''Amphidromus'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of tropical air-breathing land snails, terrestrial

pulmonate Pulmonata or pulmonates, is an informal group (previously an Order (biology), order, and before that a Class (biology), subclass) of snails and slugs characterized by the ability to breathe air, by virtue of having a Respiratory system of gastro ...

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 ...

s in the family Camaenidae. The shells of ''Amphidromus'' are relatively large, from to in maximum dimension, and particularly colorful. During the 18th century, they were among the first

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Gui ...

n land snail shells brought to Europe by travelers and explorers. Since then, the genus has been extensively studied: several comprehensive monographs and catalogs were authored by naturalists and zoologists during the time period from the early 19th to the mid 20th centuries. Modern studies have focused on better understanding the evolutionary relationships within the group, as well as solving taxonomic problems. The genus ''Amphidromus'' is unusual in that it includes species that have dextral shell-coiling and species that have sinistral shell-coiling. In addition, some species within this genus are particularly notable because their populations simultaneously include individuals with left-handed and right-handed shell-coiling. This is an extremely rare phenomenon, and very interesting to biologists. Studies focused on the soft anatomy of ''Amphidromus'' are scattered and fragmentary. Information on the internal anatomy is known only from a few species, and no larger, comparative morphological study has ever been carried out. Species in the genus ''Amphidromus'' are arboreal — in other words, they are tree snails. However, more detailed information on their habits is still lacking. The general feeding habits of these snails are unknown, but a few species are known to feed on microscopic

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately fr ...

lichens A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.terrestrial algae. ''Amphidromus'' themselves are preyed upon by birds, snakes, and probably also by smaller mammals such as rats.

Taxonomy and history

The generic name is derived from the

ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic pe ...

words ' (), meaning "on both sides", and ' (), meaning "running", alluding to the different chiralities of the shells. The shells of ''Amphidromus'' are relatively large, and quite colorful; considerable numbers of them were among the first

n land snail shells brought back to Europe by travelers and explorers during the 18th century. Comparatively speaking, malacologists have gathered a much smaller number of specimens. Several species and forms were described before 1800, most of them with inadequate locality data. At least two names — '' Amphidromus laevus'' (Müller, 1774) and the form '' A. perversus'' f. ''aureus'' Martyn, 1784 – still (as of 2017) have not yet been reported from a precise locality. During the first half of the nineteenth century, many species and varieties were named, again usually with poor locality data. Not until Eduard von Martens (1867) published his

monograph A monograph is a specialist work of writing (in contrast to reference works) or exhibition on a single subject or an aspect of a subject, often by a single author or artist, and usually on a scholarly subject. In library cataloging, ''monogra ...

was there an attempt to cover the entire complex of species within this genus. The 1867 monograph contained considerable information both on the variation within the genus, and on the problems of the geographic distribution of the species. Many concepts that originated with von Martens are still (as of 2017) in use. In 1896, Hugh Fulton organized 142 specific and varietal names into eighteen species groups containing a total of 64 species. When Henry Augustus Pilsbry's 1900 monograph ''

Manual of Conchology George Washington Tryon Jr. (20 May 1838 – 5 February 1888) was an American malacologist who worked at the Academy of Natural Sciences in Philadelphia. Biography George Washington Tryon was the son of Edward K. Tryon and Adeline Savidt. ...

Pilsbry H. A. (1900). ''

, structural and systematic, with illustrations of the species. Second series: Pulmonata''
Volume 13
Australasian Bulimulidae: ''

Bothriembryon ''Bothriembryon'' is a genus of tropical air-breathing land snails, terrestrial pulmonate gastropod mollusks in the family Bothriembryontidae. B. J. Smith (1992) made the last review of the genus summarizing all known data. Distribution The ...

'', '' Placostylus''. Helicidae: ''Amphidromus''. 253 pp., 72 plates
page 184
appeared, the number of species in the genus ''Amphidromus'' had increased to 81, and these were placed in nineteen groups. Pilsbry's study has remained the only illustrated monograph of the genus, and it is still considered indispensable for any serious study of the genus. Since 1900, the major taxonomic studies on ''Amphidromus'' have been faunistic (a study of the fauna of some territory or area) in scope. The papers of American malacologist Paul Bartsch (1917, 1918, 1919) on the Philippine species, Bernhard Rensch (1932) on the

Lesser Sunda Islands The Lesser Sunda Islands or nowadays known as Nusa Tenggara Islands ( id, Kepulauan Nusa Tenggara, formerly ) are an archipelago in Maritime Southeast Asia, north of Australia. Together with the Greater Sunda Islands to the west they make up ...

forms, and Tera van Benthem Jutting (1950, 1959) van Benthem Jutting T. (1950). "Critical studies of the Javanese pulmonate land-shells of the families Helicarionidae, Pleurodontidae, Fruticicolidae and Streptaxidae". ''Treubia'' 20(3): 381–505, 107 figs. on Javan and Sumatran populations are especially comprehensive. Potentially the most valuable contribution is that of Curt Haniel (1921), Haniel C. (1921). "Variationsstudie an Timoresischen ''Amphidromus'' Arten". ''Zeits. Induct. Abstamm. und Vererbungsl.'' 25(1–2): 88 pp., 5 plates. who discussed the variation within '' A. contrarius'' and '' A. reflexilabris'' on

Timor Timor is an island at the southern end of Maritime Southeast Asia, in the north of the Timor Sea. The island is divided between the sovereign states of East Timor on the eastern part and Indonesia on the western part. The Indonesian part, ...

; the variations in color and form were well illustrated in a series of color plates. Literature published after 1900 contains many scattered descriptions of new color forms and subspecies. Of the 309 names in the nomenclatural list, 111 (35.9%) were published after Pilsbry (1900). Adolf Michael Zilch (1953) listed type specimens in the Senckenberg Museum, and illustrated many previously unfigured species.

Frank Fortescue Laidlaw Frank Fortescue Laidlaw (1876–1963) was a British biologist, working particularly in the fields of entomology, herpetology, and malacology. Laidlaw named a number of species of snails, including the land snail genus '' Colparion'' Earlier in h ...

& Alan Solem (1961) recognized 74 species by name, and considered that material from the Banda Islands probably represented an undescribed species. Eleven of the species recognized by Laidlaw & Solem were described after the appearance of Pilsbry's monograph. However, several species recognized by Pilsbry have subsequently been subordinated to subspecific or varietal status, and a few names have been transferred to incertae sedis, since they are based on hundred-year-old references that have not been substantiated by more recent collectors. In fact, the study by Laidlaw & Solem (1961) forms a supplement to Pilsbry's monograph with his extensive plates, and many of Laidlaw & Solem's conclusions concerning the relationships of color forms described as species were taken not so much from new samples, but from the extent of variation that was outlined by Haniel (1921) in his pioneer study.

Characterization

Species in the genus ''Amphidromus'' usually have smooth, glossy, brightly colored, elongate or conic, dextrally or sinistrally coiled shells. The shells are moderately large, ranging from to in maximum dimension, having from 6 to 8 convex whorls. Their color pattern is usually monochromatic yellowish or greenish, but can be variegated. 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 ...

is oblique or ovate in shape, without any teeth or folds, and with the aperture height ranging from two-fifths to one-third of total shell height. The peristome is expanded and/or reflected, and is sometimes thickened. The columella may be straight or recurved, and the parietal callus is weak to well-developed, and the umbilicus may be open or closed. The

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 ...

is spatulate, has cusped teeth arranged in rows, usually with a monocuspid central tooth and bicuspid or tricuspid lateral teeth. The jaw is thin and weak, with low flat ribs. The pallial region is sigmurethrous, with a very long, narrow kidney. The genitalia are that of typical camaenids, with a long seminal receptacle, a short penis with low insertion of the retractor muscle, and a short or long epiphallic caecum (flagellum and appendix). The spermatophores have a pentagonal outline in

cross-section Cross section may refer to: * Cross section (geometry) ** Cross-sectional views in architecture & engineering 3D *Cross section (geology) * Cross section (electronics) * Radar cross section, measure of detectability * Cross section (physics) **Abs ...

. ''Amphidromus'' are typically arboreal animals.

Shell description

The shells of ''Amphidromus'' are relatively large, from one to three inches high, and colorful. ''Amphidromus'' has an elongate-conic or ovate-conic helicoid shell of 5 to 8 whorls. The shell may be thin and fragile, or very heavy and solid, with no known correlation of shell structure with distribution or habitats.

Shell coiling

In some species within this genus, the shell coils invariably to the right, and in many others just as invariably to the left. However, a significant number of species in this genus are " amphidromine"; this term means that both left- and right-handed shell coiling are found within the same population. One could say they are " polymorphic" for the direction of shell coiling, but because there are only two possible types of shell coiling, they are described as " dimorphic" in coiling. The two types of shell coiling occur in some species in approximately equal numbers, other species have a distinct predominance of one phase. There is as yet no information on the heredity of this character in ''Amphidromus''. Because almost all other species of amphidromine gastropods, such as ones within the genera '' Partula'' and ''

Achatinella ''Achatinella'' is a tropical genus of colorful land snails in the monotypic Achatinellidae subfamily ''Achatinellinae''. Species are arboreal pulmonate gastropod mollusks with some species called Oʻahu tree snails or kāhuli in the Hawaiian l ...

'', have already become extinct, the genus ''Amphidromus'', containing over 110 species, is uniquely useful for the study of the

evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...

asymmetry Asymmetry is the absence of, or a violation of, symmetry (the property of an object being invariant to a transformation, such as reflection). Symmetry is an important property of both physical and abstract systems and it may be displayed in pre ...

in animals, and this is why the

conservation Conservation is the preservation or efficient use of resources, or the conservation of various quantities under physical laws. Conservation may also refer to: Environment and natural resources * Nature conservation, the protection and manageme ...

of this genus is of essential importance to biologists. File:Amphidromus floresianus shell 2.png, In '' A. floresianus'', subgenus ''Syndromus'', shell coiling is normally sinistral. Scale bar 10 mm. File:Amphidromus perversus natunensis shell 2.png, Shells in the amphidromine species '' A. perversus'' can be dextral, as shown here. File:Amphidromus perversus natunensis shell 3.png, But shell coiling in ''A. perversus'' can also be sinistral, as shown here. File:Amphidromus perversus shell.jpg, Abapertural view of a sinistral shell (left), and apertural view of a dextral shell (right) of ''A. perversus''

Shell shape and sculpture

Amphidromus atricallosus leucoxanthus 01

The whorls of the shell of species of ''Amphidromus'' are moderately convex and, with only a few exceptions, are smooth or have a faint

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 ...

of growth lines. However, a sculpture of moderately heavy oblique radial ribs has appeared at least four separate times in the genus, and can be seen in the following species: '' Amphidromus costifer'' Smith from Binh Dinh Province in Vietnam; '' A. begini'' Morlet from Cambodia; '' A. heccarii'' Tapparone-Canefri from Celebes; and the '' A. palaceus''-'' A. winteri'' complex from Java and Sumatra. Correlated with the ribbing is a light, monochrome coloration, and a thin shell with a large

and a flaring lip. Many solid shells in other species do show a slight roughening of the surface, but this is very different from the ribbed sculpture mentioned above. The aperture is generally large, varying from about two-fifths to one-third the height of the shell, often within the same population. Usually the lip is at least somewhat expanded, and in forms such as '' A. reflexilabris'' Schepman and '' A. winteri'' (Pfeiffer) var. ''inauris'' Fulton, the lip can only be called flaring. In '' A. perversus'' (Linnaeus) and most other thick-shelled species, the lip is internally thickened, forming a "roll" in its expansion, and has a very heavy parietal callus. In thin-shelled species, the lip is usually a simple reflected edge. The umbilical area can be partially open, nearly closed, or sealed. This feature sometimes provides a useful criterion for specific identification. The angle of the parietal wall varies, but no precise information on this has been compiled. Generally the whorls of the shell increase rather regularly in size, however, species which are probably closely related, such as '' A. sinistralis'' (Reeve) and '' A. heccarii'' Tapparone-Canefri, can have quite different degrees of whorl increment. No attempt has been made to express these differences meristically, since most of the available material was inadequate for statistical treatment. Actual dimensions of the shell vary greatly both within and between species. The minimum adult size is about 21 mm high, the observed maximum about 75 mm. There is not much variation in adult size within species: only a few species, notably '' A. maculiferus'', '' A. sinensis'' and '' A. entobaptus'', have a variation in adult size that is greater than seven or eight millimeters in total.

Shell coloration

Amphidromus perversus butoti infraviridis shell

The single most major aspect of shell variation within the genus is the color patterning. In general, many arboreal snails are brightly colored, obvious examples being the bulimulid genera ''

Drymaeus ''Drymaeus'' is a large genus of medium-sized air-breathing, tropical land snails, terrestrial pulmonate gastropod molluscs in the subfamily Peltellinae of the family Bulimulidae.MolluscaBase eds. (2020). MolluscaBase. Drymaeus Albers, 1850. Ac ...

'' and ''

Liguus ''Liguus'' is a genus of large tropical air-breathing land snails, more specifically arboreal or tree snails, terrestrial pulmonate gastropod mollusks in the family Orthalicidae. These snails are especially notable for their relatively larg ...

'', the cepolid '' Polymita'', and the camaenid '' Papuina''. However, '' Polymita'', ''

'' and ''Amphidromus'' are particularly noted for their color variations. The basic ground color of ''Amphidromus'' appears to be yellow, and this color is usually (except for '' Amphidromus entobaptus'') confined to the surface layers of the shell, since worn specimens appear to be nearly devoid of color. In some species the background color is whitish, and a few have dark background colors. The apical whorls are pale, purple, brown, or black, and this sometimes varies within a population (as in '' A. quadrasi''). A few species, for example '' A. schomburgki'', have a deciduous green periostracum. Continuous zonal patterns can take the form of whitish sub sutural bands ('' A. similis''), heavy subperipheral pigmentation ('' A. perversus'' var. ''infraviridis''), subsutural color lines ('' A. columellaris''), broad spiral color bands ('' A. metabletus'', '' A. webbi''), or narrow spiral bands ('' A. laevus''). Interrupted zonation can consist of the interruption of bands into spots in ('' A. maculatus''); highly irregular splitting of zones ('' A. perversus'' vars. ''sultanus'' and ''interruptus''); formation of oblique radial streaks which run parallel to (in '' A. inversus'') or cross (in '' A. latestrigatus'') the incremental growth lines; or almost every conceivable combination and variation of these factors. Often the pattern will change radically from the apex to the body whorl (in '' A. quadrasi'' vars.). The aperture, parietal callus, columella, lip, and umbilical region are variously marked with pink, brown, purple, white, or black. Haniel (1921) includes several color plates which clearly demonstrate the extent of color variation within two species of the ''Syndromus'' type. '' A. perversus'' and '' A. maculiferus'' of the subgenus ''Amphidromus'' are equally variable, whereas species such as ''A. inversus'' and '' A. similis'' are almost uniform in coloration. In shells of most of the species in the subgenus ''Amphidromus'', resting stages are marked by the deposition of a brown or black radial band called a varix. This appears to be rare in the subgenus ''Syndromus'', although the shell of ''A. laevus'' does show evidence of interruption of the spiral banding after a resting phase.

Species recognition

Species recognition is based on combinations of minor structural variations in the shape, aperture, whorl contour, umbilical region, and color pattern. It appears to be the case that many species have a stable color pattern, while other species seem to vary tremendously. Adequate unselected field samples will enable a better understanding of the relative stability or variability of particular species in single localities.

Anatomy

Information concerning the soft anatomy of ''Amphidromus'' is widely scattered and fragmentary. The most complete account is that of Arnold Jacobi (1895) on specimens from Great Natuna ( Natuna Islands) and Djemadja ( Anamba Islands). Unfortunately, although it is clear that anatomical differences exist in the two species Jacobi dissected, unfortunately we do not know which forms he worked on, because he had incorrectly identified his material. In his paper he referred to the two species as '' Amphidromus chloris'' and the ''interruptus'' phase of ''A. perversus''. However, that is not possible, because in reality '' Amphidromus chloris'' is a species found only in the Philippine Islands, and the ''interruptus'' phase of ''A. perversus'' is not present in the Natuna Islands. Carl Arend Friedrich Wiegmann (1893, 1898) discussed portions of the anatomy of '' A. adamsii'', '' A. porcellanus'', '' A. contrarius'', and '' A. sinistralis''. Walter Edward Collinge (1901, 1902) briefly noted features of '' A. palaceus'' and '' A. parakensis'' (reported as ''A. perversus''). Haniel (1921) dissected ''A. contrarius'' and '' A. reflexilabris'', and Bernhard Rensch published a few scattered notes in his various faunistic surveys. A few earlier notes are mentioned in Pilsbry (1900). Characters such as the long, narrow kidney with reflexed ureter and closed secondary ureter, the penial complex with distinct penis, which is continuous with the epiphallus, epiphallic caecum (a flagellum and an appendix), unbranched gametolytic duct, lack of vaginal accessory organs, and the basic condition of the nervous and retractor muscle systems support the inclusion of ''Amphidromus'' in the family Camaenidae. This group of snails occur in a wide variety of

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

s in the

tropics The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also refer ...

Eastern Asia East Asia is the eastern region of Asia, which is defined in both geographical and ethno-cultural terms. The modern states of East Asia include China, Japan, Mongolia, North Korea, South Korea, and Taiwan. China, North Korea, South Korea ...

and

Australasia Australasia is a region that comprises Australia, New Zealand and some neighbouring islands in the Pacific Ocean. The term is used in a number of different contexts, including geopolitically, physiogeographically, philologically, and ecologic ...

, and is one of the most diverse families in the

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...

Stylommatophora Stylommatophora is an orderPhilippe Bouchet, Jean-Pierre Rocroi, Bernhard Hausdorf, Andrzej Kaim, Yasunori Kano, Alexander Nützel, Pavel Parkhaev, Michael Schrödl and Ellen E. Strong. 2017. Revised Classification, Nomenclator and Typification ...

. Though Laidlaw & Solem (1961) provided no more additional details on the anatomy of ''Amphidromus'', subsequent studies by distinct authors, e.g., Bishop (1977) and Solem (1983), have demonstrated that the reproductive system can provide valuable data for species recognition. dissection"> File:Amphidromus areolatus reproductive system.png, '' Amphidromus areolatus''; at – atrium; e – epiphallus; fl – flagellum; fo – free oviduct; gd – gametolytic duct; gs – gametolytic sac; ov – oviduct; p – penis; pr – penial retractor muscle; v – vagina; vd – vas deferens File:Amphidromus flavus reproductive system.png, '' Amphidromus flavus''; at – atrium; e – epiphallus; fl – flagellum; fo – free oviduct; gd – gametolytic duct; gs – gametolytic sac; ov – oviduct; p – penis; pr – penial retractor muscle; v – vagina; vd – vas deferens File:Amphidromus fuscolabris reproductive system.png, '' Amphidromus fuscolabris''; at – atrium; e – epiphallus; fl – flagellum; fo – free oviduct; gd – gametolytic duct; gs – gametolytic sac; ov – oviduct; p – penis; pr – penial retractor muscle; v – vagina; vd – vas deferens File:Amphidromus roseolabiatus reproductive system.png, '' Amphidromus roseolabiatus''; ap – appendix; at – atrium; e – epiphallus; fl – flagellum; fo – free oviduct; gd – gametolytic duct; gs – gametolytic sac; ov – oviduct; p – penis; pr – penial retractor muscle; v – vagina; vd – vas deferens File:Amphidromus syndromoideus reproductive system.png, '' Amphidromus syndromoideus''; ap – appendix; at – atrium; e – epiphallus; fl – flagellum; fo – free oviduct; gd – gametolytic duct; gs – gametolytic sac; ov – oviduct; p – penis; pr – penial retractor muscle; v – vagina; vd – vas deferens File:Amphidromus xiengensis reproductive system.png, '' Amphidromus xiengensis''; at – atrium; e – epiphallus; fl – flagellum; fo – free oviduct; gd – gametolytic duct; gs – gametolytic sac; ov – oviduct; p – penis; pr – penial retractor muscle; v – vagina; vd – vas deferens

Diversity and phylogeny

Prior to 1900, the similarity in shape of the shell of ''Amphidromus'' to that of South American tree snails in the family

Bulimulidae Bulimulidae is a taxonomic family of medium-sized to large, air-breathing, tropical and sub-tropical land snails, terrestrial pulmonate gastropod molluscs in the superfamily Orthalicoidea.MolluscaBase eds. (2020). MolluscaBase. Bulimulidae Tryon ...

had misled taxonomists. However, the dissections made by Wiegmann and Jacobi clearly showed that the inner anatomical features of ''Amphidromus'' were the same as those of the Asian-Indonesian Camaenidae, and that the resemblance of the shell of ''Amphidromus'' to that of bulimulids was merely an example of parallelism. ;Subgenera and species Laidlaw and Solem (1961) recognized 75 species in the genus ''Amphidromus'', and placed another seven names under '' incertae sedis''. In 2010, 87 species in the genus ''Amphidromus'' were recognized.Chan S.-Y., Tan S.-K. & Abbas J. B. (2008). "On a new species of ''Amphidromus'' (''Syndromus'') (Gastropoda: Pulmonata: Camaenidae) from Rotti Island, Indonesia". ''Occasional Molluscan Papers'' 1: 1–5
PDF

Internet Archive
/ref>Chan S.-Y. & Tan S.-K. (2008). "On a new species of ''Amphidromus'' (''Syndromus'') (Gastropoda: Pulmonata: Camaenidae) from Sumba Island, Indonesia". ''Occasional Molluscan Papers'' 1: 6–10
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Internet Archive
/ref> Species within the genus ''Amphidromus'' are divided into two subgenera, as in the following list: * Subgenus ''Amphidromus'' Albers, 1850 Originally described as ''Helix perversus'' by Linnaeus in 1758, ''

Amphidromus perversus ''Amphidromus perversus'' is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Camaenidae. MolluscaBase eds. (2020). MolluscaBase. Amphidromus perversus (Linnaeus, 1758). Accessed through: World R ...

'' is the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specim ...

of the genus ''Amphidromus'', by the subsequent designation of Eduard von Martens (1860). Species in the subgenus ''Amphidromus'' are amphidromine (left-handed and right-handed snails occur within the population) with a few exceptions. Four dextral taxa are: '' A. givenchyi'', '' A. protania'', '' A. schomburgki dextrochlorus'' and ''A. inversus annamiticus''; and one sinistral: '' A. atricallosus classiaris''. These species usually have shells which have ht following characteristics: they are large (height often exceeding ); they have a height/width ratio of less than 1.85; and a shell color which is yellowish or greenish. Anatomically they have a long epiphallus and flagellum, and an appendix is usually present. * Subgenus '' Syndromus'' Pilsbry, 1900 All but two species within the subgenus ''Syndromus'' are sinistral. The exceptions are the amphidromine '' A. glaucolarynx'' and the dextral '' A. kruehni''. The type species of the subgenus ''Syndromus'' is '' A. contrarius'' Müller, 1774, by the subsequent designation of Adolf Michael Zilch (1960). Species in the subgenus ''Syndromus'' have smaller shells (height usually less than and height/width ratio greater than 1.85), with variable color pattern. They also have a short epiphallus and flagellum, lacking an appendix. A third possible subgenus, ''Goniodromus'' Bülow, 1905 (type species ''Amphidromus büllowi'' Fruhstorfer, 1905), is also cited in the literature, though its subgeneric status is yet to be confirmed. ;Phylogeny Molecular analyses of partial sequences of

16S rDNA 16 S ribosomal RNA (or 16 S rRNA) is the RNA component of the 30S subunit of a prokaryotic ribosome (SSU rRNA). It binds to the Shine-Dalgarno sequence and provides most of the SSU structure. The genes coding for it are referred to as 16S rRN ...

of 18 distinct species carried out by Sutcharit and colleagues (2007) indicate that ''Amphidromus'' is a monophyletic group. In their study, different cladograms obtained through distinct methods such as

maximum parsimony In phylogenetics, maximum parsimony is an optimality criterion under which the phylogenetic tree that minimizes the total number of character-state changes (or miminizes the cost of differentially weighted character-state changes) is preferred. ...

, neighbor joining and

maximum likelihood In statistics, maximum likelihood estimation (MLE) is a method of estimating the parameters of an assumed probability distribution, given some observed data. This is achieved by maximizing a likelihood function so that, under the assumed stat ...

were congruent among themselves. Though the

topology In mathematics, topology (from the Greek words , and ) is concerned with the properties of a geometric object that are preserved under continuous deformations, such as stretching, twisting, crumpling, and bending; that is, without closing ...

obtained for the subgenus ''Amphidromus'' was fairly consistent with current taxonomy, the phylogeny of sinistral ''Syndromus'' species showed no such correspondence. Also according to their results, enantiomorphy seems to be the ancestral state of shell coiling in the genus ''Amphidromus'', which is contrary to the general expectation of dextrally coiled shells as an ancestral condition. Despite being morphologically identical, some specimens supposedly belonging to three species, namely ''Amphidromus semitessellatus'', ''A. xiengensis'' and ''A. areolatus'', apparently had polyphyletic origins of mtDNA haplotypes. This resulted in the same species simultaneously appearing in distinct clades along the topology: for instance, ''A. areolatus'' can be found in two different clades in Sutcharit and colleague's (2007) cladogram, clustered respectively with ''A. xiengiensis'' and also with ''A. semitesselatus''. According to the authors, these results could be explained by convergent and polymorphic shell color patterns (e.g., the shells of the specimens had very similar colors and shape, though the mtDNA markers showed significant differences). Alternatively, they could also be the result of

introgressive hybridization Introgression, also known as introgressive hybridization, in genetics is the transfer of genetic material from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with one of its parent species. Introg ...

or ancestral polymorphism of mtDNA. In any case, analyses of phylogeography using other markers ( nuclear markers or other mtDNA markers) or additional morphological characters would still be necessary to further clarify these issues.

Fossil history

Currently, no reliable pre-human fossil occurrences of ''Amphidromus'' have been recorded. Tera van Benthem Jutting (1932) reported finding several specimens of '' A. filozonatus'' which had been eaten in prehistoric times by natives, in Sampoeng Cave, central Java; and a few years later (van Benthem Jutting, 1937, pp. 92–94) the same author reported a single specimen of '' A. palaceus'' from the Trinil Beds of Java. Neither record predates human occupancy, and therefore these shed no light on the pre-human history of ''Amphidromus''.

Ecology

Meghalaya Abode of the Clouds India Nature in Laitmawsiang Landscape

Distribution

The genus ''Amphidromus'' ranges from eastern India, in south-western Asia (limited to the north by the

Himalayas The Himalayas, or Himalaya (; ; ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the planet's highest peaks, including the very highest, Mount Everest. Over 10 ...

), to northern Australia (limited eastward by

Weber's Line Max Carl Wilhelm Weber van Bosse or Max Wilhelm Carl Weber (5 December 1852, in Bonn – 7 February 1937, in Eerbeek) was a German-Dutch zoologist and biogeographer. Weber studied at the University of Bonn, then at the Humboldt University in B ...

). ''Amphidromus'' species are found in localities as follows: from the

Garo Hills The Garo Hills (Pron: ˈgɑ:rəʊ) are part of the Garo-Khasi range in Meghalaya, India. They are inhabited by the Garo people. It is one of the wettest places in the world. The range is part of the Meghalaya subtropical forests ecoregion. De ...

and Khasi Hills of Meghalaya in northeastern

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...

; throughout

Burma Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John C. Wells, Joh ...

Malay Peninsula The Malay Peninsula ( Malay: ''Semenanjung Tanah Melayu'') is a peninsula in Mainland Southeast Asia. The landmass runs approximately north–south, and at its terminus, it is the southernmost point of the Asian continental mainland. The ar ...

Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...

Laos Laos (, ''Lāo'' )), officially the Lao People's Democratic Republic ( Lao: ສາທາລະນະລັດ ປະຊາທິປະໄຕ ປະຊາຊົນລາວ, French: République démocratique populaire lao), is a socialist s ...

Cambodia Cambodia (; also Kampuchea ; km, កម្ពុជា, UNGEGN: ), officially the Kingdom of Cambodia, is a country located in the southern portion of the Indochinese Peninsula in Southeast Asia, spanning an area of , bordered by Thailand ...

Vietnam Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making ...

as far east as the

Sulawesi Sulawesi (), also known as Celebes (), is an island in Indonesia. One of the four Greater Sunda Islands, and the world's eleventh-largest island, it is situated east of Borneo, west of the Maluku Islands, and south of Mindanao and the Sulu ...

, Banda Islands,

and the Tenimber Islands (but not on Ceram, Buru, Halmahera, Batjan Island, the Obi Islands, the Aru and Kei Islands or the Talaud Archipelago and some Celebesian satellite islands); in the southern

Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

, notably

Mindanao Mindanao ( ) ( Jawi: مينداناو) is the second-largest island in the Philippines, after Luzon, and seventh-most populous island in the world. Located in the southern region of the archipelago, the island is part of an island group of ...

and the Balabac, Palawan; and in northern Australia (solely represented by '' Amphidromus cognatus'').

Habitat and feeding habits

''Amphidromus'' species are arboreal land snails. Further information concerning the habits and mode of life of the species of ''Amphidromus'' is almost non-existent, however, these snails have generally been collected while they were crawling on trees or shrubs. The diet of ''Amphidromus'' is unknown, but '' Amphidromus atricallosus perakensis'' is thought to feed on microscopic

lichens A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular micr ...

.Lok A. F. S. L. & Tan S. K. (2008). "A review of the Singapore status of the green tree snail, '' Amphidromus atricallosus perakensis'' Fulton, 1901 and its biology". ''Nature in Singapore'
1
225–230
PDF
/ref>

Life cycle

Despite the great diversity within this genus, as of 2017, comprehensive life-history studies of ''Amphidromus'' species are still lacking; only a few observations of behavior of species within the genus exist, and these observations are scattered throughout the literature. A study by Eugen Paravicini (1921) described egg-laying behaviour in '' Amphidromus palaceus'' var. ''pura'' at Palimanan, West Java. According to Paravicini's observations, in October, 1920, locals from West Java brought in two "nests" containing snails that had just begun depositing their eggs; one snail had folded the exterior leaves of a young

bamboo Bamboos are a diverse group of evergreen perennial flowering plants making up the subfamily Bambusoideae of the grass family Poaceae. Giant bamboos are the largest members of the grass family. The origin of the word "bamboo" is uncertain, ...

shoot and gummed them together into a pointed cornet. The shoot hung vertically with the narrow end pointed upward, and the wide opening below. The upper part of the sack was filled with eggs when collected. The snail descended slowly, rotating around its longitudinal axis, and deposited eggs until the entire cavity was filled up. If a crack in the basket exposed eggs to the air, they quickly dried up. Two days after capture, egg-laying was finished, and the snail closed the opening by folding over more leaves. Probably four days were spent in egg-laying, since the cavity was half filled at the start of observations. A second nest of similarly folded mango leaves contained 234 eggs. The volume of eggs in each case greatly exceeded the size of the snail, indicating that the eggs must be encapsulated just before deposition. The capsules were very thin, and dried quickly upon any exposure to the air. October marked the start of the

rainy season The rainy season is the time of year when most of a region's average annual rainfall occurs. Rainy Season may also refer to: * ''Rainy Season'' (short story), a 1989 short horror story by Stephen King * "Rainy Season", a 2018 song by Monni * '' ...

and probably this is the normal breeding period. Eggs of ''A. porcellanus'' were reported by van Benthem Jutting (1950, p. 493) to have started hatching only ten days after being laid. Similar nest-building habits have been reported for other species, but no complete study of a life cycle has been published. Up until 1961, no information was available on the cycle of activity, longevity, rate of growth, etc. Schilthuizen et al. (2005) described the spatial structure of a population of ''A. inversus'' in Malaysia. Schilthuizen et al. (2007) found that there is

sexual selection Sexual selection is a mode of natural selection in which members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (in ...

in mating with snails of the opposite chirality. This means that the left-handed snails mate more often with right-handed snails than they do with snails of the same coiling. Additionally there are anatomical adaptations of the

spermatophore A spermatophore or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especially salamanders and arthropods, and transferred in entirety to the female's ovipore during reproduction. Spermatophore ...

and of the female part of the reproductive system of gastropods, reproductive system for the success of these matings.

Predators

Predators of ''Amphidromus'' snails include the red-crowned barbet ''Megalaima rafflesii'',Wee J. (2006). "Red-crowned barbet feeding on snail". http://besgroup.talfrynature.com/2006/06/01/red-crowned-barbet-feeding-on-a-snail/ . Accessed 9 May 2010. and probably other bird species. Asian snakes in the genus ''Pareas'' are known to feed on ''Amphidromus'' species by removing the soft parts from the shells. Many shells of ''Amphidromus'' were found in the den of a rat in Malaysia.

References

This article incorporates public domain text from the reference.

Frank Fortescue Laidlaw, Laidlaw F. F. & Alan Solem, Solem A. (1961)
"The land snail genus ''Amphidromus'': a synoptic catalogue"
''Fieldiana Zoology'' 41(4): 505–720.

External links

{{Taxonbar, from=Q3977888 Amphidromus, Taxonomy articles created by Polbot