Marstonia comalensis
Marstonia comalensis | |
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lectotypes of Marstonia comalensis. Scale bar is 1.0 mm.
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Scientific classification | |
Kingdom: | Animalia |
Phylum: | |
Class: | |
(unranked): | |
Superfamily: | |
Family: | |
Subfamily: | |
Genus: | |
Species: | M. comalensis
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Binomial name | |
Marstonia comalensis | |
Synonyms[3] | |
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Marstonia comalensis is a species of minute
, United States.Marstonia comalensis is large for this genus. It has an ovate-conic, openly umbilicate
This species has often been confused with
Taxonomy
In 1906,
Distribution
The type locality is
Records published by Hershler & Liu (2011)[3] considerably expanded the geographic range of Marstinia comalensis, which lives in springs and fluvial habitats spread among four river basins in south-central Texas.[3] Almost all of these localities are on the Edwards Plateau.[3] 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.[3] The species has been live collected at only 12 localities and only two of these have been re-visited since 1993.[3]
Hershler & Liu (2011)[3] were unable to confirm a previous report by Cable & Isserhoff (1969)[7] of this species from a drainage canal near Galveston Bay.[3]
Hershler & Liu (2011)[3] 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.[3]
Shell description
The
The operculum is thin, amber, narrowly ovate, multispiral with eccentric nucleus.[3] The last 0.25 whorl is sometimes frilled on outer side; inner side having well developed rim near outer edge.[3] The attachment scar border is sometimes weakly thickened near the nucleus.[3]
Anatomy
The cephalic
Radula has about 36 well-formed rows of teeth.[3] Central teeth are about 38 μm wide with convex cutting edge.[3] There are 3-8 lateral cusps. Central cusp are pointed or hoe-shaped, parallel-sided proximally or tapering throughout.[3] 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.[3] Central cusp is pointed or hoe-shaped.[3] There are 2-5 lateral cusps (inner) and 3-7 (outer).[3] Outer wing is broad, flexed, with about 140% length of cutting edge.[3] Basal tongue weakly is developed. Inner and outer marginal teeth both have 14-21 cusps and basally positioned rectangular wing.[3]
Hypobranchial gland is large, overlapping rectum and part of genital duct, thickened alongside kidney.[3] Style sac is longer than remaining portion of stomach, posterior stomach have small caecal appendix.[3]
Reproductive system: Testis is large (1.75 whorls), composed of compound lobes, broadly overlapping stomach anteriorly.[3] Seminal vesicle is opening near anterior edge of testis, composed of a few thickened coils, positioned along ventral side of anterior 33% of testis.[3] Prostate gland is small, pea-shaped, with about 50% of length in pallial roof.[3] Anterior vas deferens opening from antero-ventral edge of prostate gland, section of duct on columellar muscle straight.[3] Penis is large, base rectangular, inner edge without folds.[3] Penial filament is short, narrow, tapering, oblique.[3] Lobe is rather medium-sized, squarish, oblique.[3] Terminal gland is narrow, usually transversely positioned along outer edge of lobe, less frequently horizontal, sometimes borne on short stalk.[3] Penial duct is narrow, near outer edge, almost straight. Penial filament has black internal pigment core along most of length.[3]
Ovary is small (0.75 whorl), composed of simple, stalked lobes. It is slightly overlapping stomach anteriorly.[3] 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.[3] 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.[3] Seminal receptacle is small, pouch-like, positioned near ventral edge of albumen gland slightly anterior to bursa copulatrix.[3] Albumen gland is largely visceral.[3] Capsule gland composed of two distinct tissue sections. Genital aperture a terminal slit.[3]
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.[3]
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.[3]
It differs from Marstonia ogmorhaphe by its smaller size, broader shell, smaller prostate gland, straight anterior vas deferens, and smaller bursa copulatrix.[3]
Habitat
Marstonia comalensis lives in cold water springs near their sources, and slack water riverine habitats.[3] It has been most commonly found on mud, aquatic vegetation and dead leaves.[3]
Conservation
This species was included in a recent federal listing petition (2007) based on its
References
This article incorporates CC-BY-3.0 text from the reference[3]
- ^ a b Pilsbry H. A. & Ferriss J. H. (1906). "Mollusca of the southwestern states. II." Proceedings of the Academy of Natural Sciences of Philadelphia 58: 123-175, plates V–IX.
- ^ a b Taylor D. W. (1975). "Index and bibliography of late Cenozoic freshwater Mollusca of western North America". University of Michigan Papers on Paleontology 10: 1-384.
- ^ .
- .
- ^ Thompson F. G. & Hershler R. (2002). "Two genera of North American freshwater snails: Marstonia Baker, 1926, resurrected to generic status, and Floridobia, new genus (Prosobranchia: Hydrobiidae: Nymphophilinae)". Veliger 45: 269-271.
- .
- ^ 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.
External links
- Media related to Marstonia comalensis at Wikimedia Commons