ...
, south-central
Texas
Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
.
Pilsbry and Ferriss differentiated this species from ''
Amnicola limosa'' (Say) and two nomina (''Amnicola cincinnatiensis''
nthony ''Amnicola peracuta'' Pilsbry & Walker) that are currently recognized as
synonyms
A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...
of ''
Cincinnatia integra
''Cincinnatia'' is a genus of very small freshwater snails that have an Operculum (gastropod), operculum, aquatic animal, aquatic gastropod molluscs in the family Hydrobiidae, the mud snails.
Species
The genus ''Cincinnatia'' is currently Monoty ...
'' (Say) by its much smaller size and noted that it further differed from the latter by its less shouldered
whorls
A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs).
Whorls in nature
File:Photograph and axial plane floral ...
.
The genus ''
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 (Bouchet & Rocroi, 2005).
...
'' 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
''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'', another genus of snail, and ''opsis'' = aspe ...
''); ''Amnicola comalensis'' was subsequently transferred to ''Marstonia'' based on this unpublished work.
Hershler et al. (2003) published a molecular
phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
analysis of the North American nymphophilines that included a specimen of ''Marstonia comalensis'' from
Old Faithful Spring in
Real County, Texas
Real County is a county located on the Edwards Plateau in the U.S. state of Texas. As of the 2020 census, its population was 2,758. The county seat is Leakey. The county is named for Julius Real (1860–1944), a former member of the 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
New Braunfels ( ) is a city in Comal County, Texas, Comal and Guadalupe County, Texas, Guadalupe counties in the U.S. state of Texas known for its German Texan heritage. It is the county seat, seat of Comal County. The city covers and had a popula ...
,
Comal County, Texas
Comal County ( ) is a county located on the Edwards Plateau in the U.S. state of Texas. As of the 2020 census, its population was 161,501. Comal County is known for its rich German-Texan and European history. Its county seat is New Braunfels.
...
.
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
The Edwards Plateau is a geographic region at the crossroads of Central Texas, Central, South Texas, South, and West Texas. It is bounded by the Balcones Fault to the south and east, the Llano Uplift and the Llano Estacado to the north, and the ...
.
Records indicate that ''Marstonia comalensis'' was historically distributed in the upper portions of the
Brazos River
The Brazos River ( , ), called the ''Río de los Brazos de Dios'' (translated as "The River of the Arms of God") by early Spanish explorers, is the 11th-longest river in the United States at from its headwater source at the head of Blackwater Dr ...
,
Colorado River (Texas)
The Colorado River is an approximately long river in the U.S. state of Texas. It is the 18th longest river in the United States and the longest river with both its source and its mouth within Texas.
Its drainage basin and some of its usually dr ...
,
Guadalupe River (Texas)
The Guadalupe River (), () runs from Kerr County, Texas, to San Antonio Bay on the Gulf of Mexico, with an average temperature of . It is a popular destination for rafting, fly fishing, and canoeing. Larger cities along it include Kerrville, Ne ...
and
Nueces River
The Nueces River is a river in the U.S. state of Texas, about 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. ''Nueces'' ...
basins, south-central
Texas
Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
.
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)
[Cable R. M. & Isserhoff H. (1969). "A protandrous haploporid cercaria, probably the larva of ''Saccocoelioides sogandaresi'' Lumsden, 1963". '' Proceedings of the Helminthological Society of Washington'' 36: 131-135.] of this species from a drainage canal near
Galveston Bay
Galveston Bay ( ) is a bay in the western Gulf of Mexico along the upper coast of Texas. It is the seventh-largest estuary in the United States, and the largest of seven major estuaries along the Texas Gulf Coast. It is connected to the Gulf of ...
.
Hershler & Liu (2011)
also analyzed previously published molecular data to evaluate the
genetic divergence Genetic divergence is the process in which two or more populations of an ancestral species accumulate independent genetic changes (mutations) through time, often leading to reproductive isolation and continued mutation even after the populations hav ...
and phylogenetic relationships of ''Marstonia comalensis'', whose
geographic range is broadly disjunct relative to other members of the genus.
Shell description
The
shell
Shell may refer to:
Architecture and design
* Shell (structure), a thin structure
** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses
** Thin-shell structure
Science Biology
* Seashell, a hard ou ...
is ovate-conic with 4.5–5.5
whorls
A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs).
Whorls in nature
File:Photograph and axial plane floral ...
.
The height of the shell is about 2.6–4.6 mm.
Protoconch
A protoconch (meaning first or earliest or original shell) is an embryonic or larval shell which occurs in some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod. In older texts it is also called ...
is near planispiral, slightly tilted, initial 0.75–1.0 whorl strongly wrinkled.
Teleoconch
The gastropod shell is part of the body of a gastropod or snail, a kind of mollusc. The shell is an exoskeleton, which protects from predators, mechanical damage, and dehydration, but also serves for muscle attachment and calcium storage. Some ...
whorls are weakly convex, often narrowly shouldered, rarely having
subsutural angulation.
The
sculpture
Sculpture is the branch of the visual arts that operates in three dimensions. Sculpture is the three-dimensional art work which is physically presented in the dimensions of height, width and depth. It is one of the plastic arts. Durable sc ...
of strong collabral growth lines, later whorls having numerous weak spiral striae.
The
aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane.
An opt ...
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
Amber is fossilized tree resin that has been appreciated for its color and natural beauty since Neolithic times. Much valued from antiquity to the present as a gemstone, amber is made into a variety of decorative objects."Amber" (2004). In Ma ...
, 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
![Marstonia comalensis](https://upload.wikimedia.org/wikipedia/commons/8/85/Marstonia_comalensis.png)
The cephalic
tentacles
In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...
are pale, except for black eyespots.
Snout
A snout is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw. In many animals, the structure is called a muzzle, rostrum, or proboscis. The wet furless surface around the nostrils of the nose of many mammals is c ...
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
The osphradium is a pigmented chemosensory epithelium patch in the mantle cavity present in six of the eight extant classes of molluscs (it is absent in the scaphopoda and monoplacophora; among cephalopoda, only the nautilus has what appears to be ...
is narrow, positioned slightly posterior to middle of ctenidium.
Radula
The radula (, ; plural radulae or radulas) is an anatomical structure used by molluscs for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food ...
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 The hypobranchial gland is a glandular structure which is part of the anatomy of many mollusks, including several different families of gastropods, and also many protobranch bivalves. This gland produces mucus as well as biologically active comp ...
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
The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are als ...
: 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.
![Marstonia comalensis oviduct](https://upload.wikimedia.org/wikipedia/commons/b/b8/Marstonia_comalensis_oviduct.png)
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
The NatureServe conservation status system, maintained and presented by NatureServe in cooperation with the Natural Heritage Network, was developed in the United States in the 1980s by The Nature Conservancy (TNC) as a means for ranking or catego ...
(G1)
NatureServe
NatureServe, Inc. is a non-profit organization based in Arlington County, Virginia, US, that provides proprietary wildlife conservation-related data, tools, and services to private and government clients, partner organizations, and the public. Nat ...
(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.
References
This article incorporates CC-BY-3.0 text from the reference
[Hershler R. & Liu H.-P. (2011). "Redescription of ''Marstonia comalensis'' (Pilsbry & Ferriss, 1906), a poorly known and possibly threatened freshwater gastropod from the Edwards Plateau region (Texas)". '']ZooKeys
''ZooKeys'' is a peer-reviewed open access scientific journal covering zoological taxonomy, phylogeny, and biogeography. It was established in 2008 and the editor-in-chief is Terry Erwin (Smithsonian Institution). It is published by Pensoft Publ ...
'' 77: 1-16. .
External links
*
{{DEFAULTSORT:Marstonia comalensis
Hydrobiidae