Gulella streptostelopsis
Encyclopedia
Gulella streptostelopsis is a species
of minute air-breathing land snail
, a terrestrial
pulmonate gastropod mollusk in the family Streptaxidae
.
Gulella streptostelopsis was described by Adolph Cornelis van Bruggen
in 2007 based on material (except for one specimen) obtained for the National Museum of Natural History in Leiden (Nationaal Natuurhistorisch Museum, formerly Rijksmuseum van Natuurlijke Historie
) by Ms H.M. Meredith (Newquay, U.K.; formerly Malawi) and her co-workers in the period 1975-1988.
The minute, almost smooth, shell (length 2.0-2.4 mm) resembles that of the genus Streptostele
, but is characterized by three-fold apertural
dentition and just under six whorls
. This taxon may represent a new genus.
. It is Latinized Greek for Streptostele-like and refers to the likeness to shells of the streptaxid genus Streptostele. The kindred epithet streptosteloides already exists in the family Streptaxidae. The original combination was Opeas streptosteloides Von Martens, 1897, but this taxon appears to be a streptaxid, now named Streptostele streptosteloides (Von Martens, 1897). In view of the similarity of the names and probable causes for confusion in possibly closely allied genera the epithet streptostelopsis was proposed.
south of about 11°S. Bruggen (2007) presumed, that this almost certainly is not a Malawi endemic. Many localities are sufficiently close to the borders of at least Zambia and Mozambique to predict occurrence in those countries, particularly as suitable habitat is available there.
It has been reported from Pemba Island, Tanzania in 2010.
about three times as long as wide and with three-fold apertural dentition consisting of single angular, labral and columellar processes. This species is generally easily recognized because of its small size and Streptostele-like shell.
The shell is small to minute, clavate, more or less tapering, greatest width well below the middle, always more than two-and-a-half times as long as wide, transparent when fresh to whitish when worn. The umbilicus is completely closed. The spire
is produced, slightly tapering or sides at most subparallel, not convex. The apex
is flattened, obtusely conical to mamillate. The shell has from five-and-a-half to just under six hardly convex whorls
, that are superficially smooth but under high magnification with faint spiral sculpture
and growth lines, growth lines turning to weak costulation behind the labrum. Sutures are somewhat impressed, fairly shallow, simple and filiform. The aperture
is subovate, sometimes distinctly squarish at base, peristome slightly incrassate and reflected, aperture not or hardly obstructed by three-fold dentition: a small angular process (usually a mere swelling), somewhat distant from and therefore not connected with apex of labrum so that there is no sinus; opposite the angular denticle there is an upper labral process in the form of a thickening of the labrum, which process does not correspond to a depression behind the labrum; finally, a very faint thickening of the lower columella may be interpreted as a columellar process.
Measurements of shell: 2.00-2.37 × 0.75-0.81 mm, l/d 2.62-3.17, lw 0.87-1.00 mm, aperture height × major diameter 0.56-0.62 × 0.44-0.50 mm, 5½->5¾ whorls. Holotype shell 2.31 × 0.78 mm, l/d 2.96, lw 1.00 mm, aperture 0.69 × 0.44 mm, >5¾ whorls. Mean values 2.18 × 0.78 mm, l/d 2.89, lw 0.93, aperture 0.59 × 0.47 mm, average values 2.19 × 0.75 mm, l/d 2.92, lw 0.94, aperture 0.59 × 0.44 mm (n = 38).
Animal so far undescribed. Some alcohol material of this species is available and should be properly evaluated, but this would involve micro-anatomy.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of minute air-breathing land snail
Land snail
A land snail is any of the many species of snail that live on land, as opposed to those that live in salt water and fresh water. Land snails are terrestrial gastropod mollusks that have shells, It is not always an easy matter to say which species are terrestrial, because some are more or less...
, a terrestrial
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
pulmonate gastropod mollusk in the family Streptaxidae
Streptaxidae
Streptaxidae is a family of air-breathing land snails, terrestrial pulmonate gastropod mollusks in theStylommatophora. Six Streptaxidae subfamilies are accepted in the 2005 taxonomy of the Gastropoda by Bouchet & Rocroi....
.
Gulella streptostelopsis was described by Adolph Cornelis van Bruggen
Adolph Cornelis van Bruggen
Adolph Cornelis van Bruggen, also known as A. C. van Bruggen or Dolf van Bruggen is a malacologist, entomologist and botanist from the Netherlands. His interest in the tropics and tropical Africa has dominated his broad scientific interest for more than 50 years now...
in 2007 based on material (except for one specimen) obtained for the National Museum of Natural History in Leiden (Nationaal Natuurhistorisch Museum, formerly Rijksmuseum van Natuurlijke Historie
Rijksmuseum van Natuurlijke Historie
The Rijksmuseum van Natuurlijke Historie was a museum in Leiden, The Netherlands. It was founded in 1820 by Royal Decree, formed from a merger of several existing collections. This happened at the instigation of Coenraad Jacob Temminck, who saw the museum primarily as a research institute...
) by Ms H.M. Meredith (Newquay, U.K.; formerly Malawi) and her co-workers in the period 1975-1988.
The minute, almost smooth, shell (length 2.0-2.4 mm) resembles that of the genus Streptostele
Streptostele
Streptostele is a genus of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the family Streptaxidae.- Distribution :Indigenous distribution of the genus Streptostele include:...
, but is characterized by three-fold apertural
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....
dentition and just under six 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...
. This taxon may represent a new genus.
Etymology
The specific name streptostelopsis is of the resemblance of StreptosteleStreptostele
Streptostele is a genus of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the family Streptaxidae.- Distribution :Indigenous distribution of the genus Streptostele include:...
. It is Latinized Greek for Streptostele-like and refers to the likeness to shells of the streptaxid genus Streptostele. The kindred epithet streptosteloides already exists in the family Streptaxidae. The original combination was Opeas streptosteloides Von Martens, 1897, but this taxon appears to be a streptaxid, now named Streptostele streptosteloides (Von Martens, 1897). In view of the similarity of the names and probable causes for confusion in possibly closely allied genera the epithet streptostelopsis was proposed.
Distribution
This minute land snail lives at series of localities of mainly between 1000 and 1500 m a.s.l. in MalawiMalawi
The Republic of Malawi is a landlocked country in southeast Africa that was formerly known as Nyasaland. It is bordered by Zambia to the northwest, Tanzania to the northeast, and Mozambique on the east, south and west. The country is separated from Tanzania and Mozambique by Lake Malawi. Its size...
south of about 11°S. Bruggen (2007) presumed, that this almost certainly is not a Malawi endemic. Many localities are sufficiently close to the borders of at least Zambia and Mozambique to predict occurrence in those countries, particularly as suitable habitat is available there.
It has been reported from Pemba Island, Tanzania in 2010.
Shell description
Gulella streptostelopsis is a minute species of Gulella s.l., with more or less tapering, almost smooth, 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...
about three times as long as wide and with three-fold apertural dentition consisting of single angular, labral and columellar processes. This species is generally easily recognized because of its small size and Streptostele-like shell.
The shell is small to minute, clavate, more or less tapering, greatest width well below the middle, always more than two-and-a-half times as long as wide, transparent when fresh to whitish when worn. The umbilicus is completely closed. The spire
Spire (mollusc)
A spire is a descriptive term for part of the coiled shell of mollusks. The word is a convenient aid in describing shells, but it does not refer to a very precise part of shell anatomy: the spire consists of all of the whorls except for the body whorl...
is produced, slightly tapering or sides at most subparallel, not convex. The apex
Apex (mollusc)
Apex is an anatomical term for the tip of the mollusc shell of a gastropod, scaphopod, or cephalopod mollusc.-Gastropods:The word "apex" is most often used to mean the tip of the spire of the shell of a gastropod...
is flattened, obtusely conical to mamillate. The shell has from five-and-a-half to just under six hardly convex 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...
, that are superficially smooth but under high magnification with faint spiral 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...
and growth lines, growth lines turning to weak costulation behind the labrum. Sutures are somewhat impressed, fairly shallow, simple and filiform. 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 subovate, sometimes distinctly squarish at base, peristome slightly incrassate and reflected, aperture not or hardly obstructed by three-fold dentition: a small angular process (usually a mere swelling), somewhat distant from and therefore not connected with apex of labrum so that there is no sinus; opposite the angular denticle there is an upper labral process in the form of a thickening of the labrum, which process does not correspond to a depression behind the labrum; finally, a very faint thickening of the lower columella may be interpreted as a columellar process.
Measurements of shell: 2.00-2.37 × 0.75-0.81 mm, l/d 2.62-3.17, lw 0.87-1.00 mm, aperture height × major diameter 0.56-0.62 × 0.44-0.50 mm, 5½->5¾ whorls. Holotype shell 2.31 × 0.78 mm, l/d 2.96, lw 1.00 mm, aperture 0.69 × 0.44 mm, >5¾ whorls. Mean values 2.18 × 0.78 mm, l/d 2.89, lw 0.93, aperture 0.59 × 0.47 mm, average values 2.19 × 0.75 mm, l/d 2.92, lw 0.94, aperture 0.59 × 0.44 mm (n = 38).
Animal so far undescribed. Some alcohol material of this species is available and should be properly evaluated, but this would involve micro-anatomy.