Sphincterochila boissieri
Encyclopedia
Sphincterochila boissieri is a species
of air-breathing land snail
, a terrestrial
pulmonate gastropod mollusk in the family Sphincterochilidae
. It lives in desert
s in Israel and Egypt.
Sphincterochila boissieri is the type species
of the genus Sphincterochila
.
desert (Israel), and Sinai desert in the Sinai Peninsula
(Egypt).
of Sphincterochila boissieri is covered perforate, thick, irregularly striated, somewhat effulgent, cretaceous and colored white. It has 5 slightly convex whorls
. The last whorl
is deflected anteriorly. The aperture
has a thick lip, projecting internally above in two thick, subconfluent tubercles.
The average width of the shell is 25 mm.
s, 4 % of ash
, and little other organic matter. Sphincterochila boissieri has no energy reserves and the amount of lipids it contains is a fraction of 1%, which is considered to be extremely low.
environments. This snail is common in areas with loess
-limestone
soils but uncommon in areas with flint
substrate.
Yom-Tov measured the maximum demographic density for Sphincterochila boissieri, encountering a value of 0.2-0.3 specimens/m² in the area of the Negev
desert he investigated in 1970. The snail Xerocrassa seetzeni
was found to be more abundant there. On the other hand, in the Northern Negev area investigated by Steinberger et al. in 1981 Sphincterochila boissieri was the most abundant snail.
Sphincterochila boissieri along with other snail species and algae are the most significant faunal and floral components of the Negev and Sinai deserts ecosystem
s.
conditions which significantly improve its desiccation tolerance
. Some of those adaptations include a thick shell with a relatively reduced aperture
(see also Machin 1967), a thick epiphragm
, and slow body surface heat conduction
. About 90% of its shell surface reflects the visible portion of the solar spectrum
, and much over 90% of the solar spectrum
itself.
Sphincterochila boissieri also produces a new epiphragm after every period of activity (see also Yom-Tov 1971).
These snails delve into the soil to depths from 1 to 5 cm while they aestivate during summer in the Negev Desert. In the vicinities of the Dead Sea
they usually either burrow themselves to depths of up to 10 cm, or aestivate hidden under stones.
All dormant snails of this species can resist ambient temperatures up to 50 °C, but temperatures of 55 °C and above are usually lethal. The soft parts of the animals body shelter inside the second and the third whorl
of its shell, where the temperature can scale up to 50.3 °C. Temperatures of up to 56.2 °C were measured and are known to occur inside the shells body whorl
, which is mostly filled with air during aestivation.
Dormant snails experience water loss of 0.5 mg per day per snail in summer, with a very low oxygen consumption rate. For these reasons, dormant Sphincterochila boissieri can survive severe drought
s for several years.
Dormant snails are known to have survived in museum collections for up to 6 years. Schmidt-Nielsen et al. in 1971 estimated their life span according to their oxygen consumption as being nearly 8 years.
, especially loess
mud after rains, lichen
s, soil algae
and surface of limestone
directly. It does not eat higher plants.
s, namely the Cairo Spiny Mouse
(Acomys cahirinus), Wagner's Gerbil
(Dipodillus dasyurus) and the Asian Garden Dormouse
(Eliomys melanurus).
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 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 Sphincterochilidae
Sphincterochilidae
Sphincterochilidae is a taxonomic family of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Helicoidea ....
. It lives in desert
Desert
A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than...
s in Israel and Egypt.
Sphincterochila boissieri is the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
of the genus Sphincterochila
Sphincterochila
Sphincterochila is a genus of air-breathing land snails, terrestrial pulmonate gastropod molluscs in the family Sphincterochilidae.Species in the genus Sphincterochila are arid-adapted.- Species :Species in the genus Sphincterochila include:...
.
Distribution
Sphincterochila boissieri lives in the NegevNegev
The Negev is a desert and semidesert region of southern Israel. The Arabs, including the native Bedouin population of the region, refer to the desert as al-Naqab. The origin of the word Neghebh is from the Hebrew root denoting 'dry'...
desert (Israel), and Sinai desert in the Sinai Peninsula
Sinai Peninsula
The Sinai Peninsula or Sinai is a triangular peninsula in Egypt about in area. It is situated between the Mediterranean Sea to the north, and the Red Sea to the south, and is the only part of Egyptian territory located in Asia as opposed to Africa, effectively serving as a land bridge between two...
(Egypt).
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...
of Sphincterochila boissieri is covered perforate, thick, irregularly striated, somewhat effulgent, cretaceous and colored white. It has 5 slightly 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...
. The last whorl
Body whorl
Body whorl is part of the morphology of a coiled gastropod mollusk.- In gastropods :In gastropods, the body whorl, or last whorl, is the most recently-formed and largest whorl of a spiral or helical shell, terminating in the aperture...
is deflected anteriorly. 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....
has a thick lip, projecting internally above in two thick, subconfluent tubercles.
The average width of the shell is 25 mm.
Anatomy and physiology
The average body mass of Sphincterochila boissieri is around 4.3 g. Such mass is divided evenly between the shell and the animals soft parts. Schmidt-Nielsen et al., in 1971, found that 56 % of the animals body mass was contained in its shell. About 80 to 90 % of the mass of the soft body parts is composed of water (according to the Yom-Tov 1970). In average, soft body parts contain 81 % of water (nearly 1400 mg of water), 11% of proteinProtein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s, 4 % of ash
Wood ash
Wood ash is the residue powder left after the combustion of wood. Main producers of wood ash are wood industries and power plants.-Composition:...
, and little other organic matter. Sphincterochila boissieri has no energy reserves and the amount of lipids it contains is a fraction of 1%, which is considered to be extremely low.
Habitat
Sphincterochila boissieri lives in desertDesert
A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than...
environments. This snail is common in areas with loess
Loess
Loess is an aeolian sediment formed by the accumulation of wind-blown silt, typically in the 20–50 micrometre size range, twenty percent or less clay and the balance equal parts sand and silt that are loosely cemented by calcium carbonate...
-limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
soils but uncommon in areas with flint
Flint
Flint is a hard, sedimentary cryptocrystalline form of the mineral quartz, categorized as a variety of chert. It occurs chiefly as nodules and masses in sedimentary rocks, such as chalks and limestones. Inside the nodule, flint is usually dark grey, black, green, white, or brown in colour, and...
substrate.
Yom-Tov measured the maximum demographic density for Sphincterochila boissieri, encountering a value of 0.2-0.3 specimens/m² in the area of the Negev
Negev
The Negev is a desert and semidesert region of southern Israel. The Arabs, including the native Bedouin population of the region, refer to the desert as al-Naqab. The origin of the word Neghebh is from the Hebrew root denoting 'dry'...
desert he investigated in 1970. The snail Xerocrassa seetzeni
Xerocrassa seetzeni
Xerocrassa seetzeni is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Hygromiidae.- Distribution :...
was found to be more abundant there. On the other hand, in the Northern Negev area investigated by Steinberger et al. in 1981 Sphincterochila boissieri was the most abundant snail.
Sphincterochila boissieri along with other snail species and algae are the most significant faunal and floral components of the Negev and Sinai deserts ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
s.
Adaptations for arid conditions
This species presents adaptations to aridArid
A region is said to be arid when it is characterized by a severe lack of available water, to the extent of hindering or even preventing the growth and development of plant and animal life...
conditions which significantly improve its desiccation tolerance
Desiccation tolerance
Desiccation tolerance refers to the ability of an organism to withstand or endure extreme dryness, or drought-like conditions. Plants and animals living in arid or periodically arid environments such as temporary streams or ponds may face the challenge of desiccation, therefore physiological or...
. Some of those adaptations include a thick shell with a relatively reduced 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....
(see also Machin 1967), a thick epiphragm
Epiphragm
An epiphragm is a temporary structure which can be created by many species of shelled, air-breathing land snails, terrestrial pulmonate gastropod mollusks. It can also be created by freshwater snails when temporary pools dry up....
, and slow body surface heat conduction
Heat conduction
In heat transfer, conduction is a mode of transfer of energy within and between bodies of matter, due to a temperature gradient. Conduction means collisional and diffusive transfer of kinetic energy of particles of ponderable matter . Conduction takes place in all forms of ponderable matter, viz....
. About 90% of its shell surface reflects the visible portion of the solar spectrum
Visible spectrum
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 750 nm. In terms of...
, and much over 90% of the solar spectrum
Spectrum
A spectrum is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The word saw its first scientific use within the field of optics to describe the rainbow of colors in visible light when separated using a prism; it has since been applied by...
itself.
Sphincterochila boissieri also produces a new epiphragm after every period of activity (see also Yom-Tov 1971).
These snails delve into the soil to depths from 1 to 5 cm while they aestivate during summer in the Negev Desert. In the vicinities of the Dead Sea
Dead Sea
The Dead Sea , also called the Salt Sea, is a salt lake bordering Jordan to the east and Israel and the West Bank to the west. Its surface and shores are below sea level, the lowest elevation on the Earth's surface. The Dead Sea is deep, the deepest hypersaline lake in the world...
they usually either burrow themselves to depths of up to 10 cm, or aestivate hidden under stones.
All dormant snails of this species can resist ambient temperatures up to 50 °C, but temperatures of 55 °C and above are usually lethal. The soft parts of the animals body shelter inside the second and the third whorl
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...
of its shell, where the temperature can scale up to 50.3 °C. Temperatures of up to 56.2 °C were measured and are known to occur inside the shells body whorl
Body whorl
Body whorl is part of the morphology of a coiled gastropod mollusk.- In gastropods :In gastropods, the body whorl, or last whorl, is the most recently-formed and largest whorl of a spiral or helical shell, terminating in the aperture...
, which is mostly filled with air during aestivation.
Dormant snails experience water loss of 0.5 mg per day per snail in summer, with a very low oxygen consumption rate. For these reasons, dormant Sphincterochila boissieri can survive severe drought
Drought
A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...
s for several years.
Life cycle
Sphincterochila boissieri is active for a few days only after rainfall during the winter season, from November to March. At this time of the year they feed, mate and lay eggs. Thus these snails are active only 5-7% of the year (nearly 18 to 26 days), and aestivate during the rest of the time.Dormant snails are known to have survived in museum collections for up to 6 years. Schmidt-Nielsen et al. in 1971 estimated their life span according to their oxygen consumption as being nearly 8 years.
Feeding habits
Sphincterochila boissieri feeds on soilSoil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
, especially loess
Loess
Loess is an aeolian sediment formed by the accumulation of wind-blown silt, typically in the 20–50 micrometre size range, twenty percent or less clay and the balance equal parts sand and silt that are loosely cemented by calcium carbonate...
mud after rains, lichen
Lichen
Lichens are composite organisms consisting of a symbiotic organism composed of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...
s, soil algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
and surface of limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
directly. It does not eat higher plants.
Predators
The known predators of Sphincterochila boissieri are rodentRodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
s, namely the Cairo Spiny Mouse
Cairo Spiny Mouse
The Cairo Spiny Mouse is a species of rodent in the family Muridae.It is found in Libya, Egypt, Sudan, Ethiopia, and Djibouti.Its natural habitats are rocky areas and hot deserts....
(Acomys cahirinus), Wagner's Gerbil
Wagner's Gerbil
Dipodillus dasyurus is distribution mainly Nile Delta, Sinai, Syria, Iraq and the Arabian Peninsula. It commonly referred to as Wagner's dipodil, Rough-tailed dipodil, or Wadi Hof gerbil.-References:...
(Dipodillus dasyurus) and the Asian Garden Dormouse
Asian Garden Dormouse
The Asian Garden Dormouse is a species of rodent in the Gliridae family.It is found in Algeria, Egypt, Iraq, Israel, Jordan, Lebanon, Libya, Morocco, Saudi Arabia, Syria, Tunisia, and Turkey....
(Eliomys melanurus).
Further reading
- Machin J. (1967). "Structural adaptation for reducing water-loss in three species of terrestrial snail". Journal of Physiology 152: 55-65.
- Yom-Tov Y. (1971). "The biology of two desert snails Trochoidea (Xerocrassa) seetzeni and Sphincterochila boissieri". Israel Journal of Zoology 20: 231-248.
- Yom-Tov Y. & Galun M. (1971). "Note on the feeding habits of the desert snail Sphincterochila boissieri Charpentier and Trochoidea (Xerocrassa) seetzeni Charpentier". Veliger 14: 86-88.
- Shachak M., Chapman E.A. & Orr Y. (1976). "Some aspects of the ecology of the desert snail Sphincterochila boissieri in relation to water and energy flow". Isr. J. Med. Sci. 12(8): 887-891. .